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Cape Town is in danger of losing trees faster than they are being replanted, making the city more vulnerable to the effects of global warming.

The increase in global temperatures, driven by fossil fuel combustion and the annual loss of nearly five million hectares of forest, presents significant vulnerabilities for urban areas.

The materials used in construction and the surfaces of cities are particularly effective at trapping and reflecting heat, exacerbating the situation.

The loss of trees and the shade they provide has a direct impact on the Urban Heat Island effect, with air and surface temperatures much higher in urban than in rural environments.

Given that over 50% of South Africa’s population resides in urban regions, coupled with the relentless rise in global temperatures, the Council for Scientific and Industrial Research (CSIR) indicates that Urban Heat Islands will progressively impact the livelihoods of residents as the urban population expands.

According to a senior researcher in African Futures and Innovation at the Institute for Security Studies, Alize le Roux, the rapidly rising temperatures due to the climate crisis are turning South Africa’s growing urban “areas into “a ticking time bomb”.

“Those most at risk are the poor, elderly and young, people living in informal dwellings without proper insulation and ventilation, those reliant on public transport, and communities without access to green spaces and water.”

GroundUp reports that a heat-mapping study by Heat Watch Cape Town found air temperature differences of up to 16.3°C across the city on 28 February. The hottest areas, where temperatures were between 38.1° and 41.6°, were in the city centre along Strand Street, and in Woodstock, as well as in Maitland and Paarden Eiland.

The well-treed Newlands and Rondebosch areas were cooler at around 31°, with Rocklands in Mitchell’s Plain, which is close to the ocean, being the coolest mapped area on the day at below 26°.

Numerous studies have found that trees are a cost-effective means of reducing heat. Trees also reduce pollution and flooding caused by rapid stormwater runoff.

Cape Town, which experiences hot and dry summers, only has about a 6% tree canopy, according to City community and health Mayco member Patricia van der Ross. The target is 10%.

 

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Arborist Francois Krige, who runs a tree felling business and spearheads the reforestation of Platbos, says we are losing trees faster than we are replacing them. Krige said the infestation of Polyphagous Shot Hole Borer beetle in the southern suburbs had led to the loss of about 6,000 trees. Heavy rainfall and strong winds this winter led to the further loss of about 2,000 trees which were uprooted.

Approximately 2,150 trees were planted by the City during the 2023/24 financial year, a big decline from the high of about 3,380 planted in the 2021/22 financial year.

The increase in the number of solar panels is also contributing to Cape Town’s ‘deforestation’. Hundreds of trees in the city have been chopped down or badly lopped to guarantee that solar panels receive full sunlight.

The solution might be to plant more non-invasive alien species in locations where the indigenous flora would not thrive. Indigenous trees might be planted once non-invasive eucalyptus species have been established as windbreaks and soil stabilisers. Pinelands and Plumstead were good examples of this according to Nicky Schmidt who is chair of the non-profit organisation Parkscapes.

“Planting of new trees need not exclude the use of appropriate exotic species provided they are non-invasive and are suited to local conditions.”

Schmidt said tough, non-invasive alien species should be used to create a tree canopy where indigenous trees would not initially survive.

Another intervention that seems to be bearing fruit is the two SUGi “pocket forests” established on the Cape Flats – one in Langa and one in Mitchells Plain – and were flourishing.

 

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Pocket forests, planted in areas as small as 9 square metres, were developed by Professor Akira Miyawaki, and mimic natural forestation by planting trees closely together to maximise density and balance, as opposed to the traditional approach of providing space for the size of each mature tree.

We’ve only just entered summer in Cape Town, and it looks to be a hot one, so let’s plant some trees people. As the saying goes: The best time to plant a tree was ten years ago, and the second best time is today.

[source:groundup]