They have survived continental drift and asteroid impacts and ice ages.

But they can and do threaten individual reefs. However, man-induced changes to marine conditions are much more sudden and can cause widepread damage to coral reefs everywhere that make take lifetimes to re-establish themselves, especially since many of the threats are unlike any the coral have had to face before. The reefs are robust to nature, but exceedingly fragile to man on short time scales.

We are not just talking about the coral itself, but the biological communities that evolve around these reefs. We are not threatening just coral species, but whole coral ecosystems. Even the coral itself is not the simple, indestructible cnidarian we may imagine it to be, it is a highly specialized symbiont of a polyp and an algae, highly dependent on its neighbors, even its predators, for its health. It's neighbors, in turn, are highly dependent on the coral.

These delicate communities are the veritable "canaries in the coal mine", indicators of environmental degradation. They also have an effect on many other other ecosystems through organisms that spend only a small but important part of their life cycles there. On a per-cubic kilometer basis, the reefs are a tiny proportion of the volume of marine biosphere, with only a miniscule fraction of its biomass, but they contain the majority of the species. Damage to a reef anywhere has a ripple effect to many other environments and species.

The most important factor to keep in mind is that the reef corals (there are many other corals worldwide which do not create reefs) are tropical water organisms. The tropical seas, because of the low dissolved oxygen content of warm water, are deserts, with very little life. The reefs, along with coastal mangrove forests (also highly threatened by man's activities), are practically the only source of biodiversity and spawning ground on these coasts. Their protection should have the highest priority, far above that given to any mere industrial use.

I am a resident of Florida, and a long time user of its maritime resources, and even during my lifetime I have seen a substantial degradation of its coral and mangrove resources, and the consequences to both sport and commercial fisheries, storm surge protection, water quality, tourism and overall quality of life.
For me, this is not just a question of economic tradeoff, but a personal matter, and a very real economic resource for my community.