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One in three tree species is in the red, new global assessment says

Seeds of Karomia gigas. Image courtesy of Kirsty Shaw/BGCI.

  • Of the 60,000 known species of trees, 440 are critically endangered, an assessment spearheaded by Botanic Gardens Conservation International (BGCI) has found.
  • There are more threatened tree species in the world today than there are threatened mammal, reptile, bird and amphibian species combined.
  • Among tree biodiversity hotspots, which boast a large number of indigenous trees, Brazil, Indonesia and Malaysia fare poorly.
  • Lack of in-country expertise is holding back such initiatives, Frank Mbago, a Tanzanian botanist, told Mongabay.

When Frank Mbago, a Tanzanian botanist, learned that the IUCN, the global conservation authority, had declared the Erythrina schliebenii plant extinct, he was wary. His skepticism was justified: in 2011, a team he helped assemble “rediscovered” the tree in the coastal forests of southern Tanzania. That expedition unearthed another species feared lost: Karomia gigas.

But with fewer than 50 individuals in the wild, the future of both trees is still far from certain. They aren’t the only ones teetering on the edge of extinction; a global report released Sept. 1 found that 440 tree species are critically endangered.

“We have assessed threatened and non-threatened species to build a global picture of the conservation needed for trees,” said Megan Barstow, a conservation officer with Botanic Gardens Conservation International (BGCI), which spearheaded the effort. Before this report, published assessments covered only 10,000 species, Barstow said. The number stands at nearly 58,500 today.

A Karomia gigas tree in Tanzania. Image Courtesy of Kirsty Shaw/BGCI.

But the picture it paints is bleak. A staggering 17,500 species are at risk of dying out; that’s one in every three tree species. There are more threatened tree species than mammal, reptile, bird and amphibian species combined.

But in the public imagination, more animated life forms often steal the limelight, leaving the flora relegated to the background. The new report shows that the living tapestry of our landscapes is also losing its rich detail. To halt the unraveling of ecosystems, we must hold tight to the planet’s tree diversity, experts say.

“If we are going to achieve an ambitious transformation of our relationship with biodiversity — one that sees us living in harmony with nature by 2050, we need to put tree species conservation at the heart of work in ecological restoration,” Elizabeth Maruma Mrema, executive secretary of the U.N.’s Convention on Biological Diversity, said in a prepared statement.

Of all tree species, about a fifth are directly used by humans, either for food, fuel, timber or other purposes. Despite this, and perhaps because of it, they are being overexploited, mismanaged and sometimes driven to extinction.

“Vegetation is safe when it is far away from people,” Mbago said, noting that forests closest to settlements are the first to be destroyed. A bird’s-eye view of things confirms this: agriculture and logging are two of the biggest threats to these sturdy, perennial plants.

The region with the highest proportion of tree species under threat (40%) is the “Afrotropics,” spanning sub-Saharan Africa, most of the Arabian Peninsula, and the islands of the western Indian Ocean.

Among tree biodiversity hotspots, which boast large numbers of indigenous trees, Brazil, Indonesia and Malaysia fare poorly. Of Brazil’s nearly 9,000 native tree varieties, 1,977 are at risk. The situation is even worse in Indonesia and Malaysia, where nearly a quarter of native species are threatened.

The problem isn’t restricted to the tropics; more than half of Europe’s native trees are in peril.

Dead baobab due to fire near Kirindy Forest. Photo by Rhett A. Butler / Mongabay.
A fire damaged baobab tree near Kirindy Forest in Madagascar. Photo by Rhett A. Butler/ Mongabay.

The report also highlights threats on islands where endemicity is high. In Madagascar, the fourth-largest island in the world, almost 60% of tree species are endangered. Fires are an annual threat and so is the year-round selective logging of rosewood and ebony trees.

On the other side of the globe, in the Caribbean islands, loggers also target hardwood trees like rosewood and mahogany. But climate change is also having an impact in the Caribbean. Sea level rise menaces coastal green cover. Extreme weather events are dangerous for trees too, some of which are adapted to a narrow band of climatic conditions.

The report compiled with the help of 60 institutions and more than 500 experts is a major step toward plugging the gaps in our knowledge about trees. A dedicated portal that presents information on conservation efforts sorted by species and geography is now live.

Even this appraisal of the perils facing trees is likely an underestimation. Many species are yet to make it into the scrapbook of modern science. “Students today think if it is not on Google, it doesn’t exist,” Mbago said. “What they don’t realize is that people have to go out into the field to collect the information that goes on the internet.”

A critically endangered Cola porphyrantha tree in Kenya. Image courtesy of Norbert Rottcher/ Kivukoni Indigenous Tree Nursery.

In Tanzania alone, there are still swaths of unexplored forests and landscapes, with new species being uncovered every year. The East African nation is lucky in many ways, Mbago said. Its history since independence hasn’t been as turbulent as other countries on the continent. Research has continued largely uninterrupted since it gained independence from Britain in 1961.

For the Afrotropics, assessments for more than half of the known tree species were consolidated and published in the last five years as part of the effort led by BGCI.

The universe of trees is expanding, but not the population of dendrologists. At least not where they are needed most, Mbago said, pointing to a lack of in-country expertise. Documenting the floral diversity of under-explored nooks of Tanzania cannot be done by helicoptering researchers. Long stretches of fieldwork, multiple visits and an understanding of local conditions often yield the most satisfying results.

“We have thousands of tree species, but not enough botanists to study them,” Mbago said.

(Banner image: Seeds of Karomia gigas. Image courtesy of Kirsty Shaw/BGCI.)


Clarke, G. P., Burgess, N. D., Mbago, F. M., Mligo, C., Mackinder, B., & Gereau, R. E. (2011). Two ‘extinct’ trees rediscovered near Kilwa, Tanzania. Journal of East African Natural History, 100(1-2), 133-140. doi:10.2982/028.100.0109

Malavika Vyawahare is the Madagascar staff writer for Mongabay. Find her on Twitter: @MalavikaVy

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