Definition (Encyclopedia of Global Warming)
Mangroves are both a genus of tropical and subtropical trees, the Rhizophora, and the family of plants to which the genus belongs, the Rhizophoracae. The term most commonly refers to an assemblage of mangrove trees and other associated trees and shrubs that includes more than one hundred species. Such an assemblage may also be called a mangrove swamp, a mangrove forest, or a mangal.
Mangroves occur in shallow, protected coastal waters, such as flats in intertidal zones, bays, and estuaries in the tropics and subtropics. They cannot survive freezing or even consistently cold water. They are usually canopied forests up to about 10 meters tall, although in rare cases old-growth mangroves can reach 40 meters in height.
Mangroves survive in a difficult niche. They must be salt-tolerant plants (halophytes), and some can thrive in water of twice the salinity of seawater. Mangrove roots can filter salt from water intake, and those growing in the most saline areas excrete salt from their leaves. Mangrove forests shade from the most salt-tolerant species on their seaward side, to the least salt-tolerant species on their landward side, and they shade to conventional forests or freshwater plants.
Mangrove mudflats tend to be oxygen poor (hypoxic), to contain toxic levels of sulfides, to be subject to periodic flooding, and to be very weak for holding trees. Consequently, mangroves have a maze of roots, some of which...
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Significance for Climate Change (Encyclopedia of Global Warming)
Theoretically, mangroves would benefit from global warming, because their tropical climate area would extend farther toward the poles. More mangroves would increase the capture (sequestration) of carbon from atmospheric carbon dioxide (CO2) and help reduce the greenhouse effect. Moreover, increased mangrove buffering of nutrient surges washing off the land would release a steadier gentle flow of dissolved organic compounds, allowing plankton and other marine plants to capture more CO2 from the air and to increase the oceans’ reflectivity. Thus, mangroves would create a significant negative feedback retarding global warming.
In practice, however, the decline of mangroves due to human development may be a significant positive driver of global warming. The percentage of Earth’s surface covered by mangroves has been cut in half (from 0.2 percent to 0.1 percent) in the last century, mostly as a result of human development. For instance, sand dredged from Biscayne Bay, Florida, buried a mangrove swamp and built a city—Miami. Recent increases in shrimp aquaculture have also caused major destruction of mangroves.
Major warming would also raise sea levels, causing mangroves to retreat from the deeper water and attempt to colonize new inland swampy areas. However, people would likely erect dikes to protect existing structures and agricultural land. Hence, the effective surface area available for mangroves...
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Further Reading (Encyclopedia of Global Warming)
Hogarth, Peter J. The Biology of Mangroves and Seagrasses. 2d ed. New York: Oxford University Press, 2007. University of York Lecturer Peter Hogarth provides an excellent introduction to mangroves.
Lieth, Helmut, Maximo Garcia Sucre, and Brigitte Herzog, eds. Mangroves and Halophytes: Restoration and Utilisation. New York: Springer, 2008. This collection of articles is focused on restoration and use of mangroves and other halophytes in the Caribbean area, especially Venezuela.
Saenger, P. Mangrove Ecology, Silviculture, and Conservation. New York: Springer, 2003. Summarizes pertinent mangrove issues, from global biological patterns to threats to methods for restoration.
Sato, Gordon, et al. “A Novel Approach to Growing Mangroves on the Coastal Mud Flats of Eritrea with the Potential for Relieving Regional Poverty and Hunger.” Wetlands 25, no. 3 (September, 2005): 776-779. Briefly summarizes the Manzanar Mangrove Initiative, which seeks to develop methods of culturing mangroves along virtually any tropical coast and of developing agricultural products from mangroves.
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