Trees take the edge off the searing heat of summer. They soak up rainwater. And, recent academic studies have shown that greenery reduces crime  and helps people battle depression.

In the next three years, Philadelphia will have thousands more of them, thanks to a smart and welcome expansion of the city's TreePhilly program. The program not only fights the heat and floods, but it improves our quality of life.

The city wants to increase the canopy by 30 percent in all neighborhoods, especially those that become urban heat islands in the summer. Some neighborhoods, such as Hunting Park, Point Breeze, and Cobbs Creek, can be 20 degrees hotter than others because they don't have enough trees to shade them. Neighborhoods with more trees, such as Chestnut Hill, Mount Airy, and Somerton, can be cooler in summer.

Help is on the way for the hot spots, as well as the rest of the city.

Earlier this month, the city announced that TD Bank pledged $1 million over three years for the program. That gift comes on top of the more than $7 million that the city, state, and Fairmount Park Conservancy are already devoting to treeing up the city over the same period, starting in 2019. Not only will the city plant more trees, but it will plant them strategically along streets that need them most. And, it will plant additional trees in city parks, especially in areas where deer have ravaged plant life.

Philadelphia will continue its yard tree program, with a slight change. Since 2012, it has given away 21,500 trees to residents to plant in their yards. Going forward, the city wants to give away 9,000 trees through community groups. Available trees, those likely to mix well into neighborhoods and adapt to city soil, include the stately willow oak, colorful crabapple, and elegant witch hazel.

For neighborhoods with yards too tiny to hold trees, the city wants to plant 3,000 street trees and almost 400 trees at neighborhood parks and recreation centers.

This effort to ease the effects of a warming planet may seem small considering the immense global threat, but it is essential in a time when the federal government has chosen to support the fossil-fuel industry instead of research and innovative technologies to battle climate change.

Yet, even in Philadelphia, where most appreciate the value of green space, not everyone is on board. Some developers promise street and landscaping trees in the dreamy renderings they use to gain city approvals, but they don't always deliver. The city requires developers to put up a $700-per-tree deposit. After two years, it takes the deposit and plants trees itself. But there's a backlog of more than 1,000 trees; that represents a lot of broken promises and shows how stretched the city is to keep up with the need for trees. If developers don't keep their side of the bargain, the city should hold up approval of future projects until they make good. It's everyone's job to make Philadelphia a more livable city.

(Individuals may donate to the TreePhilly program at https://secure.qgiv.com/for/tre)