Global Short Term Trend: Relatively stable to decline of 30%
Comments: Studies cited by USFWS (2004) indicate that losses of vernal pool habitat (the natural breeding habitat of this species) were about 1.5% annually in the 1980s and 1990s and likely will continue at a similar rate. Assuming a generation time of 8 years (generation time is the average age of parents of the current cohort), the breeding habitat decline (and consequently the population decline) would be roughly 36% over three generations (24 years; see IUCN Red List criteria). Additional reductions due to hybridization, effects of non-native species, and other factors (see USFWS 2004) would increase the extent of population reduction. Hence, a recent/ongoing population reduction of more than 30% over three generations would not be an unreasonable projection.
In Santa Barbara County, of 14 documented breeding sites, half have been destroyed or have suffered severe degradation since mid-1999 (USFWS 2000).
Sonoma County population: in the past two years, four breeding sites have been destroyed or have suffered severe degradation; only seven remain (USFWS 2002).
Global Long Term Trend: Decline of 30-70%
Comments: Eliminated from 55-58% of historical breeding sites; reportedly about 75% of the historical vernal pool breeding habitat has been lost (Holland 1998) (though some question the reliability of this estimate).