At the edge of oceans, mangrove roots twist and tangle. They are anchors, propping the tropical trees and shrubs upright in the soft sediment and shallow waters of the coastal intertidal zone.
Mangroves flourish in high-salinity waters that would kill most other plants by secreting or excluding salt. Some filter salt through root membranes, letting in only water. Others have specialized leaf glands that secrete the excess salt, discarding it later when the leaves fall.
Mangrove forests are some of the Earth's most valuable and stabilizing ecosystems, providing shelter, food and nursing grounds for land and sea creatures alike.
Some are home to insects, birds, lizards, monkeys and even the occasional tiger. Oysters and barnacles take up residence underwater. Mussels and snails may burrow in the mud. There are even a few cases of tree-climbing crabs.
Mangroves' sturdy trunks and tangled branches brace the shore against storm surges. Their entwined roots stall sediments from washing out to sea. Like other forests, mangroves also play a critical role in carbon sequestration.
There are about 70 mangrove species worldwide, and they range in height from shrub short to skyscraper tall. Some have prop roots cascading down from their branches or shallow, widespread buttress roots for added support.
Those exposed roots also facilitate the transport of oxygen to living tissues. Some mangroves even have aerial roots called pneumatophores that crop up from underground, helping them survive in oxygen-poor, waterlogged soil.
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