Mangroves and Tropical Coastal Ecosystems

Mangroves are salt-tolerant trees and shrubs, drawn from some 70 to 80 species across roughly 20 plant families, that colonize the intertidal zone of tropical and subtropical coastlines where few other woody plants can survive prolonged exposure to saltwater and waterlogged, low-oxygen sediment. Genera such as Rhizophora, the red mangroves, with their distinctive arching prop roots that lift the trunk above the highest tides, and Avicennia, the black mangroves, which instead send up pencil-like breathing roots called pneumatophores through the mud to obtain oxygen, illustrate two of the several independently evolved physiological solutions to the same basic problem of rooting in salty, anoxic mud while remaining regularly submerged. Using globally consistent satellite data, Chandra Giri and a team of co-authors estimated in their widely cited 2011 paper in Global Ecology and Biogeography that the world's remaining mangrove forests then covered approximately 137,760 square kilometers across 118 countries, with the largest single share found in Asia, followed by Africa and the Americas.