Wildlife in the dead zone: on the eve of the 25th anniversary of the nuclear accident at Chernobyl in Ukraine, Patrick Evans reports on the ongoing and occasionally heated debate over the disaster's effect on the local wildlife.
'When they have their babies, they use abandoned domestic pastures to rear them,' says Denis Vishnevskiy, as he quietly watches a harem of seven wild Przewalski's horses grazing in the light of the setting sun, just 16 kilometres south of the site of the world's worst nuclear accident at Chernobyl in Ukraine.
Vishnevskiy, an author and ecologist, works for Ekocentre, a Ukrainian government organisation that monitors the environment within the area known as the Chernobyl exclusion zone. 'Wild animals are using what we've left behind,' he continues. 'Perhaps, for human beings, this is a very sad place, but for animals, it's fine.'
Vishnevskiy's words are evocative, but their accuracy is another matter. They form part of a debate that is currently raging over this seemingly benighted patch of land, 90 minutes' drive to the north of the Ukrainian capital of Kiev, and the wildlife that inhabits it.
On one hand, anecdotal and scientific reports suggest that 25 years after the catastrophic graphite fire in the Number 4 reactor released a cloud of radioactive material, local populations of wolf, lynx, elk, wild boar, deer, eagles, bats and other animals, such as these Przewalski's horses, are thriving. Yet a rival scientific position exists, which claims that biodiversity inside the Chernobyl exclusion zone is actually decreasing.
The exclusion zone was created to keep people away from the worst localised radioactive contamination caused by the accident. In recent years, it has become synonymous with the resilience and resurgence of nature, and has attracted numerous scientific studies.
The implications of studying radiation's impact on wildlife here are particularly important. Humans are animals, too, so understanding what is happening in the exclusion zone can potentially help us to understand how human populations would cope with being exposed to significant levels of radiation on a daily basis.
Wildlife studies at Chernobyl began a year after the accident, but most of the current debate revolves around a series of recent publications by Dr Tim Mousseau of the University of South Carolina and Dr Anders Moller of University Paris-Sud.
Mousseau and Moller's work is focused primarily on the effects of radiation on mutation rates in birds and insects. In a collection of more than 30 scientific papers published between 2001 and 2011, their work strongly indicates a wide range of negative effects on Chernobyl's wildlife. These range from albinism, sperm irregularities, increased death rates and reduced brain size in birds to reduced abundance of invertebrates including bumblebees, spiders, butterflies and dragonflies.
In their most recent article, published in the Bulletin of the Atomic Scientists, tthey found that in the most contaminated areas, the species richness of the forest bird community was 50 per cent lower than it was in areas with normal background radiation. Even more dramatically, they found a 66 per cent drop in bird numbers overall.
The shock value of Mousseau and Moller's findings inevitably attracts media attention, but they simultaneously draw criticism from rival scientists. Ironically, one of their most vocal critics, Ukrainian radioecologist Dr Sergey Gaschak, who has been working inside the exclusion zone since 1990, worked with them to gather some of their field data.
'Most results reported in Moller and Mousseau's articles are unconvincing, and sometimes very doubtful,' Gaschak says. 'There was only one period and only a few locations in the zone when and where biodiversity reduced after the accident. It was in the most contaminated sites in the vicinity of the destroyed reactor, and in the "hottest" spots of radioactive fallout on remote territories. There was so much radioactivity that few organisms could survive. Indeed, diversity reduced among animals and plants, vertebrates and invertebrates.
'However, after ten years, dose rates decreased by thousands of times due to the decay of radionuclides, and conditions became more acceptable for most species,' he continues. 'Diversity recovered. Even in the Red Forest [a ten-square-kilometre area around the plant that was razed and buried following the accident, still considered to be one of the world's most heavily polluted sites], young pine trees can survive, despite the fact that coniferous plants are the most sensitive to radiation.'
Despite his scepticism about Moller and Mousseau's findings, Gaschak does agree that there is evidence of radiation stress in the local wildlife. 'For some individuals, it becomes lethal,' he says. 'But for the population as a whole, it's already almost insignificant.
'Before the accident, people living around Chernobyl favoured monocultural forest plantations, fields and gardens,' he continues. 'They tried to "improve" nature, to adapt it to human needs. This led to a reduction of diversity. After people were evacuated, nature began to live by its own rules.'
Gaschak believes that local populations of ungulates such as wild boar, roe deer and elk have increased; although these animals, and predators such as wolves, are subject to widespread illegal hunting, especially on the Ukrainian side. 'Now the Chernobyl exclusion zone is actually a source for a number of species for surrounding regions, and the populations of some species in Chernobyl, such as elk, are the highest in Ukraine.'
In response to Gaschak's claims, Mousseau says that 'the proper comparison for animals in the zone isn't animals outside the zone, but animals in other similar "wildlife refuges". Just because hunting (legal and otherwise) keeps animal populations down in most of Ukraine doesn't make Chernobyl an Eden for wildlife--it just makes the rest of Ukraine unsuitable!'
