An international team of researchers led by Stellenbosch University is reporting that plants are vanishing at a shocking rate across three biodiversity hotspots in South Africa. The study revealed that 79 plants have been confirmed extinct in the last 300 years in the Cape Floristic Region, the Succulent Karoo, and in Maputaland-Pondoland-Albany.
According to the researchers, the biodiversity loss estimated for these three hotspots represents almost half of the known plant extinctions in 10 of the regions that are recognized as having the most diverse wildlife on the planet.
Led by Professor Jaco Le Roux and Dr. Heidi Hirsch, the researchers analyzed 291 plant extinctions that have taken place in ten biodiversity hotspots and six coldspots since the year 1700. Overall, the study area covered about 15 percent of the Earth’s land surface.
Agriculture was found to be the primary driver of extinctions in South Africa, followed by urbanization and invasive species.
The study also revealed that plant extinctions over the past three centuries have leveled off to about 1.26 extinctions per year since the 1990s. However, when this number hit its peak, it was at least 350 times the historical rate that was established prior to human disturbances.
The scientists predict that, within the study area, an additional 21 plant species will vanish by 2030 and 110 plant species will be lost by the end of the century. These results are strikingly different from the findings of some previous studies which suggest that half of all the Earth’s 390,000 plant species may disappear by 2100.
“This would translate into more than 49,000 extinctions in the regions we studied over the next 80 years, which seems unlikely, bar a cataclysmic event such as an asteroid strike!” explained the researchers.
Regardless, the study authors emphasised that biodiversity loss and climate change are the biggest threats faced by humanity.
“Along with habitat destruction, the effects of climate change are expected to be particularly severe on those plants not capable of dispersing their seeds over long distances.”
Professor Le Roux pointed out that regional datasets provide valuable data to make general inferences around plant extinctions and the drivers underlying these extinctions. However, data is still very much lacking for many hotspots, such as those in Madagascar and Hawaii, which is why these regions were not included in the study.
“A lack of up-to-date lists prevents us from gaining a more complete and precise picture of what we are losing, and at exactly what rate,” said Dr. Hirsch.
The experts believe that the only way to truly understand the magnitude of the plant extinction crisis is by urgently initiating regional or national biodiversity assessments.
“While our study suggests that modern plant extinctions are relatively low, it is important to keep in mind that plants are exceptionally good at ‘hanging in there.’ Some of them are among the longest living organisms on earth today and many can persist in low densities, even under prolonged periods of unfavorable environmental conditions,” said Professor Le Roux. “A recent report, for example, indicated that 431 plant species, previously thought to be extinct, have been rediscovered.”
In other words, plant species may not be completely doomed even when they are down to just a few remaining individuals. This makes it particularly challenging to accurately quantify plant extinction rates.
The study is published in the journal Current Biology.
By Chrissy Sexton, Earth.com Staff Writer