Wildfires are a frequent summer fixture in western America. While they actually support biodiversity in areas that have evolved with fire, in recent years they have become both more common and more intense. The two largest ever recorded fires in California both occurred in the last year, as did the six most destructive fires. Of this summer’s fires, one was the largest, and another the second most destructive. Humans and habitats unused to such intense fire are under increasing threat, and climate change is the driving factor. It causes several different changes in the environment, which come together to create the perfect firestorm.
Melting snow plays a vital role in keeping forest environments moist. Most of that snow comes from mountains that are near the forests, which channel water downhill towards the woods as the snow melts. In cooler conditions, the process is fairly slow and thus keeps the forests hydrated, and therefore harder to catch fire, for a long period.
Unfortunately, rising temperatures have caused all of the snow to melt about four weeks earlier this year than it typically used to. Earlier springs topload the forests’ water supply instead of spreading it out over time, causing the soil to be dry for a much larger part of the year
When the increasingly high temperatures of summer arrive, the forest is left without an important line of defence against extreme fire and extended period of vulnerability to the flames. This problem is only going to get worse if temperatures continue to rise as snow starts to melt even earlier.
Rising temperatures are also changing precipitation patterns in ways that encourage fires. There are two big factors at work. Both of them are bad on their own, but the combination of the two makes them even worse.
Evaporation is the first culprit. Higher temperatures naturally cause more water to transform from liquid into vapour. With more water naturally housing itself in the air, rivers and plants run dry more easily, creating the perfect conditions for fires to start and spread.
The greater accumulation of water vapour in the air doesn’t just cause drought. When rain does fall, it falls harder. These deluges can be destructive in their own right, but it also creates briefer periods where the forests are acceptably wet, followed by longer periods of dryness – rather than a safer, more consistent pattern.
Trees in wildfire-prone areas have evolved to survive and thrive in wildfire conditions, possessing adaptations such as harder leaves, denser bark, fire-resistant seeds, and higher water content in external structures. But thanks to the above factors, many trees are so dry that they simply burn too well to make it through the blazes in once piece. The end result is devastating rather than regenerative fires that are more common, spread more quickly, and destroy far more trees than the fires of the past.
The increased rate of wildfires forces humans to intervene to protect people living in risk-prone areas. Unfortunately, many of our interventions can actually make the problem worse. The plants in these areas actually benefit from small fires, as they clear out undergrowth and debris without affecting the canopy above. But humans have often suppressed such fires, meaning a greater proportion of the fires that do happen are the uncontrollable, devastating type. Most people who actually manage forests are aware of this, but the combination of pressure from the public and poor budgeting practices from governments make it very hard to deal with the issue.
A Growing Problem
Wildfires have been getting more and more common in California. That is a big problem, and not just because it means more people will see their homes and lives goes up in flames.
Many forests are struggling to grow back in the aftermath of these larger, more frequent fires. The plants in these forests evolved to deal with fires that were different from the intense behemoths we see today, whose flames reach beyond the resistant lower structures and destroy the vulnerable canopy. The increased frequency gives them less time to recover. The end result? Many more dead trees. Less seeds. More erosion. These harder growing conditions leave forests simply unable to recover without a big break.
The Warming Cycle
Climate change and wildfires come together to propagate a vicious positive feedback loop. Trees naturally remove greenhouse gases from the atmosphere, which helps to slow warming. The wildfires both reduce the planet’s ability to pull those gases out of the air, and release the carbon trapped in the burning trees. This two-pronged acceleration of greenhouse gas accumulation accelerates warming, which in turn leads to more wildfires, that in turn burn and destroy more trees. We can only break this cycle and save our forests by using our ballots and wallets to support the fight against climate change. So what are you waiting for?