Research has linked urban trees to a reduction in crime, happier people, and better school performance
Planting a tree in a city improves the health of each person who sees it. From reducing crime and improving well-being to protection against the consequences of climate change, urban tree planting needs to be at the top of city planners’ agendas. Food & Trees for Africa (FTFA), a food security, environmental sustainability and greening non-profit, has planted more than 4-million trees in communities around South Africa, and will continue to create green havens for the country’s residents.
South Africa’s green inequity hurts poorer communities
Many urban areas in South Africa lack green spaces. A 2020 study found widespread green inequity in the country’s cities, with green areas concentrated in wealthy neighbourhoods. Townships and poorer areas have few parks, gardens and green spaces –– let alone established trees –– depriving these residents of their multiple benefits.
At the same time, the country, and the continent as a whole, is witnessing unprecedented urbanisation, with people flocking to cities in search of economic opportunities. According to the World Bank, two out of every three people in South Africa live in a city.
City planners need to include indigenous trees and green spaces in their urban development and rehabilitation plans. Failure to do so will significantly harm residents’ experiences of their city, their health and well-being, and make them more vulnerable to climate change.
More than just a pretty tree –– the link between trees and crime reduction
A 2018 study out of Portland in the United States aimed to determine whether the city’s green infrastructure initiative reduced neighbourhood violence, and found a link between the introduction of curb-side trees and a reduction in violent crime. The city planted new trees along streets in previously underserved communities, and over the course of years violent crime in the area reduced. “This effect was especially pronounced in neighborhoods with lower median household income,” the researchers wrote. “These findings suggest that the inclusion of new street trees in underserved neighborhoods may be one solution to the endemic of violence in such neighborhoods.”
Moreover, a 2019 scientific review of 45 similar studies investigating the connection between trees and crime reduction confirmed the Portland finding. “By providing evidence that access to nature has a mitigating impact on violence in urban settings, city governments and communities are empowered to support these interventions,” they said.
Trees help learners learn –– particularly in disadvantaged areas
There is also a compelling relationship between learners’ school performance and the greenness of their environment. In another American study, published in the journal Frontiers in Psychology in 2018, researchers compared the performance of learners in 318 Chicago public schools with satellite images of their surroundings. They found that learners in schools and neighbourhoods with trees performed better than those in areas without trees and greenery –– even adjusting for pupil/teacher ratios, bilingualism, school size, and the sex split. “To determine what forms of green cover were most strongly tied to academic achievement, tree cover was examined separately from grass and shrub cover; only tree cover predicted school performance,” the researchers noted.
A Canadian study confirmed this greenness-performance link, and found that the greatest impact of the tree cover was in schools that had the most external challenges. “Our results suggest that urban school districts can improve children’s academic performance by increasing tree cover, in particular by focusing on socio-economically disadvantaged schools,” they write.
This green effect benefited learners of all ages. In Toronto, Canada, the proportion of tree cover in the school environment was a significant predictor of learners’ performance.
Fighting urban heat islands one tree at a time
Although cities are hubs of economic opportunity, they are also going to become increasingly uncomfortable places to live as global temperatures rise. Urbanised areas, with the concrete buildings, pavements and roads, absorb and trap heat. Known as the “heat island effect”, this phenomenon means that urban areas will experience much higher temperature rises than the surrounding countryside.
In areas without trees, residents will feel the consequences of these temperatures. In affluent areas, people will turn to air conditioning and push up their energy consumption (and carbon footprint), but in poorer areas like townships, residents will suffer under unrelenting South African heat.
Trees are an important way to combat urban heat islands. In Nigeria, researchers found that temperatures under trees were up to eight degrees lower than outside their shade. But the cooling effect depended on the trees planted. FTFA, which has been planting trees in under-resourced communities in South Africa for 30 years, opts to plant indigenous trees that consume less water than alien species and are more likely to survive harsh environmental conditions.
Trees, quite simply, make people feel better
In addition to their crime-fighting, learning-promoting, and cooling capabilities, trees just make people feel happier.
In Leipzig, Germany, researchers investigated how tree cover influenced the prescription of antidepressants. Their study, published in the journal Scientific Reports, followed almost 10,000 people and those living within 100m of a high density of street trees were less likely to have antidepressant prescriptions. This effect was even more marked for individuals with low socio-economic status.
However, in South Africa green spaces are usually only in affluent areas. The majority of its city residents live under “green apartheid”, according to the authors of the first research paper looking at the distribution of green infrastructure in South African cities.
Not only do cities’ poorer residents struggle with poverty and a lack of services, they are also being deprived of the trees and greenery that would improve their daily lives. We need to plant more trees in cities, and share the benefits of nature. Donate trees to under-resourced communities in South Africa now.