Scientists project that at least half of all living species could ultimately disappear due to habitat loss alone, creating a mass extinction on a scale comparable to those that have ended past geologic eras. Apart from habitat loss, other agents of human-caused extinction are now at work. Even more species could disappear as a result of pollution, overhunting, overfishing and inadvertent introduction of exotic species into weakened ecosystems. Hanging over the future of all life is the puzzle of how global climate will change in coming centuries as a result of human influences, and how these changes will affect ecosystems and the species they support. Not all species are at risk, however.
Evolution is resilient.
A small percentage of species from pigeons, to weeds, to microbial parasites have proliferated beyond their pre-human numbers or ranges. Rapidly evolving pests and disease-causing organisms could swell their ranks. Humanity itself, with more than 30 times the population density it ever could have achieved without agriculture, now appears to have become the central organizing reality around which non-human life will evolve. Each of us can take action to preserve the planet's wealth of living species. This report's recommendations are addressed to policymakers, to scientists and conservationists, and to the general public.