radioactivity on the whole good for nature

Because people stay away from radioactive places.  The area around Chernobyl where people fear to tread is full of life.  Because people aren't fucking with the life in there.  The animals don't have normal lifespans, but the natural response is more frequent litters.  The voles demonstrate this trend, and maybe the result is going to be voles that are more resistant to ill effects of radioactivity some day.

Now, people are fishing the fuck out of the seas, and several food fishes have crashed and stayed crashed.  The remedy is therefore to make the fish radioactive somehow so that people will leave them alone for a long long time.

>>4
A vole is a small rodent resembling a mouse but with a stouter body, a shorter hairy tail, a slightly rounder head, smaller ears and eyes, and differently formed molars (high-crowned and with angular cusps instead of low-crowned and with rounded cusps). There are approximately 155 species of voles. They are sometimes known as meadow mice or field mice in North America. Vole species form the subfamily Arvicolinae with the lemmings and the muskrats.