Pushing the Boundaries
The Chernobyl nuclear disaster left behind a highly toxic landscape. Thirty-two years hence, the area around the Ukrainian ghost town of Pripyat largely reverted to forest. Despite the contamination, wildlife gradually took over. Hints of recovery emerged as animal species began to thrive, free from the disruptive influence of human activity. And for the first time, researchers recorded evidence of a young wolf boldly venturing away from the danger zone.
The grey wolf travelled 369 kilometres (229 miles) from its home.
Scientists said it was the first time they are aware of an animal leaving the Chernobyl Exclusion Zone, and covering such a distance. They believe it is perhaps a precursory sign of how native populations might spread in the future, and how far their mutated genes could potentially spread.
The research was published in the European Journal of Wildlife Research.
The Chernobyl Exclusion Zone
The Chernobyl nuclear disaster will be remembered for a long time, as one of the worst failures of civil engineering.
On 26 April 1986, the accidental explosion of Reactor 4 of the Chernobyl power station, inside the then Soviet Union, released a blast of radiological material that was 10 times bigger than that of the Hiroshima bomb.
Thirty-one people died as a direct consequence.
Following the accident, 116,000 people were permanently evacuated from the hazardous Chernobyl Exclusion Zone (CEZ). A radioactive gas and dust cloud notoriously drifted in the wind, before precipitating across parts of central and southern Europe.
The CEZ stretches over 4,000 km2 in Ukraine, and across neighbouring Belarus.
The location remains heavily contaminated. Too contaminated to be habitable safely.
How Much Radiation is Dangerous?
Chernobyl residents were forced to evacuate in areas where surface soil concentrations of caesium-137 exceeded 1,480 kBq/m2.
Within the initial 30 kilometre radius zone, the first evacuees received an average effective dose of 33 mSv over the 24-hour period before they left.
Countless lives were affected by the long-term exposure to radiation.
Today, radioactive water, ground soil, and air are still affecting those living around the Zone.
Three decades on, human residency remains extremely sparse there.
On the Human Side
Currently, about five million people live in low-contaminated areas of Belarus, the Russian Federation and Ukraine with levels of radioactive caesium deposition greater than 37 kBq/m2.
Among them, about 270,000 people continue to live in areas classified by authorities as Strictly Controlled Zones (SCZs) where radioactive caesium contamination exceeds 555 kBq/m2.
Studying Genetic Mutations
The CEZ has drawn significant scientific interest for the high radiation levels present in its unique environment. Over the years, the unknown consequences of the accident have been the subject of much speculation about the fate of the wildlife that remained in the abandoned area.
Several studies of the Chernobyl exclusion zone indicated major radiation effects and pronounced reductions in populations at dose rates well below those thought to cause significant impacts.
A study of several hundred birds belonging to 48 different species also demonstrated that birds inhabiting highly radioactively contaminated areas had smaller brains compared to other birds from clean areas.
After an initial drop in numbers, however, long-term data showed no evidence of a negative influence of radiation on mammal abundance.
The Red Forest
Near the nuclear power facility, a dense smog of radioactive dust scorched a large area of vegetation.
The “Red Forest“, as it became known, got its nickname from the rusty orange colour of its dead Scotch pine trees. Birch trees, survived, indicating that plant species may vary considerably in their sensitivity to radiation.
The post-disaster cleanup operations saw a majority of the pine trees hastily bulldozed, and the highly irradiated wood subsequently buried in trenches to reduce the hazard.
At the time, the primary concern of the Chernobyl “Litigators” was to eliminate the risk of further propagation of radioactive dust around the region in the event of a forest fire. The trenches were then covered with a thick carpet of sand, and planted with pine saplings. Many experts now fear that, as the wood decays, radioactive contaminants will leach into the ground water.
Waste graveyards were described as a radiation emergency in 2006, because no-one knows where they all are, or what is in them. Designed to be temporary, unlined, leaky trenches were quickly dug and filled with low to medium-level radioactive waste after the nuclear blast. Only half of them were mapped and inventoried, and an estimated 500 trenches have still to be assessed.
The site of the Red Forest remains one of the most highly contaminated areas in the World today. Its soil continues to emit significant radiation.
The area has largely reverted to forest, and has been overrun by wildlife because of a lack of competition with humans for space and resources.
The Greys’ Domain
Notwithstanding the human exodus, the CEZ has actually become a haven for animal populations, particularly wild boars and grey wolves (Canis lupus). And far from turning into an ecological void, the lack of competition with humans for space and resources has benefited the growth of wildlife inside the CEZ.
Grey wolves have thrived in Chernobyl. Wolves are natural predators. They travel in packs. They hunt and breed…
While relative abundances of elk, roe deer, red deer and wild boar within the Chernobyl exclusion zone are similar to those in four (uncontaminated) nature reserves in the region, recent estimates say there are over seven times the population density of wolves in the exclusion zone as there are in the nature reserves outside it.
After three decades of chronic radiation exposure, wolf abundance is more than 7 times higher in the region.
Little is known about the long-term effect of ionising radiation exposure on the Chernobyl population of wolves and scientists are still trying to understand what impact radioactive contamination had on the environment.
The actual dose depends on the level of ambient radiation. But not only so.
The actual dose also depends on the presence of a number of radioactive substances in the environment. Wolves, and other wildlife, are exposed to these substances from the diet they consume.
Long-standing controversy persists on the fate of wildlife within the CEZ following human abandonment of the area. Regardless of contamination, the end of human activities, such as agriculture, hunting and forestry, in the exclusion perimeter, has undeniably proved beneficial to the Chernobyl Greys.
The Lone Wolf of Chernobyl
Using GPS telemetry, scientists documented the first long-distance movements of a young (1-2 years) male wolf away from the CEZ into the surrounding landscape in February 2015.
The researchers fitted the wolf with a GPS collar.
Over a 21-day period, the wolf travelled 369 kilometres from its home range centre.
Prior to dispersal, the wolf consistently maintained a home range of about 28 km2, with daily displacements rarely exceeding 5 km.
With the onset of dispersal, daily displacements increased to a mean distance of 16.8 km.
The dispersal of a young wolf so far from its home ground is an important observation.
Where the Wolf Roams
These findings might not just apply to wolves.
The nuclear disaster site has seen animal life seemingly flourish without interference from human activity.
It is entirely reasonable to assume that similar things are happening with other local wildlife species as well.
Indeed, it suggests that the Chernobyl Exclusion Zone may serve as a source for some wildlife populations outside of the CEZ.
Additionally, it raises questions about the potential spread of radiation-induced genetic mutations to populations in uncontaminated areas.
What Future for the Wolf?
The Chernobyl catastrophe and its radioactive aftermath caused considerable environmental and public health impact. Greenpeace estimated that a total of 100,000 to 400,000 people could die of health issues related to the accident at Chernobyl.
At the time of the accident, a large increase in the incidence of thyroid cancer occurred among children and young adults who lived in the most contaminated areas of Belarus, the Russian Federation and Ukraine. This was mainly due to the ingestion of radioactive iodine-contaminated milk. (WHO, 2006)
More than 1,800,000 human survivors – more than two thirds of their total number – still live in zones of radiological contamination in Ukraine. Among them, there are more than 400,000 children. However, no data exist on their radiation doses, which diminish the validity of estimates of health effects of acute and long-term radiation exposure.
For the young wolves of Chernobyl, the peregrinations are just beginning. And as long as people stay away, “Wormwood” Forest remains the domain of the Greys…