According to the nonprofit CarbonPlan, which analyzes the scientific integrity of carbon offsets, at least six large sites in California, Oregon, and Washington have burned over the past five years. The California Air Resources Board, which oversees the state’s offset market, has an insurance system designed to protect against such disasters. But a growing number of forest ecologists, climate modelers, and policy experts argue that the insurance system, known as the “buffer pool,” was never based on sound science — and that now, as forests burn more severely and frequently across the West, it could be in danger of collapse.
Researchers combed through thousands of historical documents for first-person accounts of fires occurring between 1673 and 1905 in the Midwestern tallgrass prairie. Their study is the first systematic analysis of the timing, causes and consequences of prairie fires in this part of the world. They report their findings in Natural Areas Journal.
A century of fire suppression has reshaped our forests. The floor is littered with material that is dense, dried, and dead. Now, climate change is highlighting why that’s a problem. Increasingly hot, dry weather has resulted in a longer, more dramatic wildfire season, and the forests are ready to ignite. The United States is struggling to keep up with the blazes year after year, so scientists and Indigenous people are pushing to bring back a centuries-old practice: burning the forests on our own terms, through prescribed burning.
Even though there have been no major wildfires in the region, East Coasters may have seen some concerning smoke-fueled air-quality warnings pop up on their weather apps this summer. The cause is cross-country plumes from Oregon’s massive Bootleg Fire, drifting all the way across the continent to New York, Philadelphia, and Toronto, 2,500 miles away.
A new study warns that that traveling smoke has detrimental health effects on Eastern populations—in fact, it found that there were more total smoke-induced asthma morbidities and mortalities in recent years in the East than in the West. The researchers say Easterners, and especially those with pre-existing conditions, should be aware of these health impacts and take steps to protect themselves, especially as wildfires are due to worsen in coming years.
In a study in the Proceedings of the National Academy of Sciences released in May 2021, our team of fire and climate scientistsand engineers found that forest fires are now reaching higher, normally wetter elevations. And they are burning there at rates unprecedented in recent fire history. Two fires burning in northern California in 2021 – the Dixie and Caldor fires – are examples: They were the first and second wildfires on record to cross the Sierra Nevada crest and burn on both sides.
While historical fire suppression and other forest management practices play a role in the West’s worsening fire problem, the high-elevation forests we studied have had little human intervention. The results provide a clear indication that climate change is enabling these normally wet forests to burn.
As wildfires creep higher up mountains, another tenth of the West’s forest area is now at risk, our study found. That creates new hazards for mountain communities, with impacts on downstream water supplies and the plants and wildlife that call these forests home.
Rising fire risk in the high mountains
In the new study, we analyzed records of all fires larger than 1,000 acres (405 hectares) in the mountainous regions of the contiguous Western U.S. between 1984 and 2017.
The amount of land that burned increased across all elevations during that period, but the largest increase occurred above 8,200 feet (2,500 meters). To put that elevation into perspective, Denver – the mile-high city – sits at 5,280 feet, and Aspen, Colorado, is at 8,000 feet. These high-elevation areas are largely remote mountains and forests with some small communities and ski areas.
The area burning above 8,200 feet more than tripled in 2001-2017 compared with 1984-2000.
Our results show that climate warming has diminished the high-elevation flammability barrier – the point where forests historically were too wet to burn regularly because the snow normally lingered well into summer and started falling again early in the fall. Fires advanced about 826 feet (252 meters) uphill in the Western mountains over those three decades.
The Cameron Peak Fire in Colorado in 2020 was the largest fire in the state’s history, burning over 208,000 acres (84,175 hectares), and is a prime example of a high-elevation forest fire. The fire burned in forests extending to 12,000 feet (3,658 meters) and reached the upper tree line of the Rocky Mountains.
We found that rising temperatures in the past 34 years have helped to extend the fire territory in the West to an additional 31,470 square miles (81,507 square kilometers) of high-elevation forests. That means a staggering 11% of all Western U.S. forests – an area similar in size to South Carolina – are susceptible to fire now that weren’t three decades ago.
Can’t blame fire suppression here
In lower-elevation forests, several factors contribute to fire activity, including the presence of more people in wildland areas and a history of fire suppression.
In the early 1900s, Congress commissioned the U.S. Forest Service to manage forest fires, which resulted in a focus on suppressing fires – a policy that continued through the 1970s. This caused flammable underbrush that would normally be cleared out by occasional natural blazes to accumulate. The increase in biomass in many lower elevation forests across the West has been associated with increases in high-severity fires and megafires. At the same time, climate warming has dried out forests in the Western U.S., making them more prone to large fires.
By focusing on high-elevation fires in areas with little history of fire suppression, we can more clearly see the influence of climate change.
Most high-elevation forests haven’t been subjected to much fire suppression, logging or other human activities, and because trees at these high elevations are in wetter forests, they historically have long return intervals between fires, typically a century or more. Yet they experienced the highest rate of increase in fire activity in the past 34 years. We found that the increase is strongly correlated with the observed warming. [View the chart showing how much U.S. wildland area burns each year]
High mountain fires create new problems
High-elevation fires have implications for natural and human systems.
High mountains are natural water towers that normally provide a sustained source of water to millions of people during dry summer months in the Western U.S. The scars that wildfires leave behind – known as burn scars – affect how much snow can accumulate at high elevations. This can influence the timing, quality andquantity of water that reaches reservoirs and rivers downstream.
The loss of tree canopy also exposes mountain streams to the Sun, increasing water temperatures in the cold headwater streams. Increasing stream temperatures can harm fish and the larger wildlife and predators that rely on them.
Climate change is increasing fire risk in many regions across the globe, and studies show that this trend will continue as the planet warms. The increase in fires in the high mountains is another warning to the U.S. West and elsewhere of the risks ahead as the climate changes.
When smoke rises from wildfires in the western United States, it pummels clouds with tiny airborne particles. What happens next with these clouds has been largely unstudied. But during the 2018 wildfire season, researchers embarked on a series of seven research flights, including over the Pacific Northwest, to help fill this gap.