Mangroves are one of the most important biomes on the planet for many crucial reasons, ecological and otherwise. These habitats, which may seem distant and exotic to many, are vital sources of marine biodiversity and are as productive at creating biomass as terrestrial rainforests and coral reefs. There are many benefits to maintaining mangroves, which require ample protection due to regular infringements by humans.
What Are Mangroves?
Mangroves are a group of small trees and shrubs numbering some 80 species. They grow in coastal saltwater zones in tropical and subtropical latitudes around the globe. They are the only trees in the world that can tolerate saltwater, excreting the excess salt through their leaves. Mangroves tend to grow numerous long roots which form nest-like structures. Some mangrove species grow roots called pneumatophores that grow upwards, absorbing oxygen while the tide has submerged the lower portion of the mangrove.
What Is a Mangrove Forest?
A mangrove forest is a collection of mangrove plants that together form a habitat. You can find mangrove forests on every continent except Europe and Antarctica, as this NASA map displays. These forests form unique habitats which shelter an immense diversity of wildlife, including numerous endemic species.
Why Are Mangroves Important?
Mangroves are important ecosystems for numerous reasons. First is biodiversity; mangroves are hotbeds for animal life, both below water and above ground. This biodiversity makes ecosystems more resilient to disease and death and therefore sustains some of the planet’s most essential resources, which provide for human sustenance and planetary health. Forty percent of the global economy relies on biological resources, and biodiversity helps ecosystems better adapt to climate change and ensure their continued production of oxygen and absorption of CO2 that slows global warming.
Mangroves are prolific sequesters of carbon dioxide and are therefore integral for combatting climate change. Although they account for under 2 percent of marine environments, mangroves are responsible for 10-15 percent of carbon burial. Mangroves are considered the most effective of all ecosystems, aquatic and terrestrial, at sequestering carbon from the atmosphere. Although the total surface area covered by mangroves is only equivalent to 3 percent of the Amazon rainforest, they sequester the same amount of carbon as 12 percent of the Amazon.
Mangroves also store large amounts of carbon in their soil, which is released when the trees are cleared. An estimated 122 million tonnes of carbon were released by mangrove clearing between 2000 and 2015. Because these forests are so efficient at sequestering and storing carbon, particularly in the small space they occupy, they are vital in combatting climate change.
Mangroves are essential coastal barriers in some regions, preventing coastal erosion from encroaching on human communities. Mangroves can absorb an estimated 70-90 percent of the energy from regular waves. They can also potentially save thousands of lives from extreme weather events like tsunamis; a comparison of two villages in Sri Lanka in the aftermath of the 2004 Indian Ocean Earthquake and Tsunami revealed that the one protected by mangroves only suffered two deaths when the exposed village suffered 6,000 deaths. The trauma of that catastrophe, which cost the lives of over 230,000 people, spurred on the cultivation and development of mangroves in Aceh province Indonesia, where citizens are developing mangroves to use as a natural barrier against future disasters.
Mangroves are highly rich in natural resources utilized by humans. They are sources of wood, fruit, honey, and numerous medicines. They also are a free and natural alternative to sea barriers and the expensive infrastructure to prevent natural disasters or erosion. Furthermore, they also clean waters that pass through them and therefore filter pollution from waterways before it arrives in the sea.
What Are The Types Of Mangroves?
Fringe
Fringe mangroves grow on shorelines in relatively thin strips of forest. These types of mangroves protect shorelines and prevent coastal erosion. They typically thrive in a high degree of salinity as they receive the tide regularly.
Basin
Basin mangroves tend to proliferate furthest from the sea in large forest areas behind fringe and riverine mangroves. They only receive the tide occasionally and so may experience only low or moderate salinity in the soil; conversely, at higher elevations, soil salinity can be very high due to evapotranspiration. Basin mangroves are highly useful for nutrient accumulation. They are generally more effective at storing carbon, neutralizing nitrogen, and immobilizing microbes and chemicals like pesticides, which leach from farms into rivers. Under carefully managed conditions, they can provide a useful way of treating wastewater.
