The Conversation

A researcher taking a photo-identification shot of a whale shark (C) Peter Verhoog, Dutch Shark Society

Every year in March juvenile male whale sharks arrive at Ningaloo Reef, Western Australia, supporting a thriving ecotourism industry. But where do they go in July once they leave this meeting site?

Results from our study, published today in Royal Society Open Science, suggests they don’t go far. By comparing identification photos of whale sharks in a collaborative study across the Indian Ocean, we have found that juvenile males appear to return to the same sites year after year.

Researchers swim alongside a whale shark at Ningaloo Reef. Peter Verhoog, Dutch Shark Society The biggest fish in the sea

Whale sharks are the largest fish in the sea, reaching sizes of more than 12 metres. These peaceful giants are filter-feeders, mostly eating tiny crustaceans, fish eggs and small fish that they sieve from the water using plates on their gills.

They reach maturity when they are around 8m long, but it can take them up to 30 years to reach this size. Because of this slow growth rate and their vulnerability to ship strikes and bycatch in fisheries worldwide, the status of whale sharks has recently been upgraded to Endangered by the IUCN Red List. If conservation strategies for the species are to be successful, we need to know where these animals are going and the places they visit on their migrations.

Whale sharks form aggregations off tropical coasts around the world that are a response to seasonal pulses in the abundance of their food. In the Indian Ocean, these occur at Ningaloo Reef as well as in the Maldives, off the coast of Mozambique, and in the Seychelles.

Because these sharks are docile and spectacular, aggregations are the target of ecotourism industries in each of these localities. To date, genetic studies have suggested the sharks in all these different aggregations form one population, implying that animals are moving between these sites. However, no direct evidence for these movements exists.

Photo-identification

Just like a fingerprint, we can identify whale sharks from their unique spot and stripe patterns. By comparing photos of a standard area on the body of a whale sharks among both years and locations, we can then determine if an individual is moving to a new location, or returning in multiple years. This method is called photo-identification.

Using the large and expanding database of whale shark photos taken by ecotourists, tour operators and researchers in the Indian Ocean, we used this method to look at movement patterns. Using a semi-automated matching program, we compared a database of over 6,000 images of whale sharks across the Indian Ocean.

The area of spot and stripe patterns on a whale shark used in photo-identification. What did we find?

From our comparison we were able to identify about 1,000 individual whale sharks, of which 35% were seen again at the same site in more than one year, and none of which were found to move across the Indian Ocean. One shark was tracked between Mozambique and the Seychelles, suggesting that regional links do occur, however on a larger scale, populations appear to be isolated and distinct.

Within these aggregations, juvenile males are returning on a regular basis. At Ningaloo, juvenile males photographed in 1992 have so far been seen up to 19 years later, with many sightings in between. In more recent years as the photograph databases have expanded with the tourism industries, we have seen some sharks returning in up to six consecutive years.

Females and adult males were rarely spotted at these sites, so it is possible that they aren’t homebodies like the young males.

A sample of the identification photos from the database. Good news for whale sharks

The absence of large-scale movements here is good news for the endangered whale shark. Conservation and management efforts can focus on smaller areas, and a lesser degree of cross-jurisidictional management will be required than if we found cross-ocean movements to be commonplace.

Researchers from the Australian Institute of Marine Science get ready to photograph a whale shark. Peter Verhoog/Dutch Shark Society

However, we need to improve our understanding of the regional movements of these animals. A computer simulation analysis study of our data indicated we need to increase the number of study sites and photos taken to get an estimate of their migration patterns at larger scales.

Mark Meekan receives funding from Quadrant Energy Ltd and the Save Our Seas Foundation for this work.

Samantha Andrzejaczek does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.

There are fewer than a thousand Graveside gorge wattles in Kakadu National Park. Parks Australia

Norfolk Island, nearly 1,500km from Australia’s east coast, is home to one of the country’s most endangered species, but you probably haven’t heard of it. Clematis dubia, a woody climber with white and hairy flowers, was known to number only 15 mature plants in 2003.

Once common on the island, this clematis illustrates what stands in the way of survival for many of our threatened plants. Around 84% of Australia’s native plants don’t occur anywhere else on Earth.

Threats to our native plants include ongoing habitat destruction, fire, invasive species, more frequent extreme weather events, and declining populations of the animals involved in their pollination and seed dispersal.

Clematis dubia is lucky to call Norfolk Island National Park home. Our national parks are places of beauty and adventure for us to enjoy. They are also a haven for many species.

But life in a national park doesn’t guarantee a species’ survival. Recently we assessed 41 endangered or significant plants that occur in Australia’s six Commonwealth National Parks, to identify ways to help these plants recover.

We found that many of these species don’t occur outside national parks, meaning the parks play a huge role in their conservation. Few of these species have been secured in living plant collections or seed banks, and very few are regularly monitored in the wild.

We have little information on either the impacts of threats or of species biology, which limits our ability to secure these species against further loss.

There were only 15 mature Clematis dubia on Norfolk Island known in 2003. Parks Australia Threats to plants

Clematis dubia lives in small and isolated populations. It faces many perils of modern life, like invasive weeds. We understand very little of its biology, including how its seeds are dispersed, how long it takes to start producing seed, and even how long it lives.

Another plant we assessed was the Graveside Gorge wattle (Acacia equisetifolia) found in Kakadu National Park. A small shrub, less than a metre tall with small yellow flowers, this wattle is listed as critically endangered.

Fewer than a thousand plants are growing in only two locations about a kilometre apart in a restricted area of the park. There is little information on the basic biology of this shrub.

Like other acacias, Graveside Gorge wattle is probably pollinated by, and provides food for, a variety of different insect species. It probably only reproduces sexually and its seeds might be dispersed by ants and probably germinate after fires. The main threat to this species is fires, especially ones that are too frequent or too intense.

As a safeguard against extinction, Parks Australia has collected seed from the Graveside Gorge wattle, which is now stored in the National Seed Bank at the Australian National Botanic Gardens in Canberra.

Hibiscus brennanii is a vulnerable shrub found in Kakadu National Park. Parks Australia Jenny Hunter, Kakadu ranger, collecting Hibiscus brennanii seed for the seed bank. Parks Australia

Seed banking can extend the longevity of seeds to hundreds of years, protecting a species from extinction and helping in its recovery should the worst happen. Germination trials at the National Seed Bank help unlock the often complex germination requirements of different species so that they can be regrown from seed.

As a result of trials with Graveside gorge wattle, the Gardens now has a living collection of this species. In Kakadu, Parks Australia is protecting the two wild populations by planning protective burning to create longer intervals between fires and reduce the likelihood of severe fires.

Protecting plants

Seed banking and living collections are two of the strategies we recommended to safeguard populations of threatened plant species. Some species may also benefit from establishing new populations outside national parks, similar to the management strategies used for vertebrate animals.

We also recommend surveying all endangered plant species in national parks that are not currently part of a formal monitoring program or that have not been surveyed within the past two years.

Finally, realising the gaps in our knowledge of the biology of and threats to many of Australia’s threatened plants, we recommend partnering with researchers and NGOs with restoration experience to draw on available scientific and on-the-ground knowledge.

And what of Norfolk Island’s endemic climbing clematis, Clematis dubia? Along with the low number of individuals, competition from weeds is a major threat to the survival of this species, so conservation efforts by Parks Australia have involved intensive weed control work, particularly to deal with the invasive guava plant.

Recent searches in likely habitat have revealed an additional 33 plants, a mix of adults and juveniles. Happily, new seedlings are now showing up in areas where guava has been removed, improving the future prospects for this species.

The report Constraints to Threatened Plant Recovery in Commonwealth National Parks was funded by the Australian Government through the Threatened Species Commissioner, Gregory Andrews. It was authored by researchers at the Centre for Australian National Biodiversity Research, a joint initiative between Parks Australia’s Australian National Botanic Gardens and CSIRO.

Linda Broadhurst receives funding from the Threatened Species Commissioner and the Australian Commonwealth Government. She is affiliated with the Australian Network for Plant Conservation.

In 2016, an isolated scientific outpost in northwest Tasmania made a historic finding. The Cape Grim Baseline Air Pollution Station measured carbon dioxide levels in the atmosphere exceeding 400 parts per million.

This wasn’t the first time the world has breached the symbolic climate change threshold – that honour was reached by the northern hemisphere in 2013 – but it was a first for the south.

Behind these recent findings is a history of Australia’s role in global scientific advancement. The Cape Grim station has now been running for 40 years and the resulting data set chronicles the major changes in our global atmosphere.

A national response

In 1798, Matthew Flinders’ encounter with Cape Grim confirmed to Europeans that Tasmania (then Van Diemen’s Land) was separated from the mainland of Australia.

Fast forward to the early 1970s and a small group of innovative scientists were hatching a plan to take advantage of Cape Grim’s isolation and unique geographical position. The site soon became one of the world’s most significant atmospheric measurement sites, meticulously measuring and recording some of the cleanest air that can be accessed on the planet.

There were two threads to the beginnings of Cape Grim. One was the young scientists at CSIRO, keen to pioneer an emerging field of science. The second was a call from the United Nations for global governments to work together to set up a network of monitoring stations. The Australian response was championed by Bill Priestley and Bill Gibbs, the respective senior climate figureheads at CSIRO and the Bureau of Meteorology.

The scientific community decided that Cape Grim was the most appropriate site for a permanent monitoring station, thereby establishing in 1976 the Cape Grim Baseline Air Pollution Station.

The first set of instruments lived in an ex-NASA caravan. Today the station is managed by the Bureau of Meteorology and housed in a permanent building that features state-of-the-art infrastructure, including a tower fitted with important monitoring equipment. Many of the early pioneering scientists are still actively involved in this research.

The first set of air monitoring instruments lived in an ex-NASA caravan. CSIRO/Bureau of Meteorology The world’s cleanest air

The station, part of the World Meteorological Organisation’s Global Atmosphere Watch network, was sited at Cape Grim to take advantage of the “roaring forties” - the prevailing westerly winds that bring clean air from over the Southern Ocean to the station.

Air that arrives at the station from the southwest is classified as “baseline” air. Having had no recent contact with land, it represents the background atmosphere and is perhaps some of the cleanest in the world.

While we focus on this clean air, most of the instruments monitor continuously, regardless of wind direction, and can detect pollution from Melbourne and other parts of Tasmania in certain conditions.

The station measures all major and minor greenhouse gases; ozone-depleting chemicals; aerosols (including black carbon or soot); reactive gases including lower-atmosphere ozone, nitrogen oxides and volatile organic compounds; radon (an indicator of changes to the land); solar radiation; the chemical composition of rainwater; mercury; persistent organic pollutants; and finally the weather.

The Cape Grim Air Archive, initiated by CSIRO in 1978 and soon adopted into the operations of the station, is now the world’s most important and unique collection of background atmospheric air samples, underpinning many research papers on global and Australian emissions of greenhouse and ozone depleting gases.

The human fingerprint

Cape Grim data are freely available and have been widely used in all five international climate change assessments (1990-2013), all ten international ozone depletion assessments (1985-2014), in four State of the Climate Reports 2010-2016 and in lower-atmosphere ozone assessments.

Measurements at Cape Grim have demonstrated the impact of human activity on the atmosphere. For example, CO₂ has increased from about 330 parts per million (ppm) in 1976 to more than 400 ppm today, an average increase of 1.9 ppm per year since 1976. Since 2010 the rate has been 2.3 ppm per year. The isotopic ratios of CO₂ measured at Cape Grim have changed in a way that is consistent with fossil fuels being the source of higher concentrations.

