For decades, conservation science has meticulously tracked the plight of tigers, pandas, and coral reefs while largely ignoring the botanical world that underpins all terrestrial life. That neglect ended this spring. A landmark study published in the journal Science has delivered the most comprehensive assessment ever conducted of flowering plants’ vulnerability: more than one-fifth of the evolutionary history carried by Earth’s angiosperms now stands at risk of permanent loss.
A Metric Built for Animals, Applied to Plants
The analytical engine behind this finding is EDGE—Evolutionarily Distinct and Globally Endangered—a scoring system developed by the Zoological Society of London in 2007. EDGE combines a species’ extinction risk with its genetic uniqueness within the broader tree of life, identifying organisms whose disappearance would prune irreplaceable branches of evolution.
For nearly 18 years, EDGE scores have spotlighted obscure animals: the aye-aye, the pangolin, the axolotl—creatures rarely featured in nature documentaries but representing ancient, isolated lineages. Rikki Gumbs of the Zoological Society of London, who co-led the new analysis, noted that the approach has allowed conservationists to flag overlooked animals for urgent protection. Plants remained comparatively invisible, dismissed, in his words, as mere backdrop for photographs of bees and tigers.
That imbalance was not due to lower stakes. It was a data problem. Assessing extinction risk for animals is challenging enough; assessing it for approximately 335,000 species of flowering plants—angiosperms—that blanket the planet required an entirely different scale of effort.
Building a Family Tree for 335,497 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 institutions, the project set out to construct a comprehensive tree of life and generate extinction-risk estimates for every known flowering plant species.
Researchers assigned EDGE scores to all 335,497 angiosperm species using molecular data cross-referenced against the IUCN Red List of Threatened Species. The effort represents the largest species-prioritization assessment ever undertaken in conservation science.
Forest described the scale of the undertaking plainly: angiosperms outnumber the largest previously EDGE-assessed animal group—ray-finned fish—by more than tenfold. Compiling comparable data for flowering plants was no small task. The resulting scores, he said, now provide 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 finding is stark. The team estimates that 21.2 percent of angiosperm evolutionary history is at risk of extinction. They identified 9,945 priority species that disproportionately account for that threatened diversity.
To put the scale in perspective: 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 roughly 13 percent. The 9,945 EDGE species represent about 3 percent of all known flowering plants, but their evolutionary weight far exceeds their numbers. Losing them would sever branches of the plant tree of life that took tens of millions of years to grow and cannot be recovered.
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 percent of vertebrate groups. Plants, in other words, 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 them for urgent attention. It appears alongside the corpse flower’s malodorous relatives, whose rare, 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 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 their work as a tool for triage rather than a eulogy. The researchers calculate that protecting just 5.9 percent of species, selected by EDGE ranking, would safeguard half of all threatened angiosperm evolutionary history—and protecting the full EDGE list would preserve 16.6 percent of it.
That is the promise embedded in the metric: 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 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 were left out of the assessments meant to operationalize that principle. That taxonomic imbalance, the authors argue, has undermined plant conservation for decades.
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.