Little is known about the lifespan and succession of a coral colony. But it is known that a single coral colony may exist for several decades up to centuries.

As mentioned before the coral polyps have natural enemies which is mainly parrotfishes, butterflyfishes and sea stars, and all these predators feed on the adult stage of the polyp.
Other predators feed on the larval stages that are especially vulnerable to predation.

To understand the following text one must first realize that a coral reef is a fragile community, which can be eliminated within a very short period of time. Within a matter of years a thousand years of community succession can be destroyed, and repairing the damage may be a very long process.

The coral reefs have existed for thousands of years, but lately the coral reefs are facing a new threat: humans. Humans have employed stress on the reef ecology, which may ultimately cause the biggest threat that corals have had to face yet. The following text will briefly summarize all the different ways humans are unintentionally threatening the existence of coral reefs:

General ocean pollution: Atmospheric deposition of unnatural substances (pesticides and other chemicals, heavy metals), accidents (oil hazards) may have disastrous effects on the coral reefs. Some of the substances released have long-term effects to the polyps while others are lethal.
 
Fertilizer runoff and runoff of untreated sewage: The nutrient enrichment from land may cause opportunistic macroalgae to prosper, thus killing the coral polyps by shading.

Deforestation: Deforestation causes an increase in the runoff of sand and mud into the near-shore waters. An increased transport of particulate matter to coastal waters may cause an increased sedimentation of particles on the coral polyps, which may cause shading of the coral polyps.

Fishing with dynamite and cyanide: How brutal this may seem, fishing with dynamite and cyanide is a common way of fishery in the Philippines.

Harvesting of exotic seafood and international seashell and aquarium trades: the harvesting of endangered species no matter what the purpose is may lead them to complete extinction.
    
Tourism: Divers and snorklers that sit on, stand on, handle corals may injure th ecoral polyps. Ordinary boat anchorage may also cause considerable harm to a coral colony when done too often.