Cape Grim has also demonstrated the effectiveness of action to reduce human impacts. The decline in concentrations of ozone-depleting substances measured at Cape Grim demonstrates the progress of the Montreal Protocol, an international agreement to phase out the use of these chemicals, and leading to the gradual recovery of the ozone hole.

Measurements at Cape Grim have contributed significantly to global understanding of marine aerosols, including some of the first evidence that microscopic marine plants (phytoplankton) are a source of gases that play a role in cloud formation. With 70% of the Earth’s surface covered by oceans, aerosols in the marine environment play an important role in the climate system.

Cape Grim data are also used by the Australian government to meet international obligations. For example, the station’s greenhouse gas data have independently verified parts of Australia’s National Greenhouse Gas Inventory, which reports Australia’s annual emissions to the United Nations Framework Convention on Climate Change. Persistent organic pollutants have been reported to the Stockholm Convention on these chemicals and Cape Grim mercury data will be reported to the Minimata Convention.

Data collected from the Cape Grim Station have been used in more than 700 research papers on climate change and atmospheric pollution. By working with universities Cape Grim is a training ground for the next generation of climate scientists.

CSIRO/Bureau of Meteorology

Melita Keywood is employed by CSIRO and receives funding from the Department of the Environment and Energy, Australian Bureau of Meteorology, University of Wollongong.

Paul Fraser receives funding from MIT, NASA, Australian Bureau of Meteorology, Department of the Environment and Energy, and Refrigerant Reclaim Australia.

Paul Krummel receives funding from MIT, NASA, Australian Bureau of Meteorology, Department of the Environment and Energy, and Refrigerant Reclaim Australia.

Sam Cleland does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.

The journal Climatic Change has published a special edition of review papers discussing major natural hazards in Australia. This article is one of a series looking at those threats.

Australia is a huge continent, but a coastal nation. About 80% of Australians live within 50km of the coast, and a sea-level rise of 1.1 metres (a high-end scenario for 2100) would put about A$63 billion (in 2008 dollars) worth of residential buildings at risk.

Anyone who lives along Sydney’s northern beaches, especially in Collaroy, saw at first hand the damage the ocean can wreak on coastal properties when the coastline was hit by a severe east coast low during a king tide in June.

There are many different factors that determine which coastal homes or suburbs are most at risk of inundation or erosion, either now or in the future. In a review published as part of a series produced by the Australian Energy and Water Exchange initiative, we investigated the causes of extreme sea levels and coastal impacts in Australia, how they have changed, and how they might change even more. While significant progress has been made over recent decades, many questions remain.

The first factor to consider is the average sea level, relative to the land elevation. This “background” sea level varies, both from year to year and season to season. Depending on where you live and what the climate is doing, background sea level can fluctuate by up to about 1m. Around Australia’s northern coastline, for example, El Niño and La Niña can cause large variations in year-to-year sea levels.

On top of this are the tides, which rise and fall predictably, and whose range varies by location and phase of the moon. Most places have two tides a day, but curiously some only have one - including Perth.

On top that again is the effect of the weather, the most notable short-term effects being storm surges and storm waves. During a surge, the storm pushes extra water onto the coast through a combination of wind pressure, wave buildup, and atmospheric pressure changes. Obviously these factors are much more localised than tides.

Extreme sea-level events, such as the one that hit Sydney in June, can arise from isolated events such as a storm surge. But more often they are due to a combination of natural phenomena that on their own may not be considered extreme. In Sydney, several factors aligned: a storm surge driven by an east coast low, an uncommon wave direction, a king tide, and a higher-than-average background sea level.

These processes already have the capacity to destroy coastal homes and infrastructure. But for the future, we also need to factor in climate change, which will raise the background sea level and may also change the frequency and intensity of storms.

Long-term trends

Average sea levels in Australian waters have been rising at rates similar to (but just below) the global average. Since 1993, Australian tide gauges show an average rise of 2.1mm per year, whereas satellite observations reveal a global average rise of 3.4mm per year.

What really counts is extreme sea levels, and these have been rising at roughly the same rate, meaning that the rising background sea level is a fairly good guide to how extremes are increasing.

The effects of a king tide on Queensland’s Gold Coast. Bruce Miller/CSIRO, CC BY

This trend will continue in the future, although more energetic storm systems may also cause larger storm surges and hence higher rates of extreme sea levels in some places. More frequent storms are also set to make extreme sea-level events more common.

By 2100, global average sea level is projected to rise by 0.28-0.61cm, relative to the period 1986-2005, if this century’s global warming can be held to about 1℃. But if greenhouse emissions continue to increase at their current rate, the world is in line for sea-level rises of 0.52-0.98cm.

This rise will not be uniform around Australia’s coastline. The east coast is likely to experience up to 6cm more sea-level rise than the global average by 2100, because of the expected warming and strengthening of the East Australian Current.

Trends in Australia’s weather and waves are harder to predict. Satellite measurements over the past 30 years suggest that waves are getting slightly higher in the Southern Ocean, and climate models suggest that this may continue. As the tropics continue to expand with climate change, the band of westerly winds over the Southern Ocean will retreat further south and strengthen, whipping up higher waves that will travel to Australia’s southern coast as swell. On the other hand, weakening winds nearer to Australia may help to dampen down wave heights. On Australia’s eastern coast, climate models suggest fewer large wave events due to decreasing storminess in the Tasman Sea in the future.

A significant challenge we face is not having the data available to monitor the changes along our southern coastline. Australia has the longest east-west continental shelf in the world, but we have only a handful of wave buoys to measure these processes; much of the coastline is not monitored despite widespread coastal management concerns.

Our understanding of extreme sea-level change in Australia is also limited by available tide gauge coverage. Only two digital tide gauge records (in Fremantle and Fort Denison) extend back to at least the early 20th century, and records elsewhere around the coast typically span less than 50 years.

However, our investigation discovered that there is an opportunity to increase the length of available records by digitising old paper tide gauge charts. This could extend several records along our southern and tropical coastlines.

We also have major gaps in our knowledge about how our coastlines will be changed by flooding and erosion. The simple methods used to predict coastal erosion may underestimate erosion significantly, particularly in estuaries.

Given the considerable urban infrastructure located within estuaries, and the fact that they are vulnerable both to coastal storms and river floods, this is one of the many crucial questions about life on the coast that we still need to answer.

Kathleen McInnes works for CSIRO Oceans and Atmosphere, and receives funding from the Commonwealth of Australia Department of the Energy and Environment National Environmental Science Program, through the Earth Systems and Climate Change Hub, and the Australian Renewable Energy Agency.

Mark Hemer works for CSIRO Oceans and Atmosphere, and receives funding from the Commonwealth of Australia Department of the Energy and Environment National Environmental Science Program, through the Earth Systems and Climate Change Hub, and the Australian Renewable Energy Agency.

Ron Hoeke works for CSIRO Oceans and Atmosphere, and receives funding from the Commonwealth of Australia Department of the Energy and Environment National Environmental Science Program, through the Earth Systems and Climate Change Hub, and the Australian Renewable Energy Agency.

Kelp forests are declining around the world and in Australia, according to two new studies.

The first, a global study published in the journal PNAS, found that 38% of the world’s kelp forests have declined over the past 50 years.

The second, published in the same PNAS edition, investigated one cause of the declines. Kelp forests in eastern Australia are losing out to tropical species as the seas warm.

Together the studies show that we need local and global solutions to prevent our underwater forests from vanishing.

Deep trouble

Satirist Jordan Shanks recently argued that marine biologists may well have the worst job on Earth. Although most people think we spend our days diving in crystal-clear blue waters, spotting whales and sailing into the sunset, this is actually quite far from the truth.

More often than not, our job unfortunately involves documenting the depressing deterioration and decline of precious marine habitats.

While bleaching of coral reefs worldwide has been front and centre in the news over the past year, in fact all of our coastal ecosystems have been affected by human impacts.

One such ecosystem is the underwater forests formed by the large seaweeds known as kelp, which dominate temperate, coastal rocky shores worldwide.

Kelp forests are found in waters off all continents, and around Australia they form the Great Southern Reef which stretches from the Queensland border to near Kalbarri in Western Australia, and contributes more than A$10 billion annually to the Australian economy.

Although this year’s global coral bleaching event has been most featured in the media, we should be at least equally concerned about the loss of kelp forests in cooler waters. Clockwise from top left: A. Vergés, Creative Commons, J. Turnbull, A. Vergés A health check for global kelp forests

In the first study, the authors provide the first ever global “health check” for kelp forests. A team of international experts compiled and analysed a data set of kelp abundance at more than 1,000 sites across 34 regions around the globe.

While 38% of the world’s kelp forests have declined, it isn’t all bad news. Just over 25% of kelp forests have actually increased in abundance.

But there is another big problem: there are many regions where kelp exists, but we have no data and simply no idea how it’s doing.

A kelp forest in South Africa. The species Ecklonia maxima is one of the few kelps that are expanding its distribution. This species is ‘the giant cousin’ of the common kelp in Australia, Ecklonia radiata. T. Wernberg

Unfortunately, Australia’s kelp forests feature heavily among the declining populations. Kelp forests have declined in Western Australia, South Australia, Tasmania and New South Wales. The causes of this loss are diverse, but share a common factor: people.

In Western Australia kelp forests were wiped out during an extreme marine heatwave, which was probably a consequence of climate change. In South Australia, the kelp has succumbed to years of pollution from nutrient-rich wastewater.

And in Tasmania, warming has enabled a kelp-eating sea urchin to jump from the mainland and graze on local kelp forests. This was compounded by overfishing of large lobsters, which normally eat the urchins.

Turning tropical

The second paper shows that a phenomenon known as “tropicalisation” of ecosystems is now threatening kelp forests in New South Wales, and potentially globally.

Tropicalisation occurs as ocean waters warm and tropical species start making a home in habitats previously dominated by cold-water species. In the case of NSW kelp forests, these tropical intruders are herbivorous fishes that eat the kelp – sometimes down to the ground.

Our initial research has shown that, over ten years, lush kelp forests have completely disappeared in some key offshore sites at the Solitary Islands Marine Park. This region is famous for bringing together a unique mosaic of tropical and temperate habitats, but our data clearly shows that tropical species are winning and starting to take over.

Screen grabs from Baited Remote Underwater Videos collected by Dr Hamish Malcolm, showing dense kelp beds back in the early 2000s that completely disappeared from 2010 onwards. Hamish Malcolm

We were able to quantify the year-by-year decline of kelp using a long-term video dataset collected by Hamish Malcolm from the NSW Department for Primary Industries.

The video footage revealed not only the gradual decline of kelp, but also helped us identify fish as central culprits behind this disappearance. Between 2002 and 2012, we saw both an increase in the number of fish bite marks on kelp and a clear rise in the abundance of warm-water seaweed-eating species.

We also ran a series of kelp transplant experiments, which identified two warm-water fish species that rapidly consumed transplanted kelp within hours: a rabbitfish and a drummer.

Interestingly, however, the species that we think had the greatest effect, surgeonfish, did not actually feed on the adult kelp. Instead, the surgeonfish rapidly consumed smaller carpet-forming seaweeds. This suggests these “tropicalising” fishes maintain deforested reefs by removing kelp while they are tiny, before they start making large fronds.

