People often argue that spending time in nature can have lasting health benefits. Because of this, many people alter their lifestyles and living situations to include more nature. But is there strong scientific evidence to support the claim that being outside can decrease the likelihood of people developing certain health problems? More specifically, could exposure to diverse outdoor plant life decrease the likelihood of children developing asthma?
Professor Roger Ulrich and his team of students at Chalmers University of Technology claim that they found strong evidence suggesting that children who grow up in neighborhoods with diverse plant life are less likely to develop asthma. Using a database called Integrated Data Infrastructure (IDI) which is essentially census data in New Zealand, the researchers were able to track where children lived from birth to age eighteen. They then used satellite images to determine the greenness of the children’s neighborhoods and health records to determine whether or not the children developed asthma.
According to the study, children who live in greener areas with diverse plant life are 6.0% less likely to develop asthma. To explain this finding, the scientists use the hygiene hypothesis. According to this explanation, children that are exposed to more microbes develop stronger immune systems and are less likely to develop conditions like asthma. Because different plants have different microbes, according to this hypothesis, children living in neighborhoods with diverse plant life are less likely to develop asthma.
However, the scientists also found that an increase in certain types of plants, even in neighborhoods with high plant diversity, is associated with an increased risk of developing asthma. For example, children who live in neighborhoods with Gorse were 3.2% more likely to develop asthma. This made me wonder, is there truly a causal relationship between diverse vegetation in a neighborhood and the likelihood of a child developing asthma? A quick google search revealed that gorse is a noxious weed that weed controllers work to remove. What types of neighborhoods provide places for gorse to grow? Because it is a noxious weed, this plant is likely only thriving in poorer neighborhoods that don’t hire landscapers and noxious weed sprayers.
There are many factors that accompany vegetation diversity that could explain the link that these researchers found between plant life and asthma development. The scientists methods did not account for the potential tie between wealth and plant diversity. It is likely that in wealthier neighborhoods, there is a more diverse display of (non-noxious) plants, while in poorer neighborhoods, there is less focus on the diversity of plant life. Essentially, there other threats that accompany poverty (and a lack of plant diversity) that could increase the chances of a child developing asthma. For example, poorer neighborhoods likely have more pollution, inadequate healthcare, and less space for children to safely play outside- on top of having lower levels of plant diversity. Could these factors be causing children in neighborhoods with high plant diversity to stay healthy, and not the plants themselves?
Referenced:
Douwes, Jeroen, and Geoffrey H. Donovan. “Children Living in Green Neighbourhoods Are Less Likely to Develop Asthma.” Medical Xpress – Medical Research Advances and Health News, Medical Xpress, 8 May 2018, medicalxpress.com/news/2018-05-children-green-neighbourhoods-asthma.html.
Donovan, Geoffrey H., et al. “Vegetation Diversity Protects against Childhood Asthma: Results from a Large New Zealand Birth Cohort.” Nature News, Nature Publishing Group, 7 May 2018, http://www.nature.com/articles/s41477-018-0151-8.
Sources:
“Gorse: Ulex Europaeus.” Washington State Noxious Weed Control Board, Washington State, http://www.nwcb.wa.gov/weeds/gorse.
Data/Society/Decision-making Spring 2019 