Integrating Multiple Ecosystem Services Into Ecological Site Descriptions

Site Descriptions (ESDs) represent an emerging tool to assist land managers and owners in understanding their landscapes and how they work, or function, in an ecological context. Ecosystem services are those resources and processes supplied by natural ecosystems and sites that can be viewed as benefits to society and, conceptually, natural capital assets with the capacity to be assigned economic values.1 The definitions of ecosystem services were formalized by the United Nations 2004 Millennium Ecosystem Assessment (MA),2 which is a report resulting from a four-year study involving more than 1,300 scientists worldwide. This report grouped ecosystem services into four broad categories: provisioning, such as the production of food and water; regulating, such as the control of climate and disease; supporting, such as nutrient cycles and crop pollination; and cultural, such as spiritual and recreational benefits. Despite the recognition provided in the MA report, there are numerous examples in which the values of ecosystem services go unrecognized, leading to great economic, cultural, biologic, and aesthetic loss. A notable example of a lack of recognition of ecosystem services can be seen in American wetland ecosystems. From the time North America was settled by Europeans until the passage of the Clean Water Act (CWA) of 1972 (which made the destruction and conversion of many wetland types illegal), wetlands were drained, filled, and otherwise converted, for use of agricultural production, mining, timber harvest, dam construction, and urban development on immense scales. Events leading to the passage of the CWA resulted in the recognition that those "swampy, mosquito infested, mucky bogs" actually did have value for something besides frogs and the occasional duck. Aided by the proclamation of "No Net Loss" of wetlands by President George Bush in 1989, the American public became aware of the long list of values and ecosystem services provided by wetlands, including groundwater discharge, flood attenuation, sediment stabilization, sediment/ toxicant retention, nutrient removal/transformation, aquatic and wildlife diversity/abundance and habitat, and a wide array of recreation opportunities. Here, we highlight, in examples from the American West, the strong role key wildlife species play in effecting transitions of ecological character and function on specific ecological sites and the services provided by those ecosystems. It is in this intersection where landscape, the potential for transition to or from desired states, the subsequent ecosystem services proffered or reduced, and the often-controversial role of certain wildlife species collide. Understanding how ecological sites can transition from one state to another is poorly understood in many cases. Our interest is in integrating wildlife conceptually and practically into the identification of ESDs; determining how some wildlife can effect transitions is another interest. Wildlife can influence our understanding of sites and their dynamics. Finally, we frame both the potential utility of the ecosystem services concept and its limitations, using examples from key ecological sites. The ecosystem service literature is large and growing, concerning itself with water cycles, energy flow, clean air and water, nutrient cycling, and other ecosystem processes. Here, we will consider ecosystem services more narrowly in the context of transitions among states and wildlife activities, briefly described below. The dynamics of soil-vegetation interactions on ecological sites are described in state-and-transition models (STMs) (Fig. 1). These STMs evaluate how sites in a particular condition, or "state," can change, or "transition," to very different states, in both biological and physical dimensions. Different states or community phases on the same site, in principle, could provide a very different combination of ecosystem services. Across much of the western United States, the majority of existing ecosystems no longer represent historical conditions. This broadly is true because of altered ecosystem processes (changes in "drivers" such as climate and land use)