Extinction risk to herring gull populations from DDT exposure

摘要

The impact of toxic chemicals on wild animals and plants can be quantified in terms of the enhanced risk of population extinction. To illustrate the method, we estimated it for herring gull(Larus argentatus) populations in Long Island(NY, USA) exposed to DDT(p, p'-dichlorodiphenyltrichloroethane)and its metabolites(abbreviated as DDTs) with a strong biomagnification effect. The method is based on a formula of the mean time to population extinction derived for a stochastic differential equation (the canonical model). The intrinsic rate of natural population growth was estimated from the doubling time of an exponentially growing population and the intensity of the environmental fluctuation from the magnitude of population size fluctuation.