“There are a lot of overlooked species that, when you get to know them, are just as charismatic and beautiful as we know them,” Gumbs said. According to the EDGE2 metric, our highest priority mammal should be the mountain pygmy opossum, a small marsupial that lives in the wild across several square kilometers in the Victorian Alps of Australia. Among the mammals for which we have no good conservation data, the most forward-looking is the long-eared betta, a close relative of the hedgehog found mainly in Laos. The EDGE ranking also counts amphibians, birds, corals, reptiles, sharks, rays and gymnosperms, a group of plants that includes conifers and cycads.
It has become fashionable to think of animals in terms of evolutionary uniqueness. The EDGE indicator is one of the indicators selected for the post-2020 global biodiversity framework, a key biodiversity convention adopted by the United Nations in December 2022. The organization that puts together the Red List of Threatened Species is the International Union for Conservation of Nature, and Nature also has a Phylogenetic Diversity Working Group, of which Gumbs is vice-chair. A growing focus, Gumbs said, is on protecting entire ecosystems that hold many evolutionarily distinct plants and animals, rather than focusing on single species.
Of course, evolutionary uniqueness is only one way to think about conservation priorities. Groups deciding which projects to fund, where to place protected areas, and which species to focus on tend to consider a myriad of factors before making any major decisions. But there is something interesting about the EDGE2 indicator, says Rafael Molina Venegas, a professor of plant biodiversity at the Autonomous University of Madrid in Spain. If you think of all species as unique books, evolutionarily distinct species are like very old, unique tomes with only a few. If you lose these rare species, the treasure trove of the world’s evolutionary history is lost forever.
There is another reason to care about evolutionary uniqueness. Molina Venegas’ work found that if we select plant species based on evolutionary uniqueness, we end up conserving more plant species that are useful to humans than if we select species using random methods. In other words, the pursuit of uniqueness seems to be a practical way to think about which species to protect.
One way to think about the EDGE metric is to imagine the end of the world. A rogue asteroid is a year away from destroying Earth. Fortunately, scientists have discovered a completely empty Earth-like planet elsewhere in the universe. All we have to do is decide which species we want to cram into our spacecraft and take to new planets. Evolutionary uniqueness might be a good place to start, says Molina Venegas. This way you can bring in a variety of creatures, each with a unique function on the new planet. “Hopefully they will complement each other in the new ecosystem that has to grow there,” he said.
In many ways, humanity is waging a slow-motion Armageddon against Earth’s biodiversity. We don’t need spaceships ready yet, but we do need to think carefully about the tools we have to stop the loss of irreplaceable species. We have tools such as scientific research, gene banks and protected areas. The way we think about biodiversity is also an important tool. Everyone wants to save animals, but we live in a world where species compete for limited conservation resources and oppose human greedy expansion. The math doesn’t add up unless we make hard decisions about which species to protect.
