Aerial of urban setting

Tree-lined streets and wooded lots do more than provide cities with splashes of green.

Trees absorb and store carbon, so they help slow global warming. Healthy urban forests also help cities cope with the effects of climate change by cooling neighborhoods and reducing stormwater runoff.

But despite these benefits, American cities are losing a large number of trees each year. Development, disease, old age, and storm damage all take a toll.

Scientists with the USDA Forest Service analyzed Google Earth images to estimate urban tree loss between 2009 and 2014.

Nowak: “In urban areas, we’re losing about 138,000 acres of tree cover per year, which is about 28 million trees.”

That’s David Nowak, co-author of the study. He says the data can help guide city planners.

Nowak: “If we want to make the future better, we have to understand what we have today as a baseline starting point. We need to start thinking about this in the context of where do we want to be 20 or 30 years from now, and not just let things happen, but try to guide it to a better future.”

He says if cities know how their tree cover is changing, they can take steps now to preserve the existing canopy and replace trees that are lost.

Reporting credit: Daisy Simmons/ChavoBart Digital Media.

Bruce Lieberman, a long-time journalist, has covered climate change science, policy, and politics for nearly two decades. A newspaper reporter for 20 years, Bruce worked for The San Diego Union-Tribune...