Urban trees rising in popularity

By Jan TenBruggencate
Advertiser Staff Writer

The government of Seoul, South Korea, touted its city's tree-planting efforts at the recent Mayor's Asia-Pacific Environmental Summit, and conference host Jeremy Harris promised expanded tree-planting in Honolulu.

Other officials at the summit said they're busy putting trees in their cities.

What's with the sudden interest in urban forestry?

In its Seoul Green Vision document published last year, the South Korean capital promised to "create environmental forests or ecological parks in industrial complexes and on idle lands in the city to absorb pollutants and noise" and to "link isolated green areas in order to provide secure habitats for mammals and make paths to allow them to move between green areas easily."

Europe is also interested in urban forestry. Denmark is financing extensive studies to determine what trees and what mixes of different tree species will most improve the city environment.

"There is a tendency in many large cities to consider green areas as potential building sites," write Thomas B. Randrup and Kjell Nilsson of the Danish Forest and Landscape Research Institute.

But the buildings and pavement that supplant vegetation decrease wind speed on the ground, increase temperatures, dust and rain, and lower relative humidity, they said.

"The quality of the urban environment, including urban green areas, is becoming increasingly recognized as a key to the economic reconstruction of European cities," Randrup and Nilsson write.

Cities and towns across the United States are active with Tree ReLeaf and other urban forestry programs, and evidence that it's a good idea increases.

Researchers at the British University of Sussex are studying the methods by which trees reduce the amount of dust in the urban environment. Other researchers have already shown that they do cut dust, and the Sussex scientists found that while all trees do it, some do it better than others. They also found that trees tend to capture dust in the particle sizes that are likely to cause human health problems. Other sources suggest that in addition to improving the air quality, trees reduce the temperature, cut noise and limit daytime glare.

And they're good for business. The Virginia Department of Forestry says people shop longer on tree-lined streets. The Maryland Department of Natural Resources said apartments and offices in areas with trees rent more quickly and are rented longer.

The U.S. Forest Service says another benefit of urban forestry is that it can "shorten post-operative hospital stays when patients are placed in rooms with a view of trees and open spaces."

A dense tree canopy also provides ready shelter from a brief tropical shower.

Jan TenBruggencate is The Advertiser's Kaua'i bureau chief and its science and environment writer. Call him at (808) 245-3074 or e-mail jant@honoluluadvertiser.com.