When the U.S. Fish & Wildlife Service proposed in September that 5.4 million acres in 31 California counties be designated critical habitat for the threatened red-legged frog, howls of outrage came from nearly every corner of the state. Builders, water agencies, local government officials and farmers decried the designation as an impending disaster with dire implications for everything from construction of affordable housing to the integrity of Southern California's precarious water supply. The volume of criticism prompted the agency to postpone the deadline for formal designation of frog habitat by two months to March 1. The scale of the proposal alone would have been sufficient to draw harsh criticism. But the frog decision was merely one of 11 habitat designations or proposals to have been issued by USFWS since early summer. That might not sound like many until you consider that only 134 of the 1,234 federally listed species have received critical-habitat designations in the 27 years since passage of the Endangered Species Act. What's more, many of the habitat designations and proposals this year were of unprecedented scale. Although USFWS issued several modest proposals pertaining to species that occur in populations of limited geographic range, other proposals were huge: 405,598 acres for the Alameda whipsnake; 513,650 acres for the coastal California gnatcatcher; 876,000 acres for the peninsular bighorn sheep; 478,400 acres for the arroyo southwestern toad. There are several reasons for the unusual congruence of habitat decisions over the past six months, as well as for their unusual scale. Some of these reasons are obvious while others are not. It is worth examining the reasons because of the insight they can provide into the economic, political, ecological and demographic forces colliding in California today. First, however, it is necessary to examine precisely what it means for the federal government to designate critical habitat. In most cases, the USFWS action is neither as protective of species as environmentalists hope nor as great an impediment to economic activity as landowners and business groups claim. The Endangered Species Act establishes three significant mechanisms for protection and recovery of an imperiled creature: listing, creation of a recovery plan and designation of critical habitat. The listing process is by far the most important from a regulatory standpoint. Once the federal government lists a species as endangered or threatened, it receives immediate protection under Section 7 of the Endangered Species Act. In general terms, this requires the federal government to ensure that no harm comes to that species or to its critical habitat, an admonition typically carried out through a process known as "consultation." Any federal agency that issues a permit required for any public or private activity — filling a wetland or altering a streambed, for example — is required to consult with USFWS or the National Marine Fisheries Service in advance of issuing that permit, to make sure it will not authorize an activity that puts a listed species in jeopardy. In addition, species listed as endangered immediately come under the protection of Section 9 of the act, which prohibits any "take" of that species — a term defined to include killing, harassing or harming individual animals or plants. (Threatened species do not automatically qualify for such protection, although the agency may extend it administratively.) The U.S. Supreme Court has ruled that the "take" prohibition can apply also to activities that destroy a listed species' habitat. Once a species has been listed as endangered (in danger of extinction in some or all of its range) or threatened (likely to become endangered in the near future), the ESA requires the federal government to develop a recovery plan. It must describe actions that will restore the species' long-term viability and allow the species to be removed from the list. The law also requires the designation of critical habitat "to the maximum extent prudent and determinable." Critical habitat is defined as specific locations within the geographic area occupied by a listed species that contain physical or biological features essential to the species' conservation. Critical habitat also includes specific locations outside the area occupied by the species at the time of listing that are determined to be essential to species' survival. From a regulatory standpoint, designation of critical habitat means little. Even in its absence, private landowners are prohibited by law from killing or harming endangered species, or destroying their habitat. And the ESA's consultation requirements apply to all federal permitting activities on private and public land regardless of whether that land falls within a critical habitat delineation. In other words, critical-habitat designation will not stop any development project that would not already have been blocked simply because it would have harmed a listed species. The habitat designation also does not impose any restrictions on use of land that has been so modified that it no longer constitutes viable habitat — urban areas, suburban back yards, most farmland. It also is unlikely that critical-habitat designation will lengthen the time it takes for applicants to get projects approved under the ESA consultation process or California Environmental Quality Act review. Again, the actual or suspected presence of an endangered species compels the same level of scrutiny, regardless of whether critical habitat has been designated. Federal agencies have been somewhat slow to complete the listing process because a backlog of candidate species, partly the result of an 18-month congressional moratorium imposed in 1995, continues to await evaluation. Agencies have been even slower to adopt recovery plans (only about half of all listed species have such plans) and to designate critical habitat. In general, USFWS and NMFS are required to undertake these steps at the time a species is listed: as a practical matter, the agencies frequently have resisted unless forced to do so. This is precisely what is happening in California: Nearly all the recent or pending habitat proposals are the result of court orders or settlements of lawsuits, most involving the Center for Biological Diversity. The Center, based in Tucson, Arizona, has targeted California ecosystems for protection through its Golden State Biodiversity Initiative. Its strategy has been to file lawsuits to compel listings for candidate species, and then to follow up with additional lawsuits to force designation of critical habitat. The Center has been extremely successful, having won ESA protection for 80 species and securing proposals to designate 7.3 million acres of critical habitat. In essence, the Center has taken control of the federal species-conservation agenda in California. It is not fair to blame the federal agencies alone for their tardiness in complying with the ESA. Acquiring the detailed data on distribution, abundance, behavior, interactions with other species, threats from human activity, ecosystem integrity and other factors required to devise a blueprint for recovery and to designate critical habitat takes time and money. But a hostile Congress in recent years has withheld funding in this area. In fact, property rights advocates in Congress have sought repeatedly to hamper NMFS and USFWS efforts to identify endangered-species habitat on private land by removing funding for such inventories from agency budgets. Now those efforts have backfired. Forced by litigation to identify critical habitat for threatened or endangered species — but frequently unable to acquire the detailed information required to precisely delineate those areas truly essential for the species' survival — USFWS has proposed or designated very general areas. In a sense, the farmers, developers and builders who have been so effective in persuading their congressional representatives to beggar the habitat-inventory process have only themselves to blame for these expansive designations. Imprecise data is not the only likely reason the recent habitat proposals have been so broad. The possibility with greater long-term significance relates to human population growth and urban development patterns. Several of this year's habitat proposals have been the sort to which Californians are accustomed: small areas for unusual creatures that never were widely distributed: 10,560 acres in Santa Cruz County for the Zayenta band-winged grasshopper; 2,566 acres in San Luis Obispo County for the Morro shoulderband snail; 4,025 acres in San Diego and Orange counties for the San Diego fairy shrimp. It is an axiom of conservation biology that small, geographically restricted populations are more vulnerable to habitat-altering catastrophe, whether that comes at the whim of nature (a volcanic eruption, for example) or at the hands of man (construction of a shopping mall). Such creatures are disproportionately represented on the endangered-species list. The conversion of California's natural landscape to farms and cities has had dire implications for geographically restricted species. But as the human population continues to grow and urban development spreads into new areas— the high desert, the Sierra foothills, rugged coastal mountains — even species that once occupied vast geographic ranges are in trouble. The red-legged frog, for example, may have been the most widely distributed amphibian in the state. At one time, the frog was common in nearly every low-elevation drainage between Redding and Baja, from the Sierra foothills to the sea. It has been eliminated from 70% of its range, and is found primarily in Monterey, San Luis Obispo and Santa Barbara counties. According to USFWS, only four areas within the entire historic range of the species harbor more than 350 adults. Regardless of litigation, political attacks on the ESA and the outraged complaints of developers and farmers, human population pressure will continue to intensify threats to California's nonhuman inhabitants. The pace and extent of habitat designations the state has seen in the past six months probably are but a preview of the future. Contacts Center for Biological Diversity, (520) 623-5252. U.S. Fish and Wildlife Service, California-Nevada Operations Office: (916) 414-6600.