Growing plants in buildings can reduce heat and produce healthy food in African cities

Growing plants in buildings can reduce heat and produce healthy food in African cities

Constantly high temperatures and associated heat stress are a major problem for people who live in cities, especially in slums and informal settlements. It is a problem that is expected to continue.

According to the latest assessment of the Intergovernmental Panel on Climate Change Report, heat exposure is expected to increase in Africa in terms of the number of working days per capita. That is, the annual number of days when the temperature is above 40.6 ℃ multiplied by the number of exposed people. exposure to heat Will reach 45 billion people-days by 2060more than triple the rate between 1985 and 2005. This would make sub-Saharan Africa’s exposure to hazardous heat one of the highest in the world.

Heat exposure challenges It is exacerbated by the lack of basic services and infrastructure, along with low housing quality, poor socio-economic conditions, and a lack of green space in slums and informal settlements.

Our latest study In Akure, southwestern Nigeria, poor residents of slums are shown to be exposed to a higher degree of heat, compared to those in rich slums. By surveying 70 residents in each neighborhood, we found that poorer households in lower-income neighborhoods were more deprived and had less ability to adapt to the heat. Housing features in the poorest neighborhood did not completely prevent overheating.

Richer families in wealthier neighborhoods were able to install features like air conditioners, ceramic tiles, and shady plants that the poor couldn’t. For example, while 78% of households have air conditioners in the affluent area, only 22% have air conditioners in the slums.

Green spaces have the potential to reduce heat, and thus improve health, particularly in high-risk urban areas such as informal settlements.

Another study She led the trial of vertical greening systems in low-income communities in Akure and Lagos – both cities in Nigeria – and Dar es Salaam in Tanzania. Experience proved that vertical greening was a solution to heat problems in slums. It had the added benefit of providing healthy food in the form of vegetables.

Reduce exposure to heat

Exposure to high temperatures It often leads to health problems.

recent study She has led in Tanzania showing the typical heat-related health problems that have been reported among people residing in informal settlements. Of the 405 residents surveyed in the study, 61% reported a rash, 42% reported malaria, 38% reported frequent headaches, 30% reported high blood pressure, 20% reported dizziness, and another 22% reported Confusion and inability to concentrate. Low labor productivity (29%) and high space cooling costs (57%) are other heat-related problems that, if not addressed, can adversely affect health conditions.

We designed and installed a vertical greening prototype made of high-density polyethylene pipes placed horizontally on the walls of some residential buildings. The prototype was planted with the original leafy vegetables. In Nigeria, jute paper (Corcoros Olitorius), Lagos spinach (Celosia Argentinaand african spinachAmaranthus viridis) was implanted. in tanzania, Amaranthus potato leaves (Ipomoea patatas), pumpkin leaves (Telfairia occidentalis) and the legume known locally as “Free, Conde”.

Vertical farm green wall.
courtesy author

Our results

These vertical gardens provided healthy vegetables for residents to eat. From a typical prototype in Nigeria, up to 1 kg of vegetables were harvested in a six-week cycle. In Dar es Salaam, different vegetables were in varying quantities. For example, pumpkin leaves yielded about 300 grams of the harvested vegetable in a 20-day cycle. for Amaranthus spp., leafy vegetables, and potato leaves, bunches weighing about 660g and 450g were harvested respectively per cycle.

A resident of Dar es Salaam He said:

We can have vegetables that could have been bought…Usually we harvest one type of vegetable twice a week, and rotate for three days for each type of vegetable, but it’s only for family use…We never harvest for sale, unless a neighbor comes to ask. Free.

A resident of Lagos He said:

I’ve been getting vegetables. Like the ones I picked up today, it’s very green as you can see. It is fresh. It nourishes the body more than what you get from the market.”

Vertical gardens also affected the indoor air temperature of the rooms they covered. Up to 2.88 maximum temperature and 0.7 minimum temperature were recorded during a 45-day field measurement campaign held in September and October 2021 in Akure.

The wall temperature dropped by as much as 5°C during the 30-day measuring campaign between December 2020 and January 2021 in Dar es Salaam.

The difference in temperature caused by vertical gardens means that residents feel more comfortable and therefore may be less at risk of heat-related health problems.

way forward

Vertical greening can be expanded. Parks and other open green spaces are usually created in formal, affluent neighborhoods. While this is a good thing, it should be complemented by policy initiatives and programs that promote vertical, community-based and citizen-led farming in dense informal settlements.

Incentives relevant to each local environment or community may help vertical greening to gain traction. There should be a strong push for vertical greening systems – for food, microclimate control and other health-related benefits.

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