Green space

What green space is

Green space is any land covered by plants, trees, grass, or natural vegetation that people can see or reach. It includes public parks, community gardens, tree-lined streets, playing fields, greenways and trails, cemeteries, and the trees and lawns on private property.

Researchers separate two things that both matter. Access is whether you can get to green space and use it, such as a park within walking distance. Exposure is how much greenery surrounds you day to day, including the trees you see from a window and the vegetation you pass on a walk. The World Health Organization recommends that everyone live within 1,000 feet of a green space of at least 1.2 acres, roughly a 5-minute walk to a park about the size of a soccer field, because that level of access is tied to measurable health gains.

Where green space comes from

Green space takes several forms, and each delivers a different benefit. Public parks are the most recognized, and the Trust for Public Land reports that about 100 million Americans, including 28 million children, do not live within a 10-minute walk of one.

Trails and greenways give people room to walk, run, and bike away from traffic, and they connect neighborhoods to larger natural areas. Street trees form a quieter kind of green space, lining sidewalks and yards where they shade pavement and filter the air. Community gardens turn vacant lots into food and shared ground, and the American Community Gardening Association counts thousands of them across US cities. Private yards add the green space closest to home, since a lawn, a garden, or a single shade tree delivers many of the same benefits as a public park for the household that has one. The USDA Forest Service estimates that urban areas across the country hold roughly 5.5 billion trees, and the tree canopy over a neighborhood is one of the clearest measures of the green space its residents live with.

Green space is not shared evenly, and the gap follows income and race. A 2020 analysis by the Trust for Public Land found that neighborhoods where most residents are people of color have access to about half as much park space per person as majority-white neighborhoods. Low-income neighborhoods have access to about a quarter as much as high-income ones.

The reason traces back decades. Many of the same neighborhoods that received less investment in parks and tree planting were shaped by historic housing and lending policies, and the effect lingers in the tree canopy today. A 2021 study in the journal Climate found that formerly redlined neighborhoods hold significantly fewer trees and run hotter in summer than other parts of the same cities. The households with the least green space are often the ones who would benefit most, since they also tend to carry higher rates of the conditions green space helps prevent.

What green space does for the body

The physical benefits start with movement. People who live near parks and trails exercise more, and the CDC reports that access to safe places for physical activity raises the amount people get. More movement lowers the risk of heart disease, obesity, and type 2 diabetes.

The benefits reach further than exercise alone. A 2018 review in the journal Environmental Research linked more green space to lower blood pressure, lower heart rate, and reduced risk of dying from heart disease. Time among trees and plants also lowers levels of cortisol, the body's main stress hormone, which eases the strain that chronic stress places on the heart and blood vessels over years.

Green space cools the body too. The EPA reports that trees and plants lower surface and air temperatures through shade and by releasing water vapor, and neighborhoods with heavy tree cover can run several degrees cooler than nearby stretches of pavement and rooftop during a heat wave. That cooling matters for health, since extreme heat kills about 700 people in the United States each year, the CDC reports, and shade is one of the simplest defenses against it.

Green space changes how people feel, and the research is strong. A 2015 study from Stanford University found that people who walked for 90 minutes in a natural setting showed less activity in the brain region tied to repetitive negative thinking than people who walked the same time in a city setting.

The mental health gains show up across large populations. Research published in JAMA Network Open found that people with more green space near their homes reported less depression and anxiety. A 2019 study in Scientific Reports found that people who spent at least 120 minutes a week in nature were substantially more likely to report good health and well-being than those who spent none. The time could be split across the week in any pattern, which means short, regular visits count as much as one long outing.

How green space connects to other land exposures

Green space works against several other exposures at once. Trees capture particulate matter and absorb some gases, and the USDA Forest Service estimates that trees remove millions of tons of air pollution across the country each year. Cleaner air matters most in the neighborhoods that carry the heaviest pollution load, which are often the ones with the least canopy.

Vegetation also blocks sound. A dense belt of trees or shrubs along a busy road absorbs part of the traffic noise that reaches a home, softening the low, steady sound that the World Health Organization links to raised blood pressure and disrupted sleep. Heat ties the exposures together. The same tree cover that filters the air and buffers the noise also cools the neighborhood, and its absence leaves a home hotter, louder, and exposed to more pollution at the same time. Green space is the exposure that pushes back against the others, which is part of why its absence carries such weight.

What a household can do

Find what is already near you first, because using green space matters more than owning it. The Trust for Public Land runs ParkServe, a free tool that maps parks by address and shows what sits within a 10-minute walk of your home. Aim for the 120 minutes a week the research points to, split however fits your life.

Bring green closer to home where you can. Planting a tree on your property adds shade, cools the house, and cleans a small share of the air, and many cities and nonprofits give away free trees to residents who ask. Even container plants on a balcony or a few pots by a window add greenery you see every day. Get involved in the space around you. Community gardens turn a vacant lot into food and shared ground, and many neighborhoods run tree-planting programs that residents can request for their street. If your area lacks parks, local advocacy works, since city parks budgets respond to residents who show up and ask. Take children outside regularly, since early time in nature builds habits and delivers the same stress and attention benefits to a developing brain that it gives an adult.