What makes coral reefs valuable?

Biodiversity: Coral reefs are essential spawning, nursery, breeding, and feeding grounds for numerous organisms. In terms of biodiversity, the variety of species living on a coral reef is greater than in any other shallow-water marine ecosystems and is one of the most diverse on the planet, yet coral reefs cover less than one tenth of one percent of the ocean floor. Coral reefs support more than 800 hard coral species and more than 4,000 species of fish.
 

Coastal Protection: Healthy coral reefs have rough surfaces and complex structures that dissipate much of the force of incoming waves; this buffers shorelines from currents, waves, and storms, helping to prevent loss of life, property damage, and erosion.  Coastlines protected by reefs are more stable, in terms of erosion, and are also a source of sand in natural beach replenishment