San Diego, CA, USA — Three years after the largest wildfire in California history wiped out whole forests and disrupted native animals, there are signs the ecosystem is slowly recovering, scientists reported Tuesday.
Several long-term studies conducted after the deadly 2003 Cedar Fire found certain trees and shrubs have re-sprouted while some animals have moved back into burned areas.
“Recovery seems to be good regardless of how severe the fire was,” said Jon Keeley of the U.S. Geological Survey’s Western Ecological Research Center in Three Rivers.
Concerns remain, however. Exotic, weed-like grasses have flourished in some charred forest land, choking off native plants and threatening to displace small mammals.
One of the hardest hit was Cuyamaca Rancho State Park, a 25,000-acre natural oasis 40 miles east of San Diego. The park was temporarily closed to the public after the Cedar Fire roared through, leveling almost all pine and conifer trees. Oak trees were burned from the ground up, but their bases mostly survived.
Researchers from San Diego State University who surveyed the park after the fire reported mixed progress. While chaparral shrubs and native wildflowers sprouted a year after the fire, a rainy season last year also led to an explosion of invasive plants, which could increase future fire hazards.
What’s worse, scientists said, pine trees have failed to regrow. Some fear that without restoration projects, forests will be dominated by oak trees and shrubs for decades to come.
“It’s puzzling why there’s so little regeneration” of pines, said San Diego State biologist Janet Franklin, who presented her study at an international wildfire conference in San Diego.
The Cedar Fire scorched more than 273,000 acres, or 427 square miles, and was historic for its size and intensity. Started by a novice deer hunter who lit a signal fire in the Cleveland National Forest east of San Diego, the blaze was fanned by Santa Ana winds through dry brush and trees. It killed 15 people and destroyed nearly 3,000 buildings including some 300 homes.
Chaparral-loving small mammals driven away by the Cedar Fire are steadily repopulating the burned land, studies show. Using remote cameras, bait stations and traps to monitor the animals, scientists found those that live in dense canopies including the big-eared woodrats, brush mice and California mice declined dramatically a year after the fire.
Both mice populations have since rebounded. But woodrats, which build nests out of sticks, are still scarce.
“Woodrats are not going to go extinct,” said Wayne Spencer, a biologist at the Conservation Biology Institute in San Diego. “But it’s going to take a long time for them to recover.”
The Cedar Fire also disrupted birds’ migratory paths. After the blaze, researchers collected data in the coniferous forests in the Cuyamaca Mountains to record bird species.
“Some birds took advantage of the burned areas while others have been affected and reduced,” said Phil Unitt of the San Diego Natural History Museum.
Nonnative birds such as the mourning dove and house finch immediately flocked to the charred forests once vegetation sprouted. But small nonmigratory birds like the mountain chickadee, California thrasher and pygmy nuthatch that make nests in shrubs or trees fared worse. Their presence decreased after the fire, but scientists were confident they will return.
Past studies focusing on the aftermath of large wildland fires have found that while flames destroy, they also help rebuild the native landscape.
“What we have found is that these systems are very resilient,” said Keeley of the USGS.