Fukushima exclusion zone

As the area remains unfit for long-term human habitation, the natural world shapes it.  There are reports of hordes of yellow spiders where farms were.

The reports of the return of wildlife after Chernobyl are well documented. So what? Returning fauna and flora are still assaulted by heavy ionizing radiation, producing large numbers of mutations, the vast majority of which are fatal or debilitating.

Wildlife is too stupid to know that it's living in a deadly zone over time. Humans aren't much brighter, but do know enough to avoid a zone of heavy ionizing radiation!

However, there are survivors.  The survivors remain to breed.  Consider the long-term consequences.