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While We Argue About Their Role in Climate Change, Trees Quietly Do Their Good Work

When my kids were little, they delighted in catching my attention by surprise. As I reacted, startled, they’d shout, “Made you look!”

Perhaps Bill Gates was playing that game recently when he called tree planting for carbon capture “complete nonsense.” He also said, “I don’t plant trees,” at a September Climate Forward event by the New York Times.

His comments certainly made me look. Based on the number of publications reporting his comments, many other people looked, too.

Gates is likely reacting to the many simplistic headlines that broadcast ambitious planting schemes with billions or trillions of trees. Perhaps the fault is in the headlines, and writers should sharpen their electronic pencils. However, if you take the time to investigate most of these headlines, you’ll likely find articles with nuanced and often complex discussions of trees, climate, and quality of life.

“Indeed, trees alone can't absorb enough carbon dioxide to stop climate change,” says Maggie Redfern, director of the Connecticut College Arboretum and founder of the volunteer group New London Trees. “Trees, however, support many natural systems, especially native trees. From creating habitats for birds and pollinators, reducing urban heat, buffering noise, cooling buildings, managing the effects of stormwater, stabilizing soil, and cleansing the air we breathe, trees do so much in addition to carbon capture.”

Under Redfern’s direction, the Conn College Arboretum is sponsoring a conference, “Planting Trees Today for a Greener Future,” on Saturday, Nov. 4, from 10 a.m. to 3:30 p.m. The meeting is part of the SALT series, “Smaller American Lawns Today,” introduced by Dr. William Niering in 1997. (Learn more: www.conncoll.edu/the-arboretum/programs-and-activities/salt-conference/)

What’s the connection between lawns and trees?

“One direct connection between tree planting and carbon savings is rarely discussed,” says Redfern. “When we reduce lawns by planting and properly mulching trees and shrubs, the reduction eliminates some of the carbon footprints of lawnmowers and leaf blowers.” She adds, “If lawn sizes are reduced across many properties, the savings in carbon emissions can add up.”

“But it is important to choose the right trees,” adds Redfern, who says this topic will be addressed at the conference. Redfern continues, “We need to plant new trees, especially in cities and neighborhoods with too little tree canopy cover, to continue serving these vital functions in the future. And we also need to protect the mature and growing trees that already provide those functions and store tremendous amounts of carbon.”

Trees and Human Health

Shirley McCarthy of Branford has a short reply for anyone who believes tree planting is nonsense. “They don’t know what they’re talking about,” she says.

McCarthy is a professor emeritus at Yale School of Medicine, where she had a 30-year career in diagnostic radiology. She is also the co-founder of Branford’s Community Forestry Commission, a board that started its work in 2009. Today, the commission interfaces with a variety of town departments, as well as the local landscape industry and the public. McCarthy was the chairperson for almost ten years and is still an active member.

What has the commission done?

“We’ve successfully raised awareness around the value of native trees,” she says. “The topic was barely discussed when we started in 2009. It’s more visible today but still poorly understood by many.”

To increase awareness of native trees over the past fourteen years, the commission has published press releases in the local paper, provided support to citizens who ask for more trees along their streets, given an annual award to a Branford business landscaped with native trees and other plants, and organized an annual Arbor Day celebration during which they plant a native tree.

Branford met the criteria to be a Tree City USA in 2009, a designation defined by the Arbor Day Foundation. Tree City signs are posted where drivers enter the town.

“We’ve also worked with the town to help save mature native trees on town land and plant new ones when the opportunity arises,” she says. A white oak (Quercus alba) was recently planted in a park where a tree came down. “White oaks are associated with up to 2,500 species of moths, butterflies, bees, and other wildlife,” says McCarthy.

Today, Branford plants 50-60 street trees each year, all native.

McCarthy says the commission promotes a 75 percent native planting standard for landscape plans presented to town land use boards.

The Branford Forestry Commission also offers landscape firms literature about the best tree mulching practices. “We discourage mulch volcanoes,” she says, referring to the harmful practice of piling mulch against tree and shrub trunks. “Mulch volcanoes are bad for tree health.” Learn more: branford-ct.gov/boards-commissions-committees/community-forest-commission.

While McCarthy knows native trees support our ecosystems, she’s better positioned than most to understand their relationship with human health.

“There’s so much known today about the relationship between trees and human health,” says McCarthy, “From blood pressure to asthma to improved immune function, we are better off with trees in our environment.”

She points to several well-designed studies that illustrate this point. “For example, research shows the more trees in a neighborhood, the lower the mortality rate. It lowered even more as trees got older and bigger. Conversely, fewer trees in a neighborhood correlate with increased premature mortality rates.”

If you’re curious about tree research, McCarthy suggests the University of Washington page that lists summaries and citations. See depts.washington.edu/hhwb/Thm_Economics.html.

Online Resources

In my work, I’ve found four online resources helpful in understanding trees' specific values, especially native trees. All are free of charge.

First, the National Wildlife Federation offers a zip code database of trees, shrubs, and other plants. It ranks the plants by the number of moths and butterflies (Lepidoptera) they support. When I enter my home zip code of 06475, I learn that native oaks, cherries, willows, birches, poplars, and maples are the most productive. The results are based on peer-reviewed research by several authors, notably Douglas Tallamy and his graduate students at the University of Delaware. See www.nwf.org/NativePlantFinder.

Second, I use the Garden Plant Finder at Native Plant Trust to find the right tree or shrub for a particular location. Given site conditions, this online tool offers upwards of thirty filters to help narrow the selections to a few species likely to survive and thrive. See Plantfinder.nativeplanttrust.org/Plant-Search.

Third, there’s i-Tree, a suite of eight online and desktop tools that analyze and illustrate the value of trees, including energy savings, stormwater management, pollutant removal, canopy size, and much more. This software suite, hosted by the USDA Forest Service, is based on many years of data collection and scientific study. See iTreetools.org/.

Fourth, learn about the “tree equity score” at American Forests. This score indicates whether there are enough trees in a neighborhood for everyone to experience the health, economic, and climate benefits trees provide. Scores are based on tree canopy, surface temperature, income, employment, race, age, language, and health factors. A 0-to-100-point system makes it easy to understand how a community fares. See scores for the shoreline towns in the illustration. To find your town’s score, visit treeequityscore.org/.

It’s easy to become bogged down in today’s noisy climate headlines, but luckily, it’s also easy to access solid information to support home and community planting decisions. Don’t wait for the kids—or famous billionaires--to startle you. Join Conn College’s excellent conference; visit the online databases. There are so many research options—and beautiful trees—at our disposal.

Kathy Connolly writes about landscape ecology and land care from Old Saybrook. Email: Kathy@SpeakingofLandscapes.com.