Assessing biodiversity intactness at multiple scales

The Southern Africa Millennium Ecosystem Assessment developed an index for quantifying the state of biodiversity. The Biodiversity Intactness Index (BII) operates at the species level, and is based on changes in species abundance, rather than changes in richness brought about by extinction. The BII uses spatial data on species richness and land use activities per ecosystem type to weight estimates, provided by taxon experts, of the reduction in abundance of all well-known species under a range of land uses. The result is a single score for a particular spatial area, with a confidence range. The index can be disaggregated in various ways, including spatially and by taxonomic group. This paper tests and confirms the ability to calculate and interpret the index at a variety of policy-relevant scales. It furthermore tests the sensitivity of the BII to normal variations in data quality and resolution of species richness and land use data, and confirms the robustness of the index in these respects.