LONDON — For decades, conservation science has meticulously tracked the extinction risk of tigers, pangolins, and coral reefs while largely ignoring the botanical world. That blind spot vanished this spring when a landmark study in the journal Science delivered the most comprehensive assessment ever conducted of flowering plants, revealing that 21.2% of their evolutionary history is at risk of being lost forever — a rate nearly double that of jawed vertebrates.
A Metric Built for Animals, Redirected to Plants
The analysis relies on a tool called EDGE — Evolutionarily Distinct and Globally Endangered — developed by the Zoological Society of London in 2007. EDGE scores combine a species’ extinction risk with its genetic uniqueness on the tree of life. For nearly two decades, the metric highlighted overlooked animals such as the aye-aye, pangolin, and axolotl — creatures representing irreplaceable evolutionary branches.
“This approach has allowed conservationists to 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 research. Meanwhile, plants remained “comparatively invisible — dismissed as mere backdrop for photographs of bees and tigers,” he added.
That imbalance was not due to lower stakes but to a staggering data problem. Assessing extinction risk for an animal is complex; assessing it for roughly 335,000 species of flowering plants — angiosperms — proved a challenge of entirely different scale.
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 researchers from the Zoological Society of London, Boise State University, and international partners, the team constructed a tree of life and generated extinction-risk estimates for every known flowering plant species. They assigned EDGE scores to all 335,497 angiosperms using molecular data cross-referenced against the IUCN Red List of Threatened Species — the largest species-prioritization assessment ever undertaken in conservation science.
“Angiosperms outnumber the largest previously EDGE-assessed animal group — ray-finned fish — by more than tenfold,” Forest said. “Compiling comparable data for flowering plants was no small task.” The scores, he explained, “provide the vital information needed to spotlight irreplaceable, threatened species that conservation efforts have often overlooked.”
The Number That Should Worry Us: 21.2%
The headline finding is stark. The team estimates that 21.2% of angiosperm evolutionary history is threatened with extinction and identified 9,945 priority species — dubbed EDGE species — that disproportionately carry that risk. For context, the comparable rate across jawed vertebrates stands at approximately 13%.
Those 9,945 species represent roughly 3% of all known flowering plants, but their evolutionary weight is disproportionate. Losing them would erase branches of the plant tree of life that took tens of millions of years to grow and can never be recovered.
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 have been dying in the dark.”
Faces of the Crisis
Among the newly flagged priority species are surprisingly familiar names. The vanilla orchid — source of the world’s most popular dessert flavoring — now ranks among plants whose evolutionary uniqueness and endangerment demand urgent attention. It joins relatives of the corpse flower, whose rare, cavernous blooms draw crowds to botanical gardens.
Then there is a stranger case: the jellyfish tree (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, with jellyfish-shaped seed pods. 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 prune an entire limb from the angiosperm family tree.
Other headline cases include Amborella trichopoda, a modest New Caledonian shrub whose evolutionary lineage split from all other flowering plants some 130 million years ago — making it the single most evolutionarily distinct angiosperm alive today.
A Roadmap, Not Just an Obituary
Despite the grim arithmetic, the study’s authors frame it as a tool for triage. The researchers calculate that protecting just 5.9% of species, selected by EDGE ranking, would safeguard half of all threatened angiosperm evolutionary history. Protecting the full EDGE list would preserve 16.6% of it.
“With finite conservation budgets and infinite need, EDGE scores offer a way to triage resources toward the species whose loss would cost evolutionary history the most,” Gumbs said.
Some translation from data to action is already underway. Buerki said his team aims 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 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.
Why It Matters Beyond the Greenhouse
The paper’s authors situate their findings within a broader argument: 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.
“Flowers and forests were never simply scenery,” Gumbs said. “They are running out of time on their own terms — and now, for the first time, science has the numbers to prove it.”
The animals typically pictured on conservation reports — pandas, polar bears, tigers — depend entirely on the quieter, rootier world sustaining them. This study offers not just a diagnosis, but a roadmap: for the first time, conservationists know exactly which botanical branches to save. The question is whether the world will act before they fall.