Why is wildfire burning less and less of the world? Actually, increasing temperatures because of global warming is a little part of the reason we see *less* burning.
Over the past days I’ve written about how we’re wrong to believe that wildfire is getting worse and is out-of-control.
But it is curious to see how many still *want* to see their prejudices confirmed: global warming and rising temperatures are causing more and more wildfire.
Well, the data clearly show they’re wrong in the very basic sense – there is not more and more wildfire, but less and less. (https://www.facebook.com/bjornlomborg/posts/10157051197598968)
But as I have also pointed out, the majority of the reason for fewer wildfires is due to better fire suppression, along with better forest management and more agriculture.
The graph in this post is intriguing because it shows the what has caused less wildfire. The researchers decompose the effects into three causes: Humans, climate and fertilization.
They decompose the effect by running the models with just humans, or with just climate or with just fertilization, and comparing it to the baseline run. (Remarkably, the result looks almost additive.)
Since 1901 humans have consistently caused *less* fire, because of firefighting and suppression, forest management and more agriculture.
Fertilization from nitrogen (mostly from air pollution from power stations and cars) has basically made green stuff grow faster and denser – in the US trees might grow 40% faster with more nitrogen. The CO₂ effect is likely to be much smaller, but with the same direction of impact (http://www.nature.com/doifinder/10.1038/ngeo721). (See also https://www.sciencedirect.com/…/artic…/pii/S0378112704000635)
And running a global fire model with and without climate impacts (that is higher temperatures, increased precipitation etc) shows that climate actually slightly *decrease* global fire.
Source: Yang et al. 2014: “Spatial and temporal patterns of global burned area in response to anthropogenic and environmental factors: Reconstructing global fire history for the 20th and early 21st centuries,” J. Geophys. Res. Biogeosci., 119, 249–263, https://agupubs.onlinelibrary.wiley.com/…/10.1…/2013JG002532 (freely available).
Notice, that it is likely that in the long run, higher temperatures and more global warming all other things equal will lead to *increased* risk of fire. Yet, this will only intensify later in the century, and even in the unrealistic worst-case scenarios (RCP8.5) is unlikely to reach levels of fire by 2100 that were normal in 1900 (https://www.biogeosciences.net/…/267/2016/bg-13-267-2016.pdf).
