Climate change is a main driving force behind the huge uptick of dangerous wildfires the western U.S. has been experiencing during the last decade — and this year is no exception. In terms of total acreage burned, the eight worst wildfire seasons since 1960 have all occurred in the last 12 years.
Warmer and drier conditions, coupled with a longer fire season, are causing bigger and hotter fires that are burning longer, causing more damage, and putting firefighters lives at risk. Dave Cleaves, climate change advisor to the chief of the U.S. Forest Service, confirmed at a recent UCS briefing that more extreme fire weather is leading to larger and more severe fires.
He also said that nearly half the Forest Service budget is now dedicated to suppressing and managing fires, preventing much needed funds from being deployed for important forest management priorities.
Anthony Westerling a fire researcher at the University of California, Merced, explained that the changes have been so rapid and noticeable in recent years because many western forests were already close to a threshold which warming conditions are pushing them over.
Climate is a crucial limiting factor in preventing forest fires. When conditions are cool and moist, fires don’t break out as much and they tend to burn less strongly. Westerling said that drier winters and a continuing warming trend are shifting the situation so that we are reaching a situation where most years will likely be as dry and as warm as they have ever been in the last century, making the risk of catastrophic fires an ever-present feature of our summers.
Further exacerbating the situation, said Craig D. Allen, an ecologist at the U.S. Geological Survey (USGS) Field Station at Bandelier National Monument in New Mexico, is that decades of active fire suppression in the West has prevented the smaller less intense surface fires that helped naturally thin forests across the west. This has caused many forests to grow denser and therefore more able to support the hotter and more intense crown fires that destroy complete stands and devastate thousands of acres at a time.
According to Allen, there is extensive scientific evidence from tree rings and fire scars in western forests that there are more fires in warmer and drier years. With conditions now trending warmer and drier in the Southwest than anything that’s been observed over the last two centuries, and average temperatures probably higher than they’ve been for at least a thousand years, Allen thinks forest ecosystems may be reaching a tipping point in the region.
Some forests may never recover from major fires or dieback caused by drought and heat. There is a very real danger that much land that is now forested will eventually be transformed into shrub or dry grassland.