Abstract
Loss and fragmentation of natural land cover due to expansion of agricultural areas is a global issue. These changes alter the configuration and composition of the landscape, particularly affecting those ecosystem services (benefits people receive from ecosystems) that depend on interactions between landscape components. Hydrological mitigation describes the bundle of ecosystem services provided by landscape features such as woodland that interrupt the flow of runoff to rivers. These services include sediment retention, nutrient retention and mitigation of overland water flow. The position of woodland in the landscape and the landscape topography are both important for hydrological mitigation. Therefore, it is crucial to consider landscape configuration and flow pathways in a spatially explicit manner when examining the impacts of fragmentation. Here we test the effects of landscape configuration using a large number (>7,000) of virtual landscape configurations. We created virtual landscapes of woodland patches within grassland, superimposed onto real topography and stream networks. Woodland patches were generated with user‐defined combinations of patch number and total woodland area, placed randomly in the landscape. The Ecosystem Service model used hydrological routing to map the “mitigated area” upslope of each woodland patch. We found that more fragmented woodland mitigated a greater proportion of the catchment. Larger woodland area also increased mitigation, however, this increase was nonlinear, with a threshold at 50% coverage, above which there was a decline in service provision. This nonlinearity suggests that the benefit of any additional woodland depends on two factors: the level of fragmentation and the existing area of woodland. Edge density (total edge of patches divided by area of catchment) was the best single metric in predicting mitigated area. Distance from woodland to stream was not a significant predictor of mitigation, suggesting that agri‐environment schemes planting riparian woodland should consider additional controls such as the amount of fragmentation in the landscape. These findings highlight the potential benefits of fragmentation to hydrological mitigation services. However, benefits for hydrological services must be balanced against any negative effects of fragmentation or habitat loss on biodiversity and other services.
Highlights
Conversion of natural land cover to agriculture is a major driver of habitat and biodiversity loss globally, with associated loss of ecosystem services (ES; Foley et al 2005)
The Land Utilization Capability Indicator (LUCI) model simulates a range of ES and trade-offs between these, in this study we focus on runoff mitigation, retention of sediments, and diffuse pollution as these are often provided by the same landscape features and respond in the same way to spatial context
Regression models show that landscape proportion was not a good predictor of mitigation when assuming a Mitigated area: the area upslope of woodland patches once hydrological routing has been accounted for This is the proxy metric to indicate provision of mitigation ecosystem services (ES), and is the dependent variable in each analysis here
Summary
Conversion of natural land cover to agriculture is a major driver of habitat and biodiversity loss globally, with associated loss of ecosystem services (ES; Foley et al 2005). Such land cover change is likely to be accelerated in the foreseeable future as a result of increased conversion of natural land to agricultural production in order to satisfy global food demand (Tilman et al 2011). The degree of change and the spatial pattern of this change may be important for ES as well as biodiversity. Fragmentation tends to reduce connectivity between habitat patches, with negative impacts on Article e02046; page 2
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