These NSW findings are by no means an isolated phenomenon. Voracious consumption by invading warm-water fish have also been linked to the loss or failure to recover of kelp forests in Japan and in Western Australia.

Frenzied feeding on transplanted kelp by a school of rabbitfish (Siganus fuscescens) is only briefly interrupted by a large predator in the Solitary Islands, eastern Australia. What can we do?

Both studies found a net decline in the abundance of kelp forests, from both local (nutrients, fishing) and global (ocean warming and its effects) effects of humans. If we want to arrest these declines, action is therefore required at both local and global scales.

Locally, water quality around some major cities has been improved. When coupled with active restoration efforts of damaged seaweeds, this can lead to conservation success stories like the return of crayweed forests to Sydney. Marine reserves, where fishing is prohibited, can also reduce the ability of warm-water species to colonise cooler habitats.

But of course, ultimately, global action is needed to prevent further climate change impacts. That includes reduction in our greenhouse gas emissions, in Australia and around the world.

Adriana Vergés receives funding from the Australian Research Council.

Peter Steinberg receives funding from the Australian Research Council.

Thomas Wernberg receives funding from The Australian Research Council and The Hermon Slade Foundation.

2016 is set to be the world’s hottest year on record. According to the World Meteorological Organization’s preliminary statement on the global climate for 2016, global temperatures for January to September were 0.88°C above the long-term (1961-90) average, 0.11°C above the record set last year, and about 1.2°C above pre-industrial levels.

While the year is not yet over, the final weeks of 2016 would need to be the coldest of the 21st century for 2016’s final number to drop below last year’s.

Record-setting temperatures in 2016 came as no real surprise. Global temperatures continue to rise at a rate of 0.10-0.15°C per decade, and over the five years from 2011 to 2015 they averaged 0.59°C above the 1961-1990 average.

Giving temperatures a further boost this year was the very strong El Niño event of 2015−16. As we saw in 1998, global temperatures in years where the year starts with a strong El Niño are typically 0.1-0.2°C warmer than the years either side of them, and 2016 is following the same script.

Global temperature anomalies (difference from 1961-90 average) for 1950 to 2016, showing strong El Niño and La Niña years, and years when climate was affected by volcanoes. World Meteorological Organization Almost everywhere was warm

Warmth covered almost the entire world in 2016, but was most significant in high latitudes of the Northern Hemisphere. Some parts of the Russian Arctic have been a remarkable 6-7°C above average for the year, while Alaska is having its warmest year on record by more than a degree.

Almost the whole Northern Hemisphere north of the tropics has been at least 1°C above average. North America and Asia are both having their warmest year on record, with Africa, Europe and Oceania close to record levels. The only significant land areas which are having a cooler-than-normal year are northern and central Argentina, and parts of southern Western Australia.

The warmth did not just happen on land; ocean temperatures were also at record high levels in many parts of the world, and many tropical coral reefs were affected by bleaching, including the Great Barrier Reef off Australia.

Global temperatures for January to September 2016. UK Meteorological Office Hadley Centre

Greenhouse gas levels continued to rise this year. After global carbon dioxide concentrations reached 400 parts per million for the first time in 2015, they reached new record levels during 2016 at both Mauna Loa in Hawaii and Cape Grim in Australia.

On the positive side, the Antarctic ozone hole in 2016 was one of the smallest of the last decade; while there is not yet a clear downward trend in its size, it is at least not growing any more.

Global sea levels continue to show a consistent upward trend, although they have temporarily levelled off in the last few months after rising steeply during the El Niño.

Droughts and flooding rains

El Niño was over by May 2016 – but many of its effects are still ongoing.

Worst affected was southern Africa, which gets most of its rain during the Southern Hemisphere summer. Rainfall over most of the region was well below average in both 2014-15 and 2015-16.

With two successive years of drought, many parts are suffering badly with crop failures and food shortages. With the next harvests due early in 2017, the next couple of months will be crucial in prospects for recovery.

Drought is also strengthening its grip in parts of eastern Africa, especially Kenya and Somalia, and continues in parts of Brazil.

On the positive side, the end of El Niño saw the breaking of droughts in some other parts of the world. Good mid-year rains made their presence felt in places as diverse as northwest South America and the Caribbean, northern Ethiopia, India, Vietnam, some islands of the western tropical Pacific, and eastern Australia, all of which had been suffering from drought at the start of the year.

The world has also had its share of floods during 2016. The Yangtze River basin in China had its wettest April to July period this century, with rainfall more than 30% above average. Destructive flooding affected many parts of the region, with more than 300 deaths and billions of dollars in damage.

Europe was hard hit by flooding in early June, with Paris having its worst floods for more than 30 years.

In western Africa, the Niger River reached its highest levels for more than 50 years in places, although the wet conditions also had many benefits for the chronically drought-affected Sahel, and eastern Australia also had numerous floods from June onwards as drought turned to heavy rain.

Tropical cyclones are among nature’s most destructive phenomena, and 2016 was no exception. The worst weather related natural disaster of 2016 was Hurricane Matthew. Matthew reached category five intensity south of Haiti, the strongest Atlantic storm since 2007. It hit Haiti as a category 4 hurricane, causing at least 546 deaths, with 1.4 million people needing humanitarian assistance. The hurricane then went on to cause major damage in Cuba, the Bahamas and the United States.

Other destructive tropical cyclones in 2016 included Typhoon Lionrock, responsible for flooding in the Democratic People’s Republic of Korea which claimed at least 133 lives, and Cyclone Winston, which killed 44 people and caused an estimated US$1.4 billion damage in Fiji’s worst recorded natural disaster.

Arctic sea ice extent was well-below average all year. It reached a minimum in September of 4.14 million square kilometres, the equal second smallest on record, and a very slow autumn freeze-up so far means that its extent is now the lowest on record for this time of year.

In the Antarctic, sea ice extent was fairly close to normal through the first part of the year but has also dropped well below normal over the last couple of months, as the summer melt has started unusually early.

It remains to be seen what impact the summer of 2016 has had on the mountain glaciers of the Northern Hemisphere.

While 2016 has been an exceptional year by current standards, the long-term warming trends mean there will be more years like it to come. Recent research has shown that global average temperatures which are record-breaking now are likely to become the norm within the next couple of decades.

Blair Trewin is a staff member of the Australian Bureau of Meteorology. The World Meteorological Organization is the United Nations' specialized agency on the state and behaviour of the Earth's atmosphere, its interaction with the land and oceans, the weather and climate it produces and the resulting distribution of water resources. 191 countries and territories are members.

The journal Climatic Change has published a special edition of review papers discussing major natural hazards in Australia. This article is one of a series looking at those threats in detail.

Storms, wind and hail do a lot of damage to Australians and their property. The 1999 Sydney hailstorm, for instance, cost A$1.7 billion in insured losses. That makes it the biggest single insurance loss in Australian history; in today’s money it would have cost more than A$4 billion.

Our understanding of wind and hail depends on the type of storm that generates them – and this is where it gets complicated. Thunderstorms can generate not just heavy rainfall but also high winds, lightning and hail, albeit in very localised areas. Large-scale storms such as tropical cyclones are a different phenomenon altogether, bringing not just destructive winds, but also storm surges and soaking rains, often over wide areas.

This complexity makes storms difficult to study, because limited research resources are spread across the many different storm types and their associated hazards.

To help address these issues, we collated and reviewed the latest knowledge and understanding of storms in Australia, covering the current scientific literature on the assessment, causes, observed trends and future projected changes of storm hazards, with a specific focus on severe wind and hail. We found that progress has been made in many areas, but also that much remains to be done.

Are we getting more or less storms?

In short - we don’t know with confidence. Despite the severity of the impacts wrought by storms, there is limited observational data for some types of storms and their associated hazards, particularly for the estimation of hail and wind.

Current estimates of the hail hazard in Australia, for example, are available only from the Bureau of Meteorology’s severe storm archive, which suffers from large uncertainties associated with biases and changing reporting practices. This makes it unsuitable for assessing the climatology of hail storms on a national scale.

Similarly, issues such as changes to Automatic Weather Stations (AWS) and limited records of atmospheric pressure observations, have hampered efforts to develop high-quality surface wind datasets across Australia. Bob Dylan might have been right when he told us “you don’t need a weatherman to know which way the wind blows,” but then again he didn’t win his Nobel Prize for meteorology.

European researchers have analysed hailstorm trends using networks of devices called “hailpads”. But these records do not exist in Australia, and so there is a significant gap in our knowledge about hailstorm histories and trends.

The projections of future wind hazard in and around Australia are equally limited and differ from region to region. For example, in the tropics, research suggests that extreme wind hazard may decrease in the future, although confidence in this prediction is low. Meanwhile, summer wind increases are possible in those parts of Australia that are subjected to East Coast Lows.

We also don’t really know what to expect from future severe thunderstorms, and while research suggests that they may become more frequent in southeastern Australia, there is a wide range of uncertainty around this projection.

For future trends in hail, again there are only a few studies currently available, but there is at least an indication of increases in hail frequency in southeastern regions.

But while the picture is very uncertain for now, we hope this uncertainty will be reduced with the help of improvements in both the observation and computational modelling of storms and their associated hazards. We are growing more confident in our predictions for tropical cyclone, forecasting that the overall number will decline, but that the strongest storms will grow stronger still.

We also hope to improve our understanding of severe thunderstorms by using remote sensing platforms to record hail and extreme wind events right across Australia. These include the GPATS lightning-detection network, the new Himawari-8 and 9 satellites, and the Bureau of Meteorology’s soon-to-be upgraded radar network. Validation of these techniques, of course, will also require high-quality direct observations of these severe weather conditions – the very thing we currently lack.

Is this where you come in?

Citizen scientists may, however, help to fill some of these gaps. There are exciting prospects for improving severe weather observations, such as the success of the mPING crowdsourced weather reports project in the United States, which allows participants to use a mobile phone app to report severe weather, which then feeds into new research.

This approach could prove to be an excellent way of getting data in such a vast and diverse landscape as Australia, while simultaneously engaging with both the public and the atmospheric science community. We could also enlist the help of scientific study groups, which bring together academics, scientists and industry partners to exchange ideas and develop research techniques.

“The storm is up, and all is on the hazard,” cried Cassius in William Shakespeare’s Julius Caesar. How true that is of storms in Australia.

If we don’t increase our observational and research abilities, we might never fully understand the impacts of severe storms, much less be able to deal with them.

Chris White receives funding from various Tasmanian State Government research funding programs, Wine Australia and the Bushfire and Natural Hazard CRC.

Jason Evans receives funding from the Australian Research Council, the National Environmental Science Programme Earth Systems and Climate Change Hub, Sydney Water, Water Research Australia, and various NSW state government research funding programs.

Kevin Walsh receives funding from the Australian Research Council and other international funding organizations.

China's concerns about air pollution from burning coal is one reason behind the emissions slowdown. China coal image from www.shutterstock.com

For the third year in a row, global carbon dioxide emissions from fossil fuels and industry have barely grown, while the global economy has continued to grow strongly. This level of decoupling of carbon emissions from global economic growth is unprecedented.

Global CO₂ emissions from the combustion of fossil fuels and industry (including cement production) were 36.3 billion tonnes in 2015, the same as in 2014, and are projected to rise by only 0.2% in 2016 to reach 36.4 billion tonnes. This is a remarkable departure from emissions growth rates of 2.3% for the previous decade, and more than 3% during the 2000s.

