Planting a tree saves conscience, not planet

If you plant some trees, is it OK to drive an Escalade?

The question isn't as silly as it sounds. People worried about global warming increasingly are trying to "offset" the carbon dioxide -- the leading greenhouse gas -- they spew into the atmosphere when they drive, fly or flick on a light. One idea popular with the eco-conscious is to have trees planted for them.

You keep driving and flying, but those trees are supposed to suck in your trail of carbon.

Whole forests have been funded by tree-loving celebrities like Leonardo DiCaprio and Coldplay, and more modest packages are proliferating.

But some researchers say planting trees -- while a good thing -- is at best a marginal solution to global warming.

Still others decry tree planters who continue to jet off to Cannes, drive their SUVs or generally fail to reduce their fuel-hungry lifestyle. To those critics, plantings and other carbon offsets are like the medieval practice of selling indulgences to wash away sins: It may feel good, but it doesn't solve much.

Groups that offer tree offsets typically rely on Web calculators requiring users to type in how many miles they drive, how much electricity they use and how far they fly. Figure out how much CO2 someone is responsible for (output), compare it to the work average trees can do (input), and you have a formula for neutralizing a person's "carbon footprint."

For $40, Trees for the Future will plant 400 trees to handle your car emissions.

How much carbon dioxide a tree can soak up varies, said John Kadyszewski of Winrock International, a nonprofit agency that works on environmental projects. A huge California redwood might have 30 tons of carbon stored while a 100-year-old pine might have less than a ton.

University of Victoria scientist Andrew Weaver fears tree offsets could steal the focus of a problem that requires technological advances and behavioral changes. "The danger is that you could actually think you're solving a problem," Weaver said.