Amphibian Population Status on NW California Landscapes: What is the Role of Anthropogenic Disturbance in Declines of Amphibians in No. California

Dr. Hartwell Welsh, Jr

Research Wildlife Ecologist

USDA Forest Service, PSW

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ABSTRACT

WELSH, HARTWELL H., JR.
USDA Forest Service, Pacific Southwest Research Station, Redwood Sciences Laboratory, Arcata, CA 95521
hwelsh@fs.fed.us

Amphibian Population Status on NW California Landscapes: What is the Role of Anthropogenic Disturbance in Declines of Amphibians in No. California

The herpetology grooup at the Redwood Sciences Lab, with assistance from the graduate students in the biology and wildlife departments at Humboldt State Univesity, has been studying the natural history, demography, and landscape ecology of amphibian assemblages in aquatic and terrestrial environments of Northern California for 21 years. A primary focus of our research has been to study the interactions between amphibian biology and human land management practices. In this talk I examine several interrelated themes that have emerged from this work. I discuss both individual species, and species assemblages, whose populaitons have declined on northern California's landscapes in response to anthropogenic natural resource management. Amphibian populations in this region have declined due to detrimental forestry practices, introductions of non-native predators, and manipulations of the natural flow regimes of north coast rivers. I review specific mechanisms that stress species by exceeding their physiological limits, and/or their fixed, evolved thresholds of ecological niche space, to explain three distinct regional amphibian population decline trajectories. I suggest possible modifications to these anthropogenic disturbance regimes that could help reverse on-going declines while still meeting human needs.