ABSTRACT
Wetlands are among the worlds richest and most productive ecosystems. They include swamps, marshes, mangroves, lakes and rivers and cover over 2 million square miles. Agriculture is the principal cause of wetland destruction, but the damming of rivers can also disrupt these delicate ecosystems. Grasslands support a wide range of wild animals, in particular birds. Much of the watershed areas of many of the worlds largest rivers are comprised of grassland. Here it performs the vital function of absorbing rainfall into underground aquifers that in turn feed into the river systems. Coral consists of thousands of invertebrate marine animals known as polyps with a hollow, cylindrical structure and a skeleton containing calcium carbonate. The loss of coral reefs is likely to reduce the fish catch of many tropical developing countries, around 25 percent of which comes from reef environments. Where reefs may have acted as barriers against erosion, their destruction may also allow the sea to encroach on coastal regions.
