But plants can be more difficult to assess than animals, because botanists can’t follow plant footprints across a savanna or hear mating calls through a tangled forest.
As a result, scientists have assessed only about 15% of species at risk of extinction. This means that we are often not sure what the world is missing until it is too late.
Within the plant kingdom, flowering plants — or angiosperms — make up the most diverse group at more than 369,000 species, and include such colorful species as Japanese wisteria and the eastern redbud tree.
There are about 34,000 species of ferns and mosses.
Conifers, or gymnosperms, such as Douglas fir and western hemlock, number just over 1,100 species.
Roots Against Extinction
On an average, about two plant species become extinct each year. In a 2019 study in the journal Nature Ecology & Evolution, scientists reported extinctions 500 times faster than the natural rate.
Plants growing on the island are at greatest risk because “there is nowhere to escape,” said Nick Lughadha.
In recent decades, scientists have worked globally to try and save rare plants.
“There is no technical reason any plant species should go extinct today,” said Colin Clubbe, a senior researcher at Kew, standing in the gardens’ Temperate House, which he has called “a cathedral for plants”.
Unfortunately, conservation efforts didn’t go far enough to save the St. Helena olive tree. Thick and bushy plant with clusters of small pink flowers, once common on a South Pacific island before becoming extinct in 2003.
“So you have a tomb for it as a species. But there’s still hope that we might one day find a survivor,” he said.
For centuries, scientists have been refining their knowledge of the world’s plant species by revisiting old survey sites and undertaking new ambitious field studies. According to Kew, they have managed to rediscover 537 plants believed to be extinct.
A Chilean crocus, Teicophilia cyanocrocus, was found sprouting south of Santiago in 2001, for example – decades after Victorian-era gardeners had written off the species as a casualty of over-collection.