Jeffrey Gogo Climate Story
Zimbabwean cities and towns are expected to become very hot in the next 25 years due to rapid urbanisation and deforestation, a new study has found. This could lead to a range of health and social complications including heat-stroke, water and energy shortage, experts warn.
Areas with day-time temperatures ranging between 36ºC and 46ºC will expand to cover about two thirds of urban areas while those averaging 18ºC to 30ºC decline, says the University of Zimbabwe study.
Heat-wise, that effectively means there will be more Karibas and Chiredzis than there are Gwerus or Nyangas — and these changes will hit townships hardest, not so much for their endemic poverty as it were for their closely-knit type of settlements that suffocate green spaces.
Currently, only 42 percent of the land area in towns and cities tip the predicted temperature scale.
The research did not highlight the actual rate of the projected temperature rise, but noted that high density areas will warm much faster compared to low and medium density areas.
This is because low density areas retain a much greater area under green vegetation.
High density areas, which are built for the poor, do not, according to Terrence Mushore, the study’s lead author.
Titled “Responses of Land Surface Temperatures and Thermal Comfort to Urban Growth in Harare Metropolitan City”, the research typically focuses on Zimbabwe’s largest metropolis, boasting a 2,2 million population, Government and company headquarters, major hospitals, and a busy transport network.
But it’s results “entail that even in other parts of Zimbabwe densely built up areas will warm more than those with large vegetation cover proportion,” Mr Mushore told The Herald Business, via email.
Housing development for the poor has been more damaging, Mr Mushore said.
In Harare, more than 75 percent of vegetation — those areas under trees, wetlands grass etc, which are key to maintaining the temperature balance — was decimated between 1984 and 2016 as high density areas expanded by 92 percent.
As a result temperatures have climbed between 0,98ºC and 1,98ºC in the 30 years to 2015 as the swelling number of people moving into the city fed into the urban development cycle that fans deforestation, the research said.
By comparison, housing development in low to medium density areas achieved a warming effect of only 0,16ºC, during the same period.
Overall, land under vegetation in the capital has dropped more than 48 percent to 24,7 square kilometres since 1984 — a mere 2,5 percent of Harare’s total land area — and pushing temperatures 0,5ºC higher, according to the study.
By 2040, high density areas are expected to have colonised an additional 15 square kilometres of the capital’s natural land, a bane for the predicted temperature spike.
“These findings offer insight into landscape surface energy balance changes arising from urbanisation, critical for urban planning, environmental governance as well and climate change management in cities,” Mr Mushore asserted.
Below is an excerpt of the interview with Mr Mushore, who goes on to discuss the methodologies used to arrive at the study’s findings, as well the actions that residents and municipalities may undertake to control damage. I am represented JG and him TM.
JG: What are the key findings of the study on future urban impact of climate change, especially the temperature effect?
TM: We are already living in the background of rising temperatures globally. However, land cover distribution causes differences in the extents of warming in an urban setting. In order to gain understanding of the relationship between land cover changes (urban growth) and near surface temperatures in Harare, we began by looking at historical patterns from 1984 to 2015. This was in the background that the population of Harare doubled between 1980 and the 2012 census. This necessitated an investigation of the implications of such growth on temperature. Land surface temperatures modulate temperatures of the lower atmosphere due to exchange of heat between the land surface and the air immediately above it. Historical analysis showed that replacement of vegetation and wetlands with dense buildings increased surface and near surface temperatures in Harare. Therefore, this increase was superimposed on an already warming climate due to other factors such as greenhouse gas concentration increases and ozone depletion. Looking into the future, assuming that historical growth patterns would persist unmitigated, we predicted that areas exposed to extreme temperatures especially in the hot season (mid-September to mid-November) will also continue to increase.
JG: Which areas are going to be hit hardest . . . and which ones will turn cooler?
TM: Densely built-up areas such as the central business district, industrial areas and high density residential areas have warmed and will warm more than the other land use/cover types. This is because vegetation cover which has a strong heat mitigation effect has been significantly removed. On the other hand buildings, tarmacs and pavements which absorb a lot of heat and cause warming have occupied a large proportion of Harare which is also predicted to continue increasing into the future. The southern half of Harare is mainly occupied by these land cover types which absorb a lot of heat and will thus be expected to warm more than the northern areas where we have most of the medium and low density residential areas.
JG: How can municipalities respond to the anticipated increase in temperature?
TM: Studies in other parts of the 0world have shown that even greenery between buildings in densely built-up areas is of heat mitigation value. Therefore, communities should be encouraged to maintain urban greenery such as lawns and trees. In the same context of urban greenery, the municipality should also maintain parks and establish more especially in densely built up areas such as high density residential areas. Studies have indicated that visiting parks and lakes during the hot days helps to maintain human thermal comfort. The other role of the municipality would be to encourage future growth patterns which take implications on temperature into consideration. An example would be to promote construction of high rise buildings (vertical development) so that there is adequate space for greenery around spaced out buildings. Other steps include research to enable identification of construction materials and patterns which promote reflection more than absorption of heat from the sun (such as retro-reflective surface). Still not common in most African countries is vegetation on roof tops in densely built-up areas such as central business district. This reduces the heat absorption effect of concrete roofs.
God is faithful.