Week of 01/28/2007

Dear EarthTalk: Which trees are best to plant to help combat global warming?

—Tim C., Perrineville, NJ

Trees are important tools in the fight to stave off global warming, because they absorb and store the key greenhouse gas emitted by our cars and power plants, carbon dioxide (CO2), before it has a chance to reach the upper atmosphere where it can help trap heat around the Earth's surface.

While all living plant matter absorbs CO2 as part of photosynthesis, trees process significantly more than smaller plants due to their large size and extensive root structures. In essence, trees, as kings of the plant world, have much more "woody biomass" to store CO2 than smaller plants, and as a result are considered nature's most efficient "carbon sinks."

According to the U.S. Department of Energy (DOE), tree species that grow quickly and live long are ideal carbon sinks. Unfortunately, these two attributes are usually mutually exclusive. Given the choice, foresters interested in maximizing the absorption and storage of CO2 (known as "carbon sequestration") usually favor younger trees that grow more quickly than their older cohorts. However, slower growing trees can store much more carbon over their significantly longer lives.

Scientists are busy studying the carbon sequestration potential of different types of trees in various parts of the U.S., including Eucalyptus in Hawaii, loblolly pine in the Southeast, bottomland hardwoods in Mississippi, and poplars in the Great Lakes. "There are literally dozens of tree species that could be planted depending upon location, climate and soils," says Stan Wullschleger, a researcher at Tennessee's Oak Ridge National Laboratory who specializes in the physiological response of plants to global climate change.

Dave Nowak, a researcher at the U.S. Forest Service's Northern Research Station in Syracuse, New York has studied the use of trees for carbon sequestration in urban settings across the United States. A 2002 study he co-authored lists the Common Horse-chestnut, Black Walnut, American Sweetgum, Ponderosa Pine, Red Pine, White Pine, London Plane, Hispaniolan Pine, Douglas Fir, Scarlet Oak, Red Oak, Virginia Live Oak and Bald Cypress as examples of trees especially good at absorbing and storing CO2. Nowak advises urban land managers to avoid trees that require a lot of maintenance, as the burning of fossil fuels to power equipment like trucks and chainsaws will only erase the carbon absorption gains otherwise made.

Ultimately, trees of any shape, size or genetic origin help absorb CO2. Most scientists agree that the least expensive and perhaps easiest way for individuals to help offset the CO2 that they generate in their everyday lives is to plant a tree
any tree, as long as it is appropriate for the given region and climate. Those who wish to help larger tree planting efforts can donate money or time to the National Arbor Day Foundation or American Forests in the U.S., or to the Tree Canada Foundation in Canada.

CONTACTS: American Forests; National Arbor Day Foundation; Tree Canada Foundation


Dear EarthTalk: Does environmental education figure prominently in classrooms these days? By that I mean not just science but an understanding of key issues and environmental stewardship.

—Mary Swan, Framingham, MA

Environmental education has long struggled for legitimacy alongside more traditional disciplines within the liberal arts and sciences. But "environmental literacy" studies in the late 1980s revealed that schoolchildren lacked basic knowledge about the natural environment. This convinced the U.S. Congress to take action, and in 1990 they passed the National Environmental Education Act, forcing the Environmental Protection Agency (EPA) to strengthen and expand environmental education nationwide through education and teacher training and the administration of grants to exemplary programs.

While many of the programs since developed by the EPA have been lauded as exemplary, a lack of funding has prevented many ideas from moving forward. According to a National Environmental Education Advisory Council report, between 1991 and 1996 the EPA received 10,000 environmental education grant applications totaling $300 million, but was only able to fund 1,200 totaling $13 million. Continued shortfalls at the EPA under the current Bush administration have forced further cutbacks.

With such a lack of federal resolve, the onus for teaching kids about the environment has fallen on local schools and individual teachers. According to the President's Council on Sustainability, because environmental education is multi-disciplinary, it is hard for teachers to work it into their narrowly defined lesson plans. Also, most teachers are not trained in environmental subjects. As a result, non-governmental organizations have become increasingly involved with classroom environmental education efforts.

One such organization is the North American Association for Environmental Education (NAAEE), a network of volunteers that provides guidelines and resources for educators and parents who want environmental education for their K-12 students. According to NAAEE's Mary Ocwieja, the group takes a "cooperative, non-confrontational and scientifically-balanced approach" to education about environmental issues. NAAEE's website, EE-Link, lets users find resources on just about any environmental topic.

Another organization, the National Environmental Education & Training Foundation, which was chartered by Congress in 1990, sponsors ClassroomEarth.org, a free website that calls itself "the best of the best" collection of environmental education programs and resources for K-12 teachers, parents and students. The site helps educators, after-school programs and home-schooling parents find up-to-date information on the most successful, well-tested and effective national environmental education programs available today.

According to NAAEE, their work and that of similar organizations is starting to pay off. Some 61 percent of U.S. K-12 teachers surveyed in 1999 claimed that they include environmental topics in their curriculum, with some devoting hundreds of hours of classroom time annually to environmental issues.

CONTACTS: NAAEE; Classroom Earth