More Trees, Please

By Andrea Watts

Civic beauty is why the practice of planting trees along city streets took root, but now the benefits of urban forests have a reach as broad as their leafy canopies. Today, trees are considered infrastructure as necessary as roads, bridges, pipes, and tunnels. It's why the Society of Municipal Arborists uses the tagline "Trees: The only infrastructure that increases in value over its lifetime."

"It used to be that an urban forestry program was described in the line item budget as beautification ... I am seeing that word 'beautification' going away," says Kathleen Wolf, a research social scientist at the University of Washington and a collaborator with the U.S. Forest Service's Green Cities Research Alliance. "The justifications for trees, as well as parks, other green elements and the urban forest, are much more about environmental services and health and wellness in communities. The essentialness, the very necessity of having these metro nature elements in our communities, is more widely recognized," she says.

We can measure the financial value of urban forests. Tools like the USFS's i-Tree allow cities to calculate the cost savings thanks to trees' other benefits, such as shade and water absorption. Using i-Tree, the Wisconsin Department of Natural Resources calculated in 2012 that the Green Bay Metro Area's street trees annually provide $1.78 million in stormwater runoff reduction, $1.81 million in energy savings, and $2.02 million in property value increases.

With these cost advantages has also come the realization that the value of urban forests spans city departments and policies.

Because their benefits contribute to multiple city services, such as stormwater management or planning, Wolf notes that communities are now finding ways to integrate the management of urban forests into other municipal services.

"I see cities figuring out how to bring nature back into the city and managing the entire package [of metro nature] using a systems approach, including working across city departments," she says.

To showcase what this integration can look like, here are three cities that leverage the value of their urban forests.

Cherry trees in Vancouver, Washington. Photo courtesy City of Vancouver.

Madison, Wisconsin

In Madison, street trees were recognized as green infrastructure well before science proved their worth. In the late 1970s, the city council passed an ordinance that required the planting of street trees when new streets were added or existing streets renovated.

Because of this decision, Madison boasts an impressive 98 percent stocking level of street trees, and of its total land area, 22.4 percent is in private and public tree canopy. (A city's stocking level is the number of planted street trees compared to the number of potential street trees.)

"In Madison, people do understand in general the concept of urban forestry," says Marla Eddy, the city forester since 2004. "They're very attuned to the value of their street trees." Sarah Lerner, a landscape architect with the parks division, attributes this understanding to Madison's historical leadership in environmental stewardship as a shared community value.

As a planner for the parks division, Lerner must now consider the future conditions in which the trees will be growing when designing projects, not just the present benefits.

"Now that we're dealing with climate change and pathogens and pests such as emerald ash borer that are ecological threats to the urban canopy, planting design from a municipality standpoint is really taking a new direction because we're not only looking at the aesthetic, but also the social and public health implications of planting a tree," she says.

"EAB has galvanized our division's relationship [with the public]," adds Eddy, referring to the emerald ash borer, "because our community is concerned about the trees going away."

Madison isn't the only community worried about the Asian beetle that has infested and killed hundreds of millions of ash trees in North America since its arrival in the early 2000s. Their loss is felt aesthetically and financially.

Removing and replacing these city trees is expensive. A study conducted by the USFS Northern Research Station in 2010 estimated the cost would reach $10.7 billion by 2019. (Although the study hasn't been updated since, the infestation has spread beyond the projections made in 2010, reports USFS researcher Bob Haight, so the cost estimates are probably accurate.)

Ashes Under Attack

A neighborhood street lined with ash trees in Madison, Wisconsin. Photo courtesy Marla Eddy.

Ash trees account for up to 40 percent of landscape and riparian ecosystems in the Midwest, but an invasive Asian beetle is decimating the population. Since their detection in 2002, the emerald ash borer has consumed more than 130,000 square miles of ash trees across North America. With no natural predators, they're nearly indestructible — and expensive to fight. As much as $10.7 billion could be spent on EAB damage control by 2019.

EAB larvae burrow under the bark of ash trees, leaving behind s-shaped tunnels, thinned canopies, and dead branches as they feed. Left photo by U.S. Department of Agriculture, Flickr (CC BY-ND 2.0). Right photo by Anna Hesser, Flickr (CC BY-NC-ND-2.0).

In less than 20 years, EAB have infested the ash trees of at least 29 states and two provinces.

