Identifying high-value regions for hydrologic ecosystem services around the globe

Abstract:

Demand is growing for global inventories and valuations of ecosystem services, and several studies have attempted this quantification. Most have used land cover as a proxy, identifying wetlands, for example, as providers of clean water. In response, it has been argued that the value of hydrologic services rests in their additionally – the ecosystem service value of a watershed lies not in the value of the water captured by it but in the change in water quantity, quality, or timing if the watershed ecosystem were to change. Determining value is thus challenging, because hydrologic response to vegetation varies based on state factors such as climate and geology. In addition, value stems from the demand for water-related services, not only from the supply of those services, so beneficiaries must be accounted for. A set of criteria were identified with the aim of identifying places where hydrologic services are likely to be valuable. The primary biophysical criterion is that vegetation be an important control on hydrologic processes. Based on a set of ecohydrologic processes known to affect potentially valuable hydrologic attributes, characteristics of places where those processes are important were identified. Proxies for likelihood of land use change are an attempt to account for additionally. Density and development status of potential downstream water users were considered as a proxy for likely ecosystem service use. Preliminary mapping of these characteristics indicates regions likely to benefit from management of hydrologic ecosystem services. The overlap between areas likely to have high-value services and regions where Watershed Investment programs are active is evaluated.