Chernobyl tree rings , before and after the accident

No those are adult carrots

To study the effects of radiation exposure on the natural environment in that area

Contrary to dystopian movies, radioactive areas like Chernobyl are actually filled with life. The radiation isn't really a threat even to humans in 99% of all areas, but humans still don't go near it which is allowing the wildlife to flourish. The only risk of the low levels of radiation is an increase in cancer which is so rare that it barely affects the short lifespan of the animals.