Annual changes in the Biodiversity Intactness Index in tropical and subtropical forest biomes, 2001-2012

Few biodiversity indicators are available that reflect the state of broad-sense biodiversity—rather than of particular taxa—at fine spatial and temporal resolution. The Biodiversity Intactness Index (BII) estimates how the average abundance of native terrestrial species in a region compares with their abundances before pronounced human impacts. BII is designed for use with data from a wide range of taxa and functional groups and for estimation at any resolution for which data on land use and related pressures are available. For each year from 2001 to 2012, we combined models of how land use and related pressures in tropical and subtropical forested biomes affect overall abundance and compositional similarity of plants, fungi, invertebrates and vertebrates, with data on anthropogenic pressures to produce annual maps of modelled BII at a spatial resolution of 30 arc seconds (roughly 1 km at the equator) across tropical and subtropical forested biomes. This is the first time temporal change in BII has been estimated across such a large region. The approach we have used to model compositional similarity uses data more efficiently than that used previously when estimating BII. Across tropical and subtropical biomes, BII fell by an average of 1.9 percentage points between 2001 and 2012, with 81 countries seeing an average reduction and 43 an average increase; the extent of primary forest fell by 3.9% over the same period. Changes are not strongly related to countries’ rates of economic growth over the same period.