Mangrove Ecology and Conservation
Published 08 Dec 2016
Mangrove ecosystems are characterised by tropical trees and shrubs that grow along estuaries, marine shorelines, and sheltered coasts where fine sediments, often with high organic content, collect in areas protected from high-energy wave action.These species are important to prevent coastal erosions and surge storms. They also provide protection to coastal communities from typhoons.
The different mangrove species have prop roots that form dense masses necessary in coastal land building and as foundations of unique ecosystems. Oysters utilize these roots, which prevent water flow, as their habitat. In areas where the roots are completely covered with water, these trees host organisms that require a hard substratum for anchoring while they filter feed. These organisms include algae, barnacles, oysters, sponges and bryozoans. Further, mangrove trees host some fishes and crustacea that are commercially valuable.
Scientists have identified five major mangrove species: black mangrove, buttonwood or white mangrove, mangrove palm, red mangrove, and mangrove apple. These trees group together in accordance with their tolerances to physical conditions like tidal ranges, anaerobic soils and intense heat; as well as their responses to other factors such as crabs’ predation of plant seedlings. Each of these groups is perse and capable of physiological adaptations to survive despite the harshness of their environment. For example, the red mangroves survive the low level of oxygen in soils by taking in air through their barks and by placing themselves up above water with stilt roots.
Due to the high salinity of the ecosystem, these species have developed mechanisms to limit salt intake. The white mangroves limit salt intake by having two glands at each leaf base that can secrete salt directly. The biggest challenge that these plants face is getting food from the inhospitable soil. To get nourishment, mangroves use their prop roots to take up gases directly from the atmosphere as well as iron from the soil.
Burke et al. (2001, quoted in Broshear 2005) is in agreement with most scientists that the region of greatest mangrove persity is in Southeast Asia, particularly around the Indonesian Archipelago. Broshear (2005) discussed in a study that from the Southeast Asian center of origin, mangrove forests have distributed themselves around the globe and have been documented to establish themselves between the tropics of Cancer and Capricorn, and rarely are they found above this latitude.
Conservation and Management
Mangrove communities all over the globe face many disturbances that could be categorised into two: natural devastation that is typically brought on by typhoons, and those resulting from the influence of human on nature.
High human populations in coastal habitats across the world are under pressure to reclaim mangrove areas for development. Mangroves are also exploited for valuable wood and fishery resources. A quarter of mangrove destruction is the result of shrimp farming (Botkin & Keller 2003), while other factors include conversion of large areas of mangrove to aquaculture and agriculture.
On top of this, global warming presents further threat to this valuable habitat. Studies have shown that species in natural environments, like the mangroves, could adapt to gradual changes in climate. However, rapid changes have often led to extinctions of species and the collapse of natural habitats. Global warming could possibly impact mangrove ecosystems in this manner.
As their importance to the marine environment has become widely accepted by scientists, various institutions launched programs to address the degradation and decline of mangrove forest ecosystems. These efforts involve legislative, management, conservation and rehabilitation.
In Australia, two of the most known mangrove ecosystems are the Darwin Harbour tropical estuary that has the Northern Territory’s largest stand of mangroves, and the Wet Tropics of Queensland.
Darwin is the capital of the Australian Northern Territory. It has an extensive coastline, a tropical climate, and strong cyclone periods. Inter-tidal mangrove and salt-marsh communities populate about 27,350 hectares, or at least two-thirds of Darwin’s vast coastlines.
The area’s growing population over the years and a relatively scarce land resulted to the reclamation of coastal fringes for the construction of houses. The reclamation projects,combined with strong cyclones, have threatened the region’s largest mangrove ecosystem.
Since 1983, the community and the Environment Centre of the Northern Territory have been campaigning for the protection and conservation of Darwin Harbour’s natural and cultural heritage. Their efforts were finally rewarded when in 2003, the government declared Darwin Harbour’s mangroves as a conservation zone. At the same time, a management plan was also released that contained key recommendations for the protection of the natural and cultural values of Darwin Harbour (Pedder 2003).
Wet Tropics of Queensland
The Wet Tropics World Heritage area covers more than 8,940 square kilometers of Queensland’s tropical, terrestrial ecoregions located in northeastern Australia. The region became part of the World Heritage in 1988, and as such, has been made one of the protected areas in the country.
The Wet Tropics rainforests contain the most complete and perse living record of the major stages in the evolutionary history of the word’s land plants, as well as one of the most important living records of the history of the marsupials and the songbirds.
Mangrove ecosystems in the region merge with the rainforest, sharing many species at the interface including Diospyros littorea, which occurs only on the landward side of mangroves. These mangroves are also hosts to salt marsh plants and epiphytes, which are among the native species in this ecoregion.
The protection of the Wet Tropics came as a result of deforestation threats and the onslaught of invasive pest species. Deforestation in the area caused defragmentation of habitats, leading to the decline of some endemic species.
Despite concerted efforts to prevent the gradual disappearance of mangrove forest ecosystems, these coastal habitats continue their decline in a global scale. There is an abundance of scientific studies and literature for management and conservation of mangroves but they needed to be disseminated to non-scientists in a format that they can use.
Stepping up previous attempts at creating a practical mangrove conservation plan, Macintosh and Ashton (2002) conducted a study in 2002 aimed at formulating a generic code of conduct for sustainable management of mangrove forest ecosystems. The authors concluded that management and conservation of mangrove biopersity are relative to each region, taking into consideration local issues and hurdles.
For programs designed to manage and conserve mangrove habitats to be successful, there should be a close coordination among lay people, biologists, and social scientists with the support of the local government.
- Australian Government Department of the Environment and Water Resources1988, Wet Tropics of Queensland, viewed 17 October 2007
- Botkin, D. and E. Keller 2003, ‘Environmental Science: Earth as a living planet’, page 2, John Wiley & Sons.
- Broshear, J 2005, Mangrove Forest Distribution, Disturbances, and Conservation, viewed 18 October 2007
- Goosem, S 2001, Queensland Tropical Rainforests, viewed 17 October 2007, http://www.worldwildlife.org/wildworld/profiles/terrestrial/aa/aa0117_full.html
- Macintosh, DJ and Ashton, EC 2002, A Review of Mangrove Biopersity Conservation and Management, The World Bank and Centre for Tropical Ecosystems Research, University of Aarhus, Denmark
- Pedder, A 2003, ‘The Environment Centre Northern Territory’, ECNT Welcomes the Long Awaited Darwin Harbour Plan of Management, 23 December, viewed 18 October 2007, http://www.ecnt.org/html/cur_marine_darwin_overview.html
- UNEP World Conservation Monitoring Centre 1988, Protected Areas Programme, viewed 17 October 2007, http://www2.wcmc.org.uk/protected_areas/data/wh/wettropi.html