“There are so many species that get overlooked here, and when you get to know them, they’re just as fascinating and beautiful as we know them,” Gums says. According to the EDGE2 metric, our highest priority mammal has to be the mountain pygmy possum, a small marsupial found within a few square kilometers of Australia’s Victorian Alps. Among mammals for which we do not have good conservation data, the most troublesome relative of the hedgehog is the long-eared gymnur, which is found mostly in Laos. EDGE levels are calculated for amphibians, birds, corals, reptiles, sharks, rays and a plant group that includes gymnosperms, conifers and cycads.
Thinking about animals has been viewed in terms of evolutionary diversity. The EDGE scale was one of the selected indicators for the Post-2020 Global Biodiversity Framework – the main biodiversity treaty adopted by the United Nations in December 2022. The group that maintains the Red List of Threatened Species, the International Union for the Conservation of Nature, also has a Task Force on Phylogenetic Diversity, of which Gumbs is vice-chair. One growing focus, rather than focusing on individual species, is protecting entire ecosystems that preserve many evolutionarily distinct plants and animals, Gumbs says.
Of course, evolutionary diversity is only one way to think about conservation priorities. Groups that decide which projects to fund, where to place protected areas, and which species to focus on look at a wide range of issues before making big decisions. But the EDGE2 measurement does reach something interesting, says Rafael Molina Venegas, professor of plant biodiversity at the Universidad Autónoma de Madrid in Spain. If you think of all species as special books, evolutionarily distinct species are like very old, unique tomes, of which there are only a handful of copies. If you lose these rare species, the beginning of the world’s evolutionary history is lost forever.
And there’s another reason to worry about evolutionary diversity. As Molina Venegas’ work has shown, if we select plant species based on their evolutionary diversity, we tend to preserve more plant species that are useful to humans than if we randomly select species. In other words, it seems like a practical way to think about which species should be protected by reaching a certain level.
One way to think about EDGE metrics is to imagine Armageddon. It’s been a year since a rogue asteroid destroyed Earth. Fortunately, scientists have identified a completely empty planet Earth somewhere else in the universe. All we have to do is decide which species we want to cram onto the spaceship and bring them to the new planet. Evolutionary diversity may not be a bad starting point, says Molina Venegas. In this way, they each bring different creatures with a special function on the new planet. “The hope is that they will support each other in the new ecosystem that will grow there,” he said.
In many ways, humans are wreaking slow-motion Armageddon on Earth’s biodiversity. We don’t need to build the space shuttle yet, but we need to think carefully about the tools we need to prevent the extinction of irreplaceable species. We have tools like scientific research, gene-banking and conservation 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 are competing for the protection of limited natural resources and against the racist expansion of humans. As long as we make strong decisions about which species to protect, the math won’t add up.