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Wetlands

Coast, Ocean, and Marine

The Geography of Non-monetary Indicators of Ecosystem Services

The economic value of wetland ecosystem services is determined by individual or societal preferences and must be measured within the context of land use/land cover configurations, human activities, and local populations and demographics. While this socio-economic context is important for a proper econometric assessment of ecosystem service values, this page discusses the development of geographic, non-monetary indicators for evaluating wetland services.

Geographic indicators can be used to evaluate the scarcity of ecosystem services in the landscape, the accessibility of sites for recreation and aesthetics, the availability of substitute or complementary services, and future risks to wetlands. Such indicators avoid the cost and complexity of econometric methods while still allowing for a socio-economic prioritization of wetlands. However, their use also makes it difficult to determine whether a site scoring highly on one measure is better or worse than a site scoring highly on another measure. Because indicators are also used for establishing ecological priorities, it is important not to combine scores from ecological prioritization with scores from socio-economic prioritization.

Examples of landscape indicators may be identified through spatial analyses using several GIS measurements (Boyd and Wainger, 2002): the distance between two points or areas; the presence of a certain feature, or the number of features within an area; the percentage of an area that has particular characteristic; and the connectivity of a certain feature with other landscape features. A wetland's "service area" can simplistically be specified as a one-half (½) mile radius around a wetland or by taking the watershed that a wetland belongs to. This however, ignores the complicated issues of scale and direction.

Local demand or mitigation

Certain wetland services or benefits accrue to a local, neighboring population. Recreation, aesthetics, and avoidance or mitigation of negative externalities such as flooding or water contamination are all examples of endpoint services. Possible indicators for water quality and flood mitigation areas are as follows:

Drinking water requires that a wetland be hydrologically connected to an aquifer used for this purpose. However, other important factors are related to both the potential for contamination from nearby sources and the local demand for drinking water. For sources of contamination, a simple GIS indicator may be the percent of the landscape covered by impervious surfaces. To identify local demand for drinking water, the number of wells within a one-half (½) mile radius might be a useful indicator.

Flood mitigation is a useful metric for wetlands that are hydrologically connected to a river network with a history of flooding. In the case of rivers, the "service area" is located downstream and in a floodplain. Within this area, the density and value of infrastructure (e.g., residential and commercial properties, roads and bridges) are useful indicators of the value of flood mitigation.

Scarcity and substitutability

Up to a certain point, scarcity increases the value of a service. Scarcity refers to the lack of a local prevalence of other wetlands. Substitutability refers to the abundance of other natural land uses that can provide similar services to those generated by wetlands. If nearby wetlands are abundant, the loss of one wetland may not lead to a significant loss of water quality benefits. If wetlands are scarce, the service lost with the wetland will tend to be more valuable. An example of a GIS indicator of this scarcity is the percent of a watershed that is occupied by wetlands. An example of an indicator for the substitutability of a service (e.g., groundwater recharge) might be the percent of a watershed that is naturally vegetated and with a limited amount of impervious surfaces.