AnimalsNuclear

Long-term Census Reveal Presence of Abundant Mammalian Community in the Chernobyl Nuclear Disaster Zone

An international team of researchers have discovered thriving populations of wildlife in the Chernobyl Exclusion Zone, bringing out the unique evidence of wildlife’s resilience in the face of chronic radiation stress. Teeming with moose, elk, roe deer, red deer, wild boar, and wolves, the Chernobyl site after nearly 30 years of chronic radiation exposure looks more like a nature preserve, than as a disaster zone.

A fire and an explosion at the Chernobyl Nuclear Power Plant in 1986, released tons of radioactive particles into the air, forcing nearly 116,000 people to be permanently evacuated from the 4,200 square km area, which is now recognized as the Chernobyl Exclusion Zone.

But, what happened with the wildlife in the abandoned area has since than become a source for continued scientific and public debate. Several previous short-term studies in the Chernobyl Exclusion Zone showed major radiation effects and heightened reductions in wildlife populations at dose rates well below those thought to cause significant impacts.

A family of moose roams free in the Chernobyl Exclusion Zone. (Image credit: Valeriy Yurko)
A family of moose roams free in the Chernobyl Exclusion Zone. (Image credit: Valeriy Yurko)

However in contrast, for the first time, a new set of evidences from a long-term census data reveals that the wild life populations in the zone are thriving with no evidence of negative radiation impact. The populations of elk, roe deer, red deer, and wild boar living within the Chernobyl exclusion zone are now similar to those found in four nearby uncontaminated nature reserves in the region.

In addition, the wolf census data in the restricted zone reveals that, they are more than seven times more in number than those in the nearby reserves. Also, helicopter surveys conducted annually in the first 10 years after the accident showed rising trends in the abundance of elk, roe deer and wild boar.

The multiyear data clearly show that a multitude of wildlife species are abundant throughout the zone, regardless of the level of radiation contamination. Our data are a testament to the resiliency of wildlife when freed from direct human pressures such as habitat loss, fragmentation and persecution.

Jim Beasley, study co-author from the University of Georgia.

Roe deer near the Chernobyl Nuclear Power Plant disaster area. (Image credit:  Tatyana Deryabina)
Roe deer near the Chernobyl Nuclear Power Plant disaster area. (Image credit: Tatyana Deryabina)

Jim Smith, a professor of environmental science at the University of Portsmouth in the U.K. and the team’s coordinator says, “It’s very likely that wildlife numbers at Chernobyl are much higher than they were before the accident.” He further notes, “This doesn’t mean radiation is good for wildlife, it is just that the effects of human habitation, including hunting, farming and forestry, are a lot worse.”

Actually, previous researchers had proposed three key hypotheses pertaining to the resilience of wildlife to the world’s worst nuclear accident. But, none of the three hypotheses postulating radiation damage to large mammal populations at Chernobyl were supported by the present empirical data.

The first hypothesis proposes that mammal abundances are negatively correlated with levels of radioactive contamination at Chernobyl. This hypothesis was not supported by the present census data. For all species, the statistical models rejected radioactive contamination as an important predictor of mammal density within the exclusion zone.

Animal abundances in the Chernobyl exclusion zone. (Top) Mean number of track counts per 10 km (in 2008–2010) for elk and wolf plotted against mean radiocaesium contamination density of each route. Analysis using linear mixed models including habitat variables found no evidence of correlation between mammal density and contamination density. (Image credit: Valeriy Yurko)
Animal abundances in the Chernobyl exclusion zone. (Top) Mean number of track counts per 10 km (in 2008–2010) for elk and wolf plotted against mean radiocaesium contamination density of each route. Analysis using linear mixed models including habitat variables found no evidence of correlation between mammal density and contamination density. (Image credit: Valeriy Yurko)

The second hypothesis proposes that densities of large mammals are suppressed at Chernobyl zone compared with those in four uncontaminated nature reserves in Belarus. Again, it was observed that this hypothesis was not supported by the empirical data. Densities of large ungulates were similar to those in four uncontaminated reserves and the wolf density was seven times higher.

Lastly, the survey data also do not support the third hypothesis, which proposed that densities of large mammals declined in the period between 1 and 10 years after the accident. Aerial survey counts of wild boar, elk and roe deer conducted during the years from 1987 to 1996 showed significant increase over time.

An abandoned house near the Chernobyl Nuclear Power Plant disaster area. (Image credit: Valeriy Yurko)
An abandoned house near the Chernobyl Nuclear Power Plant disaster area. (Image credit: Valeriy Yurko)

It is true that extremely high doses of radiation during the first six months in the aftermath of the accident did significantly affect the animal health and reproduction at Chernobyl. However, the present trend analysis doesn’t show any potential long-term radiation damage to mammal populations.

Researchers note that, the increase in elk and wild boar populations in the Chernobyl exclusion zone occurred at a time when these species were undergoing a rapid decline in former Soviet Union countries owing to major socio-economic changes. They also speculate that, before the Chernobyl accident, mammal population densities were likely depressed due to hunting, forestry and agriculture.

This unique census data may help in understanding the potential long-term impact of the more recent nuclear accident in Fukushima, Japan. Researchers strongly feel that the results will help society balance the negative impacts to wildlife from chronic radiation exposures as against how “the removal of humans alleviates one of the more persistent and ever growing stresses experienced by natural ecosystems.”

Reference:

“Long-term census data reveal abundant wildlife populations at Chernobyl”, Tatyana Deryabina et al, Current Biology, October 2015.

Feature Image, (Image credit: Valeriy Yurko)
Caption: Wild boar in a former village near the Chernobyl Nuclear Power Plant.

Ravindra Krishnamurthy

Ravindra Krishnamurthy is a freelance science writer covering science, tech, the environment, health, food, and culture.

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