In recent times, mangrove communities have come under increasing threat from development pressures. Some of the more direct threats to mangrove communities have emerged from development proposals requiring reclamation of mangrove land, for example airport runway construction, port expansions and road development. In the short term, there is considerable potential for these projects to result in positive economic gains. However, in the medium to long term these gains may well be diminished by the negative economic outcomes that may arise from the loss of the ecosystem goods and services provided by the mangrove communities.
Perhaps one of the most commonly identified services provided by mangrove communities is the provision of a nursery habitat for juvenile fish. The shallow water environment of the mangrove estuary area and the mangrove roots themselves protect these juvenile fish from predators like larger fish and birds((Nickerson, Donna. J. 1999. Trade-offs of mangrove area development in the Philippines. Ecological Economics, 28:279-298)). Furthermore, the survival of juvenile fish is aided by the long residence time of water amongst the mangroves, which is facilitated by the mangrove roots. This creates a relatively calm water environment where larvae and juvenile fish can settle((Nickerson, Donna. J. 1999. Trade-offs of mangrove area development in the Philippines. Ecological Economics, 28:279-298)). When mangroves are removed from an estuarine environment, many of these ecosystem services that aid the survival and production of fisheries can be either lost or diminished in value. For instance, it has been suggested that the comparatively smaller amounts of food produced by a diminished mangrove area will cause a decline in the rate of reproduction amongst mangrove dwelling fish to decline. Primarily this is because the fish will divert energy away from reproduction to competition for an ever-smaller reserve of food((Nickerson, Donna. J. 1999. Trade-offs of mangrove area development in the Philippines. Ecological Economics, 28:279-298)). At the same time, the limited availability of food and the smaller habitat size associated with mangrove removal will result in weaker and more exposed fish populations vulnerable to increased rates of predation((Nickerson, Donna. J. 1999. Trade-offs of mangrove area development in the Philippines. Ecological Economics, 28:279-298)). Considering that many commercially important fish species spend some part of their life-cycle in mangrove environments, commercial and recreational fisheries are likely to suffer fish declines and by association negative economic consequences as a result of mangrove removal. This then has negative economic consequences for regional economies that have substantial input from fish based industries.
Assimilation of waste
Mangrove communities regulate water quality((Ibid. Gilber, A.J. and Janssen, R. 1998. Use of Environmental Functions to Communicate the Values of a Mangrove Ecosystem under Different Management Regimes. Ecological Economics, 25:323-346.)). This service is particularly important where the surrounding region contains seagrass or coral reefs given that these habitats are particularly vulnerable to deterioration if water quality declines((Opcit. Nickerson 1999)). If coral reefs and seagrass habitats were to be lost, numerous highly valuable ecosystem goods and services would also be lost. For instance, many coral reefs, seagrass and the organisms found amongst these habitats have considerable tourism value. Also, many recreational and commercial fish species spend part of their life cycle in coral reefs and seagrass areas((Costanza, R, d’Arge, R, de Groot, R, Farber, S, Grasso, M, Hannon, B, Limburg, K, Naeem, S, o’Neill, R, Paruelo, J, Raskin, R, Sutton, P, and van den Belt, M. The Value of the World’s ecosystem services and Natural Capital. Nature 387: 253-260. Zann, Leon P. State of the Marine Environment Report for Australia: The Marine Environment Technical Annex: 1.The State of the marine environment : report for Australia. Technical annex. 1, The marine environment / edited by Leon P. Zann, Patricia Kailola.)). Furthermore, coral reefs provide buffers against strong wave energy, protecting the coast against erosion((Global coral reef alliance. Reef restoration and shore protection, coastal erosion and shore protection.http://www.globalcoral.org/_oldgcra/reef_restoration_and_shore_prote.htm)). If mangroves were removed from the estuarine area, it is possible that the deterioration in water quality could impair the services provided by the seagrass and coral reef communities((Opcit. Nickerson 1999)). This is particularly likely in the case of coral reefs, given that these communities are already under considerable stress world wide due to, amongst other pressures, the effects of climate change((Intergovernmental Panel on Climate Change. Coral reefs, mangroves and seagrasses. Climate change 2001: working group II: Impacts, adaptation, and vulnerability. http://www.grida.no/publications/269)).
To conclude, mangrove communities provide crucial ecosystem services that support many economically important industries including recreational and commercial fishing, and tourism. Looking at the big picture, the economic losses that will occur in the long term should be seriously considered before mangroves are removed for development purposes.
Robinson, J., Cully, T., Coastal CRC