Threats to Coral Reefs Around the World
Coral reefs are home to over 25 percent of all marine life and are among the world's most fragile and endangered ecosystems. In the last few decades, mankind has destroyed over 35 million acres of coral reefs. Reefs off of 93 countries have been damaged by human activity. If the present rate of destruction continues, 70% of the world's coral reefs will be killed within our lifetimes.

Major threats to coral reefs include:
Sedimentation
Construction along coasts, inshore construction, mining or farming upstream, or logging in tropical forests causes soil to erode and rush downstream into the ocean and onto coral reefs. This dirt, silt, or sand can make the water cloudy or muddy, smothering the coral which can't get enough light to survive.

Mangrove trees and seagrasses which normally act as filters for sediment are also being rapidly destroyed. This has led to an increase in the amount of sediment which reaches coral reefs. Mangrove forests are often cut for firewood or removed to create open beaches. They are also destroyed by prawn harvesters to open up areas to create artificial prawn farms.

Cyanide Fishing
Commercial fishing fleets often use cyanide and other poisons to stun and capture valuable reef rish. This method is often used to catch tropical fish for aquariums and is now used to capture fish for "live fish" restaurants. This fishing technique poisons not only the fish, but the coral polyps and other creatures in the area as well. In the Philippines, up to 400 thousand pounds of cyanide are sprayed and dumped onto the reefs each year - less than 10% of the coral reefs in this area remain healthy.

Fishing with Explosives
Over-fished reefs and desperate fishermen produce a deadly combination when reefs are dynamited to harvest small fish. Fisherman prepare bombs made out of materials such as potassium nitrate (a common fertilizer) to cause large explosions which kill all the fish in the surrounding area and reduce nearby coral to lifeless rubble.

Water pollution
Petroleum products and other chemicals dumped near coastal waters eventually find their way to the reefs. Oil and gas leaked or spilled near a coral reef poison coral polyps and other marine life. Trash dumped into the water can also kill coral reef life. Plastic bags get caught in the stomachs of turtles and fish, causing them to starve to death. Trash can also cover coral reefs, blocking off the sunlight needed to keep the reefs alive. Lost or discarded fishing nets - called "ghost nets" - can snag on reefs and strangle to death thousands of fish that get caught in them.

Human Run-off
Fertilizers and sewage dumped into coastal waters encourage rapid algae growth which chokes coral polyps, cutting off their supply of light and oxygen. Over-fishing makes this problem even worse because the fish that would normally eat the algae have been captured and killed.

Careless recreation
Careless boating, diving, fishing, and other recreational uses of coral reef areas can cause damage to coral reefs. Dropping anchors onto reefs can crush or break coral. When people grab, kick, walk on, or collect coral, they also contribute to coral reef destruction.

Collection and Dredging
Removing coral to be used for construction material or sold as souvenirs also threatens coral reefs, as does the dredging and dynamiting of coral for construction in coral reef areas.


Global warming
Coral reefs are also threatened by global warming. There has been an unprecedented increase in the number of coral bleaching events during the past 2 decades (which have had some of the warmest years in history). When ocean temperatures get too high, coral polyps lose the symbiotic algae inside them, causing them to turn white, or "bleach," and eventually die.

Global warming trends may also lead to more extreme and unpredictable weather. An increase in tropical storms could do extensive physical damage to coral reef ecosystems. Rising sea levels may become a serious threat to coral reefs and to small island nations based on coral reef atolls.