A sweeping new analysis reveals that 21.2% of angiosperm evolutionary diversity is at risk, with nearly 10,000 priority species identified for urgent conservation.
For decades, conservation science has meticulously tracked the plight of endangered animals—from the pangolin to the axolotl—while plants remained largely invisible to the same rigorous assessment tools. That disparity ended this spring with the publication of a landmark study in Science that delivers the most comprehensive diagnosis yet of the botanical world’s fragility: more than one-fifth of the evolutionary history carried by Earth’s flowering plants now stands to vanish.
“This is the first time we’ve been able to quantify what we stand to lose among flowering plants on a global scale,” said Rikki Gumbs of the Zoological Society of London, who co-led the analysis. “Plants have been treated as background—as scenery for photographs of bees and tigers. This changes that.”
A Metric Built for Animals, Applied to Plants
The tool behind the finding is called 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. For nearly 20 years, the metric illuminated the plight of overlooked animals: the aye-aye, the pangolin, the axolotl—creatures representing entire, irreplaceable branches of evolution that rarely headline nature documentaries.
Applying EDGE to plants posed a fundamentally different challenge. Whereas assessing extinction risk for animals is manageable in scale, evaluating roughly 335,000 species of flowering plants—angiosperms—required unprecedented data collection and computational power.
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 collaborators from the Zoological Society of London, Boise State University, and international partners, the research 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 species using molecular data cross-referenced against the IUCN Red List of Threatened Species—making it 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 described the undertaking as “no small task,” adding that the scores now provide “the vital information needed to spotlight irreplaceable, threatened species that conservation efforts have often overlooked.”
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, with 9,945 priority species disproportionately accounting for that threatened diversity. For context, 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 EDGE species represent roughly 3% of all known flowering plants, but their evolutionary weight is disproportionate to their numbers. Losing them would mean erasing branches of the plant tree of life that took tens of millions of years to grow and cannot be recovered.
Perhaps most sobering is 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 plants whose evolutionary uniqueness and endangerment mark it for urgent attention, alongside the corpse flower’s malodorous relatives, whose rare 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. 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—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 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 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 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 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.
It is a reminder that the animals typically pictured on the covers of conservation reports—the pandas, the polar bears, the 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 running out of time on their own terms—and now, for the first time, science has the numbers to prove it.”