Riverine
Riverine mangroves line the banks of rivers and are flooded by the river and the sea. The combination of fresh and salt water makes riverine mangroves some of the most productive ecosystems in the world. Biodiversity is at its strongest in riverine mangroves. Riverine mangroves are also effective at trapping sediments flushed into rivers by upstream excavation and development, which would otherwise wash into the sea and cling to and damage other invaluable ecosystems like coral reefs.
Overwash
Overwash mangroves are similar to fringe mangroves, except they are located on small islands, submerged regularly by the sea. They tend to be populated by highly salt-resistant mangrove species and are often favored by bird species, being ideal roosting spots, cut off as they are from terrestrial predators.
Dwarf
Dwarf mangrove forests are forests where the trees can grow five feet or 1.5 meters tall. This is usually due to the type of soils in which dwarf forests grow, which are rocky, low in nutrients, and suffering from high salinity. Dwarf mangroves thrive in the extreme north and south of mangrove ranges.
Where Are Mangroves Found?
Mangroves are found all over the tropical and subtropical areas of the world. Indonesia is the country with the most mangroves. Brazil, Malaysia, Papua New Guinea, and Australia also have mangrove forests.
Mangrove Animals and Which Food Chain Occurs in a Mangrove Ecosystem?
Many animal species live in the unique environment of the mangrove forest. For example, reef fish use the mangrove forests as spawning places for their young. The dense roots make for a secluded harbor, with many places to hide. Mangroves are also useful for young fish to develop safe from predators.
Reef fish aren’t the only marine beneficiaries; mudskippers thrive in the warm waters, even climbing trees with their impressive pectoral muscles. Sharks also use the forests as nurseries for their young. Multiple crab species call mangroves their home, including the suitably named mangrove tree crab, a single species found on the Atlantic coast of the Americas from Georgia to Brazil consumes mangrove leaves, various insects, and scavenged meat. The mud lobster, another mangrove crustacean, provides a strong example of ecological interdependence. They dig around for food in the mud, which creates large burrows. These burrows also make excellent homes for snakes and mangrove saplings, perpetuating the health of the ecosystem.
It is not only below the water that mangroves encourage diversity. The proboscis monkeys of Borneo live exclusively in mangrove swamps. Bats thrive in mangroves, particularly the mangrove Sonneratia, which opens its flowers at dusk and whose nectar proves irresistible to bats, who carry pollen from the flowers and fertilize the forest. They also provide refuges for endangered and charismatic species like the Bengal tiger, who prowl the Sundarbans mangroves, the delta in India and Bangladesh where the Ganges, Meghna, and Brahmaputra rivers meet.
Mangroves have a unique food chain. Worms and crabs are near the bottom. They eat debris in the mud. Fish are next in the food chain. They eat the small worms and crabs. The fish then fall prey to birds, crocodiles, and even mammals like tigers. These larger apex predators will, in turn, target herbivorous mammals, like proboscis monkeys. They feed on the fruits of the mangrove trees.
Why Are Mangroves Being Destroyed?
Over the past four decades, 35 percent of mangrove forests have been destroyed. In countries like India, Vietnam, and the Philippines, over half of the mangrove forests have been cleared. There are a wide variety of causes for this destruction. Mangroves have previously been considered foul-smelling and unproductive and have been cleared for profitable agriculture or tourism businesses.
Neighboring communities which have long relied on mangroves for resources like firewood, animal fodder, construction wood, and charcoal have in some places begun to overexploit the forests, reducing them through deforestation. Mangroves that thrive in the brackish water, where salt and fresh water mingle, can be jeopardized by dams and irrigation schemes upriver, which reduce the freshwater content in deltas and undermine the water conditions in which mangroves thrive.
