Nearly 40% of plant species are very rare and vulnerable to climate change

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Nearly 40% of the world's terrestrial plant species are classified as very rare, and these species are the most threatened with extinction as the climate continues to change, according to new research by the University of Arizona-LED Research.

The results are published in a special issue of Science Advances that coincides with the 2019 United Nations Climate Change Conference, also known as COP25, in Madrid. COP25 brings nations together to act on climate change. The international meeting will take place from December 2 to 13.

"When we talk about global biodiversity, we had a good approximation of the total number of terrestrial plant species, but we didn't really know how many there really are," said lead author Brian Enquist, professor of ecology and evolutionary biology at the University of Arizona.

Thirty-five researchers from institutions around the world have worked for 10 years to compile 20 million observations of the world's terrestrial plants. The result is the largest set of botanical biodiversity data ever created. Researchers hope that this information can help reduce global biodiversity loss by informing strategic conservation measures that take into account the effects of climate change. Translated with (free version)

They discovered that there are about 435,000 unique terrestrial plant species on Earth.

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"So it's an important number to have, but it's also an accounting issue. What we really wanted to understand was the nature of this diversity and what will happen to it in the future," said Mr. Enquist. "Some species are found everywhere, like the Starbucks of plant species. But others are very rare. Think of a small independent coffee shop."

Enquist and his team revealed that 36.5% of all terrestrial plant species are "extremely rare".This means that they have only been observed and recorded less than five times.

"According to ecological and evolutionary theory, one would expect many species to be rare, but the actual number of observed species we found was actually quite surprising," he says. "There are many more rare species than expected."

In addition, the researchers found that rare species tend to cluster in a handful of hot spotssuch as the Northern Andes in South America, Costa Rica, South Africa, Madagascar and South-East Asia. They found that these regions have remained climatologically stable as the world emerged from the last ice age, allowing such rare species to survive.

But just because these species have enjoyed a relatively stable climate in the past does not mean that they will have a stable future. The research also revealed that these hotspots of very rare species are expected to experience a disproportionately high rate of future climate change and human disturbance," said Dr. Enquist.

"We have learned that in many of these regions, human activity is increasing, particularly in agriculture, cities and villages, land use and clearing. So it's not exactly the best news," he says. "If nothing is done, all this indicates that there will be a significant reduction in diversity - mainly of rare species - because their small numbers make them more vulnerable to extinction.

And it is these rare species that science knows very little about.

By focusing on the identification of rare species," this work is better able to highlight the dual threat of climate change and human impact on regions that are home to a large proportion of the world's rare plant species and highlights the need for strategic conservation to protect these cradles of biodiversity," said Patrick Roehrdanz, co-author of the document and Chief Scientist at Conservation International.

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