Comparing Ecosystem Goods and Services Provided by Restored and Native Lands

摘要

We determined the relative benefits for eight categories of ecosystem goods and services associated with native and restored lands across the conterminous United States. Less than 10% of most native US ecosystems remain, and the proportion that is restored varies widely by biome. Restored lands offer 31% to 93% of native land benefits within a decade after restoration, with restored wetlands providing the most economic value and deserts providing the least. Restored ecosystems that recover rapidly and produce valuable commodities return a higher proportion of total value. The relative values of the benefits provided by restoration vary both by biome and by the ecosystem goods and services of interest. Our analysis confirms that conservation should be the first priority, but that restoration programs across broad geographic regions can have substantial value. “No net loss” policies should recognize that restored lands are not necessarily equivalent to native areas with regard to estimated ecosystem benefits.nnHumans influence every ecosystem on Earth, leading to impairment of natural ecosystem structure and function (MEA 2005). Converting native land to row-crop agriculture, suppressing fire, diverting water flow, increasing nutrient and toxic pollution, altering global precipitation patterns and gas concentrations, and homogenizing and lowering global biodiversity are a few of the ways humans have altered ecosystems. North American forests, savannas, and grasslands have experienced substantial losses, whereas woody savanna, shrubland, and desert areas have expanded because of desertification and woody expansion into grasslands (Wali et al. 2002), inevitably leading to changes in ecosystem function.nnConserving native land cover is an important component of maintaining ecosystem structure and function. Preservation is not always a viable management option, because many regions lack sufficiently large undisturbed areas to sustain biota and ecosystem function without improvement. Therefore, restoration is an essential activity for modern land management and conservation (Hobbs and Harris 2001). Setting achievable goals for restoration policies covering broad regions involves not only defining ecological potential in the region but coupling that potential with societal demands and economic feasibility. Valuation of ecosystem goods and services can help managers estimate long-term economic feasibility (Costanza et al. 1997). This coupling of the success of restoration with the value of ecosystem benefits leads to a definition of restoration as “the process of restoring one or more valued processes or attributes” of an ecosystem (Kahn 1995). The restoration of specific ecosystem goods and services, in addition to merely restoring the native complement of species in an area, has thus become the focus of many restoration ecologists.nnEstimating some of the benefits of lands used by humans can be fairly straightforward, particularly when the commodities produced have market value (e.g., the annual value of crops produced per hectare) and when externalities are ignored. Ascribing an economic value to some ecosystem goods and services, by contrast, can be difficult (Kahn 1995, Costanza et al. 1997), and sectors of the economic community have criticized such valuation (Bockstael et al. 2000, Spash and Vatn 2006). Nonetheless, ecosystems provide some recognized benefits, and the valuation of these benefits could become a major tool for directing policy and making land-use decisions (Turner et al. 2007). Attempts to document the relationship between land restoration and the improvement of the supply rates of ecosystem goods and services have been made mainly in small-scale studies. We explore the hypothesis that the temporal trajectory of ecosystem goods and services supplied by restored lands varies across ecoregions and among the different goods and services. We test this hypothesis with respect to restoration across broad regions (i.e., continental), but some of the principles could be refined and applied also to specific restoration projects. We focus on the effects of restoration on ecologically based temporal trends in rates of benefit production from ecosystem goods and services, because that is an area where ecologists can provide useful information for use in future cost-benefit analyses.nnOur analysis involved four steps. First, we defined our ecosystem goods and services. Second, we defined restoration and created a “restoration index” to compare the value of native and restored lands. Third, we defined the ecoregions in our study and calculated the area of native and restored lands within each ecoregion. Last, we conducted a literature review to collect the data needed to parameterize our restoration index.