Fun Facts About Mangroves
Mangroves are trees and shrubs that grow in the tropical and subtropical coastal environment. The term mangrove refers to a number of species from different families which inhabit the land and ocean interface and are able to cope with the extreme salinity found in seawater. Mangroves are in fact angiosperms (or flowering plants) and have therefore evolved from terrestrial plants that have migrated back to the ocean environment.
Mangroves Are The Only Trees Which Grow In Salty Seawater
Mangroves have it rough! They grow in the harsh intertidal environment along the coastline, at the land and ocean interface, where they not only have to deal with the high levels of salinity found in seawater, but the constant ebb and flow of the tide. When the tide recedes, solar radiation leads to the evaporation of the water retained in the soil, leading to an increase in the salinity levels to which the mangroves are exposed. At low tide, the mangrove roots, which are often stilted, are also exposed to higher temperatures and lack of moisture before the tide returns, and they are once again flooded and cooled.
Different Mangroves Have Different Adaptations To Deal With Harsh Environmental Conditions
Typically, mangrove forests are not species rich in terms of the number of “true” mangrove tree species found in an area – this is due largely to the harsh conditions of the environment which limit the capacity of many species to survive. The most species rich mangrove forests are found in Southeast Asia, particularly in Indonesia. The major mangrove species come from the following families: the Avicenniaceae (black mangrove), Combretaceae (buttonwood or white mangrove), Arecaceae (mangrove palm), Rhizophoraceae (the red mangroves), Lythraceae (mangrove apple).
Even within a habitat, different mangrove species are typically found within distinct zones depending on the range of environmental conditions they can withstand.
Red mangrove species are often found within the lower zone along the shoreline, as their stilt roots allow them to prop themselves above the water level, and they are able to absorb air through specialized pores, called lenticels, in their bark. Black mangroves are usually found on higher ground, where they produce specialized root-like structures called pneumatophores, which are also covered in lenticels and allow the plant to absorb air. As the soils in which these mangrove species live are anaerobic (low-oxygen) – being able to absorb gases directly from the air is highly beneficial, and an example of an adaptation which allows them to survive in their environment.
Mangroves also have to survive in a very salty environment, which can affect water regulation within the plants. In order to limit salt intake, red mangroves have highly suberized roots which are highly impermeable, and exclude sodium salts from the rest of the plant. Red mangroves also have vacuoles in their cells where they can store salts, which do make it past the roots.
White and gray mangroves, on the other hand, secrete salt directly from glands at the base of their leaves.
Mangroves Are An Example Of Convergent Evolution
Although different species of mangroves have similar mechanisms to cope with the harsh conditions associated with living in the intertidal zone, such as the variable salinity, range in temperatures, anaerobic soils and intense sunlight, this is an example of convergent evolution, and not because the different species are closely related. Different mangrove species actually come from a number of unrelated tree families that have become more similar over time as they respond to sharing a similar environment.
They Remove Heavy Metal Traces From The Environment
Because of the extensive network of roots of the mangroves, sediment becomes trapped and builds up over time. Heavy metals found in the ocean also accumulate within the sediment due to the filtration effect of the roots. When mangrove forests are lost due to deforestation or for aquaculture, these heavy metals are released back into the water column and can affect local wildlife.
Mangroves Prevent Erosion And Protect The Coastline During Storm Surges And Tsunamis
In addition to building up sediment and accumulating heavy metals, the mangroves stabilize the sediment and dissipate wave energy, which prevents the shoreline from washing away, especially during abrasive weather conditions such as hurricanes and tropical storms. This protects the coastline and prevents it from being destroyed.
Mangrove Forests Are An Important Habitat And Nursery Environment For Many Marine Animals
As mangroves are fairly shallow environments, many fish utilize the area as nurseries, as the small juvenile fish are more protected in the shallow environment from larger predators. Many of the species have important commercial or recreational value, and healthy mangrove forests are associated with increased biodiversity in near-shore environments, even outside of the mangrove itself. In permanently submerged systems, the roots host a variety of filter-feeding organisms, such as algae, oysters, sponges, bryozoans and barnacles.
Mangroves Are An Effective Source Of Blue Carbon
Mangrove forests are five times more effective per hectare at storing carbon than tropical, terrestrial forests. This makes them a valuable asset in the fight against climate change, as levels of greenhouse gases, such as carbon dioxide, are steadily increasing, causing a rise in global temperatures. Mangroves also export this carbon to other systems, where it forms an important part of the food chain, as carbon is one of the main building blocks of organic compounds and is therefore critical for life to function.
Mangroves Biomes Are Highly Threatened
There are many threats to mangroves around the world, including deforestation for wood and to make way for aquaculture farms, increased urbanization and habitat loss, pollution, sea-level rise and climate change. Temporary aquaculture is a particular threat to mangroves in many parts of the world, especially in Thailand, Mexico and Indonesia, as the waste which accumulates during farming of fish or crustaceans, such as shrimp, is toxic and can often prevent the rehabilitation of an area.
Mangroves In Thailand And Madagascar Are Important For Honey Production
In many places, mangrove forests are threatened because they are harvested for their wood. But, because mangroves are such a valuable ecosystem engineer and a blue carbon storage, conservationists try protecting mangroves by finding alternate sources of income for local communities to prevent them from cutting down the trees. In Madagascar and Thailand, mangrove honey production is a form of non-destructive income generation. Silk pods, from endemic silkworm species, are also collected from the mangroves in Madagascar for wild silk production.