BIODIVERSITY AND HUMAN HEALTH
Executive Summary, page 5
by Joseph Dougherty

Ecosystem Services as an Example of Biodiversity Value

The value of biodiversity can be measured and quantified in many ways, but one of the most palpable is when hard dollar figures are placed on the resources and services we derive from the natural environment, a discipline called resource economics.

Soil Formation and Protection

The estimated value of natural soil formation and protection is 17.1 trillion U.S. dollars (Costanza 1997). Without this ecosystem service, agricultural and wilderness areas would cease to function as we know them today. Biodiversity is fundamental in the formation and maintenance of soil structure, as well as its retention of moisture and nutrient levels.

Soil formation begins when large rocks are broken down into finer particles. Lichen play a key role in starting this slow and gradual process. Trees and other vegetation then further the process as their roots break up the rock, absorbing minerals and improving water penetration. By taking up raw nutrients from the decaying rocks and converting them into living tissue, the plants contribute organic matter to the soil mixture, through leaf litter and other decaying tissues, which support the decomposers that are the vital last step in the soil formation process. A rich community of microorganisms, fungi, and invertebrates populates healthy soils, recycling organic materials and improving soil conditioning. Some plants, such as legumes, develop specialized roots where symbiotic microbes live and absorb atmospheric nitrogen, “fixing” the nitrogen into the soil in forms usable by the plants. Plant root systems can also absorb and bind with minerals, such as iron and aluminum, which may be semitoxic to other vegetation, thus paving the way for successional species to gain a toehold in the biome (Attiwill 1987).

Many kinds of organisms, from giant trees to microscopic organisms still unknown to science, are involved in the process of soil formation. Yet this community is easily disrupted by excessive human interference with the landscape. The loss of biodiversity — through vegetation clearing, monocropping, terrestrial engineering, wetland drainage, etc. — contributes to the leaching of nutrients, accelerated erosion of topsoil, salinization of floodplain soils, and laterization of soils. The net effect of biodiversity loss is a reduction in the land’s potential productivity and an increase in the likelihood of devastating damages from uncontrolled storm runoff. Protecting soil by maintaining biodiversity, on the other hand, preserves the productivity of terrestrial and nearshore aquatic systems. It also helps protect people and wildlife from the dangers of uncontrolled runoff.

Using crop rotation and mixed plantings, especially those that incorporate legumes, maintains high vegetative yields through recurrent nitrogen fixation. This reduces the costs of agricultural production in both economic (by reducing the quantity of fertilizers used) and social (by maintaining biodiversity) terms. Healthy tracts of mixed vegetation safeguard coastlines and riverbanks from erosion and help prevent landslides. In the U.S. alone, more than 1500 buildings crumble every year due to coastal erosion. Along the Atlantic Coast, beaches retreat two to three feet per year, and along the Gulf Coast, the erosion rate is six feet per year (Dean 2000). These losses are closely correlated with the removal of native plants, such as beach grass (Ammophila breviligulata), which stabilizes the coastal sand dunes. In the Pacific Northwest, clearcut logging operations have destroyed the spawning grounds of many salmon rivers by denuding mountain slopes of the plants that hold soil in place during heavy rains. The silt-laden runoff pours into the salmon streams, covering the pebbly bottoms that the salmon require for spawning with a layer of mud. As a result, salmon stocks have plummeted in the north Pacific. Strong erosion-control buffer zones, such as riparian reserves and mangrove estuaries, protect the health of riverine and coastal fisheries and also prevent the degradation of coral reefs by siltation.

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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.