부산대학교 도서관

A new method to evaluate the extinction risk of natural populations enhanced by exposure to toxic chemicals was proposed. The extinction risk of herring gull (Larus argentatus) in Long Island, NY caused by ∑DDT (p, p'-Dichlorodiphenyltrichloroethane) and its metabolites (called ∑DDT) was calculated. As a top predator, herring gull suffers severely by the biologically concentrated DDT. The canonical model is adopted to evaluate the mean extinction time. The intrinsic rate of growth r is estimated from the doubling time of a fast growing population; the intensity of environmental fluctuation 6e2 is from the magnitude of population size fluctuation. Based on an age-structured matrix model with biological concentration factor and the decrease in fertility caused by the exposure to ∑DDT, we can estimate the decrease in the mean extinction time of herring gull population for different concentration of ∑DDT in the environment. Risk equivalent, defined as the fraction of habitat loss that causes the same decrease in the mean extinction time as a given exposure to toxic chemicals, is very useful in evaluating the ecological risk and in management of toxic chemicals.