Pirocene: Megafires are reshaping the world – 10/22/2023 – Environment

On August 15, a small fire was detected in the hills above West Kelowna, British Columbia, Canada. The landscape was dry, and the wind was strong. Over the next few days, the modest fire turned into a raging conflagration.

It spread across the valley towards Okanagan Lake. The wind blew embers across the water, sparking new fires around the city of Kelowna.

“I barely slept the night the West Kelowna fires crossed the lake,” said Karen Hodges, who lives in Kelowna. “I could see the fires from my window. And then I kept thinking about the people I know in the valley and where their houses were.”

Hodge, a conservation ecologist at the University of British Columbia Okanagan, also found herself concerned about wildlife. She had been studying western owls that nest right in the heart of that fast-moving, sweeping fire. “A fire at that speed would be difficult for animals to evacuate,” she said.

Did the owls manage to escape in time? And after Canada’s worst wildfire season on record, what would be left for survivors?

Fire is a natural phenomenon: some species actually benefit from its effects, and even those that don’t can be remarkably resilient in the face of flames. But as the fires intensify, they are beginning to outpace nature’s ability to recover.

“Not all fires have the same impact,” said Morgan Tingley, an ecologist at UCLA (University of California at Los Angeles). “These megafires are not good for ecosystems.”

Megafires, which are much larger than typical wildfires, have an immediate ecological impact, killing plants and animals that could have survived more contained fires. In the long term, changes in fire patterns could drive some species to extinction, transform landscapes and completely reshape ecosystems.

This incendiary era, which some scientists call the Pyrocene, could lead to “a massive transformation of the habitats that exist on the planet,” Hodges said. “Right now, everyone is talking about fires and smoke and who dies, because of the immediacy of this fire year. But in reality, the long-term consequences are much more serious and long-lasting.”

Surviving the flames

Fire has been a planetary phenomenon for hundreds of millions of years, and plants and animals that evolved in fire-prone regions have adapted to periodic fires. Some trees have roots that can regrow even if the trunk burns, while the mere smell of smoke will awaken some animals from torpor, a form of mild hibernation.

But in many regions and ecosystems, fires are becoming larger and more severe. In the United States, wildfires burn much more land today than they did three decades ago, especially in western states.

Globally, the risk of catastrophic fires could increase by more than 50% by the end of the century, as reported by the United Nations.

Climate change is partly to blame, scientists said, but there are also other factors, such as the expansion of highly flammable invasive grasses, which helped the deadly fires on Maui, Hawaii, spread so quickly.

More than a century of fire suppression has also left some forests thick with trees, providing more fuel for the flames. “When fires arrive, they burn with greater intensity,” said Chris French, deputy chief of the US National Forest System.

Even fire-adapted organisms can be defeated. In northern Australia, crested lizards can survive low-intensity fires by hiding in the tree canopy. But during severe fires, when the flames rise, lizards that use this strategy can perish.

Fires are also spreading to ecosystems where flames are an unknown threat. The megafires that broke out in Australia in 2019 and 2020 burned the country’s rainforests, which contained many plants that cannot regenerate after burning.

Fires that consume more fuel can also produce more smoke per unit area burned, threatening animals far from the flames. “All air-breathing animals will be affected by smoke exposure because the chemicals in smoke are toxic,” said Olivia Sanderfoot, an ecologist at UCLA.

Smoke inhalation can cause more than respiratory problems. Months after severe peatland fires produced record air pollution in Indonesia in 2015, Bornean orangutans vocalized less frequently and their voices became harsher.

From the ashes

Animals that survive the inferno must then find food, water and shelter in hot, dry, bare landscapes where the risk of predation is high. (Surrounded by weakened prey, some predators thrive after fires.)

Fortunately, fires tend to burn unevenly, devastating some areas of trees while sparing others. These unburned islands could be a lifeline for fire-sensitive species like caribou, which feed on highly flammable lichen as well as thin-barked trees. But some of today’s fires are leaving fewer of these oases.

“You can walk half a kilometer and you won’t see a single living tree,” said Andrew Stillman, an ecologist at Cornell University’s Laboratory of Ornithology. “Increasingly, these fires appear to be creating habitat conditions that are outside the norms to which these species are adapted.”

This can be true even for fire-loving animals like the black-backed woodpecker. The birds build nests in burned trees and feed on the beetle larvae that colonize the charred trunks. However, Stillman and Tingley found that they prefer areas of burned trees near areas of live, leafy trees, which protect their young from being captured by predators.

After the massive Rim Fire in California in 2013, scientists looked for woodpeckers in nearly 500 locations across the extensive burned area. They found only six birds. “Even though it created all this great burn habitat, it wasn’t the right kind of burn habitat,” Tingley said.

Fewer clusters of live trees can also reduce growth again. “In many places, we are not getting regeneration because the seed source has been lost,” said French of the National Forest System. “Honestly, it looks like someone came in and just detonated a bomb.”

Burnt and bare soil, which does not absorb rain well, can also hinder regeneration. Flash floods after fires can wash ash and sediment into rivers and streams, polluting water, killing fish and altering the course of waterways.

Extinction and evolution

In Canada’s Northwest Territories, repeated fires have completely transformed some forests. In one place, towering jack pines have given way to grasses and some “small, bushy cottonwoods” that have lightweight seeds that can be carried by the wind, said Ellen Whitman, a scientist who researches wildfires at Natural Resources Canada.

“It’s a very different place,” she added.

Change is not necessarily bad. Fires can promote delayed regeneration in places where flames have been artificially suppressed, and forests are not inherently superior to other ecosystems.

Old-growth prairies, which are hotspots of biodiversity, are also threatened; in some places, prairies have turned to forests, in part due to fire suppression. “So maybe, in some ways, a little bit of balance is being restored,” Whitman said.

But it can take a long time for new grassland areas to develop biodiversity, and landscape transformations have cascading effects.

In the Amazon, patches of forest subject to frequent fires began to resemble savannas; In these locations, scientists found that ants and butterflies that preferred forests declined, while species that preferred open habitats became established.

Today, increased fire activity could push more than a thousand species of plants and animals to the brink of extinction, scientists have calculated. And many plants and animals are already facing multiple stressors.

In Canada, western short-eared owls are threatened by deforestation and the expansion of invasive barred owls.

“Then you set fire to that, like something additional that kills some of them, stresses others and changes the habitat — you know, suddenly you have a lot to deal with,” Hodges said.

The fire in West Kelowna has burned some of the trees where owls nest, she said, and the outlook is bleak for a young GPS-tagged bird that one of her students was tracking.

“Her last known location was right in the middle of the fire that spread so quickly,” Hodges said. “And we haven’t detected the signal since.”