Given this good news, we have an extraordinary opportunity to extend the changes that have driven the slowdown and spark the great decline in emissions needed to stabilise the world’s climate.

This result is part of the annual carbon assessment released today by the Global Carbon Project, a global consortium of scientists and think tanks under the umbrella of Future Earth and sponsored by institutions from around the world.

Global CO₂ emissions from the combustion of fossil fuels and industry. Emissions in 2016 (red dot) are based on a projection. Fossil fuel and industry emissions

The slowdown in emissions growth has been primarily driven by China. After strong growth since the early 2000s, emissions in China have levelled off and may even be declining. This change is largely due to economic factors, such as the end of the construction boom and weaker global demand for steel. Efforts to reduce air pollution and the growth of solar and wind energy have played a role too, albeit a smaller one.

The United States has also played a role in the global emissions slowdown, largely driven by improvements in energy efficiency, the replacement of coal with natural gas and, to a lesser extent, renewable energy.

What makes the three-year trend most remarkable is the fact that the global economy grew at more than 3% per year during this time. Previously, falling emissions were driven by stagnant or shrinking economies, such as during the global financial crisis of 2008.

Developed countries, together, showed a strong declining trend in emissions, cutting them by 1.7% in 2015. This decline was despite emissions growth of 1.4% in the European Union after more than a decade of declining emissions.

Emissions from emerging economies and developing countries grew by 0.9% with the fourth-highest emitter, India, growing at 5.2% in 2015.

Importantly, the transfer of CO₂ emissions from developed countries to less developed countries (via trade of goods and services produced in places different to where they are consumed) has declined since 2007.

CO₂ emissions from the combustion of fossil fuels and industry for the top 4 global emitters.

Deforestation and other changes in land use added another 4.8 billion tonnes of CO₂ in 2015, on top of the 36.3 billion tonnes of CO₂ emitted from fossil fuels and industry. This is a significant increase by 42% over the average emissions of the previous decade.

This jump in land use change emissions was largely the result of increased fires at the deforestation frontiers, particularly in Southeast Asia, driven by dry conditions brought by a strong El Niño in 2015-16. In general, though, long-term trends for emissions from deforestation and other land use change appear to be lower for the most recent decade than they were in the 1990s and early 2000s.

The carbon quota

When combining emissions from fossil fuels, industry, and land use change, the global economy released another 41 billion tonnes to the atmosphere in 2015, and will add roughly the same amount again this year.

We now need to turn this no-growth to actual declines in emissions as soon as possible. Otherwise, it will be a challenge to keep cumulative emissions below the level that would avoid a 2℃ warming, as required under the Paris Agreement.

As part of our carbon budget assessment, we estimate that cumulative emissions from 1870 (the reference year used by the Intergovernmental Panel on Climate Change to calculate carbon budgets) to the end of 2016 will be 2,075 billion tonnes of CO₂. The remaining quota to avoid the 2℃ threshold, assuming constant emissions, would be consumed at best in less than 25 years (with remaining quota estimates ranging from 450 to 1,050 billion tonnes of CO₂). Ultimately, we must reduce emissions to net zero to stabilise the climate.

The carbon budget to keep mean global temperature below 2℃ above pre-industrial levels with more than 66% probability, showing used carbon budget (black) and remaining carbon budget (red). Values rounded to nearest 50 billion tonnes of CO₂. The remaining quotas are indicative and vary depending on definition and methodology. Rogelj et al. 2016, Nature Climate Change

Pep Canadell receives funding from the National Environmental Science Program - Earth Systems and Climate Change hub.

Corinne Le Quéré is affiliated with the UK Committee on Climate Change.

Glen Peters receives funding from the Research Council of Norway.

Rob Jackson receives funding from the U.S. National Science Foundation and Departments of Energy and Agriculture. He is a member of Stanford's Natural Gas Initiative, an industry affiliates program, working to reduce methane emissions.

Stunned. Shocked. Speechless. Devastated. Political tsunami. These were the key words rising to the surface of the babble of conversations that took place in the corridors of the climate negotiations in Marrakech on Wednesday 9 November – the day Donald Trump won the US presidency.

A climate denier, Trump has vowed to tear up the historic Paris Agreement along with the Obama administration’s Clean Power Plan, which seeks to slash greenhouse emissions from power plants. He has also given the green light to renewed fossil fuel exploitation in the United States.

Oil and gas stocks unsurprisingly rose, and coal stocks soared, on his victory day. If implemented, Trump’s promises would make it impossible for the United States to reach its national pledge under the Paris Agreement to reduce emissions by 26-28% relative to 2005 by 2025.

At the moment, Trump’s previous declaration of climate change as a hoax perpetrated by the Chinese to undermine US industry looks particularly poignant.

His election is a dramatic turnaround from the years of constructive bilateral climate diplomacy by the Obama administration with China, which culminated in the joint US-China statement on climate change in November 2014. This joint announcement of the headline national action plans by the world’s two biggest emitters (together covering 40% of global emissions) injected significant momentum into the negotiations leading to the Paris Agreement in 2015.

But now the US elections have delivered not just a presidential victory against action on climate change, but made it much easier for Trump to deliver on his plans than it was for Obama. The Republican Party is now set to control all four branches of government: the House of Representatives, the Senate, the Presidency and soon the Supreme Court (once Trump nominates a new judge following the death of Justice Scalia, bringing the number of judges back to nine, with a conservative majority). This leaves only the media and civil society to speak up for a safe climate in the face of the national government’s agenda.

Turning back time

Seasoned negotiators and observers at Marrakech with long memories recalled the moment in 2001 when former president George W. Bush declared that the United States would withdraw from the Kyoto Protocol, the predecessor to the Paris Agreement. This withdrawal cast a long shadow over the negotiations, which was finally lifted with the Obama administration’s re-engagement with climate change that made the Paris breakthrough possible.

Yet the world today is very different to what it was in 2001. The Paris Agreement is now in force after a speedy ratification, the US share of global emissions has declined, and renewable energy is now much cheaper. Many US states, cities and businesses will continue to work towards reducing emissions, and many Republican politicians have let go of their aversion to renewable energy in response to public and business pressure.

In short, much of America and the rest of the world will continue to build momentum under the Paris Agreement, despite the changing of the guard in Washington DC.

Given Trump’s record of policy flip-flopping, it also remains an open question as to how far he will actually go to undo the diplomatic climate legacy of the Obama administration. Much will depend on who takes over as Secretary of State, and how the State Department assesses the broader diplomatic consequences of withdrawing from the Paris treaty, particularly in terms of transatlantic relationships. European Council president Donald Tusk has already invited Trump to attend a US-EU summit. We might therefore see some easing of Trump’s hard anti-climate talk, much as his social rhetoric softened on election night. Trump the President may not be quite the same as Trump the candidate.

Moreover, under Article 28 of the Paris Agreement it will take a total of four years for any formal withdrawal by the United States to take effect. If the US were to turn its back on these legal niceties and abandon its obligations during this period, it would be widely regarded as a climate pariah state. In contrast, China will enjoy its rising status as a climate leader.

Meanwhile, after the initial pause to digest the shock of Trump’s victory, the negotiators at Marrakech have got back down to their business, which is to fill in the implementation details of the Paris Agreement.

Robyn Eckersley receives funding from the Australian Research Council to research a project called 'What makes a climate leader?'

A US withdrawal would be game over for the Paris Agreement, but there's still hope for the climate. NASA's Marshall Space Flight Center/Flickr, CC BY-NC

November 9 will likely become the day that the Paris Agreement died, but not when the goal of limiting warming to 2℃ slipped out of reach.

President Donald Trump can, and likely will, drop out of the Paris climate agreement. Direct withdrawal will take four years.

But Trump could instead drop out from the overall climate convention under which the agreement operates. That would only take one year and would result in automatic withdrawal from the Paris Agreement.

It would shortcut any hopes that Paris would bind Trump’s hands for some time.

As I’ve argued in my research, a US withdrawal from the Paris Agreement would be its death knell.

A predictable loose cannon

Trump has also promised a range of further destructive international and domestic actions on climate and energy. These include cutting all international climate financing, rescinding energy regulations, reopening federal and offshore areas for coal and oil development and abolishing the clean power plan.

There is some hope that Trump is a loose cannon who may renege on his previous promises. Such hope is ultimately false. Trump has already appointed noted climate denier Myron Ebell as the head of his Environmental Protection Agency transition team.

More importantly, the Republican establishment supports this approach to climate policy. The agreed Republican platform of July rejects the Paris Agreement and calls for it to be submitted to the Senate (where it would be defeated) as well as an end of all funding to the UN climate convention. Their domestic policies are best summarised as “drill, baby, drill!”

It is foolish to believe that Trump would oppose his own party, and many of the voters of the US “rust belt” whose support he relied on, in an attempt to save the Paris Agreement.

Trump may be unpredictable in some regards, but his approach to climate change is not.

Counting the losses

Trump’s climate policy would lead to the US overshooting its already inadequate 2030 climate targets. The US needs additional measures on top of the Clean Power Plan to meet the targets established by Obama.

The US withdrawing from the Paris Agreement, or blatantly missing its climate targets, could be near fatal for a deal which relies on global ambition. The Paris Agreement relies on two things: increasing ambition through peer pressure, and a signal to markets and the public.

Both peer pressure and the signal will be shredded by a rogue, Trump-led United States.

States will be unlikely to feel pressured if the world’s second largest greenhouse emitter is polluting unabated. The effects of US recalcitrance were all too clear in the case of the Kyoto Protocol, which the United States simply refused to ratify. Trust would be undermined and excuses for inaction amplified if the US abandons international efforts again.

Any signal that existed from the framework of Paris would be largely extinguished. Already fossil fuels stocks have surged post-election despite a downturn in the rest of the market. Renewable energy share prices have plummeted. The idea of the signal hinged on broad participation creating investor confidence in international law. US withdrawal and the breaking of commitments will shatter any belief that investors may have had in Paris.

The Paris Agreement sacrificed binding emissions cuts and finance in order to ensure US participation. The few benefits it had were derived from broad participation, including from the United States. Such benefits will be lost by a US dropout.

Paris will likely survive as a structure. Countries will continue with the global show-and-tell, trading unbinding pledges every five years for some time to come. It will go on, but it will cease to be a large source of hope or change.

Opportunities for the future

A Trump presidency will also create opportunities for renewed action internationally.

Trump promises to usher in an age of protectionism, scrapping free trade agreements such as the Trans-Pacific Partnership (TPP) and North American Free Trade Agreement (NAFTA). He has vowed to brand major trading partners such as China as “currency manipulators”.

At the same time nationalism and discontent with free trade have surged in Europe. China has scaled up its domestic renewable energy and climate policies and is looking to formally establish a national emissions trading scheme next year.

Both a protectionist Trump administration that has dropped out of Paris and trends in the European Union and China could bring the idea of climate trade measures back to the table.

The Paris Agreement could be amended to use trade measures against countries who are not part of the deal. Such a move could not be adopted until the next conference in November 2017. Amending the agreement would only require a three-quarters majority vote, but is still unlikely to garner the support to be adopted under the painfully slow and convoluted UN process.

