For nearly two decades, conservation science possessed a powerful tool for identifying the world’s most irreplaceable and endangered species—yet it was applied almost exclusively to animals. That disparity ended this spring when a sweeping study published in the journal Science delivered the first comprehensive assessment of extinction risk across Earth’s flowering plants, revealing that more than one-fifth of angiosperm evolutionary history now stands on the brink of disappearance.
A Metric Built for Animals Finally Applied to Flora
The tool at the heart of this analysis is EDGE—Evolutionarily Distinct and Globally Endangered—a metric developed by the Zoological Society of London in 2007. EDGE scores combine a species’ extinction risk with its genetic uniqueness within the broader tree of life, flagging creatures that represent entire, irreplaceable branches of evolutionary heritage.
For nearly 20 years, EDGE assessments highlighted overlooked animals such as the aye-aye, pangolin and axolotl—species rarely featured in nature documentaries yet carrying immense evolutionary weight. Meanwhile, plants remained largely invisible to this protective framework.
Rikki Gumbs, a researcher at the Zoological Society of London who co-led the new analysis, said the approach has let conservationists identify overlooked animals in urgent need of protection for almost two decades. Plants, he noted, were dismissed as mere backdrop for photographs of bees and tigers.
That imbalance stemmed not from lower stakes but from a data problem. Assessing extinction risk across roughly 335,000 species of flowering plants—angiosperms—presented a challenge of scale far exceeding any previous EDGE application.
Building a Family Tree for a Third of a Million Species
The research team, led by Félix Forest, a plant evolutionary biologist at the Royal Botanic Gardens, Kew, in collaboration with scientists from the Zoological Society of London, Boise State University and international partners, undertook an unprecedented task: constructing a tree of life and generating extinction-risk estimates for every known flowering plant species on Earth.
Researchers assigned EDGE scores to all 335,497 angiosperm species using molecular data cross-referenced against the IUCN Red List of Threatened Species. This represents the single largest species-prioritization assessment ever conducted in conservation science.
Forest described the scale of the undertaking, noting that angiosperms outnumber the largest previously EDGE-assessed animal group—ray-finned fish—by more than tenfold. The scores, he said, now provide vital information needed to spotlight irreplaceable, threatened species that conservation efforts have often overlooked.
A Stark Figure: 21.2%
The study’s headline finding is sobering. 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.
That 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 approximately 13%.
The 9,945 species carrying this risk, designated as EDGE species, represent roughly 3% of all known flowering plants, yet their evolutionary weight far exceeds their numbers. Losing them would eliminate branches of the plant tree of life that took tens of millions of years to develop and cannot be recovered.
Perhaps most troubling is how little formal attention these species have received. Sven Buerki, a botanist at Boise State University and study contributor, 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, he said, have been dying in the dark.
Faces of the Crisis
Among the newly flagged priority species are familiar names with surprising conservation statuses.
The vanilla orchid, source of the world’s most popular dessert flavoring, now ranks among the plants requiring urgent attention. Close behind are relatives of the corpse flower, whose rare, cavernous blooms draw crowds to botanical gardens whenever they open.
Then there is the jellyfish tree, or Medusagyne oppositifolia, found nowhere on Earth except a handful of rocky outcrops on the Seychelles island of Mahé. Believed extinct until a few surviving individuals were rediscovered in the 1970s, it is the sole member of its genus, named for its jellyfish-shaped seed pods. Fewer than 100 mature jellyfish trees are thought to survive in the wild, confined to four small populations near the 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. By the study’s measure, it is the single most evolutionarily distinct angiosperm alive today.
A Roadmap for Action, Not an Obituary
Despite its grim arithmetic, the study’s authors frame their work as a tool for triage rather than a eulogy. 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 mechanism for directing resources toward the species whose loss would cost evolutionary history the most.
Some 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 only where it grows but how evolutionarily irreplaceable—and how endangered—it is. At Kew, the EDGE metric has already begun shaping decisions inside the institution’s living collections, guiding which specimens horticulturists prioritize for cultivation and seed-banking.
Broader Implications for Biodiversity Policy
The paper’s authors situate their findings within a long-standing argument in conservation biology: global biodiversity policy has consistently treated evolutionary diversity as worth protecting, yet plants were left out of the assessments meant to operationalize that principle. That taxonomic imbalance, they 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.
The animals typically pictured on 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.
Related reading: For those interested in learning more about plant conservation priorities, the IUCN Red List of Threatened Species provides ongoing updates on extinction risk across all taxonomic groups. The Royal Botanic Gardens, Kew offers public resources on its State of the World’s Plants reports, which complement the EDGE findings with broader biodiversity data.