The death of coral reefs due to rising water temperatures, a product of climate change, can also affect mangroves. The reefs regulate the strength of waves. With coral reefs disappearing, stronger waves can hit mangroves which wash away nutrients and prevent saplings from taking root.
Finally, pollution is killing mangroves. The primary contributors are the pesticides and fertilizers used in agriculture, which leach into waterways before arriving at mangroves. Agriculture, in general, has been reported to be the leading cause of mangrove destruction. Oil spills can also suffocate the trees, as has been the case in the mangrove-rich Niger delta of Nigeria.
Shrimp Farming
Shrimp farming is also fuelling the clearing of mangrove forests. In the U.S., the average per capita consumption of shrimp is four pounds per annum, which tracks with an increased demand for shrimp in the developed world in recent decades.
Shrimp farming is a profitable industry, and it is particularly appealing in the developing nations of South East Asia, where the industry is often encouraged by governments. Shrimp farming rates more than quintupled between 1988 and 2008, with expansions mainly taking place in China, Thailand, and Indonesia. However, although shrimp farming may be lucrative in the short term, the devastation wrought on the mangroves creates problems that are destructive to the livelihoods of many aspects of society.
Shrimp farming creates significant pollution and wastes land. The shrimps are raised in large deposits of waste, bits of feed, pesticides, antibiotics, and chemicals which are often siphoned off or washed out into the ocean, harming neighboring ecosystems. Eventually, these accumulations become too toxic, the original pools are abandoned, and new pools are made. This is a fundamentally unsustainable process, especially when it comes at the expense of crucial mangrove habitats.
Sea Level Rise
Rising sea levels, caused by the climate crisis, also pose a significant threat to mangrove forests. In previous eras, forests would retreat inland as a response to rising sea levels. However, this is often not possible today due to the abundance of human development near coastlines. Mangrove forests like the Sundarbans are retreating at an alarming rate, with nearly 71 percent of its shoreline receding by 200 meters per year.
Rising sea levels wash away mud, depriving mangroves of the soil they thrive in and eventually leading to the mangroves dying from oxygen deprivation. Therefore, the continuation of global heating, the melting of the polar ice caps, and the rising sea levels will also destroy mangroves, so vital for carbon reduction, thus accelerating the process.
Invasive Species
Invasive species were often assumed to be absent from mangrove forests due to their unique saltwater adaption seen as hostile to conventional plant species. However, invasive species are threatening mangroves and are looking to undermine their ability to regenerate themselves and impact their unique wildlife varieties.
Examples of this include the introduction of nilgais, a type of Asian antelope, to Texas for hunters, but they eat mangrove leaves at a high rate. Introduced rats and cats in the Galapagos Islands have proved devastating for the archipelago’s unique fauna and have driven the Galapagos mangrove finches into critically endangered status.
How Can You Help?
As a consumer, you can reduce your contribution to various underlying causes of mangrove destruction. So, for example, you could remove farmed shrimp from your diet to undermine the financial incentives to clear mangroves for aquaculture. Indeed, like agriculture, in general, is propelling mangrove clearance adopting a plant-based diet, which requires an average of 75 percent less land to support it, can help.
If you live in an area with mangroves, investigate what local organizations, government branches, or charities are working to preserve them and volunteer your time or resources to them. Alternatively, you could try and visit mangrove areas as a traveler to support ecotourism industries that benefit from the beauty of mangroves, and therefore have an incentive to preserve them.
The Road Ahead
Mangroves only occupy around 0.1 percent of the globe’s surface area. Yet, they are unique environments crucial to global health and both marine and terrestrial biodiversity. They protect coastal communities from natural disaster and erosion, sequester and store carbon more effectively than any other biome, and teem with vibrant forms of life and economic value. As efficient tools against climate change and distinctive ecosystems, they deserve maintenance and protection for the benefit of their diverse animal inhabitants and the ecosphere at large.
