One researcher, biologist Timothy Mousseau at the University of South Carolina, is critical of the tree frogs study. He says the sampling of frogs was not comprehensive enough to show a distinction between those inside and outside the exclusion zone, arguing that the occurrence of melanisation does not correlate with current levels of radioactivity around the Chernobyl disaster site.
Burraco pushes back against these points. The frogs, he notes, were sampled from a variety of areas with differing radiological exposures that are otherwise similar in terms of habitat, for example. He also notes that radiation levels have changed since the time of the accident.
Another scientist, radiobiologist Carmel Mothersill, professor emeritus at McMaster University, says the 2022 paper is “sound” in terms of its methodology and she points out that the authors are cautious in how they interpret the data.
In truth, this is a classic example of the kind of disagreement that has bubbled away for years among scientific investigators of Chernobyl’s wildlife. First there is the question of responses – how do you know that some unusual feature documented in an organism is caused specifically by exposure to radiation and not, say, other contaminants in the landscape such as heavy metals, which are also known to pollute the area?
Similar debates surround reports about genetic patterns in the genomes of feral dogs living around Chernobyl, for example. There’s no hard evidence that this was caused by their exposure to radiation. Studies have also shown that bank voles living in contaminated sites around Chernobyl carry higher levels of genetic diversity in their mitochondria – the tiny energy generators inside their cells – compared to those in non-contaminated areas. These differences might be attributable to mutations caused by exposure to radiation but other factors could also be at work.
A changed landscape
Mothersill points out that many pine trees, which are especially sensitive to radiation, died after exposure to fallout. Birch trees took over in some locations, she says, creating a completely different kind of forest: “It’s teeming with trees and wildlife but it’s not the same as it was before the accident.” Animals living there will naturally respond differently to that changed environment and this alone, rather than radiation per se, could explain differences in those animals.
After residents were evacuated following the Chernobyl disaster, the forest began to take over the town of Pripyat in modern-day Ukraine.
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