Fishing

• According to Ocean World, fishing in coral reefs has destroyed the coral reefs. Fishermen chuck sticks of dynamite into the water and, when the explosives go off, scoop up the stunned fish. Yet, the dynamite also kills the coral and other life and leaves living organisms without their habitat. Fishermen also use poisons, such as cyanide, to catch fish. Ocean World reports that the poison can kill 90 percent of the fish as well as the reefs.
  
  

Warming Water

• Increasing ocean temperatures, which Ocean World attributes to global warming, have led to coral reef bleaching, which is a tell-tale sign of coral death. The algae that live in coral give it color. When coral bleaches, that means the algae have died or left the reefs. The warmer waters have also caused a harmful kind of algae that kills coral by covering it and blocking it from the sun.
  
  

Pollution

• The Coral Reef Alliance reports water pollution as one of the leading causes of coral reef degradation. Oil, pesticides and fertilizers are a few of the chemicals that people have pumped into the oceans that are killing coral and other aquatic life. The chemicals cause nitrogen levels to increase in the water, fostering the growth of harmful algae. Floating trash can also block sunlight from reaching reefs. Sea turtles occasionally mistake plastic bags for jellyfish and eat them, causing them to block the reptiles' digestive tracks and they starve to death.
  
  

Coastal Development

• The Coral Reef Alliance reports that coastal development is another threat to coral reefs. When people move along costs, construction and other industries, such as farming, lead to soil erosion. The eroded sediments then float over coral reefs and block sunlight. Developers have also built structures, such as piers, at the locations of coral reefs. Development also leads to aforementioned problems like pollution and fishing.
  
  

Tourism

• According to the Coral Reef Alliance, careless tourism threatens coral reefs. Coastal growth has spurred the development of tourist areas around the world. This has led to increased levels of pollution. Tourist attractions, such as scuba diving, have also led to coral loss because people aren't always aware of how fragile reefs are. Curious and unaware tourists may grab a piece of coral to study it, but it dies.
  
  

Consequences

• Extinction of coral and the other species it supports, and economic losses are possible with the loss of coral reefs. More than 1 million species, 25 percent of all marine life, live in reefs, making coral the most inhabited habitat in the world, according to the Coral reef Alliance. The conservation group also states coral reefs provide about $375 billion in income every year. Another loss for people tied to the loss of reefs is protection from nature as coral reefs serve as barriers against tides and storms. Coral also serves as a source for medical discoveries. Scientists have used coral organisms to find treatments for illnesses such as heart disease, ulcers and certain types of cancer.