Are you sure? A forest grew on my grandpa's field automatically about 15 years after he stopped using it (mostly as a cow pasture). Nobody planted anything, we

Are you sure? A forest grew on my grandpa's field automatically about 15 years after he stopped using it (mostly as a cow pasture). Nobody planted anything, we just left it be. In 2008 this was a grass field, we made campfires there. Now it's a forest: https://goo.gl/maps/rSeprtz7orYAwVPY8 https://goo.gl/maps/rSeprtz7orYAwVPY8 In fact if you don't mow a lawn for a few months saplings start appearing :) Forests are perfectly good at spreading by themselves, they evolved for millions of years to do that. If you want more trees you just need to let them grow.