Dying quiver trees sentinels for climate change pressures on species
In the early 2000s, Wendy Foden discovered one of the first examples of the impact of climate change on nature: the iconic, long-lived quiver trees of the Northern Cape and Namibia were dying off from regional warming and water constraints.
“That was a really big deal globally. Everyone got really excited, and the BBC and others came to film them,” recalls Foden, associate professor in the department of botany and zoology at Stellenbosch University.
But less than 20 years later such impacts are commonplace, she says. “Tens of thousands of species have been impacted, across every ecosystem on the planet. Each example is a unique tale of plants or animals trying to survive, and this at only 1°C of temperature rise.
The prospect of going beyond 1.5°C is terrible, especially forAfrica.”
What Foden finds heartening is that species are adaptive. “So, if we slow down the temperature rise and cap it at 1.5°C, our systems may see some reshuffling and look a little different, but we’ll keep most of what makes SA’s nature so remarkable.”
Foden, the chair of the International Union for Conservation of Nature and Natural Resources (IUCN) Species Survival Commission (SSC), a climate change specialist group, is
lead author of a major new IUCN co-authored paper, “Climate change vulnerability assessment of species”, published in the journal WIREs Climate Change.
The paper, authored by 18 leading scientists, all members of the IUCN SSC specialist group, warns how time is running out for many species. “This paper provides practical guidance on how to measure their overall vulnerability in a way that is thorough and comparable, from the tundra to equatorial rainforests,” says Foden.
The paper is a result of the scientists “stepping back and looking at the big picture of where we’ve come from and where we still need to go... This is an important field that has emerged and is growing fast as the climate change problem escalates,” says Foden.
It comes amid growing evidence of the increasing likelihood of extinc- tions from climate change, citing the case of the Bramble Cay melomys, a mouse-like rodent, which in 2016
became the first documented case of climate-induced extinction among contemporary mammals.
The golden toad from Costa Rica, too, was declared extinct because of a combination of factors including climate change, she says. “But there are many species that are impacted and some quite close to extinction.”
In addition to exerting direct pressure on species, climate change interacts with existing threats such as habitat loss, disease and over-harvesting, making their impacts more severe.
South Africa, says Foden, doesn’t have a monitoring programme to systematically track climate change impacts on biodiversity “nor to test the effectiveness of the actions we take to minimise them. This is a big priority”.
For Foden, quiver trees are sentinels for the climate change pressures to which all species are being exposed. “Because they grow so slowly and live so long, they provide a living record of the conditions of the past. We’ve been monitoring them over the past 20 years, across their distribution range in the Northern Cape and Namibia. We’re seeing a clear trend of die-back in the hotter northern and low altitude parts of their range (as in the Namib) and lots of new babies and juveniles in the cooler southern parts (succulent Karoo) where cool temperatures previously limited their spread.”
"As quiver trees have a very large north-south distribution spanning 2000km, the expansion in the south should be able to compensate for and keep up with the die-back up north. But for rare and localised species, which are often the most threatened already, this may not be the case. Such changes are also much harder to detect. Quiver trees are sentinels for the climate change pressures to which all our species are being exposed.
How species in SA are being affected by climate change:
◆Research has shown how 70 frog species have experienced range contractions from climate change and land-cover changes in SA. South African frogs as a whole have shifted an
average of 47.6m upslope to cope with the changing climate.
◆Birds are experiencing changes in the timing of migration and breeding, population declines and range contractions and some biomes such as fynbos and savanna are experiencing broad shifts in bird species.
◆Bleaching has been recorded on SA’s coral reefs with research showing a steady decline of soft corals and increase of hard corals.
◆Research has shown how rock lobster have experienced a sharp decline in growth rates, an increase in mass strandings and a large shift in distribution with far-reaching ecological consequences, with climate change playing a significant role.