1 Changes in Biodiversity and Th eir Consequences for Human Health

Human actions and their eff ects on the environment are indisputably the major forces driving changes in biodiversity at both global and local levels. Human-driven climate change, habitat destruction, invasive species introductions, and nitrogen deposition all result in biodiversity losses (Sala et al. 2000). Some of the general impacts of impover-ished biodiversity include decreased food production, decreased food security, the loss of resources for indigenous medicine, diminished supplies of raw materials for new phar-maceuticals and biotechnology, and threats to water quality (Grifo and Rosenthal 1997). Th ere is general agreement among the scientifi c community that maintenance of natural levels of biodiversity is necessary for proper ecosystem functioning and the provision of ecosystem services (e.g., the benefi ts people receive from nature) to humankind (Chapin et al. 2000; Schulze and Mooney 1994). Research indicates that it is the diversity of biota across the world’s ecosystems that underpins the capacity of the Earth’s ecosystems to provide most of its goods and services (MEA 2003; Rapport, Costanza, and McMichael 1998; Sala et al. 2000; Schulze and Mooney 1994; WRI 2000). However, impacts on human health have largely been focused on direct impacts, such as rising human disease exposure due to increased disease vector populations left unchecked by predators. While such blatant consequences of anthropogenic disruption are important, they represent only a fraction of unwanted outcomes. More subtle and more indirect eff ects have oft en been suggested, but very few rigorous scientifi c studies document explicit links between natural biodiversity, its degradation, and human health. Several authors have addressed the link between biodiversity and ecosystem func