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What are Mangroves?
Red Mangrove in their natural habitat
Mangroves are a highly productive ecosystem with important economic and environmental functions. In the wild, mangrove stands serve as protection for fish, crabs, oysters, lobsters and shrimp. Their roots provide attachment surfaces for marine organisms such as colorful sponges and oysters. Mangrove forests filter out pollution, stabilize sediments, hold nutrients, protect the shoreline from erosion and provide food, nesting and nursery areas for many animals, including at least 220 fish species, 24 reptile and amphibian species, 18 mammal species and 200 bird species. Mangroves have been exploited for firewood and charcoal, used in the construction of dwellings, furniture, boats and fishing gear in the Far East. They are an important source of tannins for dying, leather preservation and oil drilling.
Above: Close up of Rizophora mangle propagule
Worldwide Mangrove Communities
The most widespread of all coastal plant species, mangrove forests are major contributors to the tropical ecosystems of the world. They occupy 75% of the world's coastal areas between latitudes 25 degrees N and 25 degrees S (approximately 240,000 square kilometers). They are sensitive to extreme temperature fluctuations as well as subfreezing temperatures.
Mangrove forests form a barrier between land and sea. Around the world, they buffer shorelines from storm winds, waves and floods. Their stabilizing root systems help prevent erosion while filtering water, maintaining quality and clarity. They have a great resiliency to major natural disturbances. Mangroves also protect the sea from the land by preventing silty runoff during heavy rains, thereby preventing the seawater from becoming cloudy. This is important in protecting nearby coral reefs, oyster beds and seagrass beds which require clear water and sunlight to grow. Studies have shown that when mangrove forests are lost, fishermen suffer substantial decreases in their catch of shrimp and fish.
Mangroves can be instrumental in the formation of salt ponds which also help protect the ocean from silt and sediment. Salt ponds are former bays which were once open to the sea, but over time were closed off by reef or mangrove growth. Once the bay is closed, the salt pond begins to act as a sink for silt and sediment which runs down hillsides in heavy rain. Without the ponds, the silt and sediment would be released directly into the ocean resulting in brown and cloudy water.
Mangrove and salt pond ecosystems have the ability to withstand domestic and industrial contamination, but so many products are dependent on mangroves, that indiscriminate dumping of sewage could easily lead to food poisoning and epidemics. Human-caused pollution, thermal pollution (hot-water outflows), heavy metals, agrochemicals, nutrient pollution (including sewage) and oil spills all have an effect on mangrove growth and survival. Mining and industrial wastes are the main sources for heavy metal pollution (especially mercury, lead, cadmium, zinc and copper).
Excessive sediment deposits can damage mangrove communities. Moderate sedimentation is beneficial to mangroves as a source of nutrients and to keep up with predicted increases in the rise of our sea levels. When excessive, sedimentation can reduce growth or even kill mangroves. Sedimentation can result not only from river floods and hurricanes, but also from human alterations to the ecosystem. Road and dam construction, mining and dredge spoils have buried and killed mangroves. Runoff from agricultural fields represent the main source of organic chemical contamination in mangrove ecosystems. Despite the possibility of burial, heavy metals and pesticides may accumulate in animals that depend on mangroves, such as fish, shrimp and oysters.
Despite laws established for mangrove protection in many countries, unregulated exploitation and deforestation continues. In the Philippines, 60% of the original mangrove area has disappeared. In Thailand, 55% of the mangrove cover has been lost over the last 25 years. Eventually, the overexplotation of mangrove forests will degrade and, ultimately, lose habitat, increase shoreline erosion, damage fisheries and lose products derived from these ecosystems.
Mangrove forests form a barrier between land and sea. Around the world, they buffer shorelines from storm winds, waves and floods. Their stabilizing root systems help prevent erosion while filtering water, maintaining quality and clarity. They have a great resiliency to major natural disturbances. Mangroves also protect the sea from the land by preventing silty runoff during heavy rains, thereby preventing the seawater from becoming cloudy. This is important in protecting nearby coral reefs, oyster beds and seagrass beds which require clear water and sunlight to grow. Studies have shown that when mangrove forests are lost, fishermen suffer substantial decreases in their catch of shrimp and fish.
Above: Mangroves on the Coral Sea at Cape Tribulation in Far Northern Queensland, Australia where they protect not only the land from the sea, but the sea from the land.
Mangroves can be instrumental in the formation of salt ponds which also help protect the ocean from silt and sediment. Salt ponds are former bays which were once open to the sea, but over time were closed off by reef or mangrove growth. Once the bay is closed, the salt pond begins to act as a sink for silt and sediment which runs down hillsides in heavy rain. Without the ponds, the silt and sediment would be released directly into the ocean resulting in brown and cloudy water.
Mangrove and salt pond ecosystems have the ability to withstand domestic and industrial contamination, but so many products are dependent on mangroves, that indiscriminate dumping of sewage could easily lead to food poisoning and epidemics. Human-caused pollution, thermal pollution (hot-water outflows), heavy metals, agrochemicals, nutrient pollution (including sewage) and oil spills all have an effect on mangrove growth and survival. Mining and industrial wastes are the main sources for heavy metal pollution (especially mercury, lead, cadmium, zinc and copper).
Excessive sediment deposits can damage mangrove communities. Moderate sedimentation is beneficial to mangroves as a source of nutrients and to keep up with predicted increases in the rise of our sea levels. When excessive, sedimentation can reduce growth or even kill mangroves. Sedimentation can result not only from river floods and hurricanes, but also from human alterations to the ecosystem. Road and dam construction, mining and dredge spoils have buried and killed mangroves. Runoff from agricultural fields represent the main source of organic chemical contamination in mangrove ecosystems. Despite the possibility of burial, heavy metals and pesticides may accumulate in animals that depend on mangroves, such as fish, shrimp and oysters.
Despite laws established for mangrove protection in many countries, unregulated exploitation and deforestation continues. In the Philippines, 60% of the original mangrove area has disappeared. In Thailand, 55% of the mangrove cover has been lost over the last 25 years. Eventually, the overexplotation of mangrove forests will degrade and, ultimately, lose habitat, increase shoreline erosion, damage fisheries and lose products derived from these ecosystems.
Note: Mangrove propagules are only available from August 1 through October 15