To reduce fire risk and meet climate targets, over 300 scientists call for stronger land clearing laws



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Without significant tree cover, dry and dusty landscapes can result.
Don Driscoll, Author provided

Martine Maron, The University of Queensland; Andrea Griffin, University of Newcastle; April Reside, The University of Queensland; Bill Laurance, James Cook University; Don Driscoll, Deakin University; Euan Ritchie, Deakin University, and Steve Turton, CQUniversity Australia

Australia’s high rates of forest loss and weakening land clearing laws are increasing bushfire risk, and undermining our ability to meet national targets aimed at curbing climate change.

This dire situation is why we are among the more than 300 scientists and practitioners who have signed a declaration calling for governments to restore, or better strengthen regulations to protect native vegetation.




Read more:
Land clearing on the rise as legal ‘thinning’ proves far from clear-cut


Land clearing laws have been contentious in several states for years. New South Wales relaxed its land clearing controls in 2017, triggering concerns over irreversible environmental damage. Although it is too early to know the impact of those changes, a recent analysis found that land clearing has increased sharply in some areas since the laws changed.

The Queensland Labor government’s 2018 strengthening of land clearing laws came after years of systematic weakening of these protections. Yet the issue has remained politically divisive. While discussing a federal inquiry into the impact of these policies on farmers, federal agriculture minister David Littleproud suggested that the strenthening of regulations may have worsened Queensland’s December bushfires.

We argue such an assertion is at odds with scientific evidence. And, while the conservation issues associated with widespread land clearing are generally well understood by the public, the consequences for farmers and fire risks are much less so.

Tree loss can increase fire risk

During December’s heatwave in northern Queensland, some regions were at “catastrophic” bushfire risk for the first time since ratings began. Even normally wet rainforests, such as at Eungella National Park inland from Mackay, sustained burns in some areas during “unprecedented” fire conditions.

There is no evidence to support the suggestion that 2018’s land clearing law changes contributed to the fires. No changes were made to how vegetation can be managed to reduce fire risk. This is governed under separate laws, which remained unaltered.

In fact, shortly after the fires, Queensland’s land clearing figures were released. They showed that in the three years to June 2018, an area equivalent to roughly 570,000 Melbourne Cricket Grounds (1,138,000 hectares) of bushland was cleared, including 284,000 hectares of remnant (old-growth) ecosystems.

Tree clearing can worsen fire risk in several ways. It can affect the regional climate. In parts of eastern Australia, tree cover reductions are estimated to have increased summer surface temperatures by up to 2℃ and southwest Western Australia by 0.4–0.8℃, reduced rainfall in southeast Australia, and made droughts hotter and longer.

Removing forest vegetation depletes soil moisture. Large, intact areas of forest typically have cooler, wetter microclimates buffered from extreme temperatures. Over time, some forest types can even become fire-resistant, but smaller patches of trees are typically drier and more flammable.

Trees also form a natural windbreak that can slow the spread of bushfires. An analysis of the 2005 Wangary fire in South Australia found that fires spread most rapidly through paddocks, rather than through areas lined with native trees.

Trends from 1978 to 2017 in the annual (July to June) sum of the daily Forest Fire Danger Index, an indicator of the severity of fire weather conditions. Positive trends, shown in the yellow to red colours, indicate increasing length and intensity of the fire weather season. Areas where there are sparse data coverage, such as central parts of Western Australia, are faded.
CSIRO/Bureau of Meteorology/State of the Climate 2018

Finally, Australia’s increasing risk of bushfire and worsening drought are driven by global climate change, to which land clearing is a major contributor.

Farmers on the frontline of environmental risk

Extensive tree clearing also leads to problems for farmers, including rising salinity, reduced water quality, and soil erosion. Governments and rural communities spend significant money and labour redressing the aftermath of excessive clearing.

Sensible regulation of native vegetation removal does not restrict existing agriculture, but rather seeks to support sustainable production. Retained trees can help deal with many environmental risks that hamper agricultural productivity, including animal health, long-term pasture productivity, risks to the water cycle, pest control, and human well-being.

Rampant tree clearing is undoing climate policy too. Much of the federal government’s A$2.55 billion Emissions Reduction Fund has gone towards tree planting. But it would take almost this entire sum just to replace the trees cleared in Queensland since 2012.




Read more:
Stopping land clearing and replanting trees could help keep Australia cool in a warmer future


In 2019, Australians might reasonably expect that our relatively wealthy and well-educated country has moved beyond a frontier-style reliance on continued deforestation, and we would do well to better acknowledge and learn lessons from Indigenous Australians with respect to their land management practices.

Yet the periodic weakening of land clearing laws in many parts of Australia has accelerated the problem. The negative impacts on industry, society and wildlife are numerous and well established. They should not be ignored.The Conversation

Martine Maron, ARC Future Fellow and Associate Professor of Environmental Management, The University of Queensland; Andrea Griffin, Senior Lecturer, School of Psychology, University of Newcastle; April Reside, Researcher, Centre for Biodiversity and Conservation Science, The University of Queensland; Bill Laurance, Distinguished Research Professor and Australian Laureate, James Cook University; Don Driscoll, Professor in Terrestrial Ecology, Deakin University; Euan Ritchie, Associate Professor in Wildlife Ecology and Conservation, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, and Steve Turton, Adjunct Professor of Environmental Geography, CQUniversity Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Tropical thunderstorms are set to grow stronger as the world warms



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A supercell thunderstorm in the US state of Oklahoma.
Hamish Ramsay, Author provided

Martin Singh, Monash University

Thunderstorms are set to become more intense throughout the tropics and subtropics this century as a result of climate change, according to new research.

