It’s big news that poison ivy thrives where there are higher concentrations of carbon dioxide? Did everyone forget elementary school science and plant life’s dependence upon carbon dioxide? Do I advocate buying and driving the most carbon dioxide–emitting vehicle you can find? No. I guess I would just like to see more common sense and less common scare in your article.

Scott Billingsley
San Antonio, Texas

Poison ivy in enhanced carbon dioxide didn’t just grow. It grew much more than woody plants did under the same conditions. That difference between a weedy vine and woody plants could mean changes in the forest communities of the future .—S. Milius