Different kinds of mangrove forests provide different goods and services
Year Published:
Study Number:
49
Author:

K. C. Ewel, R. R. Twilley & J. E. Ong

Abstract:

The goods and services that mangrove forests provide to society are widely understood but may be too generally stated to serve as useful guidelines in decision-making. Understanding the differences between fringe, riverine, and basin forests may help to focus these guidelines and to determine the best use of a particular forest. Fringe mangroves are important primarily for shoreline protection. Riverine forests, which are likely to be the most productive of the three types of forests, are particularly important to animal and plant productivity, perhaps because of high nutrient concentrations associated with sediment trapping. Basin forests serve as nutrient sinks for both natural and anthropogenically enhanced ecosystem processes and are often important sources of wood products. Exploitation of a forest for one particular reason may make it incapable of providing other goods and services.

Main Results and Conclusions:
  • Three categories of mangrove forest types are described:
    • Fringe: tide-dominated, intermediate productivity (Pool, Lugo & Snedaker 1975), receive full effect of tidal changes, prop roots, buttresses, and pneumatophores are common (84)
    • Riverine: river-dominated, most productive forest type ((Pool, Lugo & Snedaker 1975), commonly flooded by river water (and sometimes tides), moderate salinity (84)
    • Basin: interior (i.e. found in large areas behind riverine and fringe mangrove), least productive forest type ((Pool, Lugo & Snedaker 1975), expected to have greater variation compared to other two, tides rarely reach limits of basin forest (84)
  • Many ecosystem goods and services are discussed:
    • Sediment trapping
      • Fringe- “Sediments deposited in fringe forests can be riverine in origin, however, having been recirculated within the nearshore waters (Wolanski, Mazda & Ridd, 1992)”(85).
      • Riverine- “…likely to be particularly important in this respect, because river waters usually carry a heavier sediment load than ocean tides… also trap sediments deposited by runoff from uplands along the landward edge of the swamp”(85).
      • Basin- “trap sediments, receiving the finest particles that are carried past riverine and fringe forests by floods and tides”(85).
    • Processing of organic matter and nutrients (threat: coastal development)
      • Organic matter export: “Estimates of carbon export to offshore waters range across two orders of magnitude; the average rate is about 210gC m-2 yr-1, with greatest export values coming from fringe mangroves (Table 2)”(86).
      • Nutrient sink: “Basin mangroves…may have higher rates of organic matter and nutrient accumulation”(87). Basin mangroves are prone to act as nitrogen sinks (87). 
      • Water Quality Improvement: Mangrove forests often receive untreated wastewater because of their ability to improve water quality. However, high volumes of untreated wastewater can damage mangrove forests (87). (Coastal Development).
    • Animal habitat (threat: aquaculture ponds)
      • Crabs, penaeid shrimp, juvenile and adult fish, higher vertebrates, birds, and many mammals use mangrove habitat (88-89).
    • Aesthetically pleasing environment
      • Mangrove forests attract tourists (89).
    • Protection from floods (threat: coastal development)
      • Fringe/Riverine-  “…particularly important for preventing shorelines from eroding, thereby not only affording shoreline protection but protecting offshore seagrass beds and coral reefs from sediment deposition as well”(90).
      • Basin- “…may assist in protection from episodic floods…both by reducing water velocity and by adding flood storage capacity behind fringe and riverine forest (90).
    • Plant Products (threat: deforestation)
      • Mangrove plant products are used as tannins, honey, medicinal products, and thatch (Hamiliton & Snadakar, 1984).
      • Timber is used for firewood, charcoal, building materials (i.e. poles & pilings), boat building material, furniture and carvings, fishing stakes, and in some cases, woodchip production (90-91).
  • Decision making based on goods and services
    • Different types of mangrove habitats offer different types of ecosystem goods and services. This is important to recognize in order to make the best management decisions. Some mangroves, for example, may be able to perform certain services better than others: “Riverine forests, with their nutrient inflows and moderate salinities are important interfaces between the more expansive basin forests and the fresh and salt water inflows. Basin forests, on the other hand, with their more restricted water flows, are often the sites of greatest human activity. Fringe mangrove forests, subject to the greatest water movement and consistently high salinity, are critical as a protective barrier for the rest of the forest and, occasionally, for human structures as well”(91).
    • In conclusion, the exploitation of a mangrove forest for a single ecosystem good or service may diminish the quality of other goods and/or the ability of other services (91). 
Works Cited:

Hamilton, L.S. & Snedaker, S.C. (1984) Handbook for mangrove area management, 123 pp. East-West Center, Honolulu HI, USA.

Pool, D.J., Lugo, A.E. & Snedaker, S.C. (1975) Litter production in mangrove forests of southern Florida and Puerto Rico. Proceedings of the International Symposium on Biology and Management of Mangroves (ed. by G. E. Walsh, S. C. Snedaker and H. J. Teas) pp. 213-237. Inst. Food Agric. Sci., Univ. Fla., Gainesvill

Wolanski, E., Mazda, Y. & Ridd, P. (1992) Mangrove hydrodynamics. Tropical mangrove ecosystems. coastal and estuarine studies 41 (ed. by A.I. Robertson & D.M. Alongi) pp. 43-62. American Geophysical Union, Washington DC.