Alan: Since cancer is largely a "disease of aging," is it possible that these animals lack life spans long enough to suffer the ill effects of radiation?

Mammals Return to Chernobyl Accident Area, Despite Ongoing Radiation

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In 1986, in the world’s worst accident of its kind, an explosion and fire at the Chernobyl Nuclear Power Plant spewed a large amount of radioactive material throughout Ukraine, Belarus and Russia.
Since that time, authorities have permanently evacuated nearly 120,000 people from the Chernobyl exclusion zone, a patchwork region spread throughout the three countries. While humans largely haven’t returned and aren’t likely to for the foreseeable future, animals have, to a degree that has surprised some scientists.  
New research suggests that these animals have not been as severely affected by radiation as once thought. A study published September 5 in the journalCurrent Biology found no correlation between how much radiation was detected in an area and the number of animal tracks found there. It also shows that populations of animals—including elk, wolf, wild boar, roe deer and fox—increased in the years following the accident, suggesting that cumulative poisoning from radiation hasn’t been reducing animal numbers.
Population estimates in the exclusion zone around Chernobyl appear to be broadly similar to what they are in other nearby wildlife reserves, the study found. For example, the scientists found the numbers of elk, red deer, roe deer and wild boar in the exclusion zone are about the same as those in four uncontaminated reserves in Belarus. But in Chernobyl, the researchers estimate there are about seven times more wolves than there are in the reserves.
Ron Chesser, a research scientist at Texas Tech University who wasn’t involved in the paper, called the study a herculean effort showing that “radiation doses in the region are not sufficient to cause a decline in the populations.”
It also “pretty well confirms what all of us who work in the zone already knew…that wildlife populations are thriving and have been for a number of years,” Chesser says.
chernobyl-wolf
A wolf seen in the Chernobyl Exclusion Zone. There are more wolves found here than in nearby uncontaminated reserves. VALERIY YURKO
Study lead author Jim Smith, from the University of Portsmouth in England, says that the paper shows that human habitation is actually the primary driver of wildlife declines. That isn’t to say radiation has no effect, but that its impact may be less important than feared. “The wildlife at Chernobyl is very likely better than it was before the accident,” he says, “not because radiation is good for animals, but human occupation is much worse.”
But Tim Mousseau, a scientist at the University of South Carolina who has worked in the Chernobyl region for 15 years, disagrees with the conclusions of the paper. He says that the paper’s methodology doesn’t allow one to conclude whether or not radiation is affecting animal populations. He argues that in other places in Europe where hunting restrictions have been lifted, populations of deer and foxes and other animals have risen more rapidly than what’s seen around Chernobyl, suggesting radiation is having an effect on limiting animal population growth.
He also says that to focus only population numbers is insufficient and potentially misleading. His work has shown that radiation in this region has caused fertility declines in various animals, especially birds, and an increase in the amount of genetic damage and health effects like cataracts, a clouding of the retina linked to radiation exposure.
“This study only applies to large mammals under hunting pressure rather than the vast majority of animals, for example most birds, small mammals, and insects, that are not directly influenced by human habitation effects,” he says. “As such, it does not address the fundamental question of the ways in which natural populations are affected by radioactive contaminants.”
The area isn’t “teeming the way you see it in other places around the world where hunting has been curtailed,” Mousseau says.
But Chesser disagrees, saying that the study shows “habitats and populations do recover and that wildlife is a lot more resilient than what we might’ve thought 50 years ago.”
All can agree, however, that this is an area of science that requires more research and is especially relevant given the contamination caused by the earthquake-driven accident at the Fukushima Daiichi nuclear plant in Japan in 2011. Mousseau says that for the most part, scientists still don’t have an in-depth understanding of how radiation affects the ecosystem as a whole. “We don’t really have the answers to these questions,” he says.