Trees are certainly beautiful. If you look closely, you might see the birds, squirrels and bugs that make their homes in them. But trees have another important role: They can help save human lives.

That’s what a new study of street tree goals in Philadelphia, Pennsylvania, has found. The study was conducted by the U.S. Department of Agriculture Forest Service. It looked at what could happen if the city increased its tree canopy — the topmost, leafy cover created by a group of trees — by 30 percent. The answer: The early deaths of 400 people a year might be prevented.

How can trees do such big job? They clean the air by absorbing pollution that can cause disease. They also absorb noise that can raise stress levels or create sleeping problems. They reduce dangerous heat by blocking the sun’s rays and cooling the air. And they improve people’s mental health.

Philadelphia isn’t the only U.S. city that wants to plant more trees. In Boston, Massachusetts, an organization called Speak for the Trees is trying to increase tree canopy by 35 percent in the next 10 years. They’re doing this by giving away 1,000 trees this year. They’re also teaching teens how to find good spots to plant new trees and take care of them.

Because of covid-19, Speak for the Trees co-founder David Meshoulam says teens will learn virtually this summer.

For six weeks, “teens will work in [online] teams to tell stories about community through the urban forest,” says Meshoulam. They’ll figure out “what was [in a neighborhood] at one point, with more or [fewer] trees. They’ll look at what people think about trees now and how they take care of them. Then they’ll figure out what the opportunities and challenges are” in planting trees in that neighborhood.

Meshoulam hopes this will help the teens become ambassadors for trees. He’s also hopes that they will be able to help his organization plant trees this fall.

“It’s a family-friendly and accessible activity that connects people back to their community and nature,” he says.

Many kids across the country aren’t able to go to camp or take summer jobs this year because of the pandemic. But they can still help trees.

To start, Meshoulam recommends walking in your neighborhood to collect data about its trees. How many trees can you find? What species are they? You can use tree identification guides to help, such as the PlantSnap app or the Peterson Field Guide books.

Upload the data to an online community science platform, such as iNaturalist. This can help scientists figure out many things, including how to protect biodiversity (the variety of plants and animals in an environment).

You can also care for trees in your neighborhood. Water young, small trees on hot days.

Consider putting up a small fence around your tree bed. Hang a sign on it asking people to keep their dogs off. Dog urine contains ammonia and salt that can harm trees or even kill them.

Want to plant a tree in your backyard or neighborhood block? Contact your city or town to find out how.

Correction: An earlier version of this story stated that 400 early deaths might be prevented by increasing Philadelphia’s tree canopy by 30 percent. It should have said 400 early deaths per year. The story has been updated.

Learn more

Download the PlantSnap app on Google Play or Apple’s App Store.

Upload data to iNaturalist: inaturalist.org.

Read about how to water street trees from the Massachusetts Urban & Community Forestry Program: masstreewardens.org/wp-content/uploads/Caring-for-New-Trees.pdf.