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Cutting EDGE: updating the science behind the species

By on July 3, 2017 in News

For the past decade, the EDGE of Existence programme has been the only conservation initiative working to avert the extinction of some of the world’s most threatened and evolutionarily unique species. After ten years, it is time to re-think how we identify EDGE priorities.


Since the inception of the EDGE programme we have identified our priority species for conservation using the EDGE algorithm—originally developed by ZSL scientists and published in 2007—which combines the Evolutionary Distinctiveness (ED) of a species with its Global Endangerment (GE). However, in the intervening years between EDGE’s inception and 10th Birthday, there have been great advances in science: in 2007 the data required to create an EDGE list only existed for mammals, but now these data are available for other groups, such as amphibians, birds, corals, reptiles and sharks. Further, researchers have expanded on the original EDGE algorithm to develop novel methods for identifying the optimal species to prioritise to conserve the evolutionary diversity of life.



Distribution of ED and EDGE scores for current taxonomic groups

Following ten years of important conservation work being directed by the original EDGE algorithm, we recognise the importance of incorporating the latest findings from the field of phylogenetically-informed conservation to ensure the species identified as EDGE priorities are as accurate as possible. Therefore, we decided to bring together the leading scientists in the field from around the world to discuss and potentially develop an updated EDGE methodology and improve the prioritisation protocol used by the EDGE team.

So, in late April 2017, key thinkers from the fields of phylogenetics and conservation—from Europe, USA and even Australia—descended upon ZSL’s London Zoo for a three-day workshop. The aim of the workshop was twofold: first, to assess and celebrate the successes achieved using the original EDGE method; and, second, to discuss how to create an updated EDGE methodology that can underpin successful conservation for the decade to come.

After an action-packed three days filled with insight, excitement and plenty of (surprisingly civil) debate, all participants had helped to develop and agree upon an updated methodology to underpin the conservation efforts of the EDGE programme. This new methodology incorporates properties previously absent from the EDGE prioritisation algorithm, but which all participants of the workshop agreed were important going forward. These included the idea of ‘complementarity’, which takes into account the evolutionary relationships of species to prioritise entire groups of closely-related species threatened with extinction. Another advance is the change from using a simple index to calculate the GE score of a species to using its probability of extinction. Though this probability is still difficult to calculate, there are reasonable estimations currently available that align with the existing GE method of the original EDGE. This new feature of EDGE provides us with ability to use the calculated probability of extinction for species when the information becomes available, which will make the EDGE prioritisation even more accurate.

Overall, the outcomes of the workshop are a fantastic step forward for the EDGE of Existence programme and the wider field of phylogenetically-informed conservation. Looking ahead, we are confident the updated EDGE methodology, with the support of those in the field who have developed the ideas incorporated, will continue to provide a solid scientific underpinning for our conservation work around the world. Now, we start the long journey of turning the new ideas into the EDGE lists of the future, with the potential of identifying even more weird and wonderful creatures that need our help.

Watch this space!


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