If we had to pay for the services that nature provides, how much would it cost? In a paper appearing in the May 15th issue of Nature, thirteen ecologists, geographers, and economists estimated this value as somewhere between $16 and 54 trillion per year.
The natural and social scientists who produced the estimate come from universities across the US. and The Netherlands, Sweden, and Argentina. The group was organized by Dr. Robert Costanza of the Institute for Ecological Economics, a joint program of the University of Maryland's Center for Environmental and Estuarine Studies and its College Park campus. The work was sponsored by the National Center for Ecological Analysis and Synthesis at the University of California at Santa Barbara.
The authors assembled information from a wide range of studies on the value of a broad range of ecosystem services. These include not only such familiar items as food production, raw materials, recreation and water supply, but also services which are less apparent, like regulation of the climate and atmospheric gases, water cycling, erosion control, soil formation, nutrient cycling and the purification of wastes.
The estimates were made for each of 17 categories of services for the range of environments on earth, including both marine and terrestrial environments. The authors' estimates indicate that coastal environments, including estuaries, coastal wetlands, beds of sea grass and algae, coral reefs, and continental shelves are of disproportionately high value. They cover only 6.3% of the world's surface but are responsible for 43% of the value of the world's ecosystem services. These environments are particularly valuable in regulating the cycling of nutrients which control the productivity of plants on land and in the sea.
Costanza and his colleagues noted that the considerable majority of the value of ecosystem services is currently outside the market system. That is, although some services, such as food production, water supply, and raw materials are traded in economic markets, most of the world's ecosystem services are not. This means that current market signals are not adequately incorporating the value of these services.
The authors acknowledge the huge uncertainties involved in their estimate, but they also suggest that their estimated values are probably very much on the low side. This is because improving the estimates (by, for example, studying more ecosystem services more intensively) would probably increase the value. The authors also caution that their economic estimates ignore the fact that many ecosystem services are "literally irreplaceable."
One practical use of these estimates is to "help modify systems of national accounting to better reflect the value of ecosystem services and natural capital." Some attempts to do this indicate a leveling of national welfare since 1970 while GNP has continued to increase. "One way to look at it," they write, is that if one were trying to replace the services of ecosystems ... one would need to increase global GNP by at least $33 trillion." Using conventional methods, the global GNP is presently around $24 trillion. A second practical use is for weighing the ecosystem services lost against the benefits of a particular project or policy. Making good decisions on questions ranging from: whether to drain the local wetland for development, to whether to curb global fossil fuel consumption in order to limit climate change all depend on adequately valuing ecosystem services.