The National Forest Service wants to know how many and what kinds of trees line Pittsburgh streets and hillsides.
Though forest service officials have spent nearly 90 years collecting data on tree populations throughout the country’s rural forests, it only started collecting urban tree data in 2014.
The urban inventory program first started with Balitmore, Md. and Austin, Texas and expanded to 15 cites, now including Pittsburgh. Officials with the forest service said they want a better understanding of urban forests, since 80 percent of Americans live in cities or urban areas.
Analysis is already underway in Pittsburgh. Supervisory Forester Mark Majewsky said about five forestry employees will spend another six weeks collecting data.
“Once you lay down this base framework, we can just monitor how the forests change over time,” he said. “You don’t really know how to manage an urban forest until you know what you have.”
Forest service employees will count the number of trees and types of species, account for any damage and track invasive plants at 200 to 250 separate survey sites, each encompassing about one-sixth of an acre.
“We’ll also see what’s out there, what’s growing, what’s being cut, what’s dying,” Majewsky said. “How the forest’s resources are changing over time.”
Matt Erb, director of urban forestry at Tree Pittsurgh, said his organization has done similar surveys of Pittsburgh’s tree population in the past. One in 2011, called an urban tree canopy analysis, found that 42 percent of the ground in Pittsburgh is covered by tree canopy.
Erb said Pittsburgh is ahead of many cities, which generally aim for at least 30 to 40 percent tree canopy cover.
“It means that we are receiving a lot of benefits from the urban forest,” Erb said. “The air quality improvements, storm water capture, the economic benefits.”
Trees can play a big part in cost savings. The Forest Service has an online analysis program called i-Tree, which helps cities track economic and other impacts of its trees. An i-Tree ecosystem analysis done in Pittsburgh last year found a $7.2 million annual economic benefit from its trees. Those savings were a result of reduced costs of heating and cooling buildings, as well as storm water absorption and other factors.
Erb said the EPA offers a similar program to track the effects of trees on health, especially in terms of air pollutants and respiratory problems.
“These computer models are kind of just the tip of the iceberg,” Erb said. “There’s a lot of other human health benefits that have yet be really quantified.”