From cultural icons to invaders and victims

South Africa’s almost 400-year-old history of oaks could end, forever changing the landscape of trees in towns and cities such as Cape Town, George, Paarl, Stellenbosch and Swellendam.

In a ___ Research paper published I South African Journal of BotanyEcologists from the Center for Invasion Biology (CIB) at Stellenbosch University’s School for Climate Studies explored the history of the introduction of the Quercus genus into South Africa, as well as its current status and the factors influencing its spread across our landscape. Changing distributions.

The first written record of the English oak (Quercus robur) dates back to 1656, allegedly introduced by John van Riebeeck, said Christian Gulden Hughes, a postgraduate student in SU’s Department of Botany and Zoology and first author of the article. had gone. “Dozens of other oak species were introduced to the Cape of Good Hope by early Dutch settlers and the British colonial government. Many oaks were later widely cultivated throughout the country and have since become the dominant species in present-day South Africa. “I’ve become one of the most widespread and recognized trees,” he explains.

But now, the species may have reached a crossroads.

Gildenhuys found that three oak species—English oak, pin oak, and cork oak—have invaded riverbanks and urban woodland interfaces in Stellenbosch and Cape Town. These oaks do not now cause major problems as invaders but may do so in the future.

At the same time, many species (including the most widespread species, Q. robor or English oak) are highly susceptible to diseases and invasive beetles such as the polyphagous shot hole borer. “Not only does this mean that centuries-old oaks are at risk, but it also means that Affected trees It must be removed before the infection spreads further,” says Guldenhoys.

Professor Dave Richardson, an ecologist at CIB and co-author, says the story of the oak in South Africa is a perfect example of how Global change is rapidly changing the role and outlook of species in urban areas.

“We must accept that the potential impact of the polyphagous shothole borer is a game-changer. As a result of this invasion, the tree forms of many towns in South Africa will be radically altered. may decide to replace. Q. Robor trees with less sensitive tree species should also consider the potential negative impacts of these species,” he explains.

The ideal would be to replace affected trees with native species that are less susceptible to pests and diseases such as PSHB. However, people’s attachment to their oak-lined streets could hamper alternative efforts and lead to conflicts between management and stakeholders, he warned.

Professor Guy Midgley, interim director of the School for Climate Studies, says trees play an important role in mitigating the effects of climate change by reducing heat stress in urban areas. On the other hand, the way thousands of diseased trees are destroyed can have a significant impact on carbon emissions.

Adding fuel to the fire is the debate about the cultural value of oaks in general. In one sector of South African society, these centuries-old trees are celebrated as part of our cultural heritage. In another area, they are perceived as unwanted relics of the colonial past.