Photo: PLOS Ecology Community
By: Jeff Atkins
Research into how nature impacts our well-being has shown that being outside makes us feel better. Images of nature alone have been shown to lift people’s mood. But is there any connection with how the natural environment affects students’ grades? Researchers Sivajanani Sivarajar, Sandy Smith, and Sean Thomas tackle this issue in their recent article, “Tree cover and species composition effects on academic performance of primary school students” in PLOS One. Using standardized performance scores for students in grades 3 and 6 from 387 schools across Toronto, combined with spatial and biological information about trees and tree cover near the schools, Sivarajar and co-authors found that even after controlling for socioeconomic factors known to affect performance, that more trees meant better academics.
Previous work on analyzing the relationship of “green space” to student performance has focused on “soft” versus “hard” surfaces—think grass versus concrete. In 2010, Rodney Matsuoka found positive associations between student performance—including standardized test scores, graduation rates, percentages of students planning to attend a four-year college, and fewer occurrences of criminal behavior—with the students’ access to views of trees and shrubs from their school. In 2014, Chih-Da Wu and co-authors showed similar relationships in student performance to “greenness” of the adjacent school area, determined from satellite data. It’s also been shown that walking along nature paths has the potential to decrease our likelihood of mental illness. The novelty of Sivarajar and co-authors work, is the strict focus on tree cover alone as a determinant of student performance. It’s not just an either-or consideration, but a strict focus on trees and what the contribute to our well-being.
To control for socioeconomic factors that affect student performance, the Learning Opportunity Index (LOI), a composite measure of the external challenges that affect student performance, was used. LOI includes variables related to income, parental education, and family status. The working assumption here is that by using LOI, all of the variance, or spread in the data, that was a function of socioeconomic variables could be explained, thus, any differences that remained, could then be compared against data on trees. The idea being, that simply being around trees or being able to see them, decreases anxiety and in turn allows students to be more comfortable and better able to achieve academically.
Interestingly, there was very little spatial correlation, meaning that “richer” schools did not necessarily have more trees than other schools. This allowed for a fairly straight-forward comparison, given the authors’ approach, which showed that tree cover had no real effect on grade 3 students, but in fact showed a positive correlation for grade 6 students, explaining an additional 13% of the variance after socioeconomic factors were removed. Admittedly, the effect is not strong, but it is significant.
Does the type of tree matter? Based on the analysis presented on looking at different tree species, it appears that having a good mix of both deciduous and conifer trees is the way to go. Something for everyone I suppose. But if you are interested, and I know I am, the most commonly planted trees in Toronto were the ones found to be most positively associated with student performance, including blue spruce, black pine, green ash, and sugar maple. But, as the authors point out, schoolyards are not the bastions of forest diversity. And though statistically significant, I would take this one with a grain of salt. But as green ash is the only one of these species that grows in my part of the world, I maybe just plant a few in the backyard to be safe.
TREES FOR GRADES
While socioeconomic factors were the strongest predictors of student performance, this analysis shows that there is in fact a positive effect on student performance from increased tree cover near the school. This is a low-hanging fruit. While the effect is noticeable for grade 6 students, it is not in-and-of-itself a cure-all. But there is very little downside here if increased tree-planting, particularly in more socioeconomically disadvantaged schools, can help to increase student performance, or help lower stress and improve mood as other studies have shown. Hedonic demand theory in economics, a method of estimating value based on preference for something, has shown time and time again that access to or view of green space has made places more desirable—emotionally, psychologically, and financially. If students are more likely to feel like the want to be in school if they are surrounded by trees and nature, I am all for it. Increased tree cover can also decrease exposure to air pollution and decrease the heat island effect that is more pronounced in urban areas. The growing fields of urban forestry and urban ecology have a lot of potential here to inform policy and contribute to our well-being, as well as intersect with fields as disparate as landscape architecture, psychology, sociology, and education in creating learning spaces that can better utilize the natural environment to create learning opportunities.