万花筒 2009-08-25&08-26 少一棵树，补种两棵（在线收听）

Drive through Aiken, South Carolina, and you can't miss the 19th century parkways shaded by 100-year-old oaks. But not all residents realize the city's treasure. Bob McCartney knows, he co-owned woodlanders - a nursery specializing in rare and unusual plants, when he wanted to branch out 30 years ago, the city let him.

"The one I'm planting is a Mexican maple, it's relatively little known in the United States. This is probably the first one to be planted in South Carolina."

McCartney has planted so many different types of trees that the entire city Aiken has grown into an arboretum.

"I couldn't even begin to walk through and tell anybody what his plannings are, because they are just way out there."

Including these mile-long stretching oaks - a virtual united nations of trees.

"All these are different oaks from all over the world, the first one there is native to Alabama and Texas, the next one to Mexico, Southern Europe, a hybrid from Holland."

Where other cities have heat island of asphalt. Aiken city's workers plant two trees for every one they remove. They know that trees build better soil, reduce water runoff, provide oxygen and valuable shade.

"It's a solution not just for the environment, we think it's a solution for the environment of your mind."

Reynolds Wolf, CNN.