I'd like to add two examples to this, one for nuclear fallout and one for decimation due to war.
In 1986, a nuclear reactor at the Chernobyl Nuclear Power Plant went critical and released nuclear contamination into much of the surrounding countryside. The nearby towns were evacuated and the forest surrounding the area was rendered inhospitable for most life… but today, just over 25 years later, there are reports that the forest has made a great recovery
, and it appears that even larger animals have returned to this exclusion zone. While there has been significant impact on some species, others are thriving, which shows how resilient nature can be when faced with nuclear contamination.
The other example I'd like to point out is Eastern France. As I'm sure you know, there was large amounts of fighting in this region in both WWI and WWII, and huge swaths of forest were decimated. Large defensive lines of trenches were dug, and artillery wiped out most of the surrounding area. Despite all this, the forest has bounced back. I can't find numbers on the amount of time, but it seems that less than 100 years is easily plausible. Society, meanwhile, rebounded MUCH faster, within just a few years…