At first glance coral reefs may not seem to be of any importance to humans, except as a tourist attraction. However corals do have a large economical value.
Humans rely on the sea for a large proportion of our food. Coral reefs together with mangrove swamps often serve as protection for many species of young fish, which will later move of to the open ocean, they are in effect a nursery ground for these fishes. Some of theses fishes are then caught for food, and thus without the reefs to provide them with a safe environment for growing, there will be less in the open ocean, directly affecting our food supply. Prawns, crabs, lobsters, and various other marine-life that also use mangrove swamps as nursery grounds, are also important to fishing industries.
Eco-tourism is a growing industry and coral reefs are on of the most common destinations for eco-tourist. Eco-tourism is a potentially profitable industry and thus has economic value to the country coral reefs are found in. This is especially important since some places where coral reefs are found in are developing countries, which would need the revenue, generated from the tourist. However this must be undertaken with great care due to the fact that tourist can hasten the demise of corals reefs if they are ignorant.
Coral reefs are also important for education as well as for research purposes. Coral reefs are one of the densest places, in terms of biological diversity, on earth. Thus it is very likely there are yet undiscovered species, which may be of value to us. Scientists have useful chemical compounds extracted from plants found in the rain forest. Reefs could yield the some other form of useful chemicals. Scientists are researching how some reefs inhabitants may help in AIDS and cancer screening.
Coral reefs also help to protect shorelines from strong erosive wave action. Without fringing and barrier reefs to protect, some coastlines would gradually be worn away.
Aside from all these reason, we have a moral obligation to protect reef organism like we do other endangered species on earth. However it is necessary to still educate people about their importance.