Follow these steps to calculate the EDGE Index at the national level for a given taxonomic group.

Data needed:

• Global ED Dataset

• National or global IUCN Red List or equivalent data

Step 1: download the ‘Global ED Dataset’

The EDGE Index tracks the extinction risk of a globally shared set of species that are above median Evolutionary Distinctiveness (ED) within their constituent taxonomic group (monophyletic clade), at the Class or Order level. The Zoological Society of London’s EDGE of Existence programme provides a global set of vertebrate species with information on whether each species is above or below the median ED for use in national-level reporting, which can be downloaded here. This list can be subset to different Classes (or ‘clades’ to enable the independent monitoring of reptile groups). For equivalent data for seed plants, please contact us here.

Step 2: match the species

National taxonomies can vary from global taxonomies for a variety of reasons. Match the species in your national taxonomy to those in the Global ED Dataset as best as possible. >80% congruence is advised for robust reporting.

Step 3: subset to national high-ED species

Once you have your set of national species matched to those in the Global ED Dataset, subset this to the set of national species that are above median ED globally using the “above.median.ED” column. This is the set of species whose extinction risk must be tracked to calculate the EDGE Index.

Step 4: calculate the EDGE Index

For however many current and historical time points for which IUCN Red List or equivalent extinction risk information is available, calculate the proportion of species that are threatened with extinction (Vulnerable, Endangered, Critically Endangered) or have gone extinct (Extinct in the Wild, Extinct) since the first time point. This is the EDGE Index.

If any components of this calculation are not possible or you need support, please contact us here.