New EDGE analysis of 335,000 species reveals 9,945 priority plants at risk, including vanilla orchids and jellyfish trees
LONDON — For nearly two decades, conservation scientists have used a powerful metric to identify animals whose extinction would erase irreplaceable branches of the evolutionary tree. But plants—the foundation of nearly every terrestrial ecosystem—were left out of that assessment. This spring, a landmark study published in the journal Science changed that, delivering the most comprehensive diagnosis yet of botanical vulnerability: more than 21% of the evolutionary history carried by Earth’s flowering plants is now at risk of disappearing.
A Metric Built for Animals Turns to the Garden
The tool behind the finding is EDGE — Evolutionarily Distinct and Globally Endangered — a scoring system developed by the Zoological Society of London in 2007. It combines a species’ extinction risk with its genetic uniqueness within the broader tree of life. For nearly 20 years, EDGE scores highlighted overlooked animals such as the aye-aye, pangolin and axolotl — creatures representing entire, irreplaceable evolutionary branches.
“This approach has let conservationists flag overlooked animals in urgent need of protection for almost two decades,” said Rikki Gumbs of the Zoological Society of London, who co-led the new analysis. “Meanwhile, plants remained comparatively invisible — dismissed as mere backdrop for photographs of bees and tigers.”
That imbalance stemmed not from a lack of stakes but from a data problem. Assessing extinction risk for a single animal species is manageable; doing so for roughly 335,000 species of flowering plants — known as angiosperms — required a massive computational and collaborative effort.
Building a Family Tree for a Third of a Million Species
Led by Félix Forest, a plant evolutionary biologist at the Royal Botanic Gardens, Kew, alongside teams from the Zoological Society of London, Boise State University and international collaborators, the project set out to construct a tree of life and generate extinction-risk estimates for every known flowering plant species on Earth.
Researchers assigned EDGE scores to all 335,497 species using molecular data cross-referenced against the IUCN Red List of Threatened Species. It stands as the largest species-prioritization assessment ever undertaken in conservation science.
Forest described the scale of the undertaking as “no small task,” noting that angiosperms outnumber the largest previously EDGE-assessed animal group — ray-finned fish — by more than tenfold. “The scores now provide the vital information needed to spotlight irreplaceable, threatened species that conservation efforts have often overlooked,” he said, “in service of the benefits — current and future — that all life on Earth depends on.”
The Number That Should Worry Us: 21.2 Percent
The headline figure is stark. The team estimates that 21.2% of angiosperm evolutionary history is at risk of extinction and has identified 9,945 priority species that disproportionately account for that threatened diversity. To put that in perspective: the figure is nearly double the equivalent risk measured across jawed vertebrates — a group encompassing everything from sharks to elephants — where the comparable rate sits at around 13%.
The 9,945 species carrying that risk — dubbed EDGE species — represent roughly 3% of all known flowering plants, but their evolutionary weight is disproportionate to their numbers. Losing them would mean losing branches of the plant tree of life that took tens of millions of years to grow and cannot be recovered once gone.
Perhaps the most sobering context comes from how little formal attention these species have received. Sven Buerki, a botanist at Boise State University and a contributor to the study, framed the disparity bluntly: more than two in five plant species are estimated to be threatened with extinction, yet fewer than one in five has ever received a formal threat assessment — compared with over 80% of vertebrate groups. “Plants,” Buerki said, “have been dying in the dark.”
Faces of the Crisis
Among the newly flagged priority species are some remarkably familiar names. The vanilla orchid — source of the world’s most popular dessert flavoring — now sits among the plants whose evolutionary uniqueness and endangerment mark it for urgent attention, alongside the corpse flower’s malodorous relatives, whose rare and cavernous blooms draw crowds to botanical gardens whenever they open.
Then there is a stranger case: the jellyfish tree, or Medusagyne oppositifolia, found nowhere on Earth except a handful of rocky outcrops on the island of Mahé in the Seychelles. Believed extinct until a few surviving individuals were rediscovered in the 1970s, it is the sole member of its genus, its jellyfish-shaped seed pods giving the species its common name. Today, fewer than 100 mature jellyfish trees are thought to survive in the wild, confined to four small populations near Seychelles’ coast. With no close living relatives, its loss would not just erase a species — it would prune an entire limb from the angiosperm family tree.
Other headline cases include ancient, solitary lineages such as Amborella trichopoda, a modest New Caledonian shrub whose evolutionary lineage split from all other flowering plants some 130 million years ago — making it, by the study’s measure, the single most evolutionarily distinct angiosperm alive today.
A Roadmap, Not Just an Obituary
For all its grim arithmetic, the study’s authors frame it as a tool for triage rather than a eulogy. The researchers calculate that protecting just 5.9% of species, selected by EDGE ranking, would safeguard half of all threatened angiosperm evolutionary history — and that protecting the full EDGE list would preserve 16.6% of it. With finite conservation budgets and infinite need, EDGE scores offer a way to direct resources toward the species whose loss would cost evolutionary history the most.
Some of that translation from data to action is already underway. Buerki said his team’s goal is to fold the results directly into Flora of the World, an online platform, so that anyone searching for a species can see not just where it grows, but how evolutionarily irreplaceable — and how endangered — it is. At Kew itself, the EDGE metric has already begun shaping decisions inside the institution’s own Living Collections, guiding which specimens horticulturists prioritize for cultivation and seed-banking.
Why It Matters Beyond the Greenhouse
The paper’s authors situate their findings within a broader argument that has circulated in conservation biology for years but rarely with plants at its center: global biodiversity policy has consistently treated evolutionary diversity as something worth protecting, yet plants — for decades — were left out of the assessments meant to operationalize that principle. That taxonomic imbalance, the authors argue, has undermined plant conservation for decades, even though the preservation of evolutionary lineages underpins both the immediate benefits people draw from ecosystems and the future of life on Earth more broadly.
It is a reminder that the animals typically pictured on the covers of conservation reports — pandas, polar bears, tigers — depend, ultimately, on the quieter, rootier world sustaining them. Gumbs’s framing captures the stakes succinctly: flowers and forests were never simply scenery. They are, this study suggests, running out of time on their own terms — and now, for the first time, science has the numbers to prove it.