Climate trade measures from the EU and or China are much more likely. The EU may be pushed by Trump’s trade policies towards imposing a carbon price on imports (carbon border tax adjustments) from the US and others. China may consider a similar move. The two could even act in tandem, creating their own bilateral climate club outside of the Paris Agreement. Such material penalties would likely force the US to eventually shift and reengage with international efforts.

Such an outcome seems unlikely for now, particularly in the politically paralysed Europe. But Trump at least opens the opportunity for such change.

The much maligned Trump will supercharge climate civil disobedience in both the US and around the globe.

The world’s best chance of avoiding dangerous global warming are a climate trade war and rampant climate disobedience.

Such actions will be more beneficial for the climate than the current Paris Agreement ever could have been. The incremental and baseless pledge and review of Paris Agreement would have never been enough to trigger the herculean transition needed.

The 2016 US election will almost certainly become the epitaph for the success of the Paris climate agreement. But it does not mean that 2℃ is necessarily out of reach; the future may not depend on the actions of an ageing superpower.

Luke Kemp has received funding from the German and Australian governments.

The program can work well for polygamous species such as gorillas. Mary Ann McDonald/shutterstock.com

A quick look at the popularity of online dating services like OkCupid and eHarmony shows us that people are pretty comfortable with letting an algorithm choose them a mate. Now we at the Flinders Molecular Ecology Lab want to do a similar thing for other animals.

With human-driven extinctions on the rise, many species are likely to be left relying on captive breeding for their survival. We hope that our algorithm will help ensure these breeding programs are successful, by pairing up matches who will have healthy, thriving offspring.

Unlike human dating services, we cannot ask a snake, fish or possum to answer questions. But we can look at their DNA. This allows us to breed individuals who are not closely related, avoiding the genetic problems that arise from inbreeding, and thus producing healthy populations with a diverse gene pool.

We have created Swinger, a computer program that uses DNA profiling to matchmake endangered animals for captive breeding - especially those that have multiple mates - and which we describe in a paper published in the journal Molecular Ecology Resources. We envision it helping to conserve many endangered animals, with the first animals being native freshwater fishes in Australia.

It’s all in the DNA

Genetic diversity is crucial, because it helps populations to adapt and evolve in response to environmental changes that they may encounter in the future. So maintaining a large gene pool is an important consideration for captive breeding programs, particularly in populations that have already dwindled to small numbers. This makes avoiding inbreeding vitally important.

Many species kept in zoos – such as pandas – have clear family relationships or are bred in pairs and so their parentage is certain. Armed with pedigree information, it is relatively easy for zoos to select unrelated breeding pairs, often by working in collaboration with other zoos.

But most animals in the world are polygamous, with each individual naturally having multiple partners, even around the same time. This is where it becomes harder to track family relationships, unless you can examine their DNA.

It’s easier with pandas - well, the choosing part at least. Ritesh251123/Wikimedia Commons, CC BY-SA

The matchmaking algorithm is also ideal for starting a captive breeding program from individuals newly brought into captivity. This is because we often have no idea about their relationships to each other, except through DNA, and they may be highly related individuals.

The very circumstances that brought about the need for captive breeding also often results in inbreeding in wild populations. This is because the population has reduced in size to the point that individuals may unavoidably breed with their close relatives. This makes it especially important to ensure breeding in captivity occurs between unrelated individuals.

Captive breeding of swingers

Even when dealing with such serious issues as extinction, we like to keep a sense of humour – hence the name Swinger, which we feel is pretty appropriate given that individuals of most species in the world are naturally polygamous. Indeed, our algorithm is just as suitable for setting up polygamous breeding groups as monogamous ones.

The algorithm is inspired by our efforts to save freshwater fishes in Australia. Native freshwater fish lineages recently became at risk of extinction due to human activities during the Millennium Drought in the Murray-Darling Basin, in southeastern Australia. The fish needed to be saved by their removal from the wild before their habitat completely dried out.

We created breeding groups of these rescued polygamous fish. This was done by using DNA information to create, by hand, “swinger” groups of unrelated individuals. The breeding was successful, with offspring reintroduced to the wild. However, the breeding groups were unavoidably sub-optimal because at that time we had no algorithm to work out the best possible mates for individuals.

Swinger is now being used to save native rainbowfish in northern Queensland. Although it is still early days, the rainbowfish breeding has been very successful, producing thousands of fingerlings that our collaborators are releasing to the wild.

We are also using Swinger to inform the design of a breeding program of endangered species of Galápagos giant tortoises previously considered extinct. These tortoises were rediscovered in a remote volcano and moved to the captive breeding facility of the Galápagos National Park. The aim is to reintroduce the captive-born offspring to the island where they evolved.

The brilliance of DNA is that it is in all living things. This means that Swinger could potentially be used to help breed all endangered species with sexual reproduction - especially, of course, the many polygamous species.

To borrow another concept from the world of human dating, there will hopefully soon be “Plenty of Fish” as a result of our efforts.

Catherine R. M. Attard has received funding from the Australian Government and other organisations.

Luciano Beheregaray receives funding from the Australian Research Council.

Jonathan Sandoval Castillo ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'a déclaré aucune autre affiliation que son poste universitaire.

The higher the plume, the bigger the problem. Jim Peaco/Wikimedia Commons

The journal Climatic Change has published a special edition of review papers discussing major natural hazards in Australia. This article is one of a series looking at those threats in detail.

Fire has been a driving force across Australia for millennia. Indeed, the health of many of our ecosystems is intrinsically dependent on fire. But bushfires are also one of our most frequent natural hazards, with a total cost estimated at A$8.5 billion per year.

In the past decade or so, extreme bushfires in southeastern Australia have burned more than a million hectares, claiming more than 200 lives and over 4,000 homes. Similar losses in other major urban areas have prompted questions about whether we are seeing a shift towards a significantly more hazardous fire regime, characterised by increasing fire frequency and intensity, and the development of catastrophic “firestorms”.

While these extreme bushfires account for only a very small percentage of fire events, they are responsible for the lion’s share of bushfire-related losses.

In contrast to typical bushfires, which spread across the landscape as well-defined burning fronts with smoke plumes perhaps a few kilometres high, extreme bushfires exhibit deep and widespread flaming and produce smoke plumes that can extend 10-15km into the atmosphere.

At these altitudes, bushfire plumes can actually develop into thunderstorms (hence the term “firestorm”). As such, extreme bushfires become much more difficult for emergency services to handle, making them all but impossible to suppress and their spread difficult to predict.

Beyond hot, dry and windy

Like other dangerous bushfires, firestorms are driven by hot, dry and windy weather. But to spawn a firestorm, a range of other conditions must also be met; these can include a rugged landscape, particularly nasty weather events that produce “spikes” in fire danger, and conditions in the upper atmosphere that allow fire plumes to grow to considerable heights.

While previous studies have considered past and projected changes in the hot, dry and windy aspect of fire danger, less research has been done on the future projections for these other types of conditions. This means that we have quite a poor understanding of how extreme bushfires might affect us in the future.

As part of a series of reviews produced by the Australian Energy and Water Exchange initiative, my colleagues and I have taken a closer look at the most catastrophic bushfire cases and the factors that drive them, beyond the usual hot, dry and gusty weather.

There has been an overall increase in the frequency of major bushfire events in southeastern Australia since the mid-19th century. In particular, in the past 15 years a major fire event has occurred every 5 years or less. While some of this increase is due to changes in land use since European colonisation, there is also strong evidence of climate-driven changes.

We found that besides increases in dangerous surface fire danger conditions, upper atmospheric conditions have also become more conducive to explosive fire growth. High levels of the c-Haines index, which signals greater potential for a fire’s plume to rise high into the atmosphere, have become considerably more prevalent since the 1980s. The effects of droughts and widespread heatwaves have also contributed to the occurrence of extreme bushfires.

Looking into the future, high c-Haines values are projected to grow more prevalent still, albeit more gradually than over recent decades. Frontal weather patterns associated with particularly bad fire days are also projected to become more frequent during this century, and rainfall is projected to decrease over southwest and southeastern Australia.

All of this suggests that extreme bushfires will become a more common occurrence into the future.

What we still don’t know

Our methods for assessing fire danger do not explicitly account for the effects of extended drought and heatwaves on larger fuel elements such as branches and logs, and so may not properly account for their effects on fire spread and heat release into the atmosphere.

There is also considerable uncertainty about how fuel loads will change into the future. It is possible that the higher fire intensities expected to result from the direct effects of a warmer, drier climate may be offset by lower fuel loads.

Our understanding of extreme fire occurrence is also hampered by the lack of long-term and prehistoric climate data, which makes it hard to work out what the “normal” level of extreme bushfires has been in the past. While charcoal records show promise in this regard, we still don’t know enough about how charcoal is generated, deposited and subsequently preserved during extreme fires.

To predict the future occurrence of extreme bushfires, we also have more work to do in understanding how the trends forecast by global climate models will play out in terms of creating regional-scale fire weather conditions. And we still need to figure out the likely effects of other large-scale patterns such as El Niño.

Given the relatively recent advances that have been made in understanding the key drivers of extreme bushfires, the field is now ready for targeted studies that will help us estimate the future risk of extreme bushfires – and how best we can confront the threat.

Jason Sharples receives funding from the Australian Research Council and the Bushfire and Natural Hazards Cooperative Research Centre.

Australia’s government has announced that it is to ratify the Paris climate agreement, which was struck 11 months ago and entered into force last Friday.

The move comes despite the election of Donald Trump, who has called climate change a Chinese-inspired hoax. Trump has pledged to turn his back on the Paris treaty after he takes office in January, although this would take at least a year and technically leave the Agreement still in force, albeit weakened.

The question for Australia is how Canberra will react to such a seismic shift in US climate policy. The last time a US president pulled the plug on international climate negotiations was in March 2001, when George W. Bush withdrew from the Kyoto treaty. Australia’s prime minister John Howard followed suit on Earth Day 2002.

The temptation for Australia’s current government would be to follow in Trump’s slipstream in much the same way. Despite its 2030 climate target being widely seen as unambitious, Australia still lacks a credible plan to deliver the necessary emissions cuts, and has no renewable energy target beyond 2020.

While Prime Minister Malcolm Turnbull may be a vocal supporter of climate action, not everyone on on his side of politics is as keen – such as MPs Craig Kelly and George Christensen. (It was not always thus under the Liberals.)

The temptation to defect might be strong, but the countervailing pressure will be much stronger that it was in 2002, and the clean energy transition is already underway. Just this week, a high-powered group of business leaders, energy providers, academics and financiers called on Turnbull to expand the renewable energy target and create a market mechanism to phase out coal.

Yet the US election has also reinvigorated Australian opponents of climate action, such as One Nation senators Pauline Hanson and Malcolm Roberts, who were cracking champagne at the prospect of Trump in the White House, and media commentator Andrew Bolt, who jubilantly described Trump’s victory as a “revolt against the left’s arrogance”.

Which bit of history will repeat?

On balance, then, it is still hard to predict Australia’s next move – and past form is little guide for future performance.

Over the past 26 years, Australia has made two largely symbolic commitments to international climate action, and one very concrete refusal.

In 1990, ahead of the 2nd World Climate Conference which fired the starting gun for the United Nations’ climate negotiations, the Hawke government announced a target of a 20% reduction by 2005.

The pledge, however, was laced with crucial caveats, like this one:

…the Government will not proceed with measures which have net adverse economic impacts nationally or on Australia’s trade competitiveness in the absence of similar action by major greenhouse-gas-producing countries.

