0Biodiversity and Ecosystem Services
Humankind derives considerable benefits not only from the products of biodiversity but also from services of ecological systems, such as water purification, erosion control, and pollination. The relationship between biodiversity and ecosystem services is complex and will be discussed in greater detail later, but in general, most ecosystem services are degraded or diminished if the biodiversity of an ecosystem is substantially diminished. Because most ecosystem services are provided freely by natural systems, we typically become aware of their value and importance only when they are lost or diminished.
Historically, ecosystem services were not generally scarce and management decisions were rarely based on their low marginal value. That is decreasingly true, particularly with regard to drinking-water quality, flood control, pollination, soil fertility, and carbon sequestration. This trend is prompting interest in developing institutional frameworks through which to restore and safeguard these services in the United States and internationally.
The value of various ecosystem services can also be seen in the costs that must be incurred to replace them. For example, natural soil ecosystems help to maintain high crop productivity, and the productivity that is lost if soil is degraded through erosion or through changes in species composition can sometimes be restored through the introduction of relatively expensive fertilizers or irrigation. Forested watersheds slow siltation of downstream reservoirs used for hydropower; a forest is altered and sedimentation increases, the hydroelectric power generating capacity lost could be replaced through the construction of new dams. Wetlands play important roles as "buffers", absorbing much stream runoff and preventing floods; if wetlands are filled, their flood-control role could be assumed by new flood-control dams.
The conversion of one type of habitat to another—such as a conversion of natural forest to agriculture or of agricultural land to suburban development—can dramatically affect a wide variety of ecosystem services. Historically, the impacts of such conversions on ecosystem services have not received attention from policy-makers and managers, for two main reasons. First, the relationship between an ecosystem and a service is typically poorly understood. The conversion of a park to a parking lot will obviously change patterns of water runoff, but other effects of habitat conversions are difficult to predict.
Second, ecosystem services are often public goods. Individual landowners who cut their forests bear little if any of the cost associated with the reduction of water quality experienced by downstream water-users. Similarly, the flood control service that is lost when landowners fill their wetlands might have little direct effect on those landowners, but the private economic benefits of land conversion to agriculture will be important . The changes in the environment occur as a result of economic activity, such as land development or cutting forests for lumber.
Therefore biodiversity has considerable benefits in ecosystem and overall human life.
