To rewild an area is to encourage it to return to its natural state. In particular, it's associated with reintroducing wild animals such as wolves or beavers or lynx.
It is, obviously, controversial, especially if it puts people under threat of being flooded (beavers) or eaten (wolves and lynx (although, really, you're very very unlikely to get eaten by either unless you go and break your leg: and then, really, being eaten would just be a way of putting you out of your misery, wouldn't it?)).
Eurasian lynx by Bernard Landgraf (User:Baerni) - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=217822
In any case, anyone not trying to raise livestock is likely to find the idea of rewilding both romantic and virtuous, especially as it's almost certainly going to be happening a long way away.
The other advantage of rewilding, of course, is that it gives one the perfect excuse to put off mowing the lawn.
Thing To Do Today: rewild somewhere. This word comes from wild, of course, the Old English form of which was wilde.