Project Blue - Roots & Shoots Canada Water Campaign

Mangrove Forests

There are over 60,000 square miles of Mangrove forests along the world’s tropical and subtropical coasts. Mangrove forests play a vital role in the lives of many coral reef fish and nesting birds, and can help to mitigate storm damage to shorelines. Currently these forests, found within intertidal areas between land and sea, are one of the most threatened ecosystems in the world. Resort development, artificial dikes, and the shrimp aquaculture industry all pose huge threats to the existence of mangroves. Continue reading to learn more about mangroves and their importance.

Mangrove trees are thought to have originated in the Indo-Malayan region, eventually spreading to India, East Africa, and finally to Central and South America, between 66 and 23 million years ago. Today, there are up to 75 species of mangrove trees worldwide, the greatest diversity of mangroves being in southeast Asia.

Mangrove forests are located along the tropical and subtropical coasts of Africa, Australia, Asia and the Americas. Indonesia, Brazil, Australia, Nigeria and Mexico support the largest areas of mangroves in the world.

To survive the low oxygen and brackish water conditions of estuaries and intertidal areas, mangrove trees have specialized, aerial root-like structures, called pneumatophores, which break through the soil at intervals for easy gas exchange (much like straws for breathing). Other mangroves, like red mangroves, are propped out of the water on stilt roots, and absorb air through pores on their bark. To prevent the absorption of salt, red mangroves have also evolved a waxy substance on their roots.

Many land and water animals make mangrove systems their home, including the southern stingray, the mud lobster, the kingfisher, the common Cayman and the jaguar.

These forests are important nursery grounds for coral reef fish, allowing them space to travel from seagrass bed ‘cribs’ to coral reef ecosystems. Coral reef fish have been found to be twice as abundant on reefs in close proximity to mangrove systems, compared to reefs that are not. Additionally, mangroves serve as nesting grounds for numerous bird species, such as the endangered bald eagle.

Mangrove forests have many benefits for shorelines. They prevent erosion via sediment accretion (balancing sediment loss while catching material washing downstream), they mitigate floods while protecting associated marine ecosystems, and they act as ‘buffer zones’ shielding coastlines from storm damage and wave action.
Mangroves improve water quality by filtering sediments and absorbing excess nitrates and phosphates, thereby preventing contamination of near shore waters. Mangroves also lessen the impacts of climate change by sequestering carbon in their leaves and storing gas in their sediment.

The biggest threat to mangrove forests is humans. Dredging of coastal areas to prepare for building, long term flooding from artificial dikes and sea walls, clogging of mangrove pores by chemical pollutants and crude oil, and removal to provide space for artificial shrimp ponds, are all contributing to the accelerated disappearance of mangrove forests.

There are many organizations working to protect these important ecosystems. For instance, the Mangrove Replenishment Initiative researches and develops effective mangrove replanting strategies. The Forestry and Agriculture Organization of the United Nations also researches strategies to preserve mangrove forests, while facilitating education workshops in areas where mangroves exist.

Sources

Download PDF