Humans have always relied on nature for environmental assets like clean water and soil formation. Today, these assets are receiving global attention as 'ecosystem services', the conditions and processes by which natural ecosystems sustain and fulfill human life. Natural ecosystems perform a diversity of ecosystem services on which human civilization depends:
1. regulating services - purification of air and water, detoxification and decomposition of wastes, moderation of weather extremes, climate regulation, erosion control, flood control, mitigation of drought and floods, regulation of disease carrying organisms and agricultural pests;
2. provisioning services - provision of food, fuel, fiber, and freshwater;
3. supporting services - formation and preservation of soils, protection from ultraviolet rays, pollination of natural vegetation and agricultural crops, cycling of nutrients, seed dispersal, maintenance of biodiversity, primary production; and
4. cultural services - spiritual, esthetic, recreational.
Although critical to human existence, ecosystem services are often taken for granted or at best, greatly undervalued. This is ironic given that many ecosystem services are very difficult and expensive to duplicate, if they can be duplicated at all. Normally, ecosystem services are considered 'free' despite their obvious economic value. For example, over 100 000 species of animals provide free pollination services, including bats, bees, flies, moths, beetles, birds, and butterflies (Figure 10). Based on the estimate that one-third of human food comes from plants pollinated by wild pollinators, pollination has been valued at US$4-6 billion per year in the US alone. Globally, the world's ecosystem services have been valued at US$33 trillion a year, nearly twice as much as the gross national product of all of the world's countries.
The idea of paying for ecosystem services has been gaining momentum. Yet, because ecosystem services are typically not sold in markets, they usually lack a market value. Given the value of natural capital, nonmarket valuation approaches are being developed by economists and ecologists to account for ecosystem services in decision-making processes. The notion being that economic valuation gives decision makers a common currency to assess the relative importance of ecosystem processes and other forms of capital.
Yet, assigning value to ecosystem services is tricky and some analysts object to nonmarket valuation, because it is a strictly anthropogenic measure and does not account for
nonhuman values and needs. Yet, in democratic countries, environmental policy outcomes are determined by the desires of the majority of citizens, and voting on a preferred policy alternative is ultimately an anthropogenic activity. A second objection to nonmarket valuation is a disagreement with pricing the natural world and dissatisfaction with the capitalistic premise that everything is thought of in terms of commodities and money. The point of valuation, however, is to frame choices and clarify the tradeoffs between alternative outcomes (i.e., draining a wetland may increase the supply of developable land for housing but does so at the cost of decreased habitat and potential water quality degradation). Finally, a third objection to nonmarket valuation stems from the uncertainty in identifying and quantifying all ecosystem services. Advocates argue that economic valuation need not cover all values and that progress is made by capturing values that are presently overlooked.
Despite the uncertainties, valuing ecosystem services can sometimes pay off. When New York City compared the coast of an artificial water filtration plant valued at US$6-8 billion, plus an annual operating cost of US$300 million, the city chose to restore the natural capital of the Catskill Mountains for this watershed's inherent water filtration services and for a fraction of the cost (US$660 million). Ultimately, the valuation of ecosystem services, even if flawed, may get ecosystem processes on the decision-making table and lead to more sustainable policies in light of ever-expanding human populations.
Ecosystem services are threatened by growth in the scale of human enterprise (population size, per-capita consumption rates) and a mismatch between short-term needs and long-term societal well-being. With a global population soon to number 9 billion people, ecosystem services are becoming so degraded, some regions in the world risk ecological collapse. Many human activities alter, disrupt, impair, or reengineer ecosystem services such as overfishing, deforestation, introduction of invasive species, destruction of wetlands, erosion of soils, runoff of pesticides, fertilizers, and animal wastes, pollution of land, water, and air resources. The consequences of degrading ecosystem services on human well-being were examined in the Millennium Ecosystem Assessment (MA) 2005, which concluded that well over half of the world's ecosystems services are being degraded or used unsustainably. The MA developed global ecological scenarios as a process to inform future policy options. These scenarios were based on a suite of models that were designed to forecast future change. The MA based its scenario analyses on ecosystem services. Specifically, scenarios were developed to anticipate responses of ecosystem services to alternative futures driven by different sets of policy decisions. Following the completion of this ambitious ecological study, there is now a growing movement to make the value of ecosystem services an integral part of current policy initiatives.
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