U.S. cities have lost more than 20% of their trees in the past 10 years, due to urban sprawl and highway construction. This has contributed to environmental and health problems that have cost an estimated $234 billion, according to the group American Forests. Gary Moll says, “America’s cities are developing a huge tree deficit.”

A four-year study of 448 urban areas using satellite imaging was compared with a similar study done 10 years ago, and it was found that there were 21% fewer trees in cities. “Trees preserve our water and prevent flooding,” says Moll. “They remove pollution from the air. They cool the environment and reduce the need for air conditioning.” This is true, but it’s important to plant trees regularly so they will eventually absorb dangerous carbon dioxide emissions, because only mature trees do this effectively?young trees actually put CO2 back into the atmosphere.

The worst examples are in Sun Belt cities. Atlanta has had the most urban tree loss, while Charlotte, North Carolina, and San Diego saved the most trees. “Charlotte looked at Atlanta’s experience and decided they didn’t want to follow it,” Moll says. “Everybody needs to include green information into their decision making. It’s simple: don’t create areas where trees can’t grow.”

Now that the fall colors are starting to show up on the trees we do have, scientists are studying the reasons why this happens. Leaves that turn yellow were yellow all the time, but this was covered up by the leaf’s green chlorophyll. But the reds of maples and other trees are harder to understand.

Jay Ingram writes in the Toronto Star that the red chemicals, called anthocyanins, act as sun blocks, protecting the leaf from too much light, now that its chlorophyll is gone. Scientists also think fall leaf colors are there to warn off bugs that may be thinking about laying their eggs on the leaves. Colorful leaves warn bugs that the tree has called up its chemical defenses, and the more brightly colored the leaves, the more powerful these defenses are.

A study in Norway shows that the most colorful trees in the fall suffered the least insect damage the following spring, because fewer eggs were laid on the leaves. Scientists have also learned that stressed trees are less brightly colored.

Bigfoot won’t hang around without trees (this book is part of our latest sale).

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