Prepared by Rahanna Juman
Acting Director/ Wetlands Ecologist
Institute of Marine Affairs
In 2015, the General Conference of UNESCO declared July 26th the annual observance of International Day for the Conservation of the Mangrove Ecosystem. Why dedicate an entire day every year to raise awareness of the importance of mangrove ecosystems as “a unique, special and vulnerable ecosystem" and promote solutions for their sustainable management, conservation and uses?
Mangroves are one of the world’s most productive ecosystems as they enrich coastal waters and serve as the ‘supermarket’ of the sea (Numbere, 2018), providing numerous services that contribute to human well-being, environmental health and poverty alleviation. It was estimated that each hectare of mangrove produces US$ 0.2 – 12,305 of fishes and US$ 17.5 – 3,412 of mixed species (Hutchison et al. 2014). In Trinidad and Tobago, the mangrove forests provide livelihoods for people who harvest and sell fish and shellfish; the most economically important is the harvest and trade of the hairy crab, the blue crab and the mangrove oyster (Maynard and Oxenford, 2014).
Many also earn a living as tour guides as mangrove forest provide invaluable opportunities for recreation and tourism. They are important tourist destinations because of their aesthetic value and high biodiversity. There is a list of almost 3,945 mangrove “attractions” in 93 countries (Spalding and Parrett, 2019). The Caroni Swamp is one of the most popular eco-tourist sites in Trinidad. It is especially popular with bird-watchers because of its rich avifauna population, and tour guides have been earning a living from the Swamp for generations.
The Caroni Swamp is one of the most popular eco-tourist sites in Trinidad & Tobago.
More than 600 million people (around 10 per cent of the world’s population) live in coastal areas that are less than 10 meters above sea level. I wonder if they know how vulnerable they are to impacts of climate change. Climate change is not something in the future; the impacts are being felt now. These include more intense rainfall events leading to landslides and floods, storm surges that cause coastal flooding and erosion, and more frequent and intense hurricanes and storms.
Mangrove forests are our main line of defence against sea level rise and storm surge. Mangrove forests act like shock absorbers dissipating wind and wave energy. They prevent coastal erosion by reducing wave impact and inducing sedimentation by colonizing and stabilizing emerging mud banks with their roots (Mazda et al. 1997). Their complex root systems, which are important for sediment stabilization, also reduce both storm surges and tsunami wave impacts further inland (Marois et al. 2015). Typically, wave height is reduced 13-66% for every 100 metres of mangrove and every hectare of mangrove and coastal marsh is estimated to be worth USD$15,161 a year in disaster-related services.
Mangroves also have a significant effect on the extent of inundation and damages caused by coastal flooding. It has been estimated that if all mangroves in the world were lost, 18 million more people would be flooded every year on average, an increase of almost 40 per cent, and the annual damages to property would increase by US $82 billion (Reguero et al. 2018). Annually, the value of Jamaica’s mangrove forests for flood risk reduction to the nation’s built capital is more than US$2,500 per hectare per year (World Bank, 2019).
Mangroves help to alleviate coastal erosion. Photo IMA.
Mangrove forest also play a significant role in stabilizing Green House Gas emissions and blunting the impacts of climate change as they trap and store carbon dioxide within their biomass (above ground woody tissue) and soils. The total amount of above ground carbon estimated to be held in mangrove forests in Trinidad and Tobago is 809,085.92 tonnes. Comparing mangrove forest carbon to terrestrial forest carbon revealed that per hectare, mangrove forests sequestered 61% more carbon than terrestrial forests in Tobago, while for Trinidad the value was 44% (Juman et al. 2021). The belowground soil carbon pool is estimated to be at least 4 times more (and likely considerably higher) than the aboveground pool, making mangrove forests amongst the highest carbon dense ecosystems in the world. However, this pool of carbon is only maintained, and increases, if left undisturbed. When mangrove forests are disturbed or destroyed, carbon dioxide is emitted from the oxidization of organic sediments and biomass, which contributes significantly to global warming.
Therefore, we cannot continue to degrade or destroy the mangroves, our natural defences, by clearing or dumping our wastewater and garbage into them. When we litter our rivers, waterways and beaches, it ends up in our mangroves. A healthy mangrove helps reduce risks from disaster as loss of mangrove forest will increase threat to human safety and increase damage to shorelines from coastal hazards such as erosion, flooding, and storm waves and surges. Mangrove loss can result in decreased coastal water quality, reduce biodiversity, eliminate fish and crustacean nursery habitats, and eliminate a major resource for human communities that traditionally rely on mangroves for numerous products and services. Furthermore, mangrove destruction can release large quantities of stored carbon and exacerbate global warming trends.
Healthy mangrove forests alleviate coastal hazards from natural disasters, contribute to good water quality, supports healthy biodiversity and more.
At the Institute of Marine Affairs (IMA), we have been conducting research and monitoring of mangrove forests so as to provide the scientific data required to effectively manage and restore these essential ecosystems so they can continue to provide ecosystem services for all citizens on our beautiful island state, and provide livelihood opportunities for many in our society. In 2021, the IMA published a book titled, ‘Mangrove Forests of Trinidad and Tobago’ that provided information on the many benefits provided by these forests, their distribution, socio-economic importance and current status. With increased awareness about mangrove forests, it is hoped that citizens of Trinidad and Tobago would become meaningfully engaged in its conservation Let us appreciate our mangrove forests. Happy International Mangrove Day!
Caring for our mangrove forests. Mangrove replanting with the IMA, Environmental Policy Planning Division and University School in 2018.
1. Hutchison, J. et al. 2014. The Role of Mangroves in Fisheries Enhancement. The Nature Conservancy and Wetlands International.
2. Juman, R., Asmath, H., Gooding, N. and Collins, G. 2021. Mangrove Forests of Trinidad and Tobago, Institute of Marine Affairs, Chaguaramas, Trinidad and Tobago
3. Marois, D. E., and Mitsch, W. J., 2015. Coastal protection from tsunamis and cyclones provided by mangrove wetlands – a review. International Journal of Biodiversity Science, Ecosystem Services & Management, vol. 11, No.1, pp. 71–83.
4. Maynard, M. and H.A. Oxenford (2014). Characterization of the Commercial Mangrove Land Crab Fishery in Trinidad. Centre for Resource Management and Environmental Studies, The University of the West Indies, Cave Hill Campus, Barbados. CERMES Technical Report No 76. 87 pp.
5. Mazda, Y., Magi, M., Kogo, M. and Hong, P.N. 1997. Mangroves as a coastal protection from waves in the Tong King delta, Vietnam. Mang. Salt Marsh. 1(2): 127–135.-9
6. Numbere, A. 2018. Mangrove Species Distribution and Composition, Adaptive Strategies and Ecosystem Services in the Niger River Delta, Nigeria. In: Mangrove Ecosystem Ecology and Function Edition: 1Chp 2. Intech Open, DOI:10.5772/intechopen.79028
7. Spalding, M. and Parrett, C.L. 2019. Global patterns in mangrove recreation and tourism. Marine Policy 110 103540
8. World Bank. 2019. “Forces of Nature: Assessment and Economic Valuation of Coastal Protection Services Provided by Mangroves in Jamaica”.