Is Australia’s current drought caused by climate change? It’s complicated

Andrew King, University of Melbourne; Anna Ukkola, Australian National University, and Ben Henley, University of Melbourne

Much of southern Australia is experiencing severe drought after a very dry and warm autumn across the southern half of the continent. Australia is no stranger to drought, but this recent dry spell, and Prime Minister Malcolm Turnbull’s visit to drought-stricken parts of the country, has prompted discussion of the role of climate change in this event.

Turnbull said that farmers need to “build resilience” as rainfall “appears to be getting more variable”. This prompted former Nationals leader John Anderson to warn against “politicising” the drought by invoking climate change. This in turn was followed by speculation from numberous commentators about the links between climate change and drought.

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So are droughts getting worse, and can they be attributed to climate change? Drought is a complex beast and can be measured in a variety of ways. Some aspects of drought are linked with climate change; others are not.

Recent warm and dry conditions have resulted in drought over parts of southern Australia.
Bureau of Meteorology

How do we measure drought?

In Australia, the Bureau of Meteorology uses rainfall deficiencies to identify regions that are under drought conditions.

Droughts are also exacerbated by low humidity, higher wind speeds, warmer temperatures, and greater amounts of sunshine. All of these factors increase water loss from soils and plants. This means that other metrics are often used to describe drought which go beyond rainfall deficiencies alone. These include the Palmer Drought Severity Index and the Standardised Precipitation Evaporation Index , for example.

This means that there are hundreds of metrics which together can provide a more detailed representation of a drought. But this also means that droughts are less well understood and described than simpler phenomena such as temperature and rainfall.

Hydrological drought, often defined by a period of low streamflow, is a response to numerous upstream processes that are unique to each river system. Hydrologists and water planners therefore often focus on directly observing and modelling runoff from water catchments.

The point here is that droughts can be multidimensional, affecting agriculture and water supplies on a wide range of spatial and temporal scales. A seasonal-scale drought that reduces soil moisture on a farm, and a decade-long drought that depletes reservoirs and groundwater supplies, can both be devastating, but in very different ways.

So is climate change affecting Australian droughts?

As we have so many ways of looking at droughts, this is a more complex question than it might first sound. Climate change may affect these drought metrics and types of drought differently, so it is hard to make general statements about the links between human-induced climate change and drought.

We know that over southern Australia, and in particular the southwest, there has been a rapid decline in winter rainfall, and that this has been linked to climate change. In the southeast there has also been a decline but the trend is harder to distinguish from the year-to-year variability.

Winter rainfall in Southwestern Australia has been in decline since the 1960s.
Bureau of Meteorology

For recent short-term droughts in southern Australia, analyses have found an increased likelihood of rainfall deficits related to human-caused climate change. Also, it has been suggested that the character of droughts is changing as a result of the human-induced warming trend.

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There is some evidence to suggest that widespread and prolonged droughts, like the Millennium Drought, are worse than other droughts in recent centuries, and may have been exacerbated by climate change. But the role of climate change in extended drought periods is difficult to discern from background climate variability. This is particularly true in Australia, which has a much more variable climate than many other parts of the world.

What does the future hold?

Future projections of drought are also difficult to constrain, as they vary across Australia and depend on the measure of drought being used. Climate models project a continuing decline in rainfall over southern Australia over the next century. Dry conditions like those seen in southeast Australia in 2006, for example, are projected to become more frequent under even low global warming targets associated with the Paris Agreement. Rainfall projections for other parts of the continent are more uncertain.

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Rainfall is projected to become more extreme, with more intense rain events and fewer light rain days. This would potentially influence what future droughts look like, and how and where water moves through the land.

River flows are also projected to decline in parts of the country, with consequences for water supply to cities, ecosystems and agriculture. In the southwest, declining rainfall has led to drastic reductions in river flows since the 1970s. This trend is expected to continue. Elsewhere, changes are more uncertain but studies have suggested that the southeast could also experience declining river flows in the coming decades.

Part of the challenge of projecting future change is related to how temperature and precipitation vary together. The relationship is a double-edged sword. Increased greenhouse gas emissions mean an increased probability that low-precipitation years are also warm, suggesting that under climate change droughts may be hotter in some parts of the world. But dry conditions also often result in warmer local temperatures, increasing water loss from soils and plants.

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Droughts are tricky

Compared with other extreme weather types, it is hard to make useful statements about how climate change is altering droughts and their impacts. Protracted droughts are also rarer than many short-term natural hazards such as heatwaves. We need much longer records to reliably understand how they are changing, but these are not always available.

Compared to heatwaves and cold spells it is harder to assess the role of climate change in droughts.
National Academy of Science

There is some evidence to suggest that climate change is exacerbating drought conditions in parts of Australia, especially in the southwest and southeast. Much more work is needed to understand the intricacies of the effects of climate change on different aspects and types of drought.

