A billion trees sounds like a lot. >>> sqrt(1e9) 31622.776601683792 # trees on a side >>> 31623*4/5280 # assume they're planted on 4' centers 2

A billion trees sounds like a lot. >>> sqrt(1e9) 31622.776601683792 # trees on a side >>> 31623*4/5280 # assume they're planted on 4' centers 23.956818181818182 # miles square So like a medium US national park. A decent contribution.