"Air pollution comes from trees," Ronald Reagan declared more than 20 years ago, soon after the start of his presidency. The remark earned him widespread derision as proof of his ignorance of environmental issues. Even his first press secretary, James Brady, teased him about it. Once when Air Force One was flying over a forest he grabbed the President by the elbow and, pointing down out of the window, said in alarm: "Look, Mr President: killer trees!"
But now new scientific research is showing that the former Hollywood B-movie star was at least partially right all along. For studies in both Britain and the United States have shown that some trees do indeed emit pollution and may even be killing forests downwind.