No more forest fires in California in a couple of decades

The peak of the wildfire season in California usually occurs between July and November, when hot, dry winds are most frequent. This year promises a hefty fire season. The west of the U.S., including California, is in extreme or even ‘exceptional’ drought and summer heatwaves are on the doorstep.

Summer fires in California increased almost 800% between the 1970’s and 2019. This number stems from before the devastating record fire season of 2020. In 2020 over 4% of the state’s roughly 100 million acres total land area burned. The first ‘gigafire’ was recorded, i.e. over 1 million acres burnt in a single fire. Which is more than double the previous record 2 years earlier. Another fire destroyed 10%-14% of mature sequoias. The chief Science from the National Park: “I cannot overemphasize how mind-blowing this is for all of us. These trees had lived for thousands of years. They had survived dozens of wildfires already.”

The cause of forest fires is pretty straightforward. More heat (also called ‘temperature-induced vapor pressure deficit’) accounts for nearly all growth in forest fires in California. California has warmed about 1.7°C / 3°F. If we continue on the path of the RCP 8.5 scenario of the IPCC, in a couple of decades there will be no more forest fires to burn in California, according to a Columbia University scientist studying wildfires in California. The scientist’s studies point out that in 2070 up to half of all trees would burn in a single year. That is of course impossible. It means that long before that the once-mighty forests of California will have given way to scrub, grassland and desert.

California is a canary in a coal mine. Research published in Science indicates that globally most (or even all!) trees alive today will not be able to survive the climate expected in 40 years. More extreme heat waves and droughts are lethal for forests. The study suggests that just as corals reached a tipping point and are bleaching on a global scale, so might forests perish on a global scale. Some trees will make way for different species associated with different biomes (such as oaks instead of spruce), others, like the forests of California, will disappear altogether.

Figure. Chance in soil moisture 2071-2020 relative to 1976-2005 under different RCP scenario’s. Stippling indicates statistical significance. Source: Lu et al. 2019.

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