A really innovative study that went beyond statistical association and actually planted trees in low-tree neighborhoods and measured the impacts.

After the plantings, the research team reassessed residents' health. They found that those living in the greened area had 13-20% lower levels of a biomarker of general inflammation, a measure called high-sensitivity C-reactive protein (hsCRP) than those living in the areas that did not receive any new trees or shrubs. Higher levels of hsCRP are strongly associated with a risk of cardiovascular disease and are an even stronger indicator of heart attack than cholesterol levels. Higher CRP levels also indicate a higher risk of diabetes and certain cancers.

A reduction of hsCRP by this percentage corresponds to nearly 10-15% reduction in the risk of heart attacks, cancer or dying from any disease.

Although several previous studies have found an association between living in areas of high surrounding greenness and health, this is the first study to show that a deliberate increase in greenness in the neighborhood can improve health.