Coral reefs are the world's most biologically rich marine ecosystems, harboring some of the world's most beautiful organisms. They provide the principal source of protein for over ten million people worldwide. Reef-based activities (principally fishing and tourism) form the economic livelihood of millions more. Clearly, the human costs of a worldwide breakdown of these ecosystems are enormous.
Yet global deterioration of coral reefs is severe and ongoing. Wholesale disintegration of reef ecosystems has occurred in some places, and collapse on a worldwide scale is a real risk.
But there is some good news, too: we know what steps the international community can take now to protect and restore reefs' ``resilience''-- their capacity to maintain integrity in the face of the environmental fluctuations that are a natural part of life in any ecosystem. We must mediate the severity of global warming, while simultaneously conserving the resilience of coral reefs.
Historically, the principal agents of reef degradation have been over-fishing and pollution, not global warming. In healthy ecosystems, when prey numbers decline, predators become malnourished, and their numbers decline, too, giving their prey a chance to recover. But human predators are different. When our prey numbers decline, their economic value tends to increase, so fishing intensifies. This means that once predator species become depleted, fishing pressure shifts towards plant-eating fish species, leading to precipitous declines in the numbers of herbivores on coral reefs.