Abstract
Modeling ecosystem services (ESs) intrinsically involves the use of spatial and temporal data. Correct estimates of ecosystem services are inherently dependent upon the scale (resolution and extent) of the input spatial data. Sensitivity of modeling platforms typically used for quantifying ESs to simultaneous changes in the resolution and extent of spatial data is not particularly clear at present. This study used the Nutrient Delivery Ratio (NDR) model embedded in InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) for ascertaining the sensitivity of the outputs to three digital elevation models (DEM), two land cover datasets, and three precipitation grids for 57 watersheds located in Georgia, United States. Multivariate regression models were developed to verify the influence of the spatial resolution of input data on the NDR model output at two spatial extents (the state of Georgia and six physiographical regions within the state). Discrepancies in nutrient exports up to 77.4% and 168.1% were found among scenarios at the state level for nitrogen and phosphorus, respectively. Land cover datasets differing in resolution were responsible for the highest differences in nutrient exports. Significance (at 5% level) of spatial variables on the model outputs were different for the two spatial extents, demonstrating the influence of scale when modeling nutrient runoff and its importance for better policy prescriptions.
Highlights
Ecosystem services (ESs) are defined as the direct and indirect benefits people obtain from ecological systems [1,2]
Scenario 8, which combined a 90 m digital elevation models (DEM) with the National Land Cover Dataset (NLCD) land cover, yielded the highest nitrogen export among all the scenarios and the precipitation grid created using weather stations data aggregated nitrogen export among all the scenarios and the precipitation grid created using weather (Figure 4). This scenario modeled a total export of 242,953 kg of nitrogen for all watersheds combined, stations data (Figure 4)
This scenario modeled a total export of 242,953 kg of nitrogen for all which gives an averagewhich of 0.433 kg/ha/year of of nitrogen
Summary
Ecosystem services (ESs) are defined as the direct and indirect benefits people obtain from ecological systems [1,2]. Correct valuation of ESs is inherently dependent upon the quantification of ESs [7] which in turn is dependent upon the scale of the input data. Defining the role of scale on the models which are typically used for quantifying ESs is essential for developing an understanding about the possible changes in ESs relative to changes in resolution and extent of the input data. This is especially true, as existing studies use different scales for quantifying ESs [8]
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