BIODIVERSITY AND HUMAN HEALTH
Executive Summary, page 6
by Joseph Dougherty

Ecosystem Services (continued)

Water Supply Protection

Natural vegetation cover in water catchments helps to maintain hydrological cycles, regulating and stabilizing water runoff, and acting as a buffer against extreme events such as flood and drought. Vegetation removal results in siltation of catchment waterways, loss of water yield and quality, and degradation of aquatic habitat, among other things. Vegetation also helps to regulate underground water tables, preventing dryland salinity which affects vast areas of Australia's agricultural lands, at great cost to the community. Wetlands and forests act as water purifying systems, while mangroves trap silt, reducing impacts on marine ecosystems.

These services translate into substantial financial benefits. An Australian study, for example, calculated the financial benefit of water supplied to Melbourne from forested catchments at over $250 million per year, an annual amount expect to grow by over $150 million in the next 50 years as logged lands are reforested (Read 1982).

Nutrient Storage and Cycling

Ecosystems perform the vital function of recycling nurients. These nutrients include the elements of the atmosphere as well as those found in the soil, which are necessary for the maintenance of life. Biological diversity is essential in this process. Plants are able to take up nutrients from the soil as well as from the air, and these nutrients can then form the basis of food chains, to be used by a wide range of other life forms. The soil's nutrient status, in turn, is replenished by dead or waste matter which is transformed by microorganisms; this may then feed other species such as earthworms which also mix and aerate the soil and make nutrients more readily available.

Climate Regulation

Vegetation influences climate at the macro and micro levels. Growing evidence suggests that undisturbed forest helps to maintain the rainfall in its immediate vicinity by recycling water vapour at a steady rate back into the atmosphere and through the canopy's effect in promoting atmospheric turbulence. At smaller scales, vegetation has a moderating influence on local climates and may create quite specific micro-climates. Some organisms are dependent on such micro-climates for their existence.

Habitat Maintenance

Ecosystem relationships resemble a web of connections from one living thing to many other living and non-living things. No ecosystem stands alone. Each is tied to adjacent areas by transition zones called ecotones. Some of these ecotones experience an edge effect, where the communities of two adjacent ecosystems overlap and intermingle in a narrow ecotone, which may be significantly more diverse than either of the primary ecosystems considered on their own.

Healthy and intact ecosystems not only allow survival, but also maintain a balance between living things and the resources (such as food and shelter) those organisms need to survive. Vegetation is integral to the maintenance of water and humidity levels and is essential for the maintenence of the oxygen/carbon dioxide balance of the atmosphere. Due to the complex nature of ecosystem relationships, the removal or disturbance of one part of the ecosystem could affect the functioning of many other components of the ecosystem. Our knowledge of these relationships is incomplete, and the results of disturbance are thus to some extent unpredictable.

Maintaining natural habitats helps ecosystem functions over a wider area. Natural habitats afford sanctuary to breeding populations of birds and other predators which help control insect pests in agricultural areas, thus reducing the need for, and cost of artifical control measures. Birds and nector loving insects roost and breed in natural habitats may range some distance and pollinate crops and native flora in surrounding areas.

Pollution Management

Ecosystems and ecological processes play an important role in the breakdown and absorption of many pollutants created by humans and their activities. These include wastes such as sewage, garbage and oil spills. Components of ecosystems from bacteria to higher life forms are involved in these breakdown and assimilative processes. Excessive quantities of any pollutant, however, can be detrimental to the integrity of ecosystems and their biota.

Some ecosystems, especially wetlands, have qualities that are particularly well suited to breaking down and absorbing pollutants. Natural and artificial wetlands are being used to filter effluents to remove nutrients, heavy metals and suspended solids, reduce the biochemical oxygen demand and destroy potentially harmful microorganisms.

Storm Protection and Recovery

Maintaining healthy ecosystems also improves the chances of recovery for plant and animal populations impacted by natural catastophies such as fires, floods, hurricanes, and even from disasters caused by humans. Inadequately conserved and isolated populations, and ecosystems which are degraded, are less likely to recover (or to recover as quickly) to their former state. Populations of biota may end up with small — possibly non-viable — genetic bases, which can lead to extinctions.

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References on this page. Click your browser's "Back" button to return to the spot you were reading.

Attiwill, P.M. and Leeper, G.W. 1987. Forest Soils and Nutrient Cycles. Melbourne University Press: Melbourne, Australia.

Costanza, R., et. al. 1997. “The Value of the World’s Ecosystem Services and Natural Capital,” Nature. 387: 256, table 2.

Dean, Cornelia. 2000. “Agency Cites Growing Danger of Erosion Along U.S. Coasts,” New York Times, 28 June 2000. Available online: http://www.nytimes.com/library/national/science/062800sci-environ-erosion.html.

Read, Sturgess and Associates. 1982. "Evaluation of Economic Values of Wood and Water for the Thomson Catchment." Report prepared for Melbourne Water.