This target was sidelined in the final United Nations Framework Convention on Climate Change, which Australia signed and ratified in 1992.

In 1997, Australia got a very sweet deal at the Kyoto climate talks, successfully negotiating an 8% increase in greenhouse gases as its emissions “reduction” target, as well as a special loophole that allowed it take account of its large reduction in land clearing since 1990. Australia signed the deal in April 1998, but never ratified it.

Kyoto’s rules hid a multitude of sins, anyway, as Oxford University’s Nicholas Howarth and Andrew Foxall have pointed out:

…its accounting rules obscure the real level of carbon emissions and structural trends at the nation-state level… it has shifted focus away from Australia as the world’s largest coal exporter towards China, its primary customer.

Although Kevin Rudd famously ratified Kyoto and received a standing ovation at the Bali Climate summit in 2007, a stronger Australian emissions reduction target was not forthcoming.

The next big moment came at the Paris negotiations of 2015. Australia’s official pledge was a 26-28% reduction on 2005 levels by 2030 – a target unveiled by the former prime minister Tony Abbott, and which met with a lukewarm response from analysts.

Since then, pressure has been building for Australia to explain how it can meet even that target, given the hostility to renewable energy among the federal government, the lack of a post-2020 renewables target, and the inadequacy of the current Direct Action policy.

And now we are looking at the prospect of a Trump presidency, already described as “a turning point in the history of climate action” and “the end of any serious hope of limiting climate change to 2 degrees”.

In a chaotic world that has confounded pollsters, it seems foolish to bet on anything. But two predictions seem sure: atmospheric concentrations of carbon dioxide will rise, and the future will be … interesting.

Marc Hudson does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.

Australia’s iconic Great Barrier Reef has suffered through the worst bleaching event in its history, part of the world’s third mass bleaching event.

However, coral reefs from the other side of the continent have also experienced unprecedented bleaching and coral death. This is bad news because the unique coral reefs of Western Australia’s northwest are home to some of the toughest coral in the world.

Western Australia’s unique coral reefs

Although much less well-known, coral reefs in Western Australia are highly diverse. They include, for example, Australia’s largest fringing reef, the World Heritage-listed Ningaloo Reef, as well as Australia’s largest inshore reef, Montgomery Reef which covers 380 square kilometres.

WA’s remote Kimberley region also features “super-corals” – corals that have adapted to a naturally extreme environment where tidal swings can be up 10m. These corals can therefore tolerate exposure to the air during low tide as well as extreme daily temperature swings.

My past research has shown that these naturally extreme conditions increase the heat tolerance of Kimberley corals but that they are nevertheless not immune to bleaching when water temperatures are unusually hot for too long.

Previously I had put these super-corals in tanks and subjected them to a three-week heatwave to see how they would respond, but I always wondered how they would cope in the wild where such events typically unfold over longer timescales. Unfortunately, I did not have to wait long to find out.

The hottest years on record

2015 was the hottest year on record and 2016 will likely be hotter still. This has caused an unprecedented global coral reef crisis. Although global coral bleaching events already occurred in 1998 and 2010, this third global bleaching event is the longest on record and still ongoing.

Sadly, in WA the Kimberley region was hit the hardest. As part of Australia’s National Coral Bleaching Taskforce, colleagues and I conducted extensive monitoring before, during and after the predicted bleaching event along the entire WA coastline. In the southern Kimberley, we also carried out aerial surveys to assess the situation on a regional level.

The severity and scale of bleaching that we observed in April was devastating. Almost all inshore Kimberley reefs that we surveyed had about 50% bleaching, including Montgomery Reef. Researchers from the Australian Institute of Marine Science found that offshore Kimberley reefs such as Scott Reef fared even worse, with 60-90% bleaching in shallow lagoon waters.

Many corals had already died from the severe bleaching in April, but the final death toll has only been revealed during visits to the Kimberley last month. Vast areas of coral reef are now dead and overgrown with algae, both at the inshore and offshore Kimberley reefs.

According to local Indigenous Rangers and Traditional Owners who assisted in the research, this appears to be unprecedented. Such events had never previously been described in their rich local history of the coastal environment.

Bleached staghorn coral on inshore Kimberley reefs in April 2016. Verena Schoepf Dead staghorn coral on the same reefs in October 2016. Verena Schoepf Some good news

There was nevertheless some good news. Corals living in intertidal areas, where they regularly experience exposure to air, stagnant water, and extreme temperature fluctuations, bleached less than corals from below the low-tide mark, where conditions are far more moderate. And importantly, the majority of intertidal corals were able to fully recover within a few months.

Similarly, researchers from the Western Australian Museum and Curtin University confirmed last month that intertidal coral reefs in the central Kimberley (Bonaparte Archipelago) were in great condition.

Overall, these observations confirm the findings from my past research which showed that highly-variable, extreme temperature environments can boost the bleaching resistance of corals.

It is also important to note that the 2016 severe bleaching event in WA was restricted to the Kimberley region. Ningaloo Reef as well as coral reefs in the Pilbara and the Abrolhos Islands all escaped the bleaching. This is great news because some of these locations are still recovering from major bleaching in 2010-11 and 2013.

Healthy coral at Ningaloo Reef in 2016. Morane Le Nohaic The future of WA’s coral reefs

Although it is now clear that WA’s coral reefs are at risk of bleaching during both El Niño (as in 2016) and La Niña years (as in 2010-11), they have some advantages over other reefs that may hopefully allow them to recover from bleaching more quickly and stay healthy in the long term.

For example, most of WA’s coral reefs are located far away from major population centres and are thus less affected by environmental threats such as poor water quality (though other threats such as oil and gas exploration do exist). We also know that their isolation, particularly in the case of offshore reefs, helped them recover from previous mass bleaching events.

Finally, it is critical that we identify coral populations worldwide that are already naturally adapted to higher temperatures and have a greater bleaching resistance, such as the Kimberley corals.

These super-corals, while not immune to climate change, should be a priority for research into the limits of coral tolerance, as well as conservation efforts.

Verena Schoepf is affiliated with the University of Western Australia, the ARC Centre of Excellence for Coral Reef Studies and the Western Australian Marine Science Institution (WAMSI). The research presented here was funded by WAMSI, the ARC Centre of Excellence for Coral Reef Studies, the PADI Foundation and an ARC Laureate Fellowship to Prof Malcolm McCulloch.

The journal Climatic Change has published a special edition of review papers discussing major natural hazards in Australia. This article part of a series looking at those threats in detail.

Australia is no stranger to heatwaves. Each summer, large areas of the continent fry under intense heat for days on end, causing power outages, public transport delays, and severe impacts to human health. The estimated impact on our workforce alone is US$6.2 billon per year. Heatwaves are also Australia’s deadliest natural hazard, accounting for well over half of all natural disaster-related deaths.

Along with our colleagues, we have taken a close look at what we know and don’t know about heatwaves in Australia, as part of a series of reviews produced by the Australian Energy and Waster Exchange initiative.

Let’s start with the stuff we know. First, we are very clear on the weather systems that drive heatwaves in Australia’s densely populated coastal areas. Typically, a persistent high-pressure system sits next to the region experiencing the heatwave, pushing hot air from the centre of Australia towards that region. The location of the high depends on the region experiencing the heatwave, but there is always one there.

These high-pressure systems are created and sustained by other weather influences farther afield, for instance. We know for instance that heatwaves in Melbourne are coupled with tropical cyclones to the northwest of Australia.

Other, longer-term variables can affect not just individual heatwaves but their patterns, timing and severity too. So heatwaves are likely to be much longer and more frequent during El Niño than La Niña phases over much of northern and eastern Australia. However, this does not influence heatwaves over Australia’s far southeast – here, the most important driver is changes to wind patterns over the Southern Ocean.

We also know that heatwave trends have increased in the observational record, and, unfortunately, that they will continue to do so. By far the strongest trend is in the number of heatwave days experienced each season. Over much of eastern Australia, this trend is as large as two extra days per season, per decade.

Looking into the future, heatwaves are projected to become more frequent, with increases of between 20 and 40 extra days per season in the north and 5-10 extra days in the south likely by the end of this century, under a “business as usual” scenario. The intensity of heatwaves over southern Australia is also increasing faster than the average temperature. This is not good news for our ageing population, our fragile ecosystems and our outdated infrastructure.

The Australian research community has been successful in leading the development of a comprehensive way to measure marine heatwaves. Just like the atmosphere, areas of the ocean can experience prolonged periods of abnormally warm temperatures. These marine heatwaves can be every bit as damaging as atmospheric ones, decimating marine habitats and killing coral.

What we don’t yet know

Perhaps surprisingly, given the amount of research and public attention that heatwaves attract, they still do not have an official definition. The Bureau of Meteorology uses a concept called excess heat factor, which looks at maximum temperatures and ensuing minimum temperatures over a three-day period, incorporating the key characteristic of heatwaves of heat tending to persist overnight. However, we still do not have a universal definition that fits all situations.

We are also unclear on how the physical mechanisms that drive heatwaves will change under ongoing greenhouse warming. Recent research suggests that background warming will predominantly drive future increases in heatwaves, with some heatwave-inducing systems moving further south. But we don’t really know how future changes to patterns such as El Niño will continue to influence our heatwaves.

We also don’t really understand the extent to which the land surface drives Australian heatwaves. European studies have shown that dry conditions leading up to heatwave season, resulting in more parched soils, are a recipe for more intense and longer events, particularly when coupled with a persistent high-pressure system.

For Australia, we know that dry soil contributed to the deadly heatwave that preceded the Black Saturday bushfires in 2009. But more extensive studies are needed to understand this complex relationship over Australian soil (pun intended).

We also need a more comprehensive understanding of marine heatwaves. So far there has been only a handful of studies describing individual events. We still don’t know how much marine heatwaves have increased over recent decades, or how their causes and severity will change in the future. Given how vulnerable we are to marine heatwaves here in Australia, this topic should be a national research priority.

Finally, we need to develop more practical predictions of how heatwaves are likely to affect people in the future. We know how bad the impacts of heatwaves can be, and we know in general terms how heatwaves will change in the future. Yet the vast majority of our projections come from global climate models. Forecasting the exact impacts calls for finer spatial detail, using regional climate models. But these models are far more computationally expensive to run, and more investment into this area is necessary.

There is no doubt that heatwaves have been, and will continue to be, an integral feature of Australia’s climate, and recent research has taught us a lot about them. But there is more work to be done if we want to safeguard Australians properly from their deadly impacts in the future.

Sarah Perkins-Kirkpatrick receives funding from the Australian Research Council.

Christopher J. White receives funding from various Tasmanian State Government research funding programs, Wine Australia and the Bushfire and Natural Hazard CRC.

Replanting trees is one of the better ways to remove carbon from the atmosphere. CIFOR/Flickr, CC BY-NC-ND

This week international leaders are meeting in Marrakech to thrash out how to achieve the Paris climate agreement, which came into force on Friday. The Marrakech meeting is the 22nd Congress of Parties (or COP22) to the United Nation’s climate convention. One of the key goals of the agreement is to limit global warming to well below 2℃, and aim to limit warming to 1.5℃.

With global greenhouse gas emissions still rising, this is a daunting task. Numerous models, including recent research, suggest we will not be able to achieve this without removing large amounts of greenhouse gases from the atmosphere later this century (known as “negative emissions”).

