The majority of California's unique plant species could lose most of their geographic ranges during the next 100 years because of climate change, according to a newly released report by biologists at several universities. The finding could have dramatic implications for land management in California, especially in areas with local or regional habitat plans.
The first-of-its-kind study projects that up to two-thirds of endemic plant species (plants that grow nowhere except California) will experience geographic range reductions of up to 80% within a century because of changing weather patterns. Many endemic species will migrate north or to higher elevations. For example, oak trees may disappear from Central California but find hospitable ground near the Oregon border. Plants that disappear from the San Diego, Los Angeles and Central Valley regions may be replaced with desert plants from Baja and the Sonoran Desert.
David Ackerly, an ecologist at University of California, Berkeley, and the study's chief author, conceded that he is not overly familiar with habitat conservation plans. But he said he would expect to see conflicts between shrinking plant ranges and the conservation plans' assumptions and techniques.
"The word restoration loses its value because restoration has backward-looking connotation," Ackerly said. "With climate change, we're saying we're going to a future that is unknown."
Since 1982, about 150 habitat conservation plans (HCPs) have been adopted in California. These plans are aimed at preserving the viability of anywhere from one to scores of endangered or threatened species, and they cover anywhere from a few hundred acres to thousands of square miles. In addition, California has 32 natural communities conservation plans (NCCPs) that seek to conserve entire ecosystems. Some of the most recently adopted conservation plans serve as both HCPs and NCCPs and cover broad areas. The plans typically are intended to guide conservation practices — as well as urban development — for 50 to 100 years.
However, Michael Beck, who heads the Endangered Habitats League's San Diego office, said he knows of no HCP or NCCP that accounts for climate change. The effects of climate change may force the re-examination of some plans, he said. Although the plans typically contain "no surprises" provisions that limit additional regulation on private landowners, the plans may be revisited if there are extraordinary circumstances or if monitoring finds the plans are failing, he said.
Work on Western Riverside County's multiple species habitat conservation plan began in 2000 and the plan was adopted in 2004 — a period during which climate change was a niche topic. "At the time, we weren't looking at a relationship between endemic plants and climate change," conceded Charles Landry, executive director of the Western Riverside Regional Conservation Authority.
Still, he said, the plan can respond to climate change. The plan defines large core areas with linkages among them, permitting species to move around. In addition, the plan requires extensive monitoring and allows for "adaptive management" techniques, he said.
"As we go through the management piece, we need to see what wildlife and plants are doing," Landry said. "For example, are we seeing more Quino (checkerspot butterfly) migration to higher areas because it is cooler? That could have a major impact on the plan."
The climate change study, Beck added, provides further backing for environmentalists' long-held contention that "bigger is better" in land conservation efforts, and that saving small slices of habitat on the margin is the wrong approach.
Ackerly insisted that much more study needs to be done. Researchers developed a model, but people should be very careful about basing land management decisions on the model at this point. The model might be helpful at the county or regional level, but probably not when managing a particular site, he said.
Ackerly said he hopes to convene a group of public and private land managers in an effort to determine what information would help the managers respond to climate change. "All planning around future biodiversity needs to take into account climate change," Ackerly said.
"I would say we're in a transition period," offered Beck. "The psychology of the implications of climate change are so overwhelming to people that it can almost make them freeze."
David Ackerly, UC Berkeley Department of Integrative Biology, (510) 643-6341.
Charles Landry, Western Riverside County Regional Conservation Authority, (951) 955-9700.
Michael Beck, Endangered Habitats League, (619) 846-3003.
"Climate Change and the Future of California Endemic Flora": www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0002502
Department of Fish & Game NCCP website: www.dfg.ca.gov/habcon/nccp
'A Sobering Picture'
The paper "Climate Change and the Future of California's Endemic Flora" was published June 25 on the PLoS One website, an online, peer-reviewed scientific journal. Lead author David Ackerly of UC Berkeley's Department of Integrative Biology was assisted by professors from Berkeley, Cal Poly San Luis Obispo, Texas Tech and Duke.
Here is an excerpt regarding land management:
"These results present a sobering picture of the potential impacts of climate change on California's diverse and distinctive flora. The severity of projected impacts is closely linked to the magnitude of climate change. That, in turn, depends crucially on human emissions of greenhouse gases over the next few decades. The projected impacts are also very sensitive to the potential rate of plant movement, and rapid dispersal could mitigate much of the impact on individual species and overall diversity. However, rapid movement by natural dispersal is unlikely on a century time-scale, except for weedy species with short generation time and highly dispersable propagules. Human assisted dispersal must be considered as a critical component of conservation and biodiversity management in the next century.
"The results of this study present a dilemma for conservation planning in the face of climate change. Future diversity will likely peak along the coast and to the north of its present concentrations. These areas are sensible priorities for conservation. Some areas of high diversity, however, will be comprised of species expanding their ranges, and these species may not represent important targets for conservation efforts.
"Areas that are projected to harbor species with shrinking ranges, on average, include many mountainous areas scattered across the study area. We identify these areas as refugia that may disproportionately contain the most ‘threatened' species. These ‘future refugia' present valuable opportunities as conservation targets. They may protect significant components of biodiversity into the next century. The number of species projected to survive in these refugia depends critically on the ability to disperse, highlighting the importance of landscape connectivity and potential restoration in the face of increasing urbanization, land use change and disturbance."