CREATING AN URBAN FOREST: CAN THE EMERALD CITY LIVE UP TO ITS NAME?

BY DIANE STEEN with RACHEL McCREA
Special to the Journal

How green is the Emerald City?

"Not very" is a pretty good guess. A recent survey conducted by the American Forestry Association found that of the 20 cities inventoried for urban forest cover, Seattle rated second from the bottom -- tied with Indianapolis.

Seattle currently has a 27 percent tree canopy within the greater city limits. The goal promoted by the Street Tree Master Plan is 40 percent. In comparison, Los Angeles currently has roughly a 50 percent cover. Newark, New Jersey has about 62 percent cover, Chicago nearly 63 percent, and Boston about 68 percent.

It is ironic that this Northwest city, famed for the beauty and diversity of its natural setting, is lacking the benefits of nature in its city streetscapes. Unlike many mid-western cities that had to plant trees to create a pleasant urban environment, Seattle's earliest fortunes were made by harvesting the region's ancient forests. Where some east coast cities still have trees planted by their earliest settlers, Seattle has not one tree that is over 100 years old.

The inception of a new Street Tree Master Plan for the city, additional plantings and improved maintenance of existing trees should begin to improve our green record.

The landscape architectural firm Worthy and Associates won the Washington State Chapter of the American Society of Landscape Architects (WASLA) Honor Award in 1995 for its work in developing a plan to increase tree cover and help the Emerald City live up to its name.

The plan is based on an inventory of existing street trees, their locations and their conditions, stored in a Seattle Engineering Department database. The planning effort also included the Parks department and City Light -- both of which have an interest in improving the conditions of Seattle street trees.

The planning process led to two recommendations to respond to the findings of the street tree inventory: the creation of a "Heritage Tree Program," and a method to increase species diversity.

Based on size, age, history, landmark character, rarity and biological values, "heritage" categories were developed to recognize Seattle's outstanding street trees. For example, the chestnut trees at Bigelow Avenue North on "Queen Anne Boulevard" are "historic heritage" trees, having been planted by a citizen initiative around 1912. By raising public awareness and promoting tree conservation, the Heritage Tree Program should lead to the preservation of unique trees and plantings throughout the city.

Many of the existing plantings are not so unique. The city's tree inventory also showed that only seven species of trees are represented in any significance along Seattle's streets. As an example, Flowering Cherries represent 26 percent of existing trees.

To guide diversification in the Seattle Street Tree Master Plan, Worthy and Associates evaluated the horticultural and physical characteristics of over 280 candidate tree species, resulting in a list of 63 tree varieties to fill seven size and use categories. By increasing diversity in Seattle's urban forest, the health and visual vibrancy of the street landscape is enhanced.

The need for trees in the city has probably never been greater. Because of their ability to replenish oxygen, filter particulate pollutants, prevent soil erosion, and create micro-climate relief from the sun's rays, healthy trees can provide benefits to the entire community. Their visual appeal, from early blooms in the spring to scarlet leaves in the fall, helps to soften the edges of concrete, asphalt and steel, reminding urban dwellers of natural systems.

As the city begins to form the urban villages that are outlined in the Comprehensive Plan, the perceived negative impacts of an increase in density can be partially offset by an increasingly pleasant and healthy urban landscape. Trees contribute to humanizing the scale of large projects, placing importance on how a person feels in and around the area. An urban forest can also promote community by providing appropriately scaled, buffered, refreshing and engaging spaces and routes where human interaction is encouraged.

The Seattle Street Tree Master Plan developed criteria for tree planting prioritization, coordinated with the Planning Department, that include these urban design benefits.

However, finding the right place to plant additional trees was no easy task.

Although arterial streets are logical settings for green corridors, very little space adjacent to main roads has conditions that are suitable for trees. Poor soils, heavy concrete and asphalt paving, exposure to exhaust fumes, and lack of easy access for maintenance crews mean that this desirable human visual corridor is not desirable for trees. In contrast, residential neighborhoods offer a healthier tree environment: less paving, better soils, more exposure to water and growth area, and fewer exhaust pollutants.

Worthy and Associates' completed plans for 480 miles of city arterials, describing suitable planting sites that would potentially accommodate up to nearly 40,000 new street trees. Funding for the new trees will continue to come from City Light's tree replacement program, capital improvement projects, and federal grant projects.

The Seattle Department of Neighborhoods also helps through its Neighborhood Matching Fund, providing cash to match community-based self-help projects. This resource is particularly important because residential neighborhoods represent the greatest opportunity to expand the urban forest canopy.

Worthy and Associates estimates that nearly a quarter million new trees could be accommodated in Seattle's residential neighborhoods.

In addition to location, the care and maintenance of new trees are equally important to their lifespan and health. It is estimated that every year the city must remove nearly 2,000 trees because they become weak through lack of water or nutrients, are damaged, or grow to interfere with power lines. The new street tree master plan emphasizes public awareness and volunteerism through the Master Plan to improve the maintenance of street trees.

Meanwhile, the city has discovered that Seattle is not lacking in volunteers concerned with the longevity and health of our future green canopy.

Under the guidance of Liz Ellis of the Seattle Engineering Department, a group called the Tree Stewards has worked since 1994 to maximize the benefits of the city's existing street trees while making the best use of the city's limited resources. Since the program's beginning, about 150 tree stewards have taken the 30 hours of training required to learn the requisites of tree care.

TREEmendous Seattle, a nonprofit tree-planting and tree advisory organization, coordinates its efforts with Tree Stewards as well as with local pea patch groups, activities at the Center for Urban Horticulture, and the Department of Parks and Recreation. Volunteers with Plant Amnesty provide technical assistance to individuals and groups concerned with proper tree planting and care. While increasing the lifespan of Seattle's street trees, they are engaged in building community.

By encouraging canopy expansion and species diversity and promoting community through public stewardship, the Street Tree Master Plan will help the Emerald City live up to its name in the 21st century.

Diane Steen is a landscape architect and environmental planner. Rachel McCrea is a staff member of Worthy and Associates.

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