Most land plants are killed by salt, but mangroves are able to get rid of the salt. Most plants die if their roots are drowned in water and have no oxygen, and in the mud of mangrove swamps, the rotting leaves usually use up all the oxygen. However mangrove trees have developed special kinds of roots that stick up out of the mud into the air to get oxygen. In the Pacific, the number of kinds of mangrove trees is greatest in the west, and gets smaller going to the east across the Pacific until the mangroves disappear. Mangrove forests in the western Pacific and Indian Ocean are bigger and richer, with different kinds of mangroves growing under different conditions.
Mangroves are also very important in the Caribbean.
Most people have thought of mangroves as noxious impenetrable swamps full of diseases, and they used to be destroyed as a public health measure, but now we know better. Mangroves are very productive coastal resources that are useful in many ways. Mangrove trees grow well in their special conditions, and, like the tropical forest, they produce a lot of leaves and other organic matter. Instead of accumulating in the soil, the leaves fall in the water, where they rot and provide food for microbes and many tiny animals. This rich food is not only eaten in the mangrove swamp, but much of it may be carried out into the lagoon or to coral reefs and other coastal fisheries areas, where it helps to feed the fish.