Bellwood et al. (2004) provide a review of the status of coral reefs in light of their world-wide decline. Coral reefs are unique ecosystems that are declining in health on a world-wide basis. This decline is due to over-harvesting, pollution, disease, and climate change. Many reefs are being stressed at rates that exceed their regenerative capacity. Reefs are an example of ecosystems that provide humans with "natural" goods and services such as fishing opportunities, tourism, aesthetic and cultural value. Bellwood et al. (2004) provide four recommendations for stemming and possibly reversing this global scale decline.
Reference
Bellwood, D. R., T. P. Hughes, C. Folke, and M. Nystrom, 2004: Confronting the coral reef crisis. Nature, 429, 827-833.