The global extinction crisis rivals global warming in its magnitude, urgency, and monumental implications for human health and welfare. Extinction is irreversible, and is now happening at a breakneck pace: across the globe, between one and 100 species are becoming extinct every day. The natural "background" rate of extinction is only one species per 100 years.
Species loss signals a potential risk to humans as well as to animals and plants. More sensitive animals -- those that fill highly specialized niches, require large tracts of undisturbed land, or breed slowly, for instance -- are the first to suffer from habitat loss, pollution, and other drastic human-induced changes. In time, as the food chain collapses, animals further up will also suffer -- including humans.
Species populations can be revitalized if serious efforts are made. For instance, the California brown pelican -- like the bald eagle -- was seriously affected by the use of DDT, which weakened the bird's eggshells so that they cracked during incubation. With the banning of DDT and other toxic pesticides, the brown pelican population is slowly rebounding. Closer to home, the South Bay's fragile population of California clapper rails has rebounded in the past decade, climbing from between 200 and 300 in 1991 to an estimated 600 to 700 in 1999 as a result of controls on invasive species.
Bay Area Biodiversity
The Bay-Delta region is one of the most biologically diverse and severely stressed ecosystems on the West Coast. With the most extensive coastal wetlands south of Alaska and the largest estuary on the American Pacific, the Bay Area is home to a vast but shrinking array of plants and animals. Loss of habitat as a result of development, along with invasive species, water diversions, agriculture, and pollution, are the prime factors driving many species toward extinction.
Wetlands loss has taken a heavy toll. More than half of the endangered species that inhabit San Francisco Bay depend on wetlands to survive, including the California clapper rail and salt marsh harvest mouse. Local fish species on the federal endangered and threatened list as the result of water diversions from the Bay-Delta estuary include the winter-run chinook salmon and the Sacramento splittail. The Alameda whipsnake, listed as threatened in 1997, has seen its numbers and habitat decimated by urban sprawl.
Preserving continuous open space and extensive wildlife habitats, improving water flows in the delta, and protecting and restoring wetlands are among the most important steps that must be taken to halt species loss.