In the past 250 years, nearly 600 plant species have gone extinct, according to a study published Monday in Nature Ecology & Evolution. That extinction rate is 500 times faster than what would be expected to occur naturally, without human intervention, scientists found.

The researchers studied centuries of scientific literature on the status of more than 330,000 plant species, in the largest survey to date of plant extinctions. Out of 1,234 species ruled extinct at some point, the team found that 571 plants remained extinct—some were later rediscovered or reclassified. That figure is four times higher than the official number publicized by the International Union for Conservation of Nature, which documents endangered and extinct species.

Even so, the study still likely doesn’t capture the entire scope of plant extinctions, says author Maria Vorontsova, a biologist at the Royal Botanic Gardens, Kew. Some “living dead” plant species, for example, may still have a few survivors but are unlikely to survive much longer in the wild.

“It is way more than we knew and way more than should have gone extinct,” Vorontsova tells The Guardian’s Damian Carrington. “It is frightening not just because of the 571 number but because I think that is a gross underestimate.”

Huge losses were concentrated on islands and in the tropics, as well as in Mediterranean climates. In Hawaii, which is known as a hotspot for biodiversity, researchers recorded 79 extinctions; South Africa’s Cape provinces saw the second highest rate with 37 extinctions.

The tropics are especially biodiverse, and because they start off with a higher number of species, it’s expected that they will also see higher rates of extinction. Even accounting for the increased biodiversity, though, the plant extinction rate in the tropics exceeded researchers’ expectations, says co-lead author Aelys Humphreys, an evolutionary biologist at Stockholm University. Islands in particular are sensitive to environmental changes and also tend to include many unique species, Humphreys tells Nature’s Heidi Ledford.

Among the extinct species are the Chile sandalwood, a tree whose fragrant wood was overused to make essential oils, and the banded trinity, an intriguing plant that grows entirely underground except for its small bluish flowers, Science’s Erik Stokstad reports.

Human activity served as the driving factor for many of these extinctions, Vorontsova tells Carrington. By clearing landscapes to make way for farmland or build cities, humans destroy huge swaths of natural habitats that serve as a home to these species. Vorontsova recalled an experience seeking out a particular grass species in Madagascar: When her team arrived at the spot where earlier scientists had once collected samples, they found only “cattle grazing, regular fires and people growing rice.”

The disappearance of plant species fits into a broader wave of extinctions caused by human activity. For years, scientists have warned that our planet is in the midst of its sixth mass extinction, akin to the prehistoric events that wiped out dinosaurs and early marine creatures. A United Nations-backed report this May found that up to one million species could die off in the near future.

However, most of the outcry around extinction has focused on animals rather than plants, authors point out—even though twice as many plant species have disappeared as mammals, birds and amphibians combined. Vorontsova referred to the imbalance as “plant blindness.”

“Animals are cute, important and diverse, but I am absolutely shocked how a similar level of awareness and interest is missing for plants,” Vorontsova tells Carrington. “We take them for granted.”

Plants are essential to functioning ecosystems, the authors point out. Even though most people can’t name off a recently extinct plant species like they could a dodo bird or passenger pigeon, understanding plant extinction is essential to predicting future biodiversity losses and coming up with conservation plans, authors write.

Such an understanding is also important for human societies, which in many ways rely on plants for our own well-being, says University of Oxford ecologist Rob Salguero-Gómez, who was not involved with the study.

"We depend on plants directly for food, shade and construction materials, and indirectly for 'ecosystem services' such as carbon fixation, oxygen creation, and even improvement in human mental health through enjoying green spaces," Salguero-Gómez tells BBC’s Helen Briggs.

Or, as author Eimar Nic Lughada puts it: “Plant extinction is bad news for all species—humans included.”