[markjenkinswpg]

It makes sense that planted trees are not thriving in ecosystems where there wasn't already trees naturally. If the conditions were so good for tree growth, you would have a lot of trees there already.

But, this brings to mind that there are places where there once were forests that humans destroyed. Why don't those locations quickly re-forest themselves?

Because, in the process of deforestation, humans destroyed the entire ecosystem that made said forests possible. Nature can't repay that ecosystem debt all that quickly and it's not sped up much by way primates plopping saplings into the soil for money and calling it a day.

Climate change is the mother of all collective action problems and one of our great filters. I dream that one of the descendants of my nieces and nephews will pass through the ensuing population bottleneck.