Rare and Vulnerable Plants

The largest botanical dataset ever has been created by scientists, who discovered that nearly 40% of land plant species are classified as ‘exceedingly rare’. And these species are found in areas that will be impacted by climate change.

New research has shown that almost 40% of global land plant species are categorised as very rare, and these species are most at risk for extinction as the climate continues to change.

The findings were published in a special issue of Science Advances that coincided with the 2019 United Nations Climate Change Conference, also known as COP25, in Madrid.

Lead author Brian Enquist, from the University of Arizona, said: “When talking about global biodiversity, we had a good approximation of the total number of land plant species, but we didn’t have a real handle on how many there really are.”

Thirty-five researchers from institutions around the world worked for 10 years to compile 20 million observational records of the world’s land plants. The result is the largest dataset on botanical biodiversity ever created. The researchers hope this information can help reduce loss of global biodiversity by informing strategic conservation action that includes consideration of the effects of climate change.

They found that there are about 435,000 unique land plant species on Earth. Enquist continues: “So that’s an important number to have, but it’s also just bookkeeping. What we really wanted to understand is the nature of that diversity and what will happen to this diversity in the future. Some species are found everywhere – they’re like the Starbucks of plant species. But others are very rare – think a small standalone café.”

The study revealed that 36.5% of all land plant species are “exceedingly rare,” meaning they have only been observed and recorded less than five times ever.

“According to ecological and evolutionary theory, we’d expect many species to be rare, but the actual observed number we found was actually pretty startling. There are many more rare species than we expected,” he added.

Moreover, the researchers found that rare species tend to cluster in a handful of hotspots, such as the Northern Andes in South America, Costa Rica, South Africa, Madagascar and Southeast Asia. These regions, they found, remained climatologically stable as the world emerged from the last ice age, allowing such rare species to persist.

But just because these species enjoyed a relatively stable climate in the past doesn’t mean they’ll enjoy a stable future. The research also revealed that these very rare-species hotspots are projected to experience a disproportionally high rate of future climatic changes and human disruption.

“We learned that in many of these regions, there’s increasing human activity such as agriculture, cities and towns, land use and clearing. So that’s not exactly the best of news. If nothing is done, this all indicates that there will be a significant reduction in diversity – mainly in rare species – because their low numbers make them more prone to extinction,” says Enquist.

And it’s these rare species that science knows very little about. By focusing on identifying rare species, “this work is better able to highlight the dual threats of climate change and human impact on the regions that harbour much of the world’s rare plant species and emphasises the need for strategic conservation to protect these cradles of biodiversity,” said Patrick Roehrdanz a co-author on the paper and managing scientist at Conservation International.