Releasing a study showing that the city of Pittsburgh's street trees create $2.4 million in value each year, Pittsburgh Mayor Luke Ravenstahl said today that his administration will plant 100 trees in neighborhood business districts and another 37 Downtown this fall.

That's a first step in addressing what advocates portrayed as a street tree gap.

"I think you'll see the numbers [of street trees] will significantly increase versus what we've done in the past," Mr. Ravenstahl said. There were few trees planted "in the last decade or so. As a result, the numbers are what they are, so we have a lot of catching up to do."

The study by Davey Resource Group, using a U.S. Forest Service evaluation model, found that the city's 29,641 street trees clean water and air, reduce stormwater runoff, lower energy bills and raise property values.

Danielle Crumrine, executive director of the nonprofit group Friends of the Pittsburgh Urban Forest, said the city has just one street tree per 11 residents, versus a tree for every three residents in the typical city.

She said the study provides the academic-quality data to justify a street tree push. It's meant "to convince people that trees are an asset worth saving," she said.

"What we don't value, we don't protect, and what we don't protect, we lose," she said. In addition to city participation in a regional push to plant 20,000 trees by 2012, she would like to see a "citizens campaign" in which city residents can get inexpensive trees to plant in their front yards.

Mr. Ravenstahl said the city has, in the past, planted inappropriate trees, causing sidewalk damage and growth into utility wires. Now the city knows what kind of trees to plant where, so they almost "take care of themselves," he said.