EDGE of Existence programme

Developed by the Zoological Society of London (ZSL), the programme aims to raise awareness of these species, implement targeted research and conservation actions to halt their decline, and to train in-country conservationists (called EDGE Fellows) to protect them.

[1] Some EDGE species, such as elephants and pandas, are well-known and already receive considerable conservation attention, but many others, such as the vaquita (the world's rarest cetacean)[2][3] the bumblebee bat (arguably the world's smallest mammal) and the egg-laying long-beaked echidnas, are highly threatened yet remain poorly understood, and are frequently overlooked by existing conservation frameworks.

[3] The Zoological Society of London launched the EDGE of Existence Programme in 2007 to raise awareness and funds for the conservation of these species.

Each of the top 100 species is given an 'EDGE-ometer' rating according to the degree of conservation attention they are currently receiving, as well as its perceived rarity in its natural environment.

An important part of the EDGE programme is a fellowship scheme which provides funding and support to local scientists.

The phylogenetic tree has the most recent common ancestor at the root, all the current species as the leaves, and intermediate nodes at each point of branching divergence.

Each segment is assigned an ED score defined as the timespan it covers (in millions of years) divided by the number of species at the end of the subtree it forms.

Potential EDGE species are those with high ED scores but whose conservation status is unclear (data deficient or not evaluated).

Examples of Critically Endangered species with very low ED scores are porites pukoensis, mountainous star coral, and the magenta petrel.