Map sources: ESRI, USGS | ESRI, HERE, GARMIN, NGA, USGS

In the Wisconsin capital, the city council recognized that effectively treating the emerald ash borer would exceed Forestry's current budget, and a loss of trees would impact stormwater management and overall benefits. In 2015 they instituted a special charge on municipal services that is "very specific for the care of the urban forest," says Eddy. For 2017, the special charge will total $3.9 million.

Madison also was the first municipality in Wisconsin to contract with a tree nursery that guarantees tree availability, allowing the city to maintain its rate of planting new trees and replacing ones that die. "Our council and elected officials saw the value in making a down payment today for trees to be delivered three years from now," Eddy said. "That's very unusual."

As part of her work, Eddy collaborates with Lerner and other parks staff when developing approved tree species lists and coordinating tree plantings when new plats are added to the city.

She is also part of the development review process. Eddy's role is to help others select the right tree not only for the present, but, more importantly, for the future.

Once the value of urban forestry was firmly established, Eddy says Madison could branch out even further, experimenting with new technologies. As part of the renovation of the downtown library in 2013, Eddy proposed using Silva Cell, "a modular suspended pavement system" that maintains road integrity while also supporting healthy root growth, resulting in larger trees that can deliver more ecosystem services, which in turn provide cost savings to the city.

"Madison was the first one to utilize this technology [but] it really took an elected official to help support this experiment [in terms of funding]," she says.

Seeing the early success, a private developer is also using Silva Cell in the public right-of-way alongside a new building being constructed downtown, because he wants large trees near his property.

Eddy puts it most succinctly as to why collaboration across departments, when it comes to urban forestry, is necessary: "The tree doesn't care which one of us is dealing with the issue."

Vancouver, Washington

In 2010, a tree canopy analysis of Vancouver, which is located across the Columbia River from Portland, Oregon, found that 5,579 acres (18.6 percent) are covered by tree canopy. The city has a target goal of 28 percent canopy cover, which is an achievable goal by 2030, and it has made a good start. According to the city's 2016 Urban Forestry Annual Report, the tree canopy increased by 17,225 square feet — the result of 1,378 trees planted — and the value of these newly planted trees over a 40-year period is estimated as $2.8 million.

For Charles Ray, the city's urban forester, maintaining a healthy urban forest is a cost-effective component of managing stormwater. In fact, demonstrating this link between stormwater and trees helped rescue the program, which faced proposed budget cuts in the early 2000s.

"In 2003 and 2004, the Urban Forestry Commission [which oversees the Urban Forestry Program] started reaching out to all the city departments and asked about the services that urban forestry provides and what services we can provide to start building the case of urban forestry's value," Ray explains. Building the case required funding an analysis, and one of Ray's first stops was public works. "We emphasized ... how trees are helping to reduce stormwater throughout the city," he says. A decrease in trees, he told them, means an increase in runoff.

Public works agreed to fund the analysis, which concluded that urban forestry "was more than just a parks program and that the city relies on the program for the services it provides throughout the city," Ray says. That recognition by agency heads and public officials led to the transition of urban forestry from the parks department to public works.

Urban forestry proactively targeted neighborhoods with the lowest canopy cover, designing planting projects for those areas. Today, with help from a local nonprofit, the department hosts four large-scale neighborhood planting parties annually, with 400 to 500 new trees and strong volunteer engagement. In the early 2000s, just 30 to 50 trees were planted each year.

Another planting priority: neighborhoods in the city's upper watershed. "I think sometimes when people think stormwater, they think riparian zone. They're not focused on the upland area [of Vancouver]," Ray says. "If we can slow or reduce the peak flow spikes after major storms by holding the water on site through trees, that reduces the volume flowing to the lowland areas."

The Urban Forestry Program works with Vancouver's Department of Community and Economic Development on project reviews to ensure tree requirements are met. This past year Ray worked with the city to update its tree conservation ordinance to comply with low-impact development requirements that were adopted in December 2016. This ordinance now addresses the value of native trees and other vegetation, as well as rain gardens with trees.

In return, DCED recognizes how the urban forest contributes to the city's livability. "Vancouver is a thriving city that is experiencing exceptional new residential and commercial growth and an increased demand for urban living and complete streets," says Teresa Brum, the economic development division manager with DCED. "As the city's urban forester, Ray helps the community understand how to design space for trees that will thrive in the urban environment and works together with planning and economic development to implement programs that will bring welcoming green space to complement our urban areas."

