Biodiversity takes a hit

October 28, 2007
Wildfires last week have engulfed nearly 360,000 acres of the county, burning the life out of plants and animals that help make the region a jewel of biological diversity.
Massive blazes also render the land less hospitable for humans by increasing the likelihood of future wildfires, debris flows, erosion and water pollution.
“These fires are a staggering tragedy for both people and nature,” said David Hogan of San Diego, a conservation manager for the Center for Biological Diversity, a national environmental group.
“This may be the last straw for endangered species that have already suffered so much habitat loss to development and overly frequent fire.”
Native chaparral and coastal sage scrub in the overlapping burn zones may not recover in time to prevent the spread of fast-growing, non-native grasses. The areas were home to most of San Diego County's more than 40 species listed as threatened or endangered by the federal government.
In addition, grasslands are more vulnerable to wildfires than healthy coastal sage scrub and chaparral. A carelessly tossed cigarette is more likely to ignite the exotic invading grasses than it would the native chaparral.
“The backcountry is converting to a simpler, more weedy, less beautiful landscape than the California most of us moved into,” said Wayne Spencer of the Conservation Biology Institute in Encinitas.
A similar pattern has played out across the West, with virtually every state in the region having to battle the problem.
In areas such as eastern Oregon and the Rockies, native plants repeatedly burned by wildfires cannot regain a foothold because cheat grass and other invaders quickly move in and dominate the terrain.
“It's widespread and it does seem to be increasing,” said Christopher Dionigi, assistant director of the National Invasive Species Council in Washington, D.C.
Russian thistle Even before the latest inferno began Sunday, drought had taken a toll on many of San Diego County's native plants. The dry conditions killed scores of oak trees and allowed bark beetles to finish off weakened pines.
Contrary to popular thought, Southern California is not a desert. Shrubland, a mix of sage scrub and chaparral, is the native landscape for much of the region between the Pacific shoreline and the foothills of coastal mountains.
For instance, nearly 90 percent of the Cleveland National Forest is shrubland rather than coniferous forest.
California has about 8.6 million acres of chaparral, but that figure is declining rapidly. From 1946 to 1987, 1.5 million acres were lost because of urban expansion, ranching and wildfires.
Likewise, development and agriculture have reduced coastal sage scrub to less than 15 percent of its expanse when California became a state.
Coastal sage and chaparral have adapted to withstand periodic fires of 20 to 60 years apart. In fact, the seeds of several native plants need fire and smoke to prepare them to germinate.
“Chaparral requires roughly 20 years or more to recover from a fire to be able to withstand a repeat fire,” said Jon Keeley, a fire ecologist with the U.S. Geological Survey near Fresno.
“The native vegetation typically doesn't recover once it has been taken over by alien grasses.”
Researchers studying the aftermath of the 2003 Cedar fire said pines and other trees in Rancho Cuyamaca State Park are not returning as quickly as originally anticipated.
Several environmentally important parts of the county have been scarred by the latest fires, but ecologists haven't been able to go into those areas to assess the extent of the damage.
Properties that appear to have sustained damage include sections of Palomar Mountain and the Ramona grasslands, Santa Ysabel Open Space Preserve and Volcan Mountain Preserve.
Last week, officials at the South County wildlife refuge were assessing fire damage and planning to keep invasive grasses from taking over on roughly 4,000 burned acres. Their efforts will include replanting native species and using herbicides to knock out unwanted plants.
Advertisement However, ecologists said, limited resources will make it impossible to apply similar measures to most of the county's charred zones.
About 60,000 acres burned in areas set aside for dozens of species under the Multiple Species Conservation Program, said Thomas Oberbauer, who oversees the county's portion of the program. The plan was created in the late 1990s to preserve open spaces while making room for development.
Scott Morrison, an ecologist with The Nature Conservancy in San Diego, said many of the organization's properties in San Diego County have been ravaged in recent days.
“What these fires remind us is that ... we need to make sure that our natural conservation lands are larger than the largest catastrophic fire we face ... so that some places remain unburned and provide a refuge for species,” Morrison said.