Biological diversity, ecology, and global climate change.

Worldwide climate change and loss of biodiversity are issues of global scope and importance that have recently become subjects of considerable public concern. Unlike classical public health issues and many environmental issues, their perceived threat lies in their potential to disrupt ecological functioning and stability rather than from any direct threat that may pose to human health. Over the last 5 years, the international scientific community and the general public have become aware of the implications that atmospheric warming might have for world climate patterns and the resulting changes in the persistence, location, and composition of ecosystems worldwide. At the same time, awareness of the magnitude of current and impending losses of the world's biological diversity has increased. Human activities are currently responsible for a species loss rate that is the most extreme in millions of years, and an alarmingly increasing rate of transformation and fragmentation of natural landscapes. We are just beginning to grasp the meaning of this loss in terms of opportunity costs to human society and the less quantifiable losses associated with simplification of natural ecosystems. In the case of both global warming and reduction of biological diversity, man is affecting nature in an unprecedented fashion, on a global scale, and with unpredictable and frequently irreversible results.