A major new study of global seed-bearing plant extinction rates has found that species are being lost four times faster than previously thought, and some 500 times faster than the natural background rate.
The study, the most comprehensive to date to assess extinction rates, found that an average of three species a year was lost between 1900 and 2018. It is based on a database of more than 330,000 species compiled by botanist Rafaël Govaerts at the Royal Botanic Gardens, Kew since 1988, and subsequent cooperation with plant evolutionary biologist Aelys Humphreys at Stockholm University.
Since 1753, the researchers concluded that some 1,234 species had been reported to be extinct, but due to factors such as reclassification, duplication and the difficulty of finding surviving plants in remote areas and rapidly changing landscapes, this figure was reduced to a final estimate of 571 presumed extinctions. But many species still surviving are considered to be ‘functionally extinct’, as they exist in small, isolated groups that are unlikely to be viable populations in the long term. Overall, the final number of extinctions is thought to be an underestimate.
Hawaii has recorded the highest loss of seed-bearing plants in the world since 1753, reporting 79 extinctions. Overall, tropical biodiversity hotspots threatened by rapidly expanding populations such as in Madagascar, the Brazilian rainforests, India and South Africa, are most at risk. Islands with high levels of endemics, plants found nowhere else, are especially vulnerable to extinction.
Trees, shrubs and other woody perennials face the greatest risk from extinction, the research shows.
Grim as the results are, the study has produced "enormously significant" results that will help target conservation efforts, according to conservation biologist Stuart Pimm of Duke University in Durham, North Carolina.
The study follows a report by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) in May, which concluded the earth’s web of life and natural capital is becoming dangerously frayed, with a million species at risk of extinction needing urgent action.