Green myths debunked

Myth: Plant more trees in the city because they absorb carbon.

Reality: The maintenance of urban trees makes it unlikely they are net storers of carbon.

New York City Mayor Michael Bloomberg is planting a million trees. That offers lots of benefits. But urban trees often require pruning by chainsaw-wielding utility workers in trucks to clear buildings and other obstacles.

"Fossil-fuel emissions from servicing add up," says Jeff Fiedler with the Nature Conservancy, meaning that over time tree care is likely to offset the gains in CO₂ stored.

Don't despair. It turns out that trees can boost energy savings. For instance, shading an air conditioner can boost its efficiency by as much as 10%, according to the Energy Department. -- E.F.

NEXT: Energy: Global warming