When Gabriel Hochberg was 4 years old, he came home one day and said, “Dad, do you know about global warming?” He explained to his dad that trees “eat the pollution.” So Gabriel, now 9, and his dad started a nonprofit, Trees for Humanity, which gives saplings away to anyone who is willing to plant them. So far, they’ve given away 10150 trees. Watch video we shot of Gabriel last year while he gave away saplings and sold t-shirts at Whole Foods. From our July 2011 cover story.