But scientists are becoming increasingly sceptical of the concept, as it may create more problems than it solves, or fail to deliver. Instead, we need to ramp up action before 2020, before even the earliest targets of the Paris Agreement.

Going negative

Some models suggest that up to 1 trillion tonnes of carbon dioxide needs to be removed from the atmosphere to meet the 1.5℃ goal.

This idea is increasingly being called out as a risky and “highly speculative” strategy to limit warming to 1.5℃, as it puts food security and biodiversity at risk, and may not even be possible to deliver. The Convention on Biodiversity has also now weighed in on the issue, declaring that carbon removal techniques are highly uncertain.

A recent report from the Stockholm Environment Institute (SEI), summarised here, argues that the scale of negative emissions assumed by many climate models is improbably high.

The key components of negative emissions are reducing deforestation, planting trees, and an untested technology called “bioenergy with carbon capture and storage” or BECCS. The involves burning plant matter to produce energy, capturing the waste CO₂, and then storing it underground. The result is less CO₂ in the atmosphere.

But there are several problems with these strategies. For one, the scale of land required for the expected level of negative emissions suggests serious social and ecological risks, since land plays a crucial role in food security, livelihoods and biodiversity conversation.

Indeed, the scale of bioenergy supply in many cases is equivalent to the current global harvest of all biomass – for food, feed, and fibre - assuming a doubling of human harvest of biomass by 2050.

The SEI paper argues that the risks and uncertainties associated with negative emissions could lock us into much higher levels of warming than intended, substantially undermining society’s overall mitigation efforts.

Better ways to remove carbon

So does all of this mean the 1.5℃ goal is out of reach? Some may think so.

However, the SEI analysis finds that if emissions were cut sufficiently quickly and ambitiously, we wouldn’t need to rely so much on negative emissions. We could also choose negative emissions methods with lower impacts on biodiversity, resource demands, and livelihoods.

The SEI analysis optimistically suggests that a maximum of 370 billion to 480 billion tonnes of CO₂ could be removed without exceeding biophysical, technological and social constraints. This would be done through protecting forests and allowing degraded forests to regenerate, along with some reforestation.

Even that would be extremely challenging to achieve, but done right, for example through community forestry and agro-ecological farming,, climate mitigation and sustainable development could go together.

In fact, securing land rights of indigenous peoples and local communities who protect and preserve the carbon stocks in forests is one of the most cost-effective forms of climate mitigation we have, with obvious social co-benefits.

Scaling up

The real threat of negative emissions is the potential to delay emissions reduction into the future. Many modelled pathways for 1.5℃ that include substantial negative emissions suggest that emissions do not begin to decline until the late 2020s.

But limiting negative emissions to lower levels would require immediate global mitigation on a scale greatly exceeding that which has so far been pledged by nations under the Paris Agreement.

We cannot wait until 2020 to speed up global action on climate change - less action now will mean more work later.

Key for strengthening pre-2020 action in Marrakech will be a facilitative dialogue on enhancing ambition and support and a high level ministerial meeting on increased ambition of 2020 commitments under the Kyoto Protocol.

Many countries, including Australia, still have completely inadequate targets for 2020, making arguments about whether they are on track to meet them or not moot.

The Moroccan government has dubbed Marrakech the “action COP”. Action here must focus on the urgent need for global emissions to begin declining before 2020, and on the finance needed to deliver it. This includes scaling up the rollout of renewable energy, halting and reversing the loss of the world’s forests, and tackling rich world consumption patterns to ensure equitable mitigation pathways.

Limiting global warming to 1.5℃ is not only possible, it is the only chance of survival for the most vulnerable communities around the world, who are increasingly exposed to rising sea levels, drought and food shortages.

As Erik Solheim, head of the UN Environment Program (UNEP), and Jacqueline McGlade, UNEP’s chief scientist, wrote in a recent report, those most vulnerable “take little comfort from agreements to adopt mitigation measures and finance adaptation in the future. They need action today”.

Kate Dooley receives funding from the Australian government through an Australian Post-graduate Award.

The great grey owl is imperiled by intensive logging of northern-hemisphere forests. Copyright Ondrej Prosicky/Shutterstock.

Life has existed on Earth for roughly 3.7 billion years. During that time we know of five mass extinction events — dramatic episodes when many, if not most, life forms vanished in a geological heartbeat. The most recent of these was the global calamity that claimed the dinosaurs and myriad other species around 66 million years ago.

Growing numbers of scientists have asserted that our planet might soon see a sixth massive extinction — one driven by the escalating impacts of humanity. Others, such as the Swedish economist Bjørn Lomborg, have characterised such claims as ill-informed fearmongering.

We argue emphatically that the jury is in and the debate is over: Earth’s sixth great extinction has arrived.

Collapse of biodiversity

Mass extinctions involve a catastrophic loss of biodiversity, but what many people fail to appreciate is just what “biodiversity” means. A shorthand way of talking about biodiversity is simply to count species. For instance, if a species goes extinct without being replaced, then we are losing biodiversity.

But there’s much more to biodiversity than just species. Within each species there usually are substantial amounts of genetic, demographic, behavioural and geographic variation. Much of this variation involves adaptations to local environmental conditions, increasing the biological fitness of the individual organism and its population.

Natural variation within two species of sea snails. Upper row: Littorina sitkana. Lower row: Littorina obtusata. Copyright David Reid/Ray Society.

And there’s also an enormous amount of biodiversity that involves interactions among different species and their physical environment.

Many plants rely on animals for pollination and seed dispersal. Competing species adapt to one another, as do predators and their prey. Pathogens and their hosts also interact and evolve together, sometimes with remarkable speed, whereas our internal digestive systems host trillions of helpful, benign or malicious microbes.

Hence, ecosystems themselves are a mélange of different species that are continually competing, combating, cooperating, hiding, fooling, cheating, robbing and consuming one another in a mind-boggling variety of ways.

All of this, then, is biodiversity - from genes to ecosystems and everything in between.

The modern extinction spasm Cumulative vertebrate species extinctions since 1500 compared to the ‘background’ rate of species losses. G. Ceballos et al. (2015) Scientific Advances.

No matter how you measure it, a mass extinctions has arrived. A 2015 study that one of us (Ehrlich) coauthored used conservative assumptions to estimate the natural, or background rate of species extinctions for various groups of vertebrates. The study then compared these background rates to the pace of species losses since the beginning of the 20th century.

Even assuming conservatively high background rates, species have been disappearing far faster than before. Since 1900, reptiles are vanishing 24 times faster, birds 34 times faster, mammals and fishes about 55 times faster, and amphibians 100 times faster than they have in the past.

For all vertebrate groups together, the average rate of species loss is 53 times higher than the background rate.

Extinction filters

To make matters worse, these modern extinctions ignore the many human-caused species losses before 1900. It has been estimated, for instance, that Polynesians wiped out around 1,800 species of endemic island birds as they colonised the Pacific over the past two millennia.

And long before then, early human hunter-gatherers drove a blitzkrieg of species extinctions — especially of megafauna such as mastodons, moas, elephant birds and giant ground sloths — as they migrated from Africa to the other continents.

In Australia, for instance, the arrival of humans at least 50,000 years ago was soon followed by the disappearance of massive goannas and pythons, predatory kangaroos, the marsupial “lion”, and the hippo-sized Diprotodon among others.

Changes in climate could have contributed, but humans with their hunting and fires were almost certainly the death knell for many of these species.

As a result of these pre-1900 extinctions, most ecosystems worldwide went through an “extinction filter”: the most vulnerable species vanished, leaving relatively more resilient or less conspicuous species behind.

Giant ground sloths such as this elephant-sized Megatherium vanished soon after humans arrived in the New World. Copyright Catmando.

And it’s the loss of these survivors that we are seeing now. The tally of all species driven to extinction by humans from prehistory to today would be far greater than many people realise.

Vanishing populations

The sixth great extinction is playing out in other ways too, especially in the widespread annihilation of millions (perhaps billions) of animal and plant populations. Just as species can go extinct, so can their individual populations, reducing both the genetic diversity and long-term survival prospects of the species.

For example, the Asian two-horned rhinoceros once ranged widely across Southeast Asia and Indochina. Today it survives only in tiny pockets comprising perhaps 3% of its original geographic range.

Three-quarters of the world’s largest carnivores, including big cats, bears, otters and wolves, are declining in number. Half of these species have lost at least 50% of their former range.

Likewise, except in certain wilderness areas, populations of large, long-lived trees are falling dramatically in abundance.

WWF’s 2016 Living Planet Report summarises long-term trends in over 14,000 populations of more than 3,700 vertebrate species. Its conclusion: in just the last four decades, the population sizes of monitored mammals, birds, fish, amphibians and reptiles have shrunk by an average of 58% worldwide.

And as populations of many species collapse, their crucial ecological functions decline with them, potentially creating ripple effects that can alter entire ecosystems.

Hence, disappearing species can cease to play an ecological role long before they actually go extinct.

Once a widespread and dominating predator, the tiger today is vanishingly rare across most of its former range. Copyright Matt Gibson Paying the extinction debt

Everything we know about conservation biology tells us that species whose populations are in freefall are increasingly vulnerable to extinction.

Extinctions rarely happen instantly, but the conspiracy of declining numbers, population fragmentation, inbreeding and reduced genetic variation can lead to a fatal “extinction vortex”. In this sense, our planet is currently accumulating a large extinction debt that must eventually be paid.

And we’re not just talking about losing cute animals; human civilisation relies on biodiversity for its very existence. The plants, animals and microorganisms with which we share the Earth supply us with vital ecosystem services. These include regulating the climate, supplying clean water, limiting floods, running nutrient cycles essential to agriculture and forestry, controlling serious crop pests and carriers of diseases, and providing beauty, spiritual and recreational benefits.

Are we preaching doom? Far from it. What we’re saying, however, is that life on Earth is ultimately a zero-sum game. Humans cannot keep growing in number and consuming ever more land, water and natural resources and expect all to be well.

Limiting harmful climate change has become a catchphrase for battling such maladies. But solutions to the modern extinction crisis must go well beyond this.

We also have to move urgently to slow human population growth, reduce overconsumption and overhunting, save remaining wilderness areas, expand and better protect our nature reserves, invest in conserving critically endangered species, and vote for leaders who make these issues a priority.

Without decisive action, we are likely to hack off vital limbs of the tree of life that could take millions of years to recover.

The Slow Loris, a primitive primate, is a denizen of intact rainforests in southern Asia. Copyright hkhtt hj

Paul Ehrlich will present a lecture on the current mass extinction, at James Cook University’s Cairns campus on November 10.

Bill Laurance receives funding from the Australian Research Council and other scientific and philanthropic organisations. He is the director of the JCU Centre for Tropical Environmental and Sustainability Science, and founder and director of ALERT--the Alliance of Leading Environmental Researchers & Thinkers.

Paul Ehrlich does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.

The Millennium drought had a huge impact on the Murray-Darling river system. suburbanbloke/Flickr/Wikimedia Commons, CC BY-SA

The journal Climatic Change has published a special edition of review papers discussing major natural hazards in Australia. This article is one of a series looking at those threats in detail.

Droughts are a natural feature of the Australian environment. But the Millennium drought (or “Big Dry”), which ran from 1997 to 2010, was a wake-up call even by our parched standards.

The Millennium drought had major social, economic and environmental impacts. It triggered water restrictions in major cities, and prompted severe reductions in irrigation allocations throughout the vast Murray-Darling Basin.

