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Mangroves for Fiji

Overview
Mangroves are a crucial part of the environment in the South Pacific due to their ability to protect the coastlines of the islands, however, most mangroves are threatened in this area. A big part of the Mangroves for Fiji project is marine conservation as they work alongside with the Fiji Shark Conservation Project because mangroves act not only as a barrier, but also as a nursery, habitat and breeding ground for many of Fiji’s invertebrates all the way to shark species. One of Fiji’s main attractions is the bull shark dive. Mangroves are important in the conservation of these sharks because the juveniles are born in the mangroves and stay there until they are big enough to travel out into the open ocean. The Fiji Shark Conservation Project and Mangroves for Fiji are privately funded projects through Projects Abroad that spread awareness about shark and mangrove conservation. Businesses in Fiji such as Beqa Adventure Divers and Uprising Beach Resort are working alongside Mangroves for Fiji in order to offset their carbon emissions.[1]

Importance of Mangroves
Mangroves are extremely important and are considered the rainforests of the sea due to their ability to host an extreme amount of biodiversity. They grow in tidal areas and are halophytes. They also excrete salt through the pores in their roots and leaves, where most plants cannot survive in salty conditions. Mangroves are mostly found in the tropics and subtropics due to the warmer temperatures year round. Since Fiji and surrounding areas are islands, mangroves protect these areas from natural disasters by stabilizing the coastlines while also providing nutrients and carbon to surrounding ecosystems. Mangroves filter out sediments to protect ecosystems such as coral reefs from being destroyed, which is important in these coastal areas that rely on their reefs for food. Mangroves are thought of as the answer to global warming because of their ability to reduce greenhouse gases and natural adaption to climate change. Protecting these ecosystems has become important for these coastal communities because of the advantages associated with them. In these coastal Pacific communities mangroves are important for the lifestyle of the people. For example, the mangroves provide a source of food and wood for building. It also is used for medicine and timber. Mangroves are often found in tourist locations where nice beach’s and reefs create an economic value to the country. However, mangroves are being destroyed all around these islands. This is due to overharvesting, urban development and effects of climate change where impacts are greatest.[1]

Photosynthesis and Carbon Sequestration
Mangroves are capable of photosynthesis through their waterproof leaves that have a thick covering. They have stomata that are sunken in pits on the underside of the leaf that allow carbon dioxide to diffuse into the leaf. The underside is coated with fine hairs that reduce airflow and currents. When these leaves fall into the water, bacteria decompose them and many nutrients are released that are needed by many species such as phytoplankton that use these nutrients to grow. Mangroves store carbon dioxide from the air in their biomass resulting in having the highest carbon net productivity. Compared to terrestrial systems that store carbon in trees or branches, mangroves store carbon in their roots on the seafloor into the soil. This is an advantage over terrestrial systems because when the plant dies, the carbon is released from the trees and branches, however, only a little is released when a mangrove is removed because the carbon is stored deep in the ground. Mangroves can thrive in different types of environments such as oxygen poor, salt and fresh water and brackish water. They are able to grow in unstable tough environments where other ecosystems would collapse.[1]

Types of Mangroves in Fiji
The three types of mangroves in Fiji are red, white and black. Each has its own level of salt tolerance, which determines its habitat. The red mangrove consists of the spotted, samoan and hybrid. The spotted mangrove (Rhizophora stylosa) is found on beachfronts where the tide is relatively low and it also may extend into areas where the waters are brackish such as estuaries or rivers. The samoan mangrove (Rhizophora samoensis) is found along most rivers. The hybrid mangrove (Rhizophora x selala) occurs only in swamps. All red mangroves have roots that are permeable to gases and impermeable to salts. They are found closest to the water because they have the highest salt tolerance with prop roots that supply air to the roots within the soil and provide stability. The black mangrove found in Fiji is the large leafed mangrove (Bruguiera gymnorhiza) and it is found at sea level among swamps. Other black mangroves may also grow on higher shorelines. These mangroves have roots specialized for gas exchange called pneumatophores. Most mangroves, such as red, have stilt roots which are extensions from the trunk that grow into the soil trapping sediments to help stabilize the forest due to the tough conditions it normally grows in along the waters edge. However, black mangroves lack these roots and the species in Fiji has elbow roots that extend up the trunk and back into the soil and then back out again. There are four types of white mangroves. The teruntum merah (Lumnitzera littorea) is located in drier regions or behind a swamp. The looking glass mangrove (Heritiera littoralis) is found along coastal forests and swamps. The blind your eye mangrove (Excoecaria agallocha) is found at or near sea level in swamps, rivers and beach thickets, however, the mangrove trees grow at the high water mark. It can grow in different soil types and can tolerate a variety of environmental conditions. The cannonball mangrove (Xylocarpus granatum) is found growing behind or with Bruguieria. The white mangroves are found behind the red and black mangroves and do not have prop roots or pneumatophores like the other types. [1]

Threats to Mangroves
There are many threats to mangroves with the main source being humans. A big factor is deforestation, which can be seen in Fiji. Mangroves are often destroyed for urban and coastal development and the runoff, such as from agriculture or development, will increase and can suffocate the forest. Other threats include aquaculture, unsustainable fishing, and pollution. A big part of the Mangrove for Fiji project is replanting mangroves in areas that have been destroyed. Climate change is affecting them as storms become more intense and frequent making it harder for the ecosystem to recover between storms as sea level rises and environmental conditions change rapidly. Without mangroves the coral reef ecosystem will diminish further decreasing the mangrove forests because the reefs act as a first barrier when the storm comes. The mangroves grow best in sheltered areas because high wave energies created by less reefs and more storms destroys the root system destroying their many ecosystem functions. Without mangroves, the food web will be altered since they are at the bottom of the food web and the environment suitable for the many species that inhabit the coastal environments may not be able to survive.[1]

Planting Mangroves
Fiji is recognizing that mangroves are vital and they are disappearing at alarming rates. Mangroves for Fiji are trying to help save the mangroves by having all of the volunteers assist in planting mangroves and getting businesses around the island to be carbon neutral. In order for panting to be successful there has to be a certain number of mangroves of a certain species per hectare, the type of substrate, depth of the water at low and high tides, salinity of the water at low tide and vegetation surrounding the plant. Mangrove seeds are called propagules. Planting propagules can be done in the natural environment where it needs to grow or it can be grown in a pot and when it shows signs of leaves it can then be planted in the environment. Mangroves are viviparous. When the seed germinates it falls and either anchors into the soil to grow or drifts in the water until it finds suitable conditions to anchor itself, where it then changes its density to float vertically instead of horizontally. This enables mangroves to be widely spread throughout an ecosystem due to currents moving the propagules into different areas.[1]