Planning impact avoidance and biodiversity offsetting using software for spatial conservation prioritisation

Context. Impact avoidance and biodiversity offsetting are measures that can be used for alleviating environmental impacts of economic development projects. Offsetting is frequently implemented via habitat restoration. Biodiversity offsets should be designed in a cost-effective manner. Aims. To investigate how spatial conservation prioritisation methods, most commonly used for reserve network design, could be used for informing impact avoidance and biodiversity offsetting. Methods. Zonation is a publicly available framework and software for grid-based, large-scale, high-resolution spatial conservation prioritisation. Zonation produces a hierarchical, balanced, and complementarity-based priority ranking through the landscape, identifying areas of both highest and lowest conservation value in one analysis. It is shown how these capabilities can be utilised in the context of impact avoidance and offsetting. Key results. Impact avoidance can be implemented by focusing environmentally harmful activity into low-priority areas of the spatial priority ranking. Offsets can be implemented via a more complicated analysis setup. First, identify development areas unavailable for conservation, which leads to a decrease in the quality of conservation value achievable in the landscape. Second, develop compensation layers that describe the difference made by allocation of extra conservation action. Running a spatial prioritisation, integrating information about where species are (representation), what areas and features are damaged (reduced condition and negative connectivity effects), and the difference made by remedial action, allows identification of areas where extra conservation effort maximally compensates for damage. Factors such as connectivity and costs can be included in this analysis. Impact avoidance and offsetting can also be combined in the procedure. Conclusions. Spatial conservation-prioritisation methods can inform both impact avoidance and offsetting design. Implications. Decision support tools that are commonly associated with reserve selection can be used for planning of impact avoidance and offsetting, conditional on the availability of high-quality data about the distributions of biodiversity features (e.g. species, habitat type, ecosystem services).