Should we plant millions of trees in Cape Town? What impact will it have on climate change? If any?

“Rising temperatures will cause more death than all infectious diseases” the Guardian Newspaper reported on 4 August 2020. As the world battles to get a handle on COVID, it doesn’t really need competition for headlines. However, if the study is correct, “the growing but largely unrecognized death toll from rising global temperatures will come close to eclipsing the current number of deaths from all the infectious diseases combined if planet-heating emissions are not constrained”.

Research indicates that a high-emissions scenario will increase global mortality rates by 73 deaths per 100,000 people by the end of the century, not far off the current death toll from HIV/Aids, TB, dengue and yellow fever. Unsurprisingly, the poorest will be the hardest hit and since South Africa has the world’s most unequal economy, it stands to reason that the large majority of South Africans will be affected.

The massive annual increase in carbon dioxide driven by fossil fuels is contributing to 90% of the additional carbon emitted into the atmosphere. The Climate Tracker website shows South Africa’s score at “highly insufficient” indicating that our National Determined Contributions fall short of our Paris Agreement commitments with temperatures in a worst case scenario rising by 4°C.

Dense, urban areas experience a heat island effect due to hardened surfaces, heat reflection from buildings and obstructed air movement which increases the risks of those living in cities. According to the World Cities Report 2020; The Value of Sustainable Urbanization report, 68% of the world’s population will live in cities by 2050, thus presenting a significant risk to a large proportion of the world’s population and an imperative for cities to take action. The photos below of a streetscape in Khayelitsha, Cape Town, illustrate the area’s high exposure to the elements. A large proportion of Capetonians live in similar areas.

The City of Cape Town’s Resilience Strategy (2019) identified the risks associated with heat waves as a significant potential threat and the Climate Strategy currently out for comment will struggle with the challenge of adaption, particularly as the economy stutters and resources become more scarce.

Cities in the global north are seeing urban forests as a significant part of adapting to these conditions and to mitigating climate change with a plan to ‘reforest’ the world, particularly in non-forested ecosystems. The Bonn challenge aims to restore 350 million hectares of degraded forests worldwide by 2030. Because the EU is only 2.8 million square kilometres most of these forests are planned for Africa where the target is for 100 million hectares by 2030, with 3.6 million hectares committed by South Africa. Cameroon and Nigeria have committed to reforesting 25% and 32% of their country’s raising concerns around the impact it will have on farming and food security.

Professor Emeritus Bond convincingly argued in an Institute of Landscape Architects (ILASA) webinar (https://vimeo.com/showcase/7162437/embed), against the propagation of urban forests as an appropriate climate mitigation response. He highlights how the Bonn challenge targets areas in South Africa that are open, non-forested, biodiverse that have been labelled as “degraded, deforested, in need of reforestation”. Because reforestation will most likely be implemented using pine and gum trees that are easy to grow, pristine, biodiverse ecosystems such as grassland savannahs or as in the Western Cape, fynbos are threatened. Fynbos, the world’s most diverse floral kingdom and a major tourist attractor, is under imminent threat across the Western Cape from urban development and climate change. And now, from inappropriate reforestation too. Are trees appropriate for the fynbos biome?

Prof Bond suggests that trees will not have a sufficient impact on rising carbon dioxide levels, which makes the sacrifice of biodiversity high. Even if Africa reached the Bonn Challenge target, it would only reduce annual carbon emissions by less than 3% and in the process threaten its water supply and impact biodiversity, which Prof Bond suggests is a high price to pay. And he’s right. Climate change is the result of an unequal, extractive economy driven by a global northern middle class. It therefore doesn’t seem reasonable to colonise the resources of the global south to address a crisis they had little part in creating. When asked what we should be doing differently, Prof Bond replied that we should be reducing our fossil fuel emissions and switching to alternative energy sources. He further recommends protecting large carbon sinks such as frozen soils and highlights the role of the Amazon forests that sequester 100 billion tons of carbon – the equivalent of ten years of human greenhouse gas emissions and agrees that restoring goat-denuded spekboom systems in places like the Eastern Cape seems like a good idea.

The role of cities, the largest greenhouse gas emitters, he reminds us, is central to climate action and although planting trees will have little impact as a mitigation measure for climate mitigation, cities could be planting trees for climate adaption that provide beauty, shade and temperature control to improve liveability.

