Landmark analysis of 335,000 species finds nearly 10,000 priority plants facing irreversible loss, conservation efforts decades behind animals
LONDON — For two decades, conservation science possessed a powerful tool for identifying animals on the brink of losing their evolutionary legacy — but flowers were left out of the equation. That gap closed this spring when an international research team published the most comprehensive assessment ever conducted of flowering plant biodiversity, revealing that more than one-fifth of the evolutionary history carried by Earth’s angiosperms now faces extinction.
Published in the journal Science, the study applied a metric known as EDGE — Evolutionarily Distinct and Globally Endangered — to every known species of flowering plant on the planet. The tool, developed by the Zoological Society of London in 2007, ranks species by combining their extinction risk with how genetically unique they are within the tree of life. Until now, EDGE scores had primarily highlighted overlooked animals such as the aye-aye, pangolin and axolotl — creatures representing irreplaceable evolutionary branches but rarely featured in conservation campaigns.
“This approach has let conservationists 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 analysis. “Plants remained comparatively invisible — dismissed as mere backdrop for photographs of bees and tigers.”
Building a Tree of Life for 335,000 Species
The research team, led by Félix Forest, a plant evolutionary biologist at the Royal Botanic Gardens, Kew, assembled collaborators from the Zoological Society of London, Boise State University and international institutions to tackle a monumental data challenge. They constructed a family tree and generated extinction-risk estimates for all 335,497 known flowering plant species, cross-referencing molecular data against the IUCN Red List of Threatened Species. The result stands as the largest species-prioritization assessment ever undertaken in conservation science.
Flowering plants outnumber the largest previously EDGE-assessed animal group — ray-finned fish — by more than tenfold. Forest described compiling comparable data 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 Alarming Numbers
The headline finding: 21.2 percent of angiosperm evolutionary history is at risk of extinction. Researchers identified 9,945 priority species that disproportionately account for that threatened diversity — roughly 3 percent of all known flowering plants, but carrying evolutionary weight far exceeding their numbers.
To grasp the scale: that rate nearly doubles the equivalent risk measured across jawed vertebrates, which sits at approximately 13 percent across animals from sharks to elephants.
Perhaps most troubling is the historical neglect these species have endured. Sven Buerki, a botanist at Boise State University and study contributor, framed the disparity bluntly: more than two in five plant species are estimated 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 have been dying in the dark,” Buerki said.
Familiar Names, Stark Futures
Among the newly flagged priority species are household names. The vanilla orchid, source of the world’s most popular dessert flavoring, now ranks among plants requiring urgent attention. Relatives of the corpse flower, whose rare blooms draw crowds to botanical gardens, also made the list.
The jellyfish tree (Medusagyne oppositifolia) presents an especially precarious case. Found only on a handful of rocky outcrops on Mahé island in the Seychelles, it was believed extinct until a few survivors were rediscovered in the 1970s. As the sole member of its genus, with fewer than 100 mature individuals surviving in four small populations, its loss would erase an entire limb from the angiosperm family tree.
Another standout is Amborella trichopoda, a modest shrub native to New Caledonia whose evolutionary lineage split from all other flowering plants approximately 130 million years ago — making it the single most evolutionarily distinct angiosperm alive today.
A Tool for Triage, Not a Eulogy
Despite the grim arithmetic, researchers frame the study as a roadmap for action. The calculations show 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.
“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,” the authors noted.
Some translation from data to action is already occurring. Buerki’s team plans to integrate results directly into Flora of the World, an online platform, so anyone searching for a species can see not only where it grows but how evolutionarily irreplaceable — and endangered — it is. At Kew, the metric is already shaping decisions inside the institution’s Living Collections, guiding which specimens horticulturists prioritize for cultivation and seed-banking.
Beyond the Greenhouse
The study situates its findings within a long-running debate in conservation biology: global biodiversity policy has consistently treated evolutionary diversity as worth protecting, yet plants were excluded from the assessments meant to operationalize that principle for decades.
“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.”
The message carries implications beyond botanical gardens. Animals typically pictured on conservation reports — pandas, polar bears, tigers — depend fundamentally on the quieter, rootier world sustaining them. Gumbs’s framing captures the stakes: “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.”