Biodiversity Intactness Index in tropical and subtropical forest biomes
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. This layer represents the average country-level change in BII between 2001 and 2012.
A decline means that biodiversity intactness has fallen between 2001 and 2012, either because the abundance of originally-present species has declined, or because species have been introduced into the system. The Planetary Boundaries framework proposes that a BII below 90% means biodiversity loss may have exceeded safe levels, potentially jeopardizing wild species’ ability to continue to deliver ecosystem services (Steffen et al. 2015).
For the years 2001 and 2012 we combined models of how land use and related pressures in tropical and subtropical forested biomes affect overall abundance and compositional similarity with data on anthropogenic pressures at a spatial resolution of 30 arc seconds (roughly 1km at the equator). For each country, the average change in BII between 2001 and 2012 is calculated (De Palma et al. 2018a).
Projecting modelled BII across space and time requires spatio-temporally explicit pressure data; however, these data vary in their resolution and in their accuracy. For instance, roads have only been included as a static layer although they can grow rapidly, and the completeness varies regionally. In addition, pressure variables include both spatial and temporal autocorrelation and the underlying diversity data does not allow for temporal dynamics of change (De Palma et al. 2018b). These difficulties mean that it is more appropriate to consider average changes across countries, and across broader time steps, rather than focusing on pixel-by-pixel differences and year-on-year changes. Not all likely important drivers can be included meaningfully in the statistical models: effects of climate change are not considered, for instance, and effects of invasive alien species and overharvesting are included only inasmuch as these drivers correlate with other drivers present in the models (e.g., human population density and road density).
The high-resolution land-use maps used in these projections do not include plantation forest; this may mean that our projections are overly conservative. We have attempted to include the effect of plantation forest by modelling plantation forest as higher-intensity secondary vegetation (under the assumption that in land-use maps, plantation forest may occur in areas classified incorrectly as secondary vegetation) (De Palma et al. 2018a).
More information and further resources are available in the indicator factsheet here.
More information and further resources are available in the indicator factsheet here.
De Palma, A., Hoskins, A., Gonzalez, R.E., Newbold, T., Sanchez-Ortiz, K., Ferrier, S., Purvis, A. (2018a). Changes in the Biodiversity Intactness Index in tropical and subtropical forest biomes, 2001-2012. bioRxiv: https://doi.org/10.1101/311688
De Palma, A., Sanchez Ortiz, K., Martin, P.A., Chadwick, A., Guillermo, G., Bates, A.E., Börger, L., Contu, S., Hill, S.L.L. and Purvis, A. (2018b). Challenges with inferring how land-use affects terrestrial biodiversity: Study design, time, space and synthesis. Advances in Ecological Research 58: 163-199.
Steffen, W., Richardson, K., Rockström, J., Cornell, S.E., Fetzer, I., Bennett, E.M., Biggs, R., Carpenter, S.R., de Vries, W., de Wit, C.A., Folke, C., Gerten, D., Heinke, J., Mace, G.M., Persson, L.M., Ramanathan, V., Reyers, B. and Sörlin S. (2015). Planetary boundaries: Guiding human development on a changing planet. Science 347: 1259855