Street Trees Pay Us Back
Stately street trees give us cool shade in summer, beauty in autumn and good green growth in the spring. They provide green of another kind, too. The same trees lining our urban streets provide millions of dollars in economic value to towns and townsfolk. It’s as if they were growing dollar bills instead of leaves.
What foresters call “street trees” are just trees that line the street in towns and cities. Most grow between the street and the sidewalk or, where no sidewalk exists, along the road. Most of the trees grow on city-owned easements.
We have long known that street trees were valuable assets, but we could not determine a dollar value for them. Recently, however, a project in the Kansas City area measured street tree benefits in dollars for several cities around the metro area. That’s how we now know, for example, that the 415,000 trees growing on city rights-of-way in Kansas City provide an average benefit of $123 per year per tree, or more than $51 million annually.
The project, undertaken by the Missouri Department of Conservation, the Mid-America Regional Council and the Kansas Forest Service, uses a USDA Forest Service computer program called i-Tree Streets. The program collects city street tree inventory data and coordinates information on tree species, size, condition and maintenance needs so cities can effectively allocate money to care for their trees.
The value of trees varies from one community to another. For example, economic benefits to cities in the Kansas City region range from $70 to $195 per street tree. North Kansas City, a small residential and industrial burg in the heart of the metro area, has 1,800 well-maintained street trees that return about $345,000 annually to the city in economic benefits. That’s an average of about $190 per tree per year.
Liberty, a suburban community, has smaller trees, many of which have been storm-damaged, in its historic neighborhoods, but they still average $70 per tree annually in benefits.
How Do Trees Grow Money?
Shade during summer means cooler temperatures around a home and cooler overall urban temperatures. In a city’s heavily developed commercial center, concrete and brick absorb summer heat and create an “urban heat island,” making city centers 5 to 15 degrees warmer than the surrounding residential neighborhoods and the rural countryside.
Street trees reduce the heat buildup. They save Kansas City more than $14.6 million annually in heating and cooling costs for building and home owners, according to the i-Tree Streets study. Even trees devoid of foliage in winter help slow cold winds and reduce heating costs in cities.
The value of trees varies from one community to another. The 415,000 trees growing on city rights-of-way in Kansas City provide an average benefit of $123 per year per tree, or more than $51 million annually.
The visual appeal that street trees add makes money for a community, too. Trees lining a street increase property values up to 15 percent, a benefit when selling a home. Higher property values, in turn, boost a community’s overall tax base, helping to pay for schools, police and streets.
Businesses benefit because shoppers like trees. Research by Kathleen L. Wolf at the University of Washington has shown that people visiting shopping areas that have trees feel they’re buying products with more value. The same product for the same price may be available elsewhere, but shoppers in areas with street trees come more often, stay longer and feel more positive about their purchases.
Some environmental benefits provided by street trees are growing in importance as climate change concerns increase. The release of carbon into the environment, from power plants for example, has been connected to an increase in greenhouse gases, which are blamed for global warming. Trees absorb carbon and store it. In fact, carbon storage is starting to have an economic value that can be bought and sold for rural forest trees. There is not yet a carbon market for urban forest trees, but it is being discussed. Kansas City’s street trees annually store carbon worth about $1.9 million.
Trees are also standing air filters that work around the clock. Studies estimate that Kansas City’s street trees provide more than $2.3 million per year in air quality benefits.
The foliage on trees also helps reduce stormwater runoff and flash flooding. Rain that falls on trees drips off leaves or runs down the trunk into soil before becoming runoff. Rain that falls onto parking lots speeds straight into storm sewers.
In Kansas City, street trees intercept almost 606 million gallons of stormwater annually, saving $16.4 million each year in costs associated with building and maintaining public stormwater systems. That’s one reason why the city is including street trees in its “Green Solutions” plan to address stormwater, as well as in its climate protection plan.
The plan calls for planting more than 120,000 street trees over the next 10 to 15 years to fill vacant spots and to have a good urban forestry program to maintain those trees along with existing trees. Trees are now recognized as a critical part of a city’s infrastructure and not just nice extras.
Not all economic benefits are reflected in the i-Tree Streets numbers. Some benefits are just now starting to be valued. For instance, street trees that shade asphalt pavement can save a city up to 60 percent on road maintenance over 30 years, saving taxpayers money. The shade helps cool the pavement, and that slows the evaporation of the oils in asphalt, helping the pavement last longer with less maintenance.
Trees as Life Savers
Other tree benefits just can’t be calculated. For instance, street trees also increase public safety. Drivers will slow their vehicles down by as much as 15 mph because trees make them feel that the street is narrower, even if it’s not, studies show. Trees bring people outside, and that alone helps reduce crime. Making space for trees between a sidewalk and the street also provides a safety zone for children playing on sidewalks and in nearby yards.
Tree-lined streets encourage people to walk or bicycle instead of driving, especially for shorter trips. This can add up to significant savings for gasoline and help reduce air pollution and traffic congestion. As another plus, walking and cycling builds better health and reduces medical costs for individuals and society.
When we do use our cars, most of us try to park in a shady spot on a hot summer day. That reduces air pollution. Shaded parked cars pollute the air less than cars parked in the sun on hot days. All the fluids, including gas and oil, are less likely to evaporate and pollute the air. Some communities in the United States now require developers to provide shade in parking lots.