In the decades after the 1986 Chernobyl disaster, wildlife paid a heavy price. Birds were found to have tumors, while some mammals suffered genetic defects and a decline in reproductive rates.
But this past year, scientists have found signs of improvement at the site of what is typically called the world's worst-ever nuclear accident.
Timothy Mousseau, a biologist at the University of South Carolina, and his colleagues found that some birds were adapting to the radioactive environment by producing higher levels of protective antioxidants. And a study in Current Biology concludes that the disaster zone is starting to look more like a de facto nature reserve teeming with elk, deer, wild boar, and wolves.
"It's very likely that wildlife numbers at Chernobyl are much higher than they were before the accident," says Jim Smith of the University of Portsmouth in the UK. "This doesn't mean radiation is good for wildlife, just that the effects of human habitation, including hunting, farming, and forestry, are a lot worse."
Earlier studies in the 1,621 square mile Chernobyl Exclusion Zone showed that high doses of radiation emitted from the explosion and subsequent fire led to pronounced reductions in wildlife populations, especially in the months after the disaster. Among those were animals living in what is called the Red Forest, so named because the trees died and turned red due to the high doses of radiation.
The new evidence, based on long-term census data, indicates the populations are recovering. The numbers of elk, roe deer, red deer, and wild boar within the exclusion zone are similar to those in four uncontaminated nature reserves in the region, according to the study. Among the most dramatic changes, however, has been the growth of wolf populations, which are now seven times higher than can be found in the nature reserves.
"Additionally, our earlier helicopter survey data show rising trends in elk, roe deer, and wild boar abundances from one to 10 years post-accident," the study authors wrote. "These results demonstrate for the first time that, regardless of potential radiation effects on individual animals, the Chernobyl exclusion zone supports an abundant mammal community after nearly three decades of chronic radiation exposures."
A critical factor in the recovery appears to be the fact the area remains off-limits to tens of thousands of people who once lived there before the disaster, which brought an end to farming and severely curtailed hunting. A similar trend has been found in the demilitarized zone between North and South Korea, where the mine-filled region has been a boon to wild boar, deer, and hundreds of bird species that winter there.
"These unique data showing a wide range of animals thriving within miles of a major nuclear accident illustrate the resilience of wildlife populations when freed from the pressures of human habitation," said Jim Beasley, a study co-author at the University of Georgia.
The authors also credited the wildlife revival to a significant drop in radiation rates since the disaster, though they noted that animals continue to accumulate radiation in their bodies.
"People say, 'Were you surprised by your findings?' In some senses, we weren't," Smith said. "We wouldn't necessarily expect to see severe effects, in other words, effects that would damage populations. We might expect to see effects on individual animals, but not on populations."
Mousseau, who was not part of the latest animal survey, called the study a "very positive move forward in conducting research concerning the potential health and environmental impacts of nuclear accidents." But he questioned findings that the entire exclusion zone was teeming with wildlife, noting that the study focused only on large mammals under hunting pressure, and not smaller mammals, insects, and most birds.
"As such, it does not address the fundamental question of the ways in which natural populations are affected by radioactive contaminants," said Mosseau, who also studies wildlife around the damaged Fukushima nuclear power plant in Japan. "This study does not address the issue of whether radiation has effects on reproduction, survival, longevity, or general health of the animals surveyed. Rather, the findings of this study are a reflection of impacts of human habitation and natural resource overexploitation in the absence of conservation measures."
Mousseau is skeptical of the suggestion that the absence of humans led to this spike in wildlife around Chernobyl.
"The authors champion the idea that the absence of humans causes an increase in population sizes of large mammals," he said. "This argument is overblown because European populations of roe deer, red deer, wild boar, wolves, lynx, and many others have increased by up to an order of magnitude during the last 30 years with no change in human presence. "If anything, there are more humans outdoors today than 30 years ago. The consensus among mammal specialists is that an increase in food abundance, partly combined with climatic amelioration, has accounted for these changes."
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