Abstract
We used data from over 100 countries to investigate the link between numbers of threatened species and per‐capita gross national product. We corrected for factors that might otherwise confound such a relationship. Our study was motivated by the continuing debate over the relationship between environmental degradation and per‐capita income. Proponents of the environmental Kuznets‐curve hypothesis argue that although environmental degradation may increase initially, increases in per‐capita income will eventually result in greater environmental quality. Theoretical objections and the lack of widespread empirical evidence recently have thrown doubt on the existence of such a pattern. Treating threat to biodiversity as one potential indicator of environmental degradation, we divided threatened species into seven taxonomic groups ( plants, mammals, birds, amphibians, reptiles, fishes, and invertebrates) and analyzed each group separately. Count‐data regression analysis indicated that the number of threatened species was related to per‐capita gross national product in five of seven taxonomic groups. Birds were the only taxonomic group in which numbers of threatened species decreased throughout the range of developed countries' per‐capita gross national product. Plants, amphibians, reptiles, and invertebrates showed increasing numbers of threatened species throughout this same range. If these relationships hold, increasing numbers of species from several taxonomic groups are likely to be threatened with extinction as countries increase in prosperity. A key challenge is to understand the interactions among consumer preferences, biology, and institutions that lead to the relationship observed for birds and to see whether this knowledge can be applied to conservation of other taxa.