The environmental law firm Earthjustice filed suit against the U. S. Fish and Wildlife Service on behalf of the Center for Biological Diversity and Pacific Rivers Council, organizations that petitioned to list the species under the ESA in February 2000. In January 2003, the service published a "warranted but precluded" decision, agreeing that the mountain yellow-legged frog warrants listing as an endangered species, but claiming listing is precluded by "expeditious progress" being made on listing of other species.
Center for Biological Diversity spokesperson Jeff Miller called the service's decision, "An obviously political and callous delaying tactic that is a recipe for extinction of the frog. Considering their terrible track record on Endangered Species Act enforcement -- not a single species listed that wasn't a result of environmental lawsuits or petitions -- the Bush administration can hardly point to 'expeditious progress' in protecting endangered species."
Noting the frog survives in as little as 10 percent of its original range in the Sierra Nevada, Deanna Spooner of the Pacific Rivers Council wondered, "How much more endangered does a species have to become before the Fish and Wildlife Service will take action? The intent of the Endangered Species Act is being subverted through administrative delay, sentencing the mountain yellow-legged frog and other species in need of immediate protection to extinction through inaction."
Miller characterized the warranted-but-precluded designation as a "regulatory purgatory" for endangered species, noting the average length of time a species remains on the list before receiving ESA protection is about 17 years. Species placed on the "warranted but precluded" list receive no legal protection, nor is there any limit on how long they may be left on the list.
The service has attempted to blame litigation and court orders to designate critical habitat as an excuse for delaying listing of vanishing species.
"The service's own scientists admit that the frog will soon be gone forever unless it receives protection, but the political appointees say the agency too busy with other priorities to do anything," said Greg Loarie an attorney with Earthjustice who is representing conservation groups. "It's pretty clear that the appointees don't consider protecting imperiled species to be much of a priority at all, because citizen lawsuits are the only way they'll do anything these days."
The mountain yellow-legged frog was historically the most abundant frog in the Sierra Nevada, ranging from southern Plumas County to southern Tulare County, at elevations mostly above 6,000 feet. In 1959, Dr. David Wake, a herpetologist with the U.C. Berkeley Museum of Vertebrate Zoology, reported so many of the frogs near Tioga Pass that, "It was difficult to walk without stepping on them." Surveys 30 years later revealed that the frogs were gone.
The service acknowledges that the frog has disappeared from the vast majority of known historical locations in the Sierra Nevada and that many of the largest populations have completely crashed in recent years; one of the largest remaining populations containing more than 2000 adult frogs in 1996 had been reduced to only two frogs by1999. Particularly disturbing are recent frog surveys in relatively pristine areas of the Sierra Nevada in the John Muir Wilderness and Kings Canyon National Park that revealed an alarming decline of more than 40 percent in the last five to seven years alone. At this rate of decline, scientists are predicting that the frog will become completely extinct in the Sierra within decades.
The species is thought to be declining primarily due to predation by non-native trout, stocked in many high-elevation Sierra lakes by the California Department of Fish and Game, which prey upon tadpoles and juvenile frogs. Other causes include habitat degradation due to livestock grazing and the impacts of drought and environmental changes caused by global warming. Disease has ravaged many frog populations recently – factors such as pesticides, acid precipitation, and increased ultraviolet radiation as a result of ozone depletion likely render frogs much more susceptible to disease. Recent research has linked pesticides that drift from agricultural areas in the Central Valley and other airborne chemical pollutants to adverse impacts to native amphibians in the Sierra Nevada; pollutants can directly kill amphibians, interrupt breeding and feeding activity and larval development, and also act as environmental stressors, which render amphibians more susceptible to disease.
The Center for Biological Diversity and Pacific Rivers Council submitted a formal petition to list the mountain yellow-legged frog in February 2000 and subsequently filed suit in May 2001 to compel the service to respond to the listing petition. In December 2001 the FWS was ordered by the Northern District Court to make a final listing determination for the species.