Why islands must protect their mangrove forests

Mangrove Mauritius Island, Trou aux Biches, lone mangrove plant growing in the shallow seawater with rocks at the back

Some years ago, mass clearance of mangrove forests on estuaries and marshes was common on small islands because they were thought to be insect breeding sites and were being used as dumps. Over time, as more knowledge was gained on this fragile yet vital environment, efforts to protect and restore degraded forests started. In Mauritius for instance, mangrove protection is included in the local law, and it is prohibited to cut down trees [1]. Some mangals are even declared as Ramsar Sites and are protected internationally. Even though mangrove forests are important elements on both continents and islands, small, remote islands, depend even more on the benefits of these swamps.

Stabilizing and protecting the coast

Just like other trees, mangrove roots trap sediment and prevent soil erosion. However, in this case, mangrove trees are key elements in preventing coastal erosion. The constant movement of waves and tides inevitably washes land away. The strong roots of these trees hold the sediment in and prevent it from scattering. What’s more, as mud is deposited on the seaward side of the forests, mangrove propagules grow and develop into new trees allowing the land to extend towards the sea.

In the same way, mangroves trees also trap sediment from the land and prevent it from getting into the sea which would otherwise disrupt the growth and development of coral reefs. Polyps need shallow clear waters to grow; where there are mangroves trees, coral reefs and seagrass forests can develop beautifully. The bogs are also important pollutant sinks. Polluted runoff accumulates in the mangrove sediment; these are then taken up by the trees and locked up in their leaves.

Protection against tsunamis

The 2004 tsunami rang the alarm bell for mangrove conservation in the tropics and subtropics. Economists and ecologists worked together to come to the conclusion that the actual benefits of mangrove forests as coastal protectors are more valued than other uses. For example, the Kulhudhufushi mangrove forest in the Maldives provided this low lying island ample protection during the tsunami [2].

Source of income for the coastal population

Healthy mangrove forests are vital for the coastal populations. Most of them are fishermen or utilize materials from the mangroves for their day to day activities. In the Solomon Islands, 85% of the population depends on the mangrove environment for their livelihoods [3]. Mangrove forests are important nursery sites for marine organisms to develop. Thus, these marshes support fisheries and crustacean catches. On the Caribbean Islands where mangroves have been destroyed by pollution and land reclamation by approximately 1.7%/year, fisheries have also decreased at the same rate [4].

Globally, the uses of mangroves amount to $1.648 billion per year [5]. As it is difficult for many islanders to have access to modern materials, they rely on what is already in their immediate environment. Local people use the wood for constructing houses and boats. In the same manner, they use dead branches for firewood. Farmers also get honey when bees pollinate mangrove flowers. Where mangroves are cleared or polluted, not only does fisheries suffer but the very bread and butter of coastal nations is at peril.

Important food source for many organisms

Mangrove trees are located on the delicate border between the land and the sea. This strategical position acts as a food center for a wide variety of organisms. Juvenile creatures that develop in the swamps get their food through the ebb and flow of seawater that carry along planktons and nutrients. Baby fishes, sharks, rays, turtles, sea birds, flamingos, mollusks all feed on the incoming materials. An intricate food web consisting of marine organisms, insects, birds, mammals, reptiles and amphibians thus exists in mangrove forests.

Unique organisms on islands that depend on mangroves

The endemic Galapagos Penguin, a critically endangered species, rely solely on the mangrove contents to feed [6].  The Mangrove Finch, also found on the Galapagos Island, is restricted only to the mangrove forest of the island, with only 100 adults left in the wild. Dugongs, a vulnerable species found in the waters between East Africa and the Vanuatu Islands west of Australia, feed on seagrass near mangroves forests [7]. They also need the shallow water near mangroves to live and reproduce successfully.

Climate change

Protection against cyclones and sea level rise

One of the most important benefits of mangrove forests to islands is undeniably their protective cover. Mangrove forests form a protective belt around islands and shield them from the impacts of violent waves and storm surges. With changes in the weather happening globally, the intensity of cyclones is expected to increase in the future. Sea level is also rising every year, with an estimated rise of up to 0.98 m by 2100 [8]. Remote islands are especially at risk of threatening cyclones and sea level rise.

Storing blue carbon

Blue carbon is the carbon that oceans and coastal ecosystems store. It has been seen that mangrove forests alone have the capacity to trap and store some 34 million metric tons of carbon per year [9]. Together with other wetland environments like marshes and kelp forests, mangrove forests can store 50-90% of emitted carbon in their sediment. In fact, mangals can store 5 to 10 times more carbon per unit area compared to tropical rainforests [10].

Mangroves must be protected

It can be seen that for many small islands, mangrove forests are an integral part of the lives of the local people whilst at the same time giving them incomparable protection against oceanic hazards. In view of the recent Paris Agreement, governments have to focus on mangrove protection and conservation more than ever before to help mitigate the effects of climate change. Policy makers have to get the most of what’s already on their territorial land than to look for measures elsewhere.

References:

  1. Appadoo, C. (2003). Status of mangroves in Mauritius. Journal of Coastal Development. Vol 7:1, pp 1-4
  2. Mangroves destruction in Maldives – island’s biggest ecocide. (2019). Sixdegrees. [Online]. Available at https://www.sixdegreesnews.org/archives/26304/mangroves-destruction-in-maldives-islands-biggest-ecocide [Accessed 25/03/2019]
  3. Saving mangroves in Solomon Islands. WorldFish. [Online] Available at https://www.worldfishcenter.org/content/saving-mangroves-solomon-islands [Accessed 25/03/2019]
  4. Ellison, A.M. and Farnsworth, E.J. (1996). Anthropogenic disturbance of Caribbean mangrove ecosystems: Past Impacts, Present trends, and future predictions. Biotropica. Vol 28, 4 part A, Special issue: Long term responses of Caribbean ecosystems to disturbances, pp 549-565.
  5. Feller, C. (2018). Mangroves. The Ocean Portal Team. [Online]. Available at https://ocean.si.edu/ocean-life/plants-algae/mangroves [Accessed 25/03/2019]
  6. Vidler, J. (2016). The importance of mangroves. Galapagos Conservation Trust. [Online] Available at https://galapagosconservation.org.uk/the-importance-of-mangroves/ [Accessed 25/03/2019]
  7. Endangered species associated with mangroves. Mangrove Action Project. [Pdf] Available at https://mangroveactionproject.org/wp-content/uploads/2018/10/Endangered-Species-PDF-02.05.13-18.24.pdf [Accessed 25/03/2019]
  8. IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp.
  9. Wright, M. (2017). Coastal wetlands excel at storing carbon. Eurekalert. [Online]. Available at https://www.eurekalert.org/pub_releases/2017-02/uom-cwe012617.php [Accessed 25/03/2019]
  10. Quarto, A. (2017). Mangroves under threat. Travindy. [Online]. Available at https://www.travindy.com/2017/10/mangroves-under-threat-tourism-watch-informationsdienst-tourismus-und-entwicklung/ [Accessed 25/03/2019]

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