As global warming heats the air and land, drying out trees and other plants, people around the world need to reset their expectations of where, when and how long wildfires will burn, warns a new global wildfire report released today.

In a sweeping look, the scientists who authored the report for the United Nations Environmental Programme project a global increase of extreme fires of up to 14 percent by 2030, 30 percent by the end of 2050 and 50 percent by the end of the century.

The rapid change in fire conditions was the “driving reason for producing the analysis we’ve done,” said Andrew Sullivan, with the Commonwealth Scientific and Industrial Research Organization in Canberra, Australia, one of the lead editors of the report. 

“Eliminating the risk of wildfires is not possible, but much can be done to manage and reduce the risks that they pose,” he said. “Integrated wildfire management, considering social and environmental dimensions and traditional and Indigenous land management, is key to adapting to current and future wildfire risk.”

Given the visibly looming threat, the U.N. experts said, governments need to shift gears dramatically, from responding to fires as they happen to investing in preparedness and resilience, which will be less expensive in the long run. Local and Indigenous knowledge can show the way by helping people relearn how to live with fire.

The report comes after two years during which extreme wildfires have burned almost nonstop in both the Northern and Southern Hemispheres, with many fires reaching unprecedented size and burning in unexpected seasons, like the recent Marshall Fire that destroyed about 1,000 suburban homes near Boulder, Colorado in late December. And as 2022 started, large and intense fires ravaged parts of Argentina and Chile, including Patagonian forests that have rarely seen large fires.

Extreme wildfires aren’t just a threat to human lives and communities. They also destroy existing landscapes and ecosystems. Researchers estimated that the 2019-2020 Australian wildfires killed or harmed between 1 billion and 3 billion animals, and some forests that burned recently will only regrow as scruffy brushland, because the climate is too warm and dry to support seedlings, and some brush areas that burn are likely to end up as grasslands that burn even more frequently. 

The frequency of fires is a critical factor in whether some ecosystems can fully regenerate, said Cam Walker, a campaign coordinator for Friends of the Earth in Australia.

“Some parts of the Australian Alps have been burnt three times in the space of a decade or so, well beyond normal fire cycles, with resulting impacts on what species grow back,” he said. Alpine ash is especially vulnerable because even though it can regenerate after fires, it takes about 20 years before they produce seeds. 

“Increased frequency of fire means that much of the mountain and alpine ash communities are likely to collapse,” he said. “Under current climate scenarios, there can be little doubt that these forest systems will be even more impacted into the second half of the century.”

Ensuring survival of these systems is a daunting task, because “the only way to do it is to keep fire out of them for at least 100 years so they can regrow into the less fire-prone old growth phase of their life cycle,” he said. “This has enormous implications for firefighting because of the additional air and ground resources we would need to achieve this goal.” 

Wildfires Are a Direct Climate Threat

The new U.N. report reinforces previous findings that the surge in wildfires also directly threatens the climate with increased planet-heating carbon dioxide emissions. In some big fire years, the scientists found, emissions from fires can add up to as much as “40 percent of the mean annual global total carbon emissions from all fossil fuels.”

The report emphasized that the expansion of fire activity in the Arctic, which is now warming three times as fast as the global average, will worsen that threat as wet boreal forests and tundra dry out and become vulnerable to ignition from lightning strikes, which are also increasing in the Arctic. 

And the climate-warming effect of wildfire emissions may still be widely underestimated, at least for certain types of fires. A study published Feb. 8 suggested that emissions from wildfires in peatlands in 2019 and 2020, with organic, flammable soil, may have been 200 to 300 percent higher than initially calculated. 

Another study published Feb. 16 in Nature showed that wildfire behavior is also crossing other critical thresholds that will lead to worse fires. The researchers, led by scientists with the Cooperative Institute for Research in Environmental Sciences’ Earth Lab at the University of Colorado, Boulder, found a huge increase in the number of “flammable nights,” when conditions remained conducive to burning at night. In today’s climate, there are 11 more flammable nights every year in the Western United States than just 40 years ago, an increase of 45 percent. 

“Night is the critical time for slowing a speeding fire, and wildfire’s night brakes are failing,” said lead author Jennifer Balch. “With continued nighttime warming, we expect to see more runaway wildfires that are more intense, faster, and larger,” she said.

“That means firefighters don’t get the breaks at night they used to get. They have to battle flames 24/7.”

The U.N. report reinforces the urgency for people in the Western United States to be prepared for unexpected fires in unusual places, said John Abatzoglou, a fire and climate researcher at the University of California, Merced.

“We have seen, and expect to see, more fire as a result of a warming and drying climate in forests that historically have had little fire,” he said. That includes higher elevation forest types like spruce-fir zones, where most big Colorado ski resorts are located, but also some of the wetter forests, like California coastal redwoods and the Cascades, he added. 

“These areas are usually too wet for widespread fire in a vast majority of years, but with longer fire seasons and increased fuel drying, there are more opportunities for these landscapes to become flammable and carry fire.”

Perhaps the most ominous warning came from another Colorado-based researcher who studied chemical traces in ancient rocks to find that forest fires expanded dramatically about 94 million years ago when Earth was warmer, with more oxygen in the atmosphere.

During a 100,000-year span in that era, fires may have burned up to 30 or 40 percent of global forests. While today’s fires are exacerbated by dry conditions, forest fires during that period increased even in wet regions due to changes in global climate, said Earth scientist Garret Boudinot, lead author of the 2020 paper in Nature Geoscience.

The research suggests the increase in fires might have been caused by an increase in oxygen in the atmosphere. Large amounts of carbon dioxide in the atmosphere, much like what Earth is projected to experience by 2100, kick-started the cycle.

He explained that Earth is starting a similar transformation right now, with carbon dioxide accumulating in the atmosphere and nutrients building up in the ocean, a process that ends with a high oxygen concentration in the atmosphere, ideal for fueling fires.

“It highlights that putting carbon dioxide into the atmosphere and nutrients into the ocean doesn’t just potentially increase global temperatures,” he said. “It has significant impacts on the fundamental biogeochemistry, or ecology, of the planet. One of the consequences of having more oxygen in the atmosphere is that it’s easier to burn fires. It’s the same reason you blow on embers to stoke a fire.”