Thunderstorms are among nature’s most spectacular phenomena, producing lightning, heavy rainfall, and sometimes awe-inspiring cloud formations. But they also have a range of important impacts on humans and ecosystems.

For instance, lightning produced by thunderstorms is an important trigger for bushfires globally, while the hailstorm that hit Sydney in April 1999 remains Australia’s costliest ever natural disaster.


Read more: To understand how storms batter Australia, we need a fresh deluge of data


Given the damage caused by thunderstorms in Australia and around the world, it is important to ask whether they will grow in frequency and intensity as the planet warms.

Our main tools for answering such questions are global climate models – mathematical descriptions of the Earth system that attempt to account for the important physical processes governing the climate. But global climate models are not fine-scaled enough to simulate individual thunderstorms, which are typically only a few kilometres across.

But the models can tell us about the ingredients that increase or decrease the power of thunderstorms.

Brewing up a storm

Thunderstorms represent the dramatic release of energy stored in the atmosphere. One measure of this stored energy is called “convective available potential energy”, or CAPE. The higher the CAPE, the more energy is available to power updrafts in clouds. Fast updrafts move ice particles in the cold, upper regions of a thunderstorm rapidly upward and downward through the storm. This helps to separate negatively and positively charged particles in the cloud and eventually leads to lightning strikes.

To create thunderstorms that cause damaging wind or hail, often referred to as severe thunderstorms, a second factor is also required. This is called “vertical wind shear”, and it is a measure of the changes in wind speed and direction as you rise through the atmosphere. Vertical wind shear helps to organise thunderstorms so that their updrafts and downdrafts become physically separated. This prevents the downdraft from cutting off the energy source of the thunderstorm, allowing the storm to persist for longer.

By estimating the effect of climate change on these environmental properties, we can estimate the likely effects of climate change on severe thunderstorms.

Stormy forecast

My research, carried out with US colleagues and published today in Proceedings of the National Academy of Sciences, does just that. We examined changes in the energy available to thunderstorms across the tropics and subtropics in 12 global climate models under a “business as usual” scenario for greenhouse gas emissions.

In every model, days with high values of CAPE grew more frequent, and CAPE values rose in response to global warming. This was the case for almost every region of the tropics and subtropics.

These simulations predict that this century will bring a marked increase in the frequency of conditions that favour severe thunderstorms, unless greenhouse emissions can be significantly reduced.

Change in frequency (in days per year) of favourable conditions for severe thunderstorms for 2081-2100, compared with 1981-2000 averaged across 12 climate models under the RCP8.5 greenhouse-gas concentration scenario. Stippling indicates regions where 11 of the 12 models agree on the sign of the change.
CREDIT, Author provided

Previous studies have made similar predictions for severe thunderstorms in eastern Australia and the United States. But ours is the first to study the tropics and subtropics as a whole, a region that is characterised by some of the most powerful thunderstorms on Earth.

What drives the increased energy?

Different climate models, constructed by different research groups around the world, all agree that global warming will increase the energy available to thunderstorms – a prediction underlined by our new research. But we need to understand why this happens, so as to be sure that the effect is real and not a product of faulty model assumptions.

My colleagues and I previously proposed that high levels of CAPE can develop in the tropics as a result of the turbulent mixing that occurs when clouds draw in air from their surroundings. This mixing prevents the atmosphere from dissipating the available energy too quickly. Instead, the energy builds up for longer and is released in less frequent but more intense storms.

As the climate warms, the amount of water vapour required for cloud formation increases. This is the result of a well-known thermodynamic relationship called the Clausius-Clapeyron relation. In a warmer climate this means the difference in the humidity between the clouds and their surroundings becomes larger. As a result, the mixing mechanism becomes more efficient in building up the available energy. This, we argue, accounts for the increase in CAPE seen in our model simulations.

In our new study, we tested this idea in a global climate model by artificially increasing the strength of the mixing between clouds and their surroundings. As expected, this change produced a large increase in the energy available to thunderstorms in our model.


Read more: Australia faces a stormier future thanks to climate change


Another prediction of our hypothesis is that days with both high values of CAPE and heavy precipitation tend to occur when the atmosphere is least humid in its middle levels (at altitudes of a few kilometres). Using real data from weather balloons, we confirmed that this is the case across the tropics and subtropics.

What this means for future thunderstorms

The models predict that the energy available for thunderstorms will increase as the Earth warms. But how much more intense will storms actually become as a result?

The answer to that question is currently uncertain, and answering it is the next job for me, and other researchers around the world.

The ConversationBut it is clear that through our continued greenhouse gas emissions, we are increasing the fuel available to the strongest thunderstorms. Exactly how much stronger our future thunderstorms will ultimately become remains to be seen.

Martin Singh, Lecturer, School of Earth, Atmosphere and Environment, Monash University

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