Мощные пожары навсегда уничтожают древние леса на западе США

Bigger, hotter fires are slowly erasing America’s great forests MIDPINES, Calif. — On a gentle slope on the western side of the Sierra Nevada, where a towering green canopy of ponderosa pines had stood for centuries, wildfires have transformed roughly 1,700 acres into brown, bare shrubland. That forest is gone for good, scientists say. Spiky shrubs and poison oak have replaced the majestic trees. All that is left of the pines are burned logs and dead branches. ADVERTISING It is part of a wider transformation that is taking place across the West, from Oregon to New Mexico, as bigger and hotter wildfires sweep through forests that have not evolved to survive such high-intensity blazes and a warmer climate. Recent studies estimate that as much as 40% of Western conifer forests will turn into shrubland by the year 2100 as a result. “This is a permanent shift from one ecosystem type to a fundamentally different one,” said Winslow Hansen, a forest ecologist at the Cary Institute of Ecosystem Studies, an independent research center in Millbrook, New York. The consequences of the shift, for people and wildlife, are expected to be profound. Researchers say that as trees disappear, winter and spring snow will melt faster, affecting wildlife as well as communities that are struggling with water shortages. Some Western states get as much as 75% of their water from snowmelt. “When you remove the forest, that snow is more susceptible to melting earlier,” said Benjamin Hatchett, an interdisciplinary scientist at Colorado State University. And he noted that a warmer, more arid climate dries out soil and pulls moisture from plants, making them more susceptible to wildfire. “That thirstier atmosphere is a big concern,” he said. Forests also absorb planet-warming carbon dioxide from the atmosphere. Bigger, older trees store more carbon than younger trees and shrubs. The loss of conifer forests today means a hotter tomorrow. To better understand these cascading effects, Hansen and Johan Eckdahl, a postdoctoral researcher at the University of California, Berkeley, visited the Sierra Nevada this month. On a 100-foot hillside plot that burned in the 2022 Oak fire, they recorded each flowering plant and shrub, filled plastic bags with soil, and checked the ground moisture and temperature with a special probe. Under normal conditions, seedlings would sprout all over after a fire. Young trees would grow and compete for space, water and light, and the forest would return after a decade or two. But the combination of more intense fires and a warmer, drier climate has stopped this age-old process of regeneration. As Hansen stood among the brush at the research site, the absence of new growth was stark. “We haven’t found one ponderosa seedling,” he said. “Ponderosa seeds have adapted to fire. That’s how they live. But the fires are just too hot for them.” Even if seedlings do take hold, they face tough odds. Across the Sierra Nevada, about one-fifth of the conifers, or cone-bearing trees, are not well suited to the current warming climate. In addition to his work at the Cary Institute, Hansen directs the Western Fire and Forest Resilience Collaborative, a group of 40 researchers who are using remote satellite sensing, 3D mapping and computer models that simulate future climate conditions to track the health of western forests. This summer, survey crews hired by the collaborative are mapping the severity of fires at more than 100 sites in California, Colorado and New Mexico. The goal is to guide researchers trying to better understand how moisture, nutrients and soil microbes influence to what extent forests will recover and how long it will take. Across the Southwest, which is drier and subject to more prolonged droughts than other areas such as the Pacific Northwest, ponderosa pine forests are particularly at risk of failing, according to Jonathan Coop, a fire ecologist at Western Colorado University who has been tracking this ecological shift for the past two decades. This month, Coop and colleagues published a study in the journal Science Advances that found wildfires are now getting so large and so fast that pine seeds can’t regenerate. The team looked at almost 3,500 wildfires from 2012 to 2023 in conifer forests in Canada and the western United States. “Forests do have innate resilience, and under normal circumstances they can take a hit or two and bounce back,” Coop said. “But circumstances just aren’t normal anymore.” As natural regeneration falters, scientists and conservationists are trying to give forests a helping hand. In Montana, for example, they’re teaming up to plant more climate-resistant seedlings from lower and warmer elevations in new areas that have burned. Kimberley Davis, a research ecologist at the U.S. Forest Service in Missoula, Montana, worked with Conservation International, a nonprofit environmental group based in Arlington, Virginia, at an experiment in the western part of the state. They took seedlings of the western larch, a native conifer that can reach 200 feet tall, from 3,400 feet and planted them in a burned area between 4,600 feet and 6,200 feet. The lower-elevation seedlings grew back better and coped with the warmer climate better than seedlings taken from higher elevations. Similar experiments of so-called assisted migration are underway in California and Washington state. “Keeping as many live trees as we can on the landscape when it burns is really important,” Davis said. “Because the seed source is so important.” All the researchers said that there’s still a fair amount of uncertainty in predicting which pine forests will survive and which ones will die. Despite the new tools of machine learning, remote sensing and genetic analysis, it’s still hard to identify a recipe for a successful forest. Scientists make calculations based on temperature, moisture and other factors, Hatchett said, “but the plants are doing their own thing.” “Biology is always going to throw you a curveball,” he said. This article originally appeared in The New York Times. © 2026 The New York Times Company