What is a mangrove?The term “mangrove” refers to both individual species and entire plant communities. Many of these species are unrelated, but they all share similar adaptations to living in salty water, low oxygen, and exposure to wind and waves. There are at least 50 species of trees and shrubs called mangroves. Individual species form habitats collectively know as mangroves.
Where are mangroves found?Mangroves are found along tropical and subtropical coasts of Africa, Asia, Australia and the Americas. The closest mangroves to us are in Florida, Texas, Louisiana, the Caribbean and Central America. The four species in the Americas are red mangrove, black mangrove, white mangrove and buttonwood. You can read about a research trip by Aquarium scientists to mangroves in Belize here and here.
Mangroves thrive in intertidal zones of sheltered shores, islands and estuaries. They grow in soft shoreline sediment and have specialized root structures that increase their stability. They can grow in soils that are too salty for other plant species because some species have specialized root membranes that exclude salt and some species excrete salt from glands on each leaf.
Why are mangroves important?For shoreline protection: Complicated networks of mangrove roots absorb pollutants and prevent coastal erosion. Seagrass beds and coral reefs depend on mangroves to maintain water quality and clarity. In areas prone to hurricanes and tsunamis, mangroves save human lives and property by reducing wave velocity by up to 75 percent.
For habitat: Many birds, fishes, reptiles, mammals and invertebrates use mangroves for foraging, roosting and breeding. One study has suggested that up to 80 percent of commercial fish in South Florida began in mangrove nurseries. In addition, many species of sharks, some similar to those in our touch tank, spend their early years among the safety of mangrove roots.
Climate change: Mangroves are carbon sinks and play an important part in the global climate by absorbing carbon dioxide from the atmosphere. Mangroves are also carbon sources. When disturbed, the soils in which mangroves grow can release carbon back into the atmosphere.
Threats to mangroves
In addition to naturally-occurring disturbances like storms and flooding, mangroves throughout the world are threatened by human activities. According to the United Nations, 20 percent of the world’s mangroves have been destroyed since 1980. Here are some of the causes:
Habitat loss/coastal development: As coastal human populations increase, mangroves are cut down to make room for urban expansion. In many countries, mangroves are considered “wastelands” and sacrificed for new residential areas, coastal resorts, roads and canals.
Seafood aquaculture: Mangroves are converted to artificial shrimp ponds to meet world shrimp demand. Often large and unregulated, these ponds displace native species and release large quantities of animal waste into surrounding areas.
Pollution: Herbicides and other pollutants damage plant and animal species. Oil spills coat mangrove prop roots and prevent oxygen uptake as well as negatively affect birds, sea turtles and other animals.