Cape Town – New research has confirmed the extinction of 79 plants in South Africa's three biodiversity hotspots - the Cape Floristic Region, the Succulent Karoo and the Maputaland-Pondoland-Albany corridor, Stellenbosch University says.
According to the study, published in the journal Current Biology this week, this represents 45.4% of all known plant extinctions from 10 of the world's 36 biodiversity hot spots.
Biodiversity hotspots are areas that harbour exceptionally high numbers of unique species, but at the same time are under severe threat from human disturbance.
An international team of researchers, led by Professor Jaco le Roux and Dr Heidi Hirsch, affiliated with the Centre for Invasion Biology at Stellenbosch, analysed a comprehensive dataset of 291 plant extinctions since 1700 in ten biodiversity hot spots and six cold spots (such as England, Germany and Russia), covering about 15% of the Earth’s land surface.
The main drivers for extinctions in South Africa were found to be agriculture (49.4%), urbanisation (38%) and invasive species (22%).
“The results of their analysis of 300 years of data show the extinction rate for plants appears to have settled at about 1.26 extinctions per year since the 1990s.
"At its peak, however, it was at least 350 times that of historical background rates during pre-human times.
"At this rate, they predict that, in the areas they studied, an additional 21 plant species will go extinct by 2030, 47 species by 2050 and 110 species by 2100.
"However, these findings stand in sharp contrast to predictions from other studies that as much as half of the Earth’s estimated 390000 plant species may disappear within the remainder of this century.”
Le Roux said regional datasets provided valuable data to make general inferences around plant extinctions and the drivers underlying these extinctions.
There were, however, still many regions in the world without a Red List of Plants, or with outdated lists, such as Madagascar and Hawaii. These "hottest" of hotspots were therefore not included in their analysis.
“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 unfavourable environmental conditions.
"A recent report, for example, indicated that 431 plant species, previously thought to be extinct, have been rediscovered. This means that many plant species may technically not be extinct, even though they only have one or a few living individuals remaining in the wild.”
The first recorded species to be lost to forestry in South Africa in the 1700s was a type of fountain bush that used to grow next to streams in the Tulbagh region, Psoralea cataracta.
In 2008, it was listed as extinct on the Red List of South African Plants.
The next species to be confirmed extinct was one of the African daisies, Osteospermum hirsutum, last seen in 1775, then the honey bush, Cyclopia laxiflora, last seen around 1800, due to agriculture, forestry and urbanisation.
The researchers emphasised that biodiversity loss, together with climate change, were 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.”