The “green” I’m talking about isn’t about protecting the trees, it’s about spending time with them…
What with coronavirus, inflation, and other daily pressures, we all need to find ways to relieve stress. One simple method is to spend time in nature, which not only improves our mood and helps us feel relaxed but also lengthens our life.
In cities, however, seeking out nature may not be easy or convenient. But what if nature could be brought to us?
A natural experiment over three decades shows how an easily applied, specific intervention, using God’s creation, reduces death considerably.
Lower Deaths From Any Cause
In the last five years alone, many studies have shown higher levels of exposure to green vegetation are linked to lower death rates from heart disease, respiratory disease or from any cause. However, all these studies use satellite data to estimate the amount of greenery. This is problematic because the natural environment only changes slowly over time and this method isn’t sensitive enough to detect the small changes that occur. In addition, satellite data can’t easily distinguish between different types of vegetation.To address these limitations researchers from the USDA Forest Service and the Barcelona Institute for Global Health took advantage of an experiment that took place between 1990 and 2019.
In that period, Friends of Trees, a non-profit organization, planted 49,246 trees along the streets of Portland, Oregon. After looking at the data, what researchers found was amazing…
Exposure to Trees Helped People Live Longer
The research team looked at the number of trees planted, covering areas in which about 4,000 people lived, in the preceding five, ten or 15 years. Then they checked the death rate statistics in each of the areas.After considering factors that influence mortality, such as income, education, and racial composition, the results show that in neighborhoods where more trees are planted, mortality rates are lower.
Specifically, each tree planted in the preceding 15 years was linked to a significant six percent reduction in deaths from heart disease and a 21 percent reduction in deaths from all causes, barring accidents. The association was stronger for men, and for both men and women over the age of 65.
Interestingly, the association between living a longer life and exposure to the trees got stronger as these trees aged and grew.
Exposure to Older Trees Lowers Death rate by 30 Percent
Each tree planted in the preceding one to five years was linked to a 15 percent reduction in death. This rose to a 26 percent reduction for trees planted six to ten years earlier. And for trees planted during the previous 11 to 15 years, the reduction in death rose to 30 percent, double that observed with trees planted in the preceding one to five years.In other words, older, bigger trees produced the largest decrease in mortality.
Geoffrey Donovan, first author of the study, explained, saying, “We observed the effect both in green and less green neighborhoods, which suggests that street tree planting benefits both. Our results provide an important evidence-base for tangible interventions (e.g., planting trees) to increase the longevity of urban residents.”
The study results are consistent with previous studies demonstrating a survival advantage with exposure to higher residential greenness. And a recent European study also found that exposure to larger trees was linked to fewer prescriptions for heart disease and mood disorders.
On the flip-side…
Loss of Trees Increases Mortality
Additional evidence, specifically for trees, comes from two studies, also led by Geoffrey Donovan, showing that loss of trees to an invasive tree pest - the emerald ash borer - is associated with increases in cardiovascular and lower-respiratory mortality.This led the authors of the latest study, published in the journal Environment International in December, to write that “in combination with our current results, these studies provide stronger evidence of a causal link between trees and human mortality, because the evidence is symmetrical - loss of trees is accompanied by increases in mortality, whereas planting trees is associated with decreases in mortality.”
The Health Benefits of Large Trees
Although this type of study cannot explain why trees reduce mortality, the authors offered some ideas based on other research studies regarding larger trees. They suggested that larger trees have a greater leaf area. This allows them to absorb air pollution, reduce high temperatures and dampen loud noise, all factors linked to greater mortality.Larger trees are also aesthetically more appealing and may therefore benefit psychological health. They may also be more effective at promoting social interaction.
