Trees in Central Park, NYC. Credit Caitlyn Wilson
It seems like a no-brainer, but sometimes you need to give evidence to city councillors: A new multi-institutional study led by UC Davis Health suggests that not all green space is created equal. Living in urban neighborhoods with more visible trees is associated with a 4% lower incidence of cardiovascular disease, while areas dominated by grass or low shrubs may be linked to higher cardiovascular risk.
The research, published in Environmental Epidemiology, analyzed more than 350 million street-level images using machine learning to distinguish between trees, grass, and other types of vegetation. The findings challenge long-held assumptions that simply adding “green space” to cities is enough to improve public health.
“Public health interventions should prioritize the preservation and planting of tree canopies,” said Peter James, associate professor in the UC Davis Department of Public Health Sciences and lead author of the study. “Urban forestry initiatives and policies that protect mature trees are likely to yield greater cardiovascular health benefits than investments in grass planting.”
Related: AI scientists from MIT get a map of a city’s trees
MIT city tree researcher maps trees in cities around the world to check their health. Via MIT.
Why trees outperform lawns
Unlike satellite imagery, which often lumps all vegetation into one category, the researchers used street-level images—similar to what pedestrians see via platforms like Google Street View—to capture real neighborhood conditions. Deep-learning models identified trees, grass, sidewalks, cars, and other features, creating a granular picture of urban environments.
Those visual data were then linked to nearly 89,000 participants in the long-running Nurses’ Health Study, tracking 18 years of medical records and death certificates. The results were striking: More visible trees → 4% lower cardiovascular disease incidence
More grass → 6% higher incidence: Other green vegetation (shrubs, bushes) → 3% higher incidence
The protective effect of trees held steady even after accounting for air pollution, population density, regional differences, and neighborhood socioeconomic status.
Green Prophet’s reporting played a significant role in saving Jaffa Boulevard’s trees in Jaffa from being cut down for a Light Rail Train. Image credit: Karin Kloosterman
Researchers suspect the negative associations with grass may be linked to pesticide use, emissions and dust from from mowing equipment, reduced cooling capacity, and weaker noise and air-pollution filtering compared to trees.
With cardiovascular disease responsible for over 900,000 deaths annually in the U.S.—nearly one in three deaths, according to the Centers for Disease Control and Prevention—even small shifts matter.
“This opens a promising avenue: improving heart health through community-level environmental change, not just individual behavior,” said Eric B. Rimm, professor at Harvard T.H. Chan School of Public Health.
Author: Karin Kloosterman
Karin Kloosterman is an award-winning journalist, innovation strategist, and founder of Green Prophet, one of the Middle East’s pioneering sustainability platforms. She has ranked in the Top 10 of Verizon innovation competitions, participated in NASA-linked challenges, and spoken worldwide on climate, food security, and future resilience. With an IoT technology patent, features in Canada’s National Post, and leadership inside teams building next-generation agricultural and planetary systems — including Mars-farming concepts — Karin operates at the intersection of storytelling, science, and systems change. She doesn’t report on the future – she helps design it. Reach out directly to [email protected]
