(Kelsey Nowak)

The U.S. Forest Service reported last year that the number of trees in 17 of 20 major American cities surveyed is declining, a development that has negative consequences for air and water quality, energy usage and air temperatures.

David Nowak, a Forest Service researcher who co-authored the study that estimates the loss of urban trees to be about four million a year, is focused on reversing this trend.

“Trees provide multiple environmental and health benefits,” said Nowak. “We want to help community leaders and the public see the whole picture so they can make better decisions and do what we need to do today so we will have a better environment in the future.”

To accomplish his goal, Nowak, along with private industry and non-governmental organizations, created an innovative web-based tool known as i-Tree (www.itreetools.org) that uses field data on the size, species and number of trees along with local air pollution and meteorological information to quantify urban forest structure, environmental effects and the value to communities.

With the data entered into the web-based tool, for example, Nowak said communities can obtain better information about the health of their trees, the ecosystem benefits, how many new trees would be desirable and where they should be planted.

“We try to help provide the big picture of the whole city system, not just small pieces of the puzzle,” said Nowak. “If you want to manage your resources, you need to know what you have and how it is changing.”

And with many cities are facing tight budgets, Nowak said, iTree can provide solid evidence about the economic advantage of adding trees to go along with the environmental and aesthetic benefits.

Pittsburgh, for example, used iTree to calculate that city trees provided a monetary benefit three times greater that the annual cost of upkeep, leading the city to develop a master plan for expanding its tree canopy. Nowak said data from iTree also provided evidence to help push forward a major tree planting initiative in New York City, and has been used in Milwaukee, Chattanooga, Tenn., and Casper, Wyo. All told, iTree has been used in more than 100 countries and has had about 12,000 users since the initial software suite was launched in 2006.

Michael Rains, director of the Forest Service’s Northern Research Station, said Nowak has been central to the development of the iTree web tool, a leading proponent of urban stewardship and an innovator in the use of statistical sampling and analysis to better understand urban forests and the ecosystem services they provide.

“He is a visionary leader, a productive scientist and the consummate public servant,” said Rains. “Dave produces things that improve people’s lives.”

Scott Maco, an executive with Davey Tree Expert Co., described Nowak as “a leader and a pioneer in urban forest science.” Maco, who has worked closely with Nowak on the iTree project, said the Forest Service researcher is collaborative, results-oriented, and has set the “national standard for urban canopy assessment.”

Nowak said most people associate the Forest Service with the vast national forests located throughout the country, not with cities. But he sees urban forestry as the future, with more than 80 percent of the population living in urban areas.

“We tend to focus on cars and roads and development, but in the background is always nature that also affects people’s lives,” said Nowak.

Nowak has helped a number of cities complete urban forest surveys and assess the data using the iTree web tool, including Chicago, Philadelphia, Baltimore, Atlanta, Boston, Kansas City, Los Angeles and San Francisco.

He said trees in these and other urban areas are being lost to old age, insects, disease and to development, requiring communities to understand what is happening and take the necessary steps to stem the negative tide. Some are being hurt more than others. The 2012 survey of 20 cities, for example, showed the biggest losses in New Orleans, Houston and Albuquerque. Only Syracuse showed a gain in tree coverage and two cities, Denver and Pittsburgh, essentially showed no change.

Nowak said it is helpful for communities to gather the data and assess their situation, but another matter getting them to actually use it in a meaningful way.

“Once you have the information, you have to get in front of the policymakers— the people who have the power to make decisions and affect change,” said Nowak. “That is the biggest challenge.”

This article was jointly prepared by the nonprofit Partnership for Public Service, a group seeking to enhance the performance of the federal government, and washingtonpost.com. Go to http://washingtonpost.com/wp-srv/politics/fedpage/players/ to read about other federal workers who are making a difference.