1. Biodiversity

The Intergovernmental Science Policy Platform on Biodiversity and Ecosystem Services (IPBES) defines biodiversity as the “variability among living organisms from all sources including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part. This includes variation in genetic, phenotypic, phylogenetic, and functional attributes…”

2. Tree of Life

A metaphor to describe the inter-relatedness of all organisms (living and extinct), based on their evolutionary history.

3. Phylogenetic tree

A visual representation of a part of the tree of life, showing the evolutionary relatedness of organisms based on their shared characters.

4. Feature diversity

The full range of different characters or ‘features’ (eg. morphological, molecular, behavioural) of a set of species.

5. Phylogenetic diversity (PD)

A measure of the evolutionary history captured by a set of species and therefore describes a fundamental aspect of biodiversity (Faith 1992). The planet’s evolutionary heritage is a form of biodiversity that ensures options for current and future generations, as recognised by IPBES. The tree of life is a storehouse of potential benefits for humanity and by conserving PD, we conserve feature diversity and thus options for humanity, and maintain biodiversity in the face of future global changes.

6. Option value

The value of retaining options for the future. In the context of PD, option value refers to the value of variety (biodiversity option value). The IPBES Conceptual Framework (Diaz et al. 2015, p. 14) referred to “the ‘option values of biodiversity’, that is, the value of maintaining living variation in order to provide possible future uses and benefits”.

7. Evolutionarily Distinct and Globally Endangered (EDGE) Species

Species that disproportionately represent threatened PD, with few close relatives on the tree of life. EDGE Species are all threatened with extinction and often are distinct in the way they look, live and behave, and embody distinct genetic diversity. They represent a unique and irreplaceable part of the world’s natural evolutionary heritage.

The EDGE metric is a prioritisation tool that comprises two components: Evolutionary Distinctiveness (ED), measures how distinct a species is on the Tree of Life and is a measure of the irreplaceability of the species; Global Endangerment (GE) measures the extinction risk of the species, utilising the IUCN Red List categories to determine the relative weightings between species, and is a measure of the vulnerability of the species. The two components are combined to identify highly distinctive and threatened species across the Tree of Life, or EDGE species.

Benjamin Tapley

Claudia Gray

Rikki Gumbs

Nisha Owen