It’s tree-planting season and the Friends of Trees Crew Leader Training begins, here in this warm church basement that is abuzz with caffeinated chatter. I’m surrounded by people in rubber boots and every variety of raincoat, all of us drinking coffee out of small church cups, eating donated baked goods. On tarps set out around the room are two displays. One has a leafy tree in a black plastic pot, its boughs bound by twine, a pair of two-by- two stakes, a shovel, rake, and a post pounder, a hard-hat. The other display holds all the same goods, except the tree is barren. It’s cold and drizzly outside. Fall is turning to winter soon. These are shiny people, all here in good cheer and with a simple purpose—to plant trees.
Friends of Trees, here in Portland, Oregon, is an urban forestry program designed to increase tree canopy cover over the city. With these shovel-in-hand efforts weekend after weekend, the city becomes more lush and leafy. In fact, Portland has the only increasing urban canopy in the nation, a statistic that is colloquially known as the “Friends of Trees effect.” As awareness of Portland’s model grows, city dwellers elsewhere are beginning to realize the importance of the interface between developed areas and natural spaces. According to the US Forest Service, “in an effort to maintain and improve the public benefits of trees, more and more cities—Atlanta, Chicago, Baltimore, Boston, New York, Los Angeles, Sacramento, Washington DC—are setting tree canopy goals.” Trees are no longer simply aesthetic adornment to homes, but are considered part of the sustainable, green infrastructure of urban development.
A couple of hours are spent sitting inside, learning the procedures to teach our volunteers. Then the volunteer planters arrive, and everyone shares a potluck lunch of warm soups, macaroni and cheese, cookies, and lemonade. Friends of Trees works build community while planting trees—by bringing neighbors together.
As the meal ends, people are divided into small work groups and tromp outside. Each crew has a set of houses in the neighborhood to visit. At each site, trees have been delivered and the holes for them have been dug. On my crew, I have someone from Environmental Services, a guy who just moved from Las Vegas and is studying horticulture, two young college students, four Hispanic teenagers from a high-school service club, and the homeowner of one of our planting sites. Three hours later, eight new trees are in the ground. Now dirt-covered and exuberant, we laugh and chat our way back to the church, wash the tools and call it a day.
Urban forestry is a blend of social and scientific necessity. With 80 per cent of the US population living in cities, use of city trees as natural resources takes on a much broader context. It includes safe-guarding against tree loss during development; treating trees as part of the infrastructure of the city; putting in place codes and policies to maximize tree preservation; expansion of private and public urban forestry programs; removal of regulatory obstacles; reduction of the heat island effect caused by development. This, for sure, is a new way of thinking. It’s a fresh approach, and aligned with the science of climate change as well as the ideas behind livable cities.
Portland’s Grey to Green Initiative works in partnership with Friends of Trees. Its concern is the use of the city’s trees in the control of storm-water run-off. The canopy of leaves of the 50-foot-tall buckeye in my yard catches rain as it falls; a mature tree can capture up to 700 gallons a year. The paperbark maple planted on Saturday, not yet as leafy and large as the buckeye, holds onto water that falls to the ground and uses it for root growth. A tree’s root system holds soil in place. In turn, some of the captured water is stored in the soil to replenish the ground water supply. As well, much of run-off water in cities contains chemicals like car oil and other debris—that gunk you see in the street drains during a downpour. When that water moves through the soil, some of the debris is filtered out. With water held in tree fiber and the soil, and with the soil stabilized and working to filter out toxins, significantly less run-off makes it into the city sewage system, to the nearby Willamette River, and out to the sea. A healthy urban forest, one composed of the newest to the oldest trees, slows run-off by about 35 per cent; in Portland, this amounts to 500 million gallons of storm water a year. Trees also allow the city to spend less building and maintaining sewage systems. Portland saves $58 million dollars—or 40 per cent of traditional sewage repair costs—per year because of its street trees. Deciduous, or leafy, trees aren’t doing all the work; evergreens actually help even more with storm water run-off, because they have needles year-round. By providing ecosystem services such as storm-water control, urban trees can be used as a cost-saving component of a city’s infrastructure.
Trees breathe carbon dioxide, a greenhouse gases, most of which—in the city—comes from vehicles. Other sources of the carbon that is emitted into the air by industry, fires, fuel burning, agriculture, and all kinds of human activity. As trees take up CO2 and other pollutants they filter the air—at the rate of 25 million pounds a year here. It takes about 20 trees to offset driving one car for 60 miles each day. The larger and healthier the tree, the more filtration. Think of the old neighborhoods full of maples, cherries, and tulip trees, working hard to help us breathe. And interestingly, researchers have discovered that urban trees begin to store carbon at an earlier age than do rural or wilderness trees.
The economic aspect of air filtration, mainly that of carbon storage, comes in the form of carbon trading. More and more, industries that send the pollutants into the air pay tree growers for the air-cleaning capacity of their trees. Cities are now able to compete in this market. In fact, buyers often pay more for credits that are attached to sustainable projects with local, social benefits, such as urban tree-planting programs.
A full tree canopy provides shade and lowers the overall temperature of a place. In the city, this is important socially—ever step into the shade of a tree on a hot day? Such cooling also works to against global warming. Cooling is particularly important in cities where heat islands occur. The lack of trees and other vegetation combined with pavement, buildings, and other human-made, sealed structures disallow the flow of energy and air. Think of walking on a sidewalk at sundown on a hot day, and passing by a brick or cement building. You can feel the heat wave bounce of its walls. That’s the heat island effect working. A 2006 study of Portland’s July temperatures reported a 20-degree difference between the well-treed Northwest quadrant and an area designated as an urban heat island.
Wildlife fare better in the city when trees provide food and shelter for them. Salmon swim our creeks on the way to the big rivers—Willamette and Columbia and coyotes roam through town. If you live here you are no stranger to the crows, squirrels, and raccoons. The tree canopy keeps river water clean for the fish and helps to moderate water temperature so they can flourish. Fruit and nuts feed many of the 200 species of birds call this city home. Squirrels live in the leafy high-rises. Travel corridors provide safety for larger creatures hoping to sneak from tree patch to tree patch for cover. These habitat resources lower incidents of wildlife encroaching on human habitat; in turn, the city is safer for all species—humans and those with scales, fur and feathers.
All of these ecosystems services add up to a boon for the city. Homeowners also cash in on street tree value. When you drive down a street under its lush canopy with boughs that reach across to make an arc overhead, know that the shade these trees provide lowers energy use, and increase property value by $14,500 per street tree. Storm-water Management credit and Clean River Rewards credit are available on your sewer bill for efforts made on the home front. Crime is lower where there are trees. People walk more in tree-dense areas. Overall livability increases when a city’s canopy is dense.
Forests in the United States are being converted for non-forest uses such as urban development and agriculture at the rate of 1 million acres a year, yet humans need trees to live. City trees provide opportunities. They provide another way for trees to work for us by shaping new economies and new types of forestry jobs. City trees significantly lower the costs of running a city. A tree-planting program costs about $5 per capita. What enthuses me about urban forestry and tree-planting programs is the opportunity for individual empowerment. In all the talk about climate change and environmental degradation it is easy to feel helpless. I have been studying conservation biology for the last two years, during which I’ve come to believe that trees can assuage many of the world’s problems. I volunteer for Friends of Trees and I am hooked.
Saturday morning, and it’s 7 AM. It’s early, but I can’t get my rubber boots on fast enough and get out the door—rain, sun, or freezing cold. I can’t stop global warming, but I can plant a tree.