Scientific American: Earth Day gets more press but the real environmental holiday this week is National Arbor Day, today! April 24th. Trees do a lot for us: provide wood, improve health, even clean up the air. And maybe get us out of a little problem we’ve created called climate change. That’s because carbon dioxide–the main greenhouse gas driving climate change–is plant food. The leaves of trees suck in sunlight and then chemically convert CO2 to carbohydrates. This process called …