What are mangroves?
Mangroves are specially adapted trees and shrubs that normally grow in or adjacent to the intertidal zone, in the tropics and subtropics. In order to survive the harsh interface between land and sea, they have evolved to the unique environmental conditions in which they are found, enabling them to thrive and develop in flooded areas with high levels of water salinity.
The Mangrove Alliance considers the mangrove ecosystem as a set of environs where mangrove species dominate the landscape, along with other associated natural ecosystems (e.g. coastal lagoons, estuaries, salt ponds, marshes, dunes) which enable the establishment and appropriate development of mangrove forests.
Mangrove ecosystems in the Americas
Mangroves in the Americas are confined to the Neotropics. According to Spalding et al. (2010), there are 12 species of mangroves distributed along the shorelines of 42 countries and island territories between North, Central and South America, and the Caribbean. Of these 12 species, 5 (41%) are listed as threatened on The IUCN Red List of Threatened Species™.
The estimated extent of mangroves in the Americas is close to 44,000 km², which represents approximately 30% of the world’s mangroves… and is equivalent to the area of mangroves lost globally during the past 30 years! The most extensive stands are found in Brazil, Mexico, Cuba, the United States, Panama and the Bahamas. The extent of mangrove habitats in Brazil, Mexico and Cuba is significant at a global level.
Benefits and ecosystem services provided by mangroves
Mangroves are one of the most productive ecosystems in the world. Because of the niche they occupy, they are known to generate many benefits to associated species, adjacent ecosystems, and human populations.
Mangroves provide a wide range of ecosystem services including: support habitat for a unique array of species such as molluscs, crustaceans, insects, fish, birds and even mammals; nursery habitat for commercially important fish species; production of timber and other forest products (like wood, medicinal plants and high quality honey); protection of the near-shore marine environment – including coral reefs and seagrass beds – from many land-based impacts (e.g. nutrients, pesticides, sediments); restriction of the flow of seawater into the river systems and inland water sources; pollution abatement, and protection against storm and wave erosion.
Of particular importance – in light of the impacts of climate change – are the regulating services provided by mangroves as natural coastal defenses from storm and tidal surges, and as carbon ‘sinks’ to mitigate further increases in carbon dioxide (CO2) levels. These services will prove to be of utmost importance to both the biodiversity and people in low-lying coastal areas. More »
Threats to Neotropical mangroves
Despite the importance of mangrove ecosystems, they are one of the most threatened ecosystems in the world. Loss of mangrove habitat has occurred in almost all countries in the Americas where it is present. Most losses have been linked to aquaculture, agriculture, urban and industrial expansion, and tourism development. Extreme weather events such as storms, hurricanes and cyclones have also played an important role in the destruction of mangrove ecosystems, that later take years or decades to recover naturally.
Other drivers for mangrove loss are clear-cutting for fuelwood, petrochemical pollution and mining. Alongside losses, remaining mangrove habitat often shows signs of degradation due to over-extraction of timber, overfishing and solid waste disposal (Spalding et al. 2010).
Mangroves and Important Bird Areas in the Americas
Mangroves are a key habitat at more than 300 Important Bird Areas (IBAs) in the Americas and are used by more than 250 species of birds as breeding habitat, for foraging and as roosting sites.
‘Mangrove’ IBAs represent critical habitat for a number of Neotropical migratory bird species (especially shorebirds, ducks and some warblers) as wintering and stop-over sites, and also breeding grounds for nesting seabirds and waterbirds. Many restricted-range birds frequent mangrove ecosystems, and some globally threatened birds rely on them seasonally.
Furthermore, there are globally threatened birds considered “mangrove endemic” species due to the strong association and affinity they have to this type of habitat. Examples of globally threatened “mangrove endemic” birds are the Critically Endangered Mangrove Finch Camarhynchus heliobates, the Endangered Yellow-billed Cotinga Carpodectes antoniae and Mangrove Hummingbird Amazilia boucardi, among others.