"If everyone planted a tree, how much land would that require? Let's say they’re planted in a square grid, 5 meters apart, so that each tree takes up an area of 25 square meters. With 7.5 billion trees, that requires 1.8 x 1011 square meters of land, or 72,000 square miles. That's roughly the size of North Dakota. That’s not too bad. I think we could do that. And with all due respect, North Dakota could use some more trees. Oh, for comparison, the Amazon rain forest has an area of 2.1 million square miles. Please don't burn it down."