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Problems Facing Our Coral Reefs

Coral reefs are hot spots of biodiversity that compare to the rain forests in terms of the number of species they contain. Like the rain forests, the coral reef ecosystems are vulnerable to human activities. The United Nations estimated in a 1998 report that more than half of the world's reefs were under threat. A substantial amount of reef habitat has already been seriously damaged by various mechanisms, all caused by humans.

Bottom Trawling
- Bottom trawling is an unsustainable fishing method that uses heavy nets to dredge the seabed, catching all the organisms in the net's path, not just the target species. It also causes serious physical damage to coral reefs. Growing awareness of how destructive the practice is has led to bans in some places, including large areas of the South Pacific.
Water Pollution
- Algal blooms, which are caused by an excess of nutrients from pollutants, such as fertilizer, sewage and even detergents, are a threat to coral reefs. Other pollutants, including oil and pesticides, are directly toxic to coral animals. Larger members of reef fauna, such as turtles, are vulnerable to plastic pollution. Plastic litter entangles and chokes hundreds of thousands of marine animals a year.
Ocean Acidification
- Some of the increasing levels of carbon dioxide in the atmosphere are absorbed by the world's oceans. The problem with this is that it lowers the pH of the water, making it more acidic. This change in water chemistry causes problems for all kinds of species, notably those with carbonate skeletons. Reef-building corals are among the many species that have such skeletons; in fact this is what reefs are built from. Increasingly acidic water can partially dissolve such skeletons, making it difficult or impossible for the organisms in question to survive. If ocean acidification continues, all the world's coral reefs could be lost.
Climate Change
- The organisms, including the coral animals and their symbiotic algae, in a coral reef are sensitive to even small changes in average temperatures. Climate change has been associated with the widespread coral bleaching events that have occurred since the end of the 20th century. Coral bleaching means that the coral animals have died, leaving only their pale calcium carbonate skeletons.
Coral Harvesting
- These threats might be accidental in nature but coral reefs also face deliberate exploitation. Harvesting of coral and shelled animals for the tourist souvenir trade and fish and colorful invertebrates for the exotic pet trade have decimated the species diversity in some areas.

Nature