Biodiversityand Human Health
The extinction of species may be the most destructive and permanent of all assaults on the global environment, for it is the only one that is truly irreversible (Wilson 1989). While species stocks may recover following mass extinction events over the course of millions of years of evolution (Myers et al. 2000), and may fill ecological niches that had once been occupied, it must be understood that these replacing species are new ones and that the unique information encoded by the DNA of the lost species is gone forever. This fact adds to the gravity of the current extinction crisis, the first that is the result of human activity.
Many have looked at the question of what will convince people to alter their behavior so as to preserve other species. Clearly, spiritual, ethical, and aesthetic values, as well as economic factors, are powerful motivating forces. But it may be argued that these considerations are not persuasive enough to result in any significant changes in personal behaviors or public policy, that they are too abstract and hard for most people to relate to, and that it will take an understanding of the direct, concrete, and personal risks to peoples' health and lives, and particularly to the health and lives of their children, for them to be motivated enough to protect the global environment. Such is the goal of this chapter—to present in summary form the potential human health consequences of species loss and the resultant disruption of ecosystems, to demonstrate that human health is inextricably linked to the health of the global environment, to make clear the central message of this new field of conservation medicine—that “man is embedded in Nature” (Thomas, 1974).
When Homo sapiens evolved some 120,000 years ago, the number of species on the earth was the largest ever (Wilson 1989), but human activity has resulted