Resilience of native amphibian communities following catastrophic drought: Evidence from a decade of regional-scale monitoring

The increasing frequency and severity of drought may exacerbate ongoing global amphibian declines. However, interactions between drought and coincident stressors, coupled with high interannual variability in amphibian abundances, can mask the extent and underlying mechanisms of drought impacts. We synthesized a decade (2009-2019) of regional-scale amphibian monitoring data (2273 surveys, 233 ponds, and seven species) from across California's Bay Area and used dynamic occupancy modeling to estimate trends and drivers of species occupancy. An extreme drought during the study period resulted in substantial habitat loss, with 51% of ponds drying in the worst year of drought, compared to 20% in pre-drought years. Nearly every species exhibited reduced breeding activity during the drought, with the occupancy of some species (American bullfrogs and California newts) declining by 25%. Invasive fishes and bullfrogs were also associated with reduced amphibian occupancy, and these taxa were locally extirpated from numerous sites during drought, without subsequent recovery- suggesting that drought may present an opportunity to remove invaders. Despite a historic, multi-year drought, native amphibians rebounded quickly to pre-drought occupancy levels, demonstrating evidence of resilience. Permanent waterbodies supported higher persistence of native species during drought years than did temporary waterbodies, and we therefore highlight the value of hydroperiod diversity in promoting amphibian stability.

Automated summary

The study found that drought resulted in substantial habitat loss for amphibians in the Bay Area of California, with almost every species exhibiting reduced breeding activity during the drought. Invasive species and bullfrogs were associated with reduced amphibian occupancy, suggesting that drought may offer an opportunity to remove invaders. Despite a historic multi-year drought, native amphibians quickly rebounded to pre-drought occupancy levels, demonstrating evidence of resilience.