Paris is leading the way with four scheduled urban forests planned for completion by the end of this year. Adding an additional 12.5 hectares of green space, will inch them closer to matching Johannesburg’s reputation as the largest man-made forest in the world. Cape Town tails behind with 7% tree coverage, falling short of the UN Food and Agriculture Organisation’s urban forest definition which is “a contiguous area with over 10% tree canopy cover”. This estimation has been made possible by The Tree Canopy Mapping Project that commenced this year using light detection and ranging data to determine height, amongst other details such as species and vegetation area. Whilst the City of Cape Town does not appear to have any active plans to expand the tree canopy or create urban forests at this time, the recently published Trees: Best Practice Guidelines (2020) will assist residents to select an appropriate tree, which may, or may not be indigenous. In addition to this guide, tree planting plans should be prepared that are specific to the various micro-climates created by the Table Mountain chain to supply further guidance.

Landscape architect, Clare Burgess reminds us that the majestic oak trees planted in some cases by early settlers for wine barrels. Together with other exotic trees such as London plane trees, they are a visible remnant of our colonial past that establish the city’s tree canopy and contribute towards Cape Town’s unique landscape character and resilience. It is also a marker of the deep divisions within the city. The “leafy suburbs” are unsurprisingly in wealthy areas.

Replicating global north forest-planting trends could be viewed as the re-colonization of Africa and the further altering of a continent’s landscape. Cities in the global south would do well to adopt a cautionary approach to the adoption of ideas that may lack sound scientific grounding, before interrogation and a deep understanding of the potential unintended consequences.

These would identify areas of high tree planting potential and specify appropriate trees to build green infrastructure, expand biodiversity corridors and mitigate climate impacts. Planning at this scale is critical for building resilience for Cape Town’s most vulnerable, many whom live in corrugated iron shacks that absorb and retain heat, such as those illustrated in the photos below taken by the author in Kensington, Cape Town.

UCT’s Cool Shack Project measured shack temperatures during the experiment as high as 47.7°C with the ambient temperature reaching 36.3°C. At temperatures this high, there are increased risks of heat stroke and heart attacks, especially for children and the elderly. Cape Town’s Resilience Strategy (2019) states that:

“…It is imperative that Cape Town understands the risk of heat waves. Temperature increases over the southwestern Cape are projected to range between 4 and 5°C over the interior by the end of the century. Temperature increases may plausibly reach 3°C by the 2040’s. Drastic increases in the number fire-danger days, very hot and heat-wave days are projects across the southwestern Cape under a low mitigation scenario.”

In urban areas where biodiversity resources are already significantly impacted and where the greatest risk of heat waves prevails, appropriate tree planting should be implemented, especially in vulnerable areas where there are known high levels of hazard and risk. Careful planning based on scientific research and plant selection based on context will assist in preventing negative impacts on biodiversity to ensure that Cape Town becomes a climate adaptive city.  

Are urban forests a colonial construct? Through a Bonn Challenge lens, it would appear that they are. But denying Capetonians trees on this basis, would be a disservice because shade trees could be a life-saving game-changer.

RESOURCES

Bonn Challenge: https://www.bonnchallenge.org/

UCT’s Cool Shack Project: https://www.urbanafrica.net/urban-voices/cool-shacks-fight-cape-town-summer-heat/

Cape Town Resilience Strategy: https://resource.capetown.gov.za/documentcentre/Documents/City%20strategies%2C%20plans%20and%20frameworks/Resilience_Strategy.pdf

Trees Best Practice Guideline: http://resource.capetown.gov.za/documentcentre/Documents/Procedures,%20guidelines%20and%20regulations/Green_Infrastructure_Programme_%20Trees.pdf

World Cities Report 2020; The Value of Sustainable Urbanization: UN Habitat : https://unhabitat.org/wcr/

The Guardian: https://www.theguardian.com/us-news/2020/aug/04/rising-global-temperatures-death-toll-infectious-diseases-study

City of Cape Town Spekboom Challenge: (https://www.thesouthafrican.com/news/spekboom-challenge-city-of-cape-town-to-grow-5-000-trees-2020/)

How are trees relevant in the climate battle? – see recording of the Institute of Landscape Architects (ILASA) webinar here – https://vimeo.com/showcase/7162437/embed