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Wednesday, November 30, 2022

After all the flooding rains we still face elevated bushfire risk for Summer 2022

You might think after the deluge of rain and flood events his year that fire risk would be low this summer.

You would be wrong.

All the rains and floods have contributed to vegetation growth adding to fuel load. When this fuel dries out with summer heat, it makes it susceptible to wildfire.

We are more likely to see grassfires this season than forest fires. But they can be equally deadly.

It is very difficult to do mechanical reduction on this fuel load while it is wet. And when the ground drys out enabling reduction in fuel loads, ANY wind will pose a danger to a hazard reduction burn getting out of control. Large parts of inland south east Australia and parts of Western Australia have been assessed as having increased fire potential.

So what does the future hold?

A new study by Australian researchers in Nature Communications says that many forests around the globe will become highly flammable for at least 30 extra days per year unless we cut emissions.

The study looked at the link between wildfires and “vapour pressure deficit” – a measure of the atmosphere’s power to suck moisture out of living and dead plants.

The authors highlight the need to reduce greenhouse gas emissions rapidly in their The Conversation article:

If humanity continues to release greenhouse gas emissions unabated, the planet is expected to warm by around 3.7℃ by the end of the century. Under this high-emissions scenario, our study finds there are forests on every continent that will experience at least 30 extra days per year above critical flammability thresholds. Under a lower-emissions scenario where global warming is limited to around 1.8℃, each continent will still see at least an extra 15 days per year crossing the threshold.

They also highlight some of the risks of increased forest flammability:

Increasing forest fires will have serious consequences. This includes potentially destabilising patterns of fire and regrowth and disrupting the carbon storage we rely on forests for. Indeed, research last year showed the role of the Amazon rainforest as a “carbon sink” (which absorbs more CO₂ that it releases) may already be in decline. We can also expect increasing harms to human health from wildfire smoke. It is estimated that around the world, more than 330,000 people die each year from smoke inhalation. This number could increase notably by the turn of the century, particularly in the most populated areas of South Asia and East Africa.

In the body of the study the authors highlight that "the Australian mega-fires of 2019-20 were estimated to have led to 429 excess deaths and a much larger number of hospitalisations due to wildfire smoke. Overall the health costs of the 2019–2020 Australian fires were close to US$1.5 billion" according to Johnston, F. H. et al. (2021)

Study Abstract

Levels of fire activity and severity that are unprecedented in the instrumental record have recently been observed in forested regions around the world. Using a large sample of daily fire events and hourly climate data, here we show that fire activity in all global forest biomes responds strongly and predictably to exceedance of thresholds in atmospheric water demand, as measured by maximum daily vapour pressure deficit. The climatology of vapour pressure deficit can therefore be reliably used to predict forest fire risk under projected future climates. We find that climate change is projected to lead to widespread increases in risk, with at least 30 additional days above critical thresholds for fire activity in forest biomes on every continent by 2100 under rising emissions scenarios. Escalating forest fire risk threatens catastrophic carbon losses in the Amazon and major population health impacts from wildfire smoke in south Asia and east Africa.


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