Humans, as part of the web of life, are not immune to events that trigger the extinction of organisms on the profound scale that appears to be currently taking place; and the implications for human health are numerous and diverse. Firstly, there are direct effects: for example, the loss of marine fisheries (over 70 percent of the major commercially fished marine stocks are overexploited and in decline), translates for many communities into a loss of reliable food supplies. This contributes to malnutrition—a rising problem, particularly in developing countries, where an estimated two billion people (approximately one-third of the global population) presently suffers from lack of adequate diet. Malnutrition reduces the longevity of a population both directly and indirectly by weakening the immune system, which renders the population more susceptible to diseases. Another direct impact is the loss of potential biological materials that are useful as medicines, both in traditional medicines and as ingredients in modern pharmacology. The loss of the inventory of biotic resources for medicinal purposes directly threatens human health. Finally, there is the loss of economic opportunity, and the loss of social cohesion that often accompanies a degrading environment. An impoverished socioeconomic condition generally is associated with a host of health threats, including substance abuse and violence.
