Baltimore's best-decorated trees, for sale or for look. Benefits the Kennedy Krieger Institute. 10 a.m.-9 p.m. Friday and Saturday, 10 a.m.-6 p.m. Sunday. $7-$13.
Baltimore's best-decorated trees, for sale or for look. Benefits the Kennedy Krieger Institute. 10 a.m.-9 p.m. Friday and Saturday, 10 a.m.-6 p.m. Sunday. $7-$13. (Matt Hazlett, Baltimore Sun Media Group photo)

Years ago, author Alice Walker published a book of poems entitled "Horses Make a Landscape Look More Beautiful." Though the landscape in her verse was rural, she might well have said the same of the urban cityscape and its mature trees. Baltimore's leafy green canopy surely makes the city a more attractive place to live, work and play. Yet it needs to be constantly maintained and expanded if future generations are to continue enjoying its benefits.

That's not something people usually think of as a high priority item on the city's agenda. But in the long run it is as vital to Baltimore's success as any other element of the urban infrastructure, and it requires a similar investment. Why, you may ask, should anyone care about the city's tree canopy? Let us count the ways.


Start with the short-term economic impact: It's been repeatedly shown that a vibrant tree canopy can reduce the utility bills of city homeowners and businesses by up to 20 percent. That's because paved areas absorb sunlight and re-emit that energy as infrared radiation, or heat. As a result, the surface temperature in cities is higher than in surrounding areas, which reflect more of the sun's energy back into space. Planting trees reduces the so-called "heat island" effect in cities, leading to cooler temperatures and lower energy costs for air-conditioning and ventilation.

Another important function of the tree canopy is its impact on public health. By helping clear the air of pollutants, trees reduce rates of asthma among city residents. They also have a calming effect on people; lower crime rates are associated with areas with a higher density of trees. And trees make any neighborhood more aesthetically pleasing. That's a vital intangible factor in Mayor Stephanie Rawlings-Blake's ambitious plan for attracting 10,000 new families to the city over the next decade.

And those are just the short-term benefits. Long-term, a flourishing tree canopy helps moderate the effects of climate change and global warming by taking carbon-dioxide out of the atmosphere and absorbing greenhouse gases from car exhausts and fossil fuel consumption. Baltimore already has made planting and maintaining new trees part of a vigorous program aimed at mitigating the effects of global climate change.

That will require not only maintaining Baltimore's present stock of some 2.5 million trees but expanding the size of its existing canopy — the percentage of the city's area shaded by trees — from its current 27.4 percent to 40 percent by the year 2037. In order to reach that goal the city will need to plant some 20,000 to 25,000 new trees annually for the next 23 years, a daunting challenge given perennially tight municipal budgets.

Baltimore officials estimate the cost of planting half a million new trees over the next two decades at about $2 million per year. Yet currently the city is spending between $400,000 and $800,000 on new trees, or less than half as much as is needed to reach its goal.

Adding to the challenge is the appearance in Druid Hill Park this summer of emerald ash borers, a voracious Asian beetle that threatens to kill thousands of white and green ash trees on city property. Since its arrival in this country eight years ago, the invasive species has wiped out millions of the trees across North America. The city will have to scramble if it hopes to save as many of its ash trees as possible.

The goal of a 40 percent tree canopy is still achievable if the city works to expand its partnerships with local and national nonprofit groups that enlist thousands of volunteers to plant new trees. It will also have to nurture those young saplings long enough for them to reach adulthood and provide the benefits we want. All city agencies are facing budget pressures, and none of them, including the forestry department, have gotten all the resources they want. But a long-term commitment to continuously expand and maintain Baltimore's green canopy is what it will take to preserve our urban forest as an asset for present and future generations.