ABSTRACT
In the past, meteors and climate change were the primary causes of extinction. However, recent extinctions are largely attributed to human caused habitat destruction and fragmentation, overexploitation via hunting/fishing/gathering, the introduction of alien species, pollution, and disease. These extinctions arise from a tragedy of the commons that results from a lack of well-defined property rights and from market prices that do not reflect the true marginal social costs and benefits of an action. The introduction of exotic species arises as exploration and trade occurs and specimens are introduced deliberately or accidently as stowaways or hitchhikers. For instance, bubonic plague was carried into the United States by rats on trading ships arriving from Asia. The plague became manifest in prairie dog colonies and contributed to the decline of both prairie dogs and the endangered black-footed ferret. Another example is the Burmese python which has populated the Everglades after being released into the wild by pet-owners. With no natural predator, the python population has grown rapidly and caused precipitous declines in rabbits, bobcats, and a host of birds in the Everglades.