With the uncertainties of a rapidly changing climate we need to bolster our adaptation plans so we are ready for the next big dry.

Andrew King, ARC DECRA fellow, University of Melbourne; Anna Ukkola, Research Associate, Climate Change Research Centre, Australian National University, and Ben Henley, Research Fellow in Climate and Water Resources, University of Melbourne

This article was originally published on The Conversation. Read the original article.

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Australia relies on volunteers to monitor its endangered species

Nik Borrow/Flickr, CC BY-NC

Matthew H Webb, Australian National University; David M Watson, Charles Sturt University, and Dejan Stojanovic, Australian National University

The King Island Scrubtit and the King Island Brown Thornbill have the dubious distinction of being considered the first and third most likely birds to go extinct in the next 20 years.

Yet the only reason we know the status of the scrubtit and the thornbill is the diligent efforts of volunteers.

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For 15 years, the Threatened Species Committee has quietly summarised the plight of Australia’s most endangered birds, feeding the information to government, including the most recent report on those species most likely to go extinct in the coming two decades.

Experts in conservation management, specialist bird researchers, dedicated birders, and passionate local landholders all give their time freely to monitor endangered species. This is not outsourcing by the government: this is unpaid work by dedicated Australians stepping up.

King Island crisis

For these two King Island species, the most current information came from surveys conducted by specialist ornithologists, who funded the surveys themselves. In surveys completed this year, a handful of scrubtit were found in just three locations. The thornbill wasn’t found at all.

Follow-up surveys at these sites throughout King Island were carried out as part of the Wings on King initiative, with local landholders and visiting birders teaming up to tally records.

Like most of southern Australia, the native vegetation of King Island has been extensively cleared. This clearing is ongoing, and slated changes to Tasmanian planning laws would allow farmers to remove up to 40 hectares per year.

A key driver of this process is the influx of beef producers to the island, attracted by King Island’s rich soils and reliable rainfalls. Large operators are moving from Queensland and buying up prime grazing land, changing the way the land is used.

Many of these changes are bad news for local wildlife. Shelterbelts and remnant forests are making way for grass to feed ever more beef cattle.

This is alarming enough for the scrubtits, for which we at least have some baseline population data and knowledge of habitat requirements. It may be even worse for the thornbill – but we can’t be sure because we know so little about its habitat requirements or key locations.

Fire is another major threat. Uncontrolled bushfires razed almost a quarter of the island in 2007, decimating the Melaleuca Swamp forest at Nook Swamp, the last stronghold for the scrubtits. Only fragments of the swamp remain. This fire also exacerbated acid sulfate soils in unburned habitats, compromising regeneration in the wetland.

Shedding staff

Yet despite these mounting challenges, the federal Department of Environment is shedding vital staff. Just last month the loss of 60 positions from the biodiversity division was announced, representing a third of the people charged with overseeing monitoring of our threatened species.

Tasmania, despite being home to more than 600 threatened species, has a threatened species section of effectively two full-time positions (one of which is not currently filled). They have an annual budget of about A$5,000, or roughly A$7.14 per species).

This abrogation of biodiversity monitoring and basic conservation management is not new. State and federal departments have been losing capacity for decades.

The embedded research units within these agencies are all but gone, and any long-term monitoring is conducted either with external funds or through dedicated individuals nearing retirement. Entire national parks have been handed over to NGOs to manage, like Pilliga and Mallee Cliffs National Parks in New South Wales. NGOs now manage an estate many times larger than our national parks.

Federal funding has shrunk dramatically, with researchers increasingly reliant on philanthropic trusts, mining offsets, and crowdfunding campaigns to cover the costs of last-ditch interventions.

Another way

You don’t have to look very far to find alternatives. New Zealand has just announced a major increase in investment in endangered species funding, $181.6 million in additional funds for conservation initiatives over the next four years.

New Zealand has long been an international leader in conservation management, eradicating feral animals from entire islands to safeguard wildlife. It is ramping up efforts under the Predator Free New Zealand initiative, which aims to eradicate all introduced predators by 2050 in what has been described as “the most ambitious conservation project anywhere in the world”.

In contrast, the deputy director of the Threatened Species Recovery Hub recently pointed out that a third of Australia’s most threatened species aren’t monitored at all.

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Eleventh-hour funding will be too late for King Island’s thornbill. It hasn’t been seen since a keen-eyed photographer happened across a single bird in 2016. Despite the valiant efforts of volunteers, inspirational videos, and direct representations and grant applications, it has an estimated 6% chance of surviving the next 20 years.

Matthew H Webb, Dr Matt Webb, Australian National University; David M Watson, Professor in Ecology, Charles Sturt University, and Dejan Stojanovic, Postdoctoral Fellow, Australian National University

This article was originally published on The Conversation. Read the original article.