5.11 Nature & Emotions
Figure 5.11: The top chart shows the frequency of various feelings by residents of Stockholm, Sweden, with noise on both sides of their apartments (after Gidlöf-Gunnarsson and Öhrström 2007). Better access to vegetation relieves a variety of negative feelings. At bottom left, two measures of well-being increase with plant species richness (after Fuller et al. 2007). At bottom right, living in more vegetated neighborhoods (measured through NDVI) reduces the likelihood of childhood obesity in high-density areas (after Liu et al. 2007).
At top of Figure 5.11, a study from Stockholm, Sweden, examined how access to green areas affected residents with and without quiet space available at their apartments, relating 500 carefully selected questionnaire responses to environmental conditions. All residents faced a road on one side, and both sides of their apartments had noise levels around 60–68 decibels. Along with questions concerning how noise affects them, they were asked about their access to green areas. In this plot, a star above a column indicates that better access to green areas has a statistically significant effect on the experience, although these effects weren’t necessarily large ones. For example, concerning annoyance at home and outdoors, access to green areas explained only about 3% of the variation. However, many features were affected positively by access to green spaces.
More than just “green,” people feel better with something that correlates with species richness. Here I show results, at bottom left, for two “feel-good” measures against plant species diversity in Sheffield, UK. Researchers define reflection as the “ability to think and gain perspective” and distinct identity as the “degree of feeling unique or different through association with a particular place.” Responses ranked these feelings on a five-point scale, being elicited during interviews from 312 users of 15 different greenspaces ranging from 1 to 24 hectares each. Also important were the number of distinct habitats within a greenspace, as well as the number of bird species present.
In addition to emotional health, a childhood obesity study from Marion County, Indiana, examined the medical records of more than 7,000 children between 3 and 18 years of age, in the different townships. Defining obesity as above the 95th percentile for their age, children living in high-density townships had lower odds of obesity when living with higher vegetation, as summarized at bottom right. In low-density townships, children living further from a brand-name supermarket had higher obesity odds. A clear mechanism exists for the former association — children with vegetation play outside more often — but the latter mechanism seems elusive. Another study in Indianapolis, Indiana, included nearly 4,000 children aged 3–16, mostly Medicaid enrollees from lower-income families. Over a two-year period, researchers observed a highly significant connection between a child’s body mass index (BMI) and the normalized difference vegetation index (NDVI) where that child lived. In that study the odds-ratio was 0.87, with a 95% confidence interval of (0.79–0.97), translating to decreased body masses with increased vegetation of 1.6 kg and 5.1 kg for girls aged 4 and 16, respectively. Researchers presume that greater activity levels provide the mechanism.
Gidlöf-Gunnarsson and Öhrström (2007) conducted the Swedish study regarding the effect of access to green areas on people’s feelings. They also examined the importance of having a quiet side to one’s apartment, finding that availability similarly important.
Fuller et al. (2007) examined how reflection and distinct identity depend on species richness in Sheffield, UK. Another interesting test they made shows that untrained people perceive species diversity that is much in line with actual empirical measures of species richness. Bird and butterfly diversity failed to produce similar trends. Significant trends in these emotional measures with plant diversity remained after correction for habitat area, which itself was positively correlated, along with habitat diversity.
Bell et al. (2008) showed the highly significant trend of the body mass index (BMI) with normalized difference vegetation index (NDVI) in the Indianapolis, Indiana, study of nearly 4,000 children aged 3–16.