The risk of fire has been worsened by global climate change, and is likely to fuel even more change as feedback loops create disastrous consequences for both humans and nature. Predicting the risks and impact of bush and wildfire is still not done well.
In a new study, a team of Yale scientists and colleagues from South Africa and the United States set more than 1,000 prescribed fires in grassy savannas, an area where 80% of the world's fire activity occurs. They tested a model that will help climate scientists to more accurately predict when and where fires will occur, as well as how they will impact global climate change.
The results are reported in the journal in June.
The American West and African savannas can suddenly switch from a nonflammable state to one where everything is burning. Predicting when the threshold will be crossed is important to understand the impact fires have now and in the future.
In Kruger National Park, in South Africa, and other savannas in Africa and the United States, fires were set by the Yale team led by Anabelle Cardoso. They took into account variables such as grassy fuel biomass, air temperature, and humidity, as well as seasonal variables such as rain.
Fire spread can be modeled the same way that public health officials predict disease outbreaks, according to their findings. Like infectious diseases, fires require a source of "ignition" ( someone who initially contracts the disease), a minimum of fuel to burn, and good environmental conditions to spread quickly.
Staver said that an area that has burned gains immunity to future fires until enough fuel regrowth is present. Climate change can affect this immunity. Both the flora and fauna are compromised.
The humidity is moderate and the temperature is high. Climate change can cause all of these conditions to get worse. The risks of intense fires and dangerous fires can be increased quickly when environmental conditions reach a certain threshold.
They are similar to switches. Things change quickly once it's flipped. It is not gradual according to Cardoso. In small amounts, fire risk does not go from low to dangerous. It can go from low to everything-is-burning without warning.
Land managers with experience are able to see how quickly fire conditions can change. Many models used by scientists to predict the effects of fires don't fully account for how much carbon is released during burn events, which could make it difficult to accurately predict future fire risks, according to the authors.
The amount of fuel available for fires in some African savannas has been reduced by the effects of global change. The American West is at a higher risk of catastrophic fires because of the drying out of fuels.
The switch can work both ways.
More information: Quantifying the environmental limits to fire spread in grassy ecosystems, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2110364119. Journal information: Proceedings of the National Academy of Sciences
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