Two Thirds Of The Earth Is Surrounded By Water

Published Date: 02 Nov 2017

Wetlands with a share of 0.0001 % among the global water sources include swamps, marshes, bogs and similar areas and are an important and vital component of the ecosystem (IUCN, 1996). A wide variety of wetlands exist across the continents because of regional and local differences in hydrology, vegetation, water chemistry, soils, topography, climate and other factors. At the earth’s surface, fresh water forms the habitat of large number of species. These aquatic organisms and the ecosystem in which they live in represent a substantial sector of the earth’s biological diversity.

Wetlands are comprised both land ecosystems that are strongly influencedby water, and aquatic ecosystems withspecial characteristics due to shallownessand proximity to land (Roggeri, H. 1995). Although various different classifications of wetlands exist,

a useful approach is one provided by the Ramsar Convention on Wetlands. It divides

wetlands into three main categories on the basis wetland habitats: (1) marine/coastalwetlands; (2) inland wetlands; (3) man-madewetlands. The marine and coastal wetlandsinclude estuaries, inter-tidal marshes,brackish, saline and freshwater lagoons,mangrove swamps, as well as coral reefsand rocky marine shores such as sea cliffs.Inland wetlands refer to such areas as lakes,rivers, streams and creeks, waterfalls,marshes, peat lands and flooded meadows.Lastly, man-made wetlands include canals,aquaculture ponds, water storage areas andeven wastewater treatment areas.

1.1 Function of Wetlands

Wetlands perform a variety of functions (Groot. 1992). First, wetlands performregulation functions - wetlands regulate ecological processes that contribute to ahealthy environment e.g. recyclingof nutrients and human waste, watershedprotection and climate regulation. A secondfunction of wetlands is called carrierfunction: wetlands provide space for activities such as human settlement,cultivation, energy production and habitatfor animals. Third, wetlands perform production functions. Wetlands provideresources for people such as food, water,raw materials for building and clothing. The last wetland function is information function in the sense that wetlands contribute tomental health by providing scientific,aesthetic and spiritual information.

The diversity in functions that wetlandsperform makes them incredibly valuableecosystems. For example, they have avery high ecological value, providingthe water and primary productivity uponwhich countless species of plants andanimals depend. Wetlands support highconcentrations of birds, mammals, reptiles,amphibians, fish and invertebrate species.It has been estimated that freshwaterwetlands hold more than 40% of all theworld’s species and 12% of all animalspecies (www.ramsar.org). Individual wetlands can beextremely important in supporting high numbers of endemic species; for example,Lake Tanganyika in Central Africa supports 632 endemic animal species (www.ramsar.org). Wetlands have more valuable economic resources when retained in their natural or semi-natural state.

Development projects have often stimulated wetland conversion largely because of lack of information and ignorance of planners about wetland functions and their role in sustainable development. Conversion or degradation of such natural capital assets will therefore not represent an increase in resource-use efficiency. Social inefficiency in wetland use is connected to the fact that wetlands are multifunctional resource and are under heavy utilization pressure.

1.2 Threats and loss of wetlands

Wetlands represent dynamic natural environments that are subjected to both human and natural forces. Natural events influencing wetlands include rising sea level, natural succession, hydrologic cycle, sedimentation, and erosion. The rise in sea level, for example, both increases and decreases the wetlands spatial extent depending on local factors.

Wetlands are under increasing stress due to the rapidly growing population, technological development, urbanisation and economic growth. Additional pressures on wetlands from natural causes like subsidence, drought, hurricanes, erosion etc., and human threats coming from over exploitation, encroachment, reclamation of vast wetland areas for agriculture (Zalakevicius, 2002), commercial and residential development, and silviculture have altered the rate and nature of wetland functions particularly in the last few decades (Beilfuss et al., 2002). The primary pollutants causing degradation are sediments, nutrients, pesticides, salinity, heavy metals, weeds, low dissolved oxygen, pH and selenium (Georges and Cottingham, 2002).

Wetland loss may be defined as the loss of wetland area, due to conversion of wetland to non-wetland areas and degradation of wetland as a result of human activity. About 50 % of the world’s wetlands have been lost in the last century, primarily through drainage for agriculture, urban development and water system regulations. It has been estimated that nearly one hectare of the world’s wetlands is getting degraded at the tick of every minute of the clock’s (Narayanan, 1992).Dugan and Jones (1992) showed that 84% of Ramsar sites has suffered, or were threatened by ecological change and, despite regulation, environmental degradation of wetlands continues today. Wetland losses in the UnitedState between European colonisation and the late-twentieth century were substantial. By the 1970s, just 40 million hectares of wetlands remained out of the 87 million hectares that were present in the conterminous 48 states when the US was created, including 3.6 million hectares lost between 1950 and 1970, 87% of which was from agricultural development (Tiner, 1984)