One of the astounding numbers I came across in my research is that while we're still cutting down primary rain forest, fifty-five times more rain forest than we're cutting down is coming back as second growth, because of the shift to cities and more-efficient agriculture. Because plants grow quicker in the tropics, the whole array of species and biodiversity is returning within a couple of decades.
As long as people either stay out of the land or step gently on it, we're seeing a revival, much as we've seen in New England. It's a little-known fact that 1845, the year Henry David Thoreau lived at Walden Pond, was the maximum point of deforestation in New England. The trees have been growing back ever since. That's why when you walk around an eastern forest, you often see stone walls left from old farm properties.
--- Arnie Cooper interview
The Sun Magazine