It’s no secret that nature makes us feel good. From medieval visionary Hildegard von Bingen’s praise of viriditas, or greenness, to the more modern theory of biophilia, people have long celebrated the life-affirming power of plants. Now scientists say regular exposure to trees and other green spaces can actually help women live longer. Their research was published today in the journal Environmental Health Perspectives. 

As the world becomes increasingly urbanized, we’ve started to realize just how precious green spaces are. Previous studies have shown that spending time in nature can reduce stress and blood pressure and ease symptoms of depression. Some studies had suggested that living near vegetation could even reduce mortality, but these studies were limited and their results somewhat contradictory. 

To definitively test the mortality hypothesis, a team of researchers drew data from the Nurses’ Health Study, which began following more than 120,000 American nurses (all women) in 1976. The study participants filled out a questionnaire about their lives and health at enrollment, and then once again every two years. For this study, researchers focused on response data from 2000 to 2008. By 2000, the pool of living participants had shrunk to 108,630. By 2008, it was down to 100,026.

Each of the study participants supplied her home address. The researchers fed those addresses into a satellite mapping program, which could then estimate the amount of vegetation in a given woman’s neighborhood. They quantified the amount of green space, then measured it against the woman’s health—more specifically, how long she lived, and if and how she had died. 

The researchers were only concerned with mortality caused by illness (not, for example, car accidents or falls), so they created nine categories based on the most common illness-related causes of death: infectious and parasitic diseases; cancer; diabetes; neurodegenerative disease; coronary heart disease; stroke; respiratory disease; kidney disease; and all other causes. 

They found that women living in areas of higher vegetation were more likely to be white, younger than average, and married to highly educated men. To nobody’s surprise, the data showed that people of higher socioeconomic status (SES) tend to live in areas with more trees. 

But even after the researchers controlled for the life-extending effects of high SES, some clear trends emerged. Women living in the greenest areas were 12 percent less likely than other women to have died in the eight years of the study. They were 34 percent less likely to die of respiratory disease, and 13 percent less likely to die of cancer.

"We were surprised to observe such strong associations between increased exposure to greenness and lower mortality rates," study co-author Peter James said in a press statement. "We were even more surprised to find evidence that a large proportion of the benefit from high levels of vegetation seems to be connected with improved mental health."

The authors say these effects may be due in part to the opportunities for exercise and socialization offered by green spaces like parks, as well as lower exposure to air pollution. They emphasize how much we stand to gain by incorporating trees and other greenery into city planning.

“We know that planting vegetation can help the environment by reducing wastewater loads, sequestering carbon, and mitigating the effects of climate change. Our new findings suggest a potential co-benefitimproving healththat presents planners, landscape architects, and policy makers with an actionable tool to grow healthier places," James said.