Global environmental change is occurring so rapidly that it is affecting the health and threatening the future of many of Earth's inhabitants, including human beings. Global warming; contamination of the air, water, and soil; and rampant deforestation have led to a collapse in biodiversity that threatens the integrity of the biophysical systems upon which all organisms depend.A basic cause of environmental degradation is human overpopulation and the nonsustainable consumption of natural resources by the human community. Everything that we have accomplished in the fields of medicine and public health could be undermined if we do not pay attention to these rapid environmental changes. As healers, human beings, and members of the biological community, we need to broaden our perspective on health and disease. Unless we devote our attention to stabilizing and repairing the ecosystem, our professional and personal accomplishments as health professionals may be swept away. Health care providers--particularly physicians--can play a role by adopting an ecosystem health perspective as we ply our trade. By helping people avoid unwanted pregnancies, by using resources parsimoniously, and by staying engaged in the natural world, we can help to prevent the collapse of the biological systems upon which we all depend.