What are the primary man-made sources of danger to coral reefs?
On their own, coral can survive for decades, but face a number of threats from humans. Pollution including oil slicks, pesticides, chemicals, heavy metals, and garbage can poison coral polyps. Fertilizer runoff and untreated sewage can introduce added nutrients to coastal ecosystems, promoting algae growth, which can overwhelm and smother the coral polyps. Deforestation can also have a devastating effect on the reefs. When trees are cut down, topsoil washes down rivers into these coastal ecosystems; the soil that settles on the reefs can smother the coral polyps and block out needed sunlight. In addition, coastal development building seaside homes, hotels, harbors can take a heavy toll on coral reefs. So can overfishing in reef areas. Certain fishing techniques, meanwhile, are especially harmful: fishermen using dynamite, cyanide, bleach, and other destructive methods destroyed about half of the coral reefs in the Indo-Pacific region during the 1980s and 1990s. Finally, the internation