Gaschak's own studies, which chiefly involve the impact of radiation on bats, have yet to prove definitive. Nevertheless, having caught and measured levels of radiation in more than 1,350 bats from 12 species over three years, he and his coauthors have found no deviations in their ecology or biology.
Another critic of Mousseau and Moller's work is Robert Baker, Horn professor of biology at Texas Tech University. Baker has published a number of papers on wildlife in Chernobyl, including studies on the American channel catfish that live in the reactor's now derelict cooling pond, but mainly focusing on rodents. Baker believes that Moller and Mousseau's work is flawed because breeding bird populations aren't good models for studying the effects of radiation. 'Birds spend most of their time in the air, not on the ground, and Moller and Mousseau's findings are based on migrating birds that only spend four months of the year in Chernobyl,' he says.
We've concentrated our studies on bank voles, which, by living in a small but highly radioactive area, are constantly exposed to radiation,' he continues. 'Yet despite using the most up-to-date DNA-sequencing techniques, we found no evidence of negative effects of radioactivity on their genome.
'The trouble is that if you report an effect, everybody's going to cover it in the media,' Baker says. 'But if you find nothing, people aren't interested. The work we've been able to do inside the exclusion zone has shown us that animals are thriving--and we believe it's because of the lack of human activity, as well as reduced hunting and poaching. It really would be striking if there was no effect from living inside the zone--but we need good science to be able to prove that, and so far, the science that's being published isn't good enough.'
With such widespread criticism being levelled against their work, what do Molter and Mousseau have to say in return? 'We have no dog in this race,' says Mousseau emphatically. 'When we first started going to Chernobyl during the late 1990s, we had no preconceived notions of what we would find. We just wanted to record what we found, and we didn't, and still don't, care whether there are positive or negative conclusions for wildlife on these contaminated territories.
'Our work is based around a single question: is there a signal of contamination effects on population distribution and abundance?' he continues. 'Our studies have shown that there is.'
Mousseau's position is that most of the claims against his and Moller's work are based on anecdotal evidence. 'For anyone visiting the exclusion zone, your first impressions are that it's not a lunar landscape,' he says. 'Visitors tend to come away with a much more optimistic view than if they had collected data over a number of years.
'We've been extremely careful about crafting our procedures that focus on the radiation part of the story,' he continues. 'If the data suggested that there were no effects, then we could and would make that claim.'
Despite the whiff of professional jealousy from all sides, there's a unifying thread among the scientists' arguments. 'The simple perspective is that too little research has been done,' says Mousseau. 'Despite the accident happening 25 years ago, there is a dearth of scientific information available, and what is available often isn't considered if it doesn't fit into a preconceived view of the effects of radiation. We strongly urge scientists to help break this mould.'
On this point, Moller and Mousseau's critics also agree. 'The point is that there isn't nearly enough science being clone inside the zone--either on animals or people,' says Mary Mycio, a journalist and author of Wormwood Forest: A Natural History of Chernobyl. 'Chernobyl has fallen off the radar. Meanwhile, people are talking about building more nuclear power stations. The problem is that we're all downwind of a nuclear accident, and until we get better funding and better science on the ground, we'll never know enough to predict the consequences of another catastrophe like Chernobyl.'
Support for these words of caution comes from the largest collation of scientific information relating to Chernobyl. In 2009, Alexei Yablokov, one of Russia's most senior scientists, author of more than 450 papers and currently chairman of the Russian Green Party, published Chernobyl: Consequences of the Catastrophe for People and the Environment. The book compiles and presents information from thousands of scientific papers, including from translations of many hundreds of works previously inaccessible to the West.
'Wildlife in the heavily contaminated Chernobyl zone sometimes appears to flourish, but the appearance is deceptive,' says Yablokov. 'Levels of incorporated radionuclides remain dangerously high for mammals, birds, amphibians, and fish. Long-term observations of both wild and experimental animal populations in the heavily contaminated areas show significant increases in morbidity and mortality that bear a striking resemblance to changes in the health of humans--increased occurrence of tumours and immunodeficiencies, decreased life expectancy, early aging, changes in blood and the circulatory system, malformations, and other factors that compromise health.
'All of the populations of plants, fishes, amphibians and mammals studied there are in poor condition,' he continues. 'This zone is analogous to a "black hole", in which there is accelerated genetic degeneration of large animals--some species may only persist there via immigration from uncontaminated areas. The Chernobyl zone is a micro-evolutionary "boiler", where gene pools of living creatures are actively transforming, with unpredictable consequences. We ignore these findings at our peril.'
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|Title Annotation:||ecology CHERNOBYL|
|Comment:||Wildlife in the dead zone: on the eve of the 25th anniversary of the nuclear accident at Chernobyl in Ukraine, Patrick Evans reports on the ongoing and occasionally heated debate over the disaster's effect on the local wildlife.(ecology CHERNOBYL)|
|Article Type:||Cover story|
|Date:||Apr 1, 2011|
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