Ray builds relationships with other departments, shares the latest urban forestry research, and communicates forestry's success. Quarterly and annual performance measure reports include the number and types of trees planted and their survival rate, number of outreach efforts and education workshops held, and number of projects reviewed.

For cities looking to leverage their existing green infrastructure and develop long-term solutions to stormwater management, Rays says they should look up. "If tree canopy throughout our communities continues to decline, we can anticipate an increase in runoff, flooding, and water pollution. By capitalizing on the shared, common mission across departments, municipalities can integrate urban forestry into their stormwater management efforts to advance a more comprehensive watershed approach."

Chattanooga, Tennessee

According to a 2010 urban ecosystem analysis report written by American Forests, Chattanooga has 51.4 percent of its total land cover (92,543 acres) in tree canopy and an additional 16,200 acres of open space that includes grass and scattered trees. In 1990, the city created the urban forestry department along with a nine-member tree commission. Gene Hyde was hired as the city forester, and this year marks his 27th in that post. Of his tenure, Hyde modestly says, "I've made a very strong effort to weave trees and urban forestry into the fabric of Chattanooga, and I think I've been reasonably successful."

Hyde bills himself as a bridge builder, and this is evident in the relationships he has developed with other city departments when it comes to promoting and protecting the urban forest. "Our water quality department certainly understands the huge role that trees play in terms of mitigating stormwater," he says. Likewise, urban forestry plays well with the electric company — which is sometimes a contentious relationship in other places. When the electric company's forester calls for the removal of a tree, forestry doesn't question the decision, and when planting trees in the right-of-way, Hyde selects species that won't interfere with the power lines.

As a landscape architect with the city's land development office and a member of the team that meets with developers, Karna Levitt serves as an advocate for the forestry department because she recognizes its value.

The Blue Trees in Chattanooga

Public Art Chattanooga brought artist Konstantin Dimopoulos to Chattanooga for a six-week residency in which he engaged the community in a series of installations and events highlighting the importance of trees by coloring them a vibrant ultramarine blue. Organic and temporary, the artwork will gradually fade away over the course of a year. The artist completed five installations with the help of nearly 300 volunteers. Watch: vimeo.com/198680837

Photo courtesy Public Art Chattanooga.

"We really have to do whatever we can to integrate trees into the city," she explains. "When you look at the environmental challenges, almost everything we have is mitigated by tree plantings or forests: pollution, heat island effect, noise, water pollution, flooding, and greenhouse gas, etc."

Chattanooga has a landscape ordinance that requires trees on private property, as well as the right-of-way. The reason for requiring trees on the right-of-way, Levitt says, is to mitigate the effects of the asphalt, as well as making for a more pleasant, shady environment for pedestrians on the sidewalk and drivers alike.

Chattanooga's Central Business District is one neighborhood that has been transformed with the addition of street trees. In the 1960s, the tree-lined center median was installed, and the result is a downtown with a healthy tree canopy that not only makes the neighborhood vibrant and attractive, but also livable. Photos courtesy Gene Hyde.

One significant change that Levitt has witnessed in her profession is the recognition of the economic value and the socioeconomic benefits of tree planting. Hyde, in turn, has leveraged outreach opportunities to educate the public about these benefits.

In 2015, The Nature Conservancy approached the city about participating in its "If Trees Could Sing" educational series. As in other a handful of other cities in Tennessee and Georgia, TNC provided signs at three different parks. Each has a QR code that, when scanned, takes people to a short video featuring famous and local musicians singing and talking about the value of trees.

Last year Chattanooga was the first city in Tennessee to host a Blue Trees exhibition by Australian artist Konstantin Dimopoulos. Using a combination of water and blue chalk, Dimopoulos colored trees along Riverfront Parkway a striking shade of indigo to spark conversation about the value of trees.

However, educating the public about the value of an urban forest only goes so far if Chattanooga's developers don't recognize the long-term value of trees, which Levitt says is a challenge. Developers "have to meet stormwater requirements, landscape requirements, and might want their property to look attractive. Why not meet all those requirements in the same square footage [by planting a tree]?"

Gene Hyde has come to this conclusion: "In urban forestry, in many cases we're not solving tree problems, we're solving people problems, and trees are the medium through which we work."

Andrea Watts is a freelance science writer who specializes in covering forestry and natural-resources topics.

Resources

The Council of Tree and Landscape Appraisers' Guide for Plant Appraisal provides information on tree appraisal in relation to environmental and ecological benefits.