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

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'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.

NEGATIVE EFFECTS

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.

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'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. …