LONDON — For nearly two decades, conservation science has methodically cataloged the world’s most irreplaceable animals—the pangolin, the axolotl, the aye-aye—while the botanical world remained an afterthought. That imbalance shattered this spring when an international research team published the first comprehensive evolutionary risk assessment for all known flowering plants, delivering a stark prognosis: more than 21 percent of the evolutionary history carried by Earth’s angiosperms is now threatened with extinction.
The study, published in the journal Science, represents the largest species-prioritization analysis ever conducted in conservation biology, covering all 335,497 known species of flowering plants. Using a metric called EDGE – Evolutionarily Distinct and Globally Endangered – researchers combined extinction risk with genetic uniqueness to identify which species would deal the heaviest blow to the tree of life if lost.
A Metric Built for Animals, Finally Applied to Flora
The EDGE framework, created by the Zoological Society of London in 2007, has long illuminated the plight of overlooked animals. Rikki Gumbs, a conservation scientist at the Zoological Society and co-lead author of the new analysis, noted that the approach has flagged unheralded species for almost two decades while plants remained comparatively invisible.
“Plants were often dismissed as mere backdrop for photographs of bees and tigers,” Gumbs said in an interview.
That neglect, researchers said, stemmed not from a lack of importance but from a staggering data gap. Assessing extinction risk for 335,000 flowering species—angiosperms that outnumber the largest previously EDGE-assessed animal group, ray-finned fish, by more than tenfold—required a herculean effort.
Building the Tree of Life for a Third of a Million Species
Led by Félix Forest, a plant evolutionary biologist at the Royal Botanic Gardens, Kew, alongside collaborators from the Zoological Society of London, Boise State University, and international partners, the team constructed a molecular family tree and cross-referenced it against the IUCN Red List of Threatened Species. The result: EDGE scores for every known flowering plant.
Forest described compiling comparable data for angiosperms as “no small task,” given the scale. The scores, he said, now provide “the vital information needed to spotlight irreplaceable, threatened species that conservation efforts have often overlooked, 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 carries sobering weight. The team estimates that 21.2 percent of angiosperm evolutionary history is at risk—nearly double the equivalent risk for jawed vertebrates, which sits at roughly 13 percent.
Within that total, researchers identified 9,945 priority species—dubbed EDGE species—that disproportionately account for that threatened diversity. Though they represent just 3 percent of all flowering plants, their evolutionary weight is immense.
“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,” said Sven Buerki, a botanist at Boise State University and study contributor. “Compared with over 80 percent of vertebrate groups. Plants have been dying in the dark.”
Familiar Names, Strange Cases
Among the newly flagged species are some surprisingly well-known names. The vanilla orchid, source of the world’s most popular dessert flavoring, now sits on the EDGE priority list, alongside relatives of the corpse flower, whose rare, malodorous blooms draw crowds to botanical gardens worldwide.
Then there is the jellyfish tree, or Medusagyne oppositifolia, found only on a handful of rocky outcrops on the Seychelles island of Mahé. Believed extinct until rediscovered in the 1970s, it is the sole member of its genus. Fewer than 100 mature individuals survive in the wild, confined to four populations. Its loss would prune an entire limb from the angiosperm family tree.
Another standout: Amborella trichopoda, a modest New Caledonian shrub whose lineage split from all other flowering plants approximately 130 million years ago. The study identifies it as the single most evolutionarily distinct angiosperm alive today.
A Roadmap, Not Just an Obituary
Despite the grim arithmetic, the authors frame their work as a triage tool. The researchers calculate that protecting just 5.9 percent of species, selected by EDGE ranking, would safeguard half of all threatened angiosperm evolutionary history. Protecting the full EDGE list would preserve 16.6 percent 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,” the authors wrote.
Some translation from data to action is already underway. Buerki said his team aims to integrate the results directly into Flora of the World, an online platform, so that anyone searching for a species can see not only where it grows but how evolutionarily irreplaceable—and how endangered—it is. At Kew, the EDGE metric has already begun guiding which specimens horticulturists prioritize for cultivation and seed-banking.
Why It Matters Beyond the Greenhouse
The study’s authors situate their findings within a broader argument: global biodiversity policy has long treated evolutionary diversity as worth protecting, yet plants were systematically excluded from the assessments meant to operationalize that principle.
“That taxonomic imbalance has undermined plant conservation for decades,” the authors argue, “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.”
As Gumbs put it: 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.