Calculating the index
The Living Planet Database (LPD) holds time-series data for over 11,000 populations of more than 2700 vertebrate species from around the world.
The global LPI is calculated using over 9000 of these population time-series which are gathered from a variety of sources such as journals, online databases and government reports.
A generalised additive modelling framework is used to determine the underlying trend in each population time-series. Average rates of change are calculated and aggregated to the species level.
Each species trend is aggregated to produce an index for the terrestrial, freshwater and marine systems. The three system indices are weighted equally within tropical and temperate regions which are then aggregated to produce the global LPI.
Understanding trends across scales
The population time-series data are augmented with further information relating to the species’ taxonomy, location and ecology, which enables the analysis of trends at different scales.
For example, subsets of populations of the LPI can provide a basis for tracking progress with respect to multi-lateral agreements such as the Convention for the Conservation of Migratory Species or the Ramsar Convention on Wetlands , for exploring trends in selected groups of species such as utilised species or specific taxonomic groups, and for producing global indices representing particular habitats or biomes.