The Millennium drought also highlighted that, compared to the rest of the world, the impacts of drought on Australia’s society and economy are particularly severe. This is mainly because our water storage and supply systems were originally designed by European settlers who failed to plan for the huge variability in Australia’s climate.

Have we learned the lessons?

Are we likely to fare any better when the next Big Dry hits? It’s important to reflect on how much we actually understand drought in Australia, and what we might expect in the future.

Our study, part of the Australian Water and Energy Exchanges Initiative (OzEWEX), had two aims related to this question. The first was to document what is known and unknown about drought in Australia. The second aim was to establish how Australia’s scientists and engineers can best investigate those unknowns.

The fact is that despite their significance, droughts are generally still poorly understood. This makes it hard to come up with practical, effective strategies for dealing with them when they strike.

One reason for this is that unlike natural hazards with more graphic and measurable impacts (such as floods, cyclones, and bushfires), droughts develop gradually over huge areas, and can last for years. Often they go unnoticed until they trigger widespread water or food shortages, or cause significant energy, economic, health or environmental issues.

By the time you know it’s arrived, a drought can already be doing damage. Bidgee/Wikimedia Commons, CC BY-SA

Drought has been described as a “creeping disaster”, because by the time a drought is identified, it is usually already well under way, the costs to fix it are mounting, and the opportunity to take proactive action has already been missed.

This is complicated still further by the uncertainties around defining, monitoring and forecasting drought – including predicting when a drought will finally end. As in the case of other natural hazards (such as drought’s polar opposite, floods), what we need most is accurate and practically useful information on the likelihood, causes and consequences of droughts in particular areas.

This is a very tricky question, not least because we still need to come up with a rigorous way to distinguish between correlation and causation. For example, are increased local temperatures a cause or a consequence of drought?

The complications don’t end there. Because droughts are so much slower and bigger than other natural disasters, they therefore have much more complicated effects on agriculture, industry and society. Bushfires can be devastating, but they also offer ample opportunities to learn lessons for the next time. Droughts, in contrast, give us limited opportunities to learn how best to prepare.

Yet prepare we must. Given Australia’s history of decades-long swings between wet and dry, and the fact that these swings are projected to grow even stronger, drought will be a key concern for Australia for a long time to come.

What to do next

We therefore make several recommendations to help boost our understanding and management of drought.

1). Reconsider the way drought is defined and monitored to remove confusion between drought causes, impacts and risks. Similarly, there is also a need to better distinguish between drought, aridity, and water scarcity due to over-extractions.

The simplest definition of “drought” is a deficit of water compared with normal conditions. But what is normal? How long does the deficit have to persist, and how severe does it need to be, to be considered a drought? What is meant by water: rainfall, snow, ice, streamflow, water in a storage reservoir, groundwater, soil moisture, or all of these?

The answers to these questions depend very much on the local situation in terms of climate and water use, which varies significantly in space and time and is why the simplest definition of drought is insufficient. We need to develop drought definitions that clearly differentiate drought from long-term changes in aridity and water scarcity, and that capture drought start, duration, magnitude and spatial extent. Such definitions should account for the differences between Australia’s climate zones, the wide variety of end-users and applications of drought monitoring information, and the diversity of droughts that have occurred in the past. There needs to be a common understanding of what a drought is and the differences between drought, aridity and human-induced water scarcity.

2). Improve documentation of droughts that took place before weather records began, in roughly 1900. This will improve our understanding of Australia’s long-term “baseline” drought characteristics (that is, how bad can droughts get? how does the worst drought on record compare with the worst that has ever occurred?), and thus provide the fundamental information needed to successfully manage droughts.

This requires compilation of longer-term and more spatially complete drought histories via the merging of palaeoclimate information with instrumental, satellite, and reanalysis data. This will help us better understand instrumental and pre-instrumental drought behaviour, and put the droughts observed in the instrumental record into context. This work will involve looking at ice cores, tree rings, different tree rings, cave deposits, corals, sediments and historical changes to river channels and floodplains.

3). Improve drought forecasting by developing more realistic models of the many factors that cause (or contribute to) drought. This will help us separate out the influences of natural variability and human-induced climate change, which in turn will help us make more accurate long-term projections.

If we can answer these big research questions, we will all be better prepared when the next big dry inevitably arrives.

Anthony Kiem receives funding from the Australian Research Council and the National Climate Change Adaptation Research Facility.

Fiona Johnson receives funding from the Australian Research Council and World Health Organisation.

Seth Westra receives funding from the Australian Research Council and various State Government research funding programs.

This week’s US Presidential election will likely be more important for climate change action than the United Nations (UN) Climate Change Conference which started in Marrakech yesterday. Whichever candidate makes it to the White House, progressive action on climate change in America, and therefore globally, is going to take a hit.

We have already seen stagnation on climate change action in the lead up to the US election. The mudslinging and controversy of the campaign has taken climate change off the front pages. Climate change has had even less visibility in the US election campaign than it did in the Australian election in July.

It was telling that Hillary Clinton, who had talked up climate policy in the primaries when competing against Bernie Sanders, dropped the climate ball as soon as she had the Democratic party’s nomination.

It wasn’t simply that there was no longer any point taking on climate change in order to win more Sanders supporters, but that climate change was so far down the list of ways Clinton could differentiate herself from the Republican candidate Donald Trump that it seemed pointless to insert it into the election campaign at all.

Trump’s worldview projects a complete abnegation of climate change, as shown by his intention to undo America’s commitment to the Paris climate agreement should he get to the White House.

Trump’s negative attitude towards climate change is another example of his belief in conspiracy theories. But his neglect of climate change is not to be found in deploying denier myths, but his abandonment of a policy stance about anything in favour of filling the airwaves with insults more suited to a bar room brawl.

For many Americans, its 240 year old system of democracy is in great danger. Because so many unemployed and dispossessed Americans feel that neither capitalism nor the two great parties can meet their needs, they are rejecting the political elites and the establishment politics that keep the unequal distribution of wealth in check.

Of course, such a system has always been part of American life. It’s just that it is now at breaking point. It is of no consequence that Trump is himself part of the US economic elite. It is enough that he has himself been a “loser” many times over, and that he speaks the reality-TV language of those who want America to be “great again” both at rallies and on social media.

Ironically, America is a greater power now than it has been in the past. But due to the automation of the increased manufacturing output in heavy industries and the reliance on China for consumer goods, unemployment and income inequality have risen to unacceptable levels. It’s now the turn of working class Americans to be the “losers of globalisation”.

This has given rise to a loss of faith in American institutions, and the celebration of Trump as a bad boy who should be able to do whatever he wants to rail against the establishment.

Many analysts have drawn the comparison between Trump’s version of America and fascism — military isolationism, the ridiculing of “others” (including Muslims, Hispanics, women, Chinese and Mexicans), high levels of paranoia (the media is “rigged”, the election is “rigged”), and the fairy tale conviction that one person alone can save America.

But the real danger for the US is in four years from now. If Trump doesn’t win the presidency, a smarter Republican candidate – one who is actually supported by the floor of the Grand Old Party, actually has policies and appeals to the disaffected – will take US politics to a climate inactive isolationist extreme.

However, a moderating force for climate change is the success of the Paris agreement, which is now in full force. The Paris agreement, which replaces the Kyoto framework, has been ratified extremely quickly by UN standards. It now has almost 100 countries signed up – needing only the 55 countries that account for 55% of global emissions.

This is impressive progress given the scale and complexity of the UN’s framework convention on climate change. The momentum of the Paris agreement provides a kind of political guardrail for achieving stronger action on climate change, leaving no country with an excuse not to join in.

The only counter-force that could reverse this momentum would be the rise of populist support for isolationism within the states signed up to the treaty. And a Trumpist America, whether it eventuates this week or in the future, offers an archetypal case.

The journal Climatic Change has published a special edition of review papers discussing major natural hazards in Australia. This article is the first in a series looking at those threats in detail.

Recent floods in New South Wales, South Australia and Victoria have reminded us of the power of our weather and rivers to wreak havoc on homes, business and even, tragically, lives.

As Dorothea Mackellar poetically pointed out, “droughts and flooding rains” have been a feature of Australia throughout history, so maybe we shouldn’t be all that surprised when they happen.

However, we also know that the reported costs of flooding in Australia have been increasing, most likely through a combination of increased reporting, increased exposure through land use change and population growth, and changes to flood magnitude and severity. So it is critical that we understand what might be causing these changes.

This was the question we asked in our review on how flood impacts have changed over time in Australia and how they may change in the future. We found that despite decades of research in these areas, there are still many gaps in what we know.

Copping a soaking

We know that floods depend not just on how much rain falls, but also on how wet the ground is before a heavy rainfall, and how full the rivers are. We also have evidence that the storms that generate heavy rainfall will become more intense in the future, because as the atmosphere warms it can hold more moisture.

This is particularly the case for storms that last just a few hours; in fact we think that these storms are the most likely to show the largest increases. In urban environments this translates to an even greater flood risk, because the concrete and hard surfaces allow this intense rain to run off quickly through storm drains and into creeks and rivers, rather than seeping into the landscape.

In larger catchments and rural areas the story is more complicated than in cities. If the soil is very wet as a result of rain over the previous weeks and months, then when a big storm hits there will be a lot of runoff. In contrast, if the soil is dry then flooding is less likely to be a problem.

Engineers currently use simple models to estimate this relationship between soil wetness and storm rainfall. But our research indicates that these simple models will need to be replaced with longer-term simulations that model all of the previous rainfall leading up to the storm.

Simple models use simple assumptions to translate rainfall risk into flood risk. But if these assumptions are incorrect, our estimates of flood risk (that is, the probability of a given flood magnitude occurring in any particular year) could be wrong. Flood risk is used to guide infrastructure assessment through cost-benefit ratios, so getting it right is important.

One of the reasons that catchment wetness varies is because of climate cycles like El Niño and La Niña. We have some idea how these and similar ocean cycles affect our climate, including the fact that they can cause fluctations in flood risk over decades-long timescales.

The difficulty here is that for most locations we only have 50 to 60 years of recorded river flow data. This makes it hard to separate out the influences of these climate cycles from other trends in flood data, such as the effect of increasing urbanisation.

There has been progressively less monitoring of streamflow in Australia over the past few decades, and this makes it even harder to understand regional changes in flood risk. Governments need to prioritise investment in data collection to allow us to improve our estimates of the risk of flooding and the associated damages now and in the future.

The recent work by the Bureau of Meteorology to develop a comprehensive set of high quality streamflow gauge data is a step in the right direction, but much more investment is needed in these areas.

Finally, we recommend that continued research into the fundamental changes likely from climate change is required. This requires climate models to be run at a range of resolutions to enable all the important climate processes for extreme rainfall to be properly represented.

Recent pressure on CSIRO’s climate modelling capabilities is concerning – the scientific questions are by no means fully answered on these topics. It is great to see the recent funding of the ARC Centre of Excellence on Climate Extremes. The work of these researchers, combined with ongoing efforts across Australia, will be important to provide better assessments on climate changes. This can help engineers and hydrologists continue to provide accurate flood risk estimates.

Fiona Johnson receives funding from the Australian Research Council and World Health Organisation.

Chris White receives funding from various Tasmanian State Government research funding programs, Wine Australia and the Bushfire and Natural Hazard CRC.

Seth Westra receives funding from the Australian Research Council and various State Government research funding programs.