Types of mangrove trees and importance post explains about what is a mangroves, three important types of mangroves, location of mangroves, and importance of mangroves.
What is a mangroves?
Mangroves are a variety of species of broad-leaved trees (10–40 feet high) lying in muddy creeks and tidal estuaries. They are located on the intermediate zone between the land and the sea and represent one of the best examples of ecotone. They require warm saline water and so they are situated along tropical coastlines. Mangrove plants survive in the saltwater zones between water and land.
Mangroves have a “complex salt filtration system” and complex root system to cope with salt water immersion and wave action. They are also adapted to the low oxygen conditions of waterlogged mud. Mangroves occur worldwide in the tropics and subtropics, mainly between latitudes 25°N and 25°S. They require high solar radiation to filter saline water through their roots. Hence, mangroves are confined to only tropical and sub-tropical coastal waters.
It has been found that there are about 80 different species of mangrove trees. Mangroves grow in areas with low-oxygen soil and in this soil slow-moving waters allow fine sediments to pile up. Mangrove forests only grow at tropical and subtropical latitudes near the equator as they cannot bear freezing temperatures. Mangrove forests serve an important role in stabilizing and reinforcing coastlands. In this way, they protect these coastlands from erosion that results from action of waves and tides that occur regularly. They act as a shield against storms. This capability of the mangrove forests has saved valuable property and countless lives around the world from imminent destruction.
Mangrove plants have several unique adaptations that allow them to survive in harsh environment. Mangroves are extremely important to the coastal ecosystems they inhabit. Physically, they serve as a buffer between marine and terrestrial communities. They protect coastlines from damaging winds, waves, and floods. Mangrove has an important role in improving water quality by filtering pollutants and trapping sediments from the land. They reduce coastal erosion.
Ecologically, they provide habitat for a diverse array of terrestrial and marine organisms. The area of mangroves has greater species diversity as it is the junction of terrestrial and marine ecosystems. They have very high salt tolerance and so some species which require this ambience also thrive upon mangroves. According to one of its oft-quoted definition, “Mangroves represent a characteristic littoral (near the sea shore) forest ecosystem and they are mostly evergreen forests that grow in sheltered low lying coasts, estuaries, mudflats, tidal creeks backwaters (coastal waters held back on land), marshes and lagoons of tropical and subtropical regions”.
Types of mangroves
Red mangroves: They grow along coastlines and are the hardiest of the three major mangrove plant types.
Black mangroves: They are named so because of their dark bark. They usually grow at slightly higher elevations than red mangroves. They have access to more oxygen because the roots are more exposed.
White mangroves: They grow at higher elevations than red and black mangroves. Generally they do not have aerial roots. But sometimes there is unique growth of peg roots when oxygen is depleted due to flood.
Location of Mangroves
There are 15.9 million hectares of mangrove forests in the warm waters of tropical oceans all over the world. Along the Atlantic coast they are found from Florida till Argentina in a vast expanse. Mangroves grow on both the western and eastern coasts of Africa. They stretch into India, Burma, and south-east Asia. Mangrove forests are also common in New Zealand and Australia.
Importance of Mangroves
Mangrove forests give sturdy support to the coastline by minimizing erosion from storm surges, currents, waves, and tides. The intricate root system of mangroves is unique as they allow them to shelter fish and other organisms in an ecologically benign environment. For example, the area of Sunderbans is the world’s largest mangrove forest and they have wider species diversity. This biodiversity hotspot is home to 180 species of trees and plants growing within its marshy boundaries, the Gangetic dolphin, estuarine crocodiles, river terrapins, hawksbill turtles, horseshoe crabs and the famous Bengal tiger. They are a World Heritage site and the biggest carbon-sink in South Asia. They have an important role in carbon sequestration and hence climate management.
Mangroves are the first line of defence against cyclones and rising seas. They also support coastal communities in multiple ways.
Mangroves provide important nesting and breeding sites for fish and shellfish, migratory birds and sea turtles. This underscores their importance to coastal fishing communities. According to a global research, an estimated 80% of the global fish catch relies on mangrove forests either directly or indirectly.
They soften the blow caused by tsunamis and cyclones. Mangroves stabilise and reinforce coastlines with their sturdy support by slowing erosion and provide natural barriers protecting coastal communities from increased storm surges, flooding and hurricanes. For example, the coastal areas with deep cover of mangroves witnessed less damage from the Indian Ocean Tsunami in 2004.
About 20 percent of India’s population lives on the coast. There are many big cities including Mumbai, Chennai, Puducherry, Thiruvananthapuram, Kochi etc. which lie on the sea shore. A robust and dense cover of mangrove forests can protect these areas, which are vulnerable both to sea level rise and to the more intense and frequent weather events caused by climate change.
Mangroves also act as great carbon sinks. Some researchers at the global level have postulated that mangroves “isolate carbon at two to four times the rate of tropical forests like the Amazon and store three to five times more carbon per equivalent area than tropical forests”.
Mangroves are used for timber, mining, agriculture, harbour development and human settlements. Mangrove areas were used earlier for commercial shrimp farming. However, using mangrove areas for shrimp farming has proved to be unsustainable now-a-days.
Mangroves are an ecosystem with multi-dimensional use. It is held that they are the “best form of coastal bioshield” as they perform a “critical role in reducing the impact of cyclonic storms, hurricanes and tsunami on human lives and properties”.
It controls/reduces soil erosion. It magnifies fishery productivity of the adjacent coastal waters. This occurs as they act as a nursery ground for commercially important fish, prawn and crabs. Additionally, they supply organic and inorganic nutrients. They are also rich in biodiversity and act as habitats for wildlife.
It is being held that “the physical environment lays the foundations and draw limits for how and where mangroves thrive, as ‘ecosystem engineers’ mangroves themselves are partially responsible for shaping their physical environment”.
The highly intricate and very structured roots of mangroves promote the trapping of sediments (i.e. from rivers) and organic debris helping them to adjust with the sea level rise, making them invaluable in promoting climate resilient coasts.
Mangroves create an excellent diverse habitat as they combine animal species of terrestrial and marine environment in a single ecosystem. Major groups range from insects, molluscs and crustaceans to fish, reptiles, birds and mammals. Mangroves are rich in food and provide shelter to offshore species which use their complex structures as nurseries. Mangroves also provide terrestrial habitat for many species. For example, the vast mangroves of the Sundarbans currently host the largest intact tiger population in the world.
Mangroves have a seminal role in the ecosystem as they nurture and nourish biodiversity as nursery grounds for many coastal and marine species and support fisheries.