Wildfires have decimated forests. Here’s why replanting trees is a challenge

Camille Stevens-Rumann crouched in the dirt and leaned over evergreen seedlings, measuring how much each had grown in seven months. “That’s two to three inches of growth on the spruce,” said Stevens-Rumann, interim director at the Colorado Forest Restoration Institute. Her research team is monitoring several species planted two years ago on a slope burned during the devastating 2020 Cameron Peak fire, which charred 326 square miles (844 square kilometers) in the Rocky Mountains of Colorado. They want to determine which species are likely to survive at various elevations, because climate change makes it difficult or impossible for many forests to regrow even decades after wildfires. As the gap between burned areas and replanting widens year after year, scientists see big challenges beyond where to put seedlings. The U.S. currently lacks the ability to collect enough seeds from living trees and the nursery capacity to grow seedlings for replanting on a scale anywhere close to stemming accelerating losses, researchers say. It also doesn’t have enough trained workers to plant and monitor trees. The Forest Service said the biggest roadblock to replanting on public land is completing environmental and cultural assessments and preparing severely burned areas so they’re safe to plant. That can take years — while more forests are lost to fire. “If we have the seedlings but we don’t have the sites prepped … we can’t put the seedlings out there,” said Stephanie Miller, assistant director of a reforestation program. Scientists, private industry and environmental agencies are acutely aware of the challenges as they consider how to restore forested landscapes in an increasingly arid region. “We need to start being creative if we want trees on our landscapes,” Stevens-Rumann said. “We’re in a place of such drastic climate change that we are not talking about whether or not some of these places will be a different kind of forest, but whether or not they will be forests at all.” Reforestation gap Four years after the Cameron Peak fire — the largest in recorded Colorado history — a smattering of wild raspberry bushes and seedlings has taken root. But the mountainside mostly is dotted with charred trees. In burn scars across the West and Southwest, areas of forests may never grow back on their own. Larger and more intense fires destroy trees that normally provide seeds for regeneration or leave burn scars so large trees can’t naturally bridge the gap. The climate also has changed so markedly that many forests can’t regrow in the same places. Even when seedlings take hold, drought and new fires often kill them. Nineteen of the 20 largest wildfires ever recorded in the contiguous U.S. have occurred in Western states since 2000, according to Sean Parks, a Forest Service research ecologist. That’s when the region slipped into an ongoing megadrought. The U.S. once was able to reliably replant burned forests. But now the gap between areas in the West that need replanting after fire and the ability to do so has grown to at least 3.8 million acres (1.5 million hectares) — and that could triple by 2050, said Solomon Z. Dobrowski, a University of Montana forest management expert and a study lead author. Forests are burning more often and especially intense and hot, which can destroy seeds that normally survive fire, harden the ground like concrete and leave barren slopes susceptible to washing away in rainstorms, polluting waterways. In 22 years since the Hayman fire on Colorado’s front range burned 182 square miles (471 square kilometers) of forest, there has been almost no tree regeneration in the most severely burned areas, researchers and the Forest Service said. In California’s Sierra Nevada, where up to 20% of the world’s mature giant sequoias and their seeds have been killed by fire in recent years, there are massive openings without seedlings. A U.S. Geological Survey study concluded some groves will never recover without replanting. But researchers say the odds of forests growing back will worsen regardless of fire intensity because of more heat and drought. That means burned forest could convert to shrubland and grassland, leading to loss of snowpack that provides drinking water and helps irrigate crops. “Over 70% of our water in the western U.S. comes from our forested ecosystems and our mountains,” Stevens-Rumann said. “And for that water to come the way we want it … at the right time throughout the year, we need to have forests, not just grasslands.” Targeted tree planting When forest ecologist Matthew Hurteau joined the University of New Mexico nine years ago, he took in the aftermath of the 2011 Las Conchas fire that decimated a huge swath of Ponderosa pine forest. Though the area had been replanted several times, most seedlings died, Hurteau said. While the average survival in the Southwest is about 25%, he said only about 13% of trees planted most