Their study, published in the open-access journal Environment International, is the first in the U.S to combine life expectancy data at the census tract level with data on parks, trees and overall neighborhood vegetation.

Prior research has suggested that parks and greenery have mental and physical health benefits for residents of urban areas, providing clean air to breathe, shade during hot weather, and open and secluded areas for recreation and mental relaxation.

The current findings extend those potential benefits and, the study authors say, provide policymakers with a blueprint for targeted green strategies that could increase longevity among predominantly Black and Latino residents of "park poor" neighborhoods and help reduce health disparities in the region.

"If policies are implemented where they are needed most, there could be a significant decrease in life expectancy disparities across Los Angeles," said Michael Jerrett, professor of environmental health sciences at the UCLA Fielding School of Public Health and corresponding author of the study.

Adding nearly a million years in life expectancy across the county

Using newly available data from the U.S. Small-Area Life Expectancy Estimates Project, the research team developed a model that quantified the relationship between life expectancy and the amount of tree canopy coverage, live green vegetation and accessible park space in Los Angeles County's census tracts. The data on greenery was drawn from the Los Angeles Department of Parks and Recreation, the U.S. Department of Agriculture, the local environmental organization Tree People and other sources.