Forty years after the world’s worst nuclear disaster, the soil and water around Chornobyl remain laced with almost half the caesium-137 that escaped from the shattered Unit 4 reactor in 1986, alongside plutonium, tritium and americium. Yet, against every expectation, the absence of humans has allowed nature to rebound in ways that some scientists describe as an accidental rewilding project on a continental scale.
Contamination and ongoing threats
The reminder of the protracted fallout from the disaster comes ahead of Sunday’s anniversary, which coincides with renewed lobbying for nuclear power and growing fears about atomic brinkmanship driven by the global oil crisis and wars in the Middle East and Ukraine. The conflict in Ukraine continues to threaten the Chornobyl site directly. Last month it was revealed that the giant containment structure — the New Safe Confinement — erected over the most radioactive area inside the defunct plant will need €500 million (£434 million) worth of repairs after being struck by a Russian drone. Preliminary assessments indicate the damage risks corrosion that could undermine long-term safety, and international donors have approved an initial €30 million for engineering and procurement work, with a target to restore full functionality by 2030.
Inside that containment structure sits an estimated four tonnes of radioactive dust, fuel pellets and other debris from the explosion on 26 April 1986 — the largest release of radioactivity in the history of nuclear energy, an event that contributed to the fall of the Soviet Union. More than 300,000 people were evacuated from the plant and the surrounding 4,200 sq km area of land in Ukraine and Belarus. Radionuclides spread across most of western Europe, raising fears of crop contamination as far away as the Lake District, Scotland and Ireland. The official death toll was approximately 30 people, mostly firefighters and plant workers, though foreign analysts warned the fallout would lead to fatal cancer for tens of thousands of others. The National Academy of Medical Sciences of Ukraine is to publish a fresh assessment this week; its last update in 2022 recognised 41,000 fatalities. A study by outside experts in 2006 estimated 4,000 to 16,000 deaths.
Since July 2024, radars have detected at least 92 Russian drones flying within a five-kilometre radius of the plant’s radiation shield. Ukraine’s top state prosecutor has warned that these flights, especially those with powerful warheads, are “extremely irresponsible” and show a “complete disregard” for safety, potentially risking a major accident.
An accidental sanctuary
Experts remain divided about the long-term effects of radiation on the environment of Chornobyl, but there is broader agreement about the benefits to wildlife and ecosystems that have emerged from excluding most of the former human residents. The Chornobyl exclusion zone (2,800 sq km) and the neighbouring Polesskiy radioecological reserve (2,170 sq km) in Belarus form one of Europe’s largest unplanned nature sanctuaries — albeit one that sits in the middle of a war zone.
“Wolf populations are seven times higher than they were before the accident because there is less human pressure,” said Jim Smith, an environmental scientist at the University of Portsmouth who has studied the region for more than 30 years. Elk, roe deer and rabbit populations are also reportedly flourishing. “The ecosystem in the exclusion zone is much better than it was before the accident,” Smith said. “It’s been a very powerful demonstration of the relative impact of the world’s worst nuclear accident, which is not so big, and the impact of human habitation, which is devastating.”
The same pattern has been observed elsewhere. In Fukushima, wild boar, Japanese macaques and raccoons have become more abundant in places evacuated after the 2011 meltdown. On the Korean peninsula, the demilitarised zone — where North-South tensions keep most humans away — has become a sanctuary that is home to 38% of South Korea’s endangered species, including white-naped cranes, Siberian musk deer, Asiatic black bears and Korean gorals.
The Chornobyl zone also hosts a remarkable range of species and natural phenomena. Hundreds of feral dogs, descendants of abandoned pets, now inhabit the zone and show genetic distinctiveness; some studies suggest rapid evolution possibly influenced by radiation and interbreeding with wolves. Melanin-rich fungi have been found growing in highly radioactive environments, with some appearing to thrive under high-radiation conditions. Reintroduced Przewalski’s horses are now a notable presence, with an estimated population of more than 120. Ukraine is also experimenting with a resumption of agriculture in the less contaminated areas. Smith co-authored a paper last year on how to assess radionuclide concentrations in wheat, maize, leafy vegetables and other potential crops.
Yet scientists warn that the picture is not one of simple recovery. Several journal papers report long-term genetic damage to some mammal, bird and plant species, particularly in areas with the highest levels of contamination. A paper published last year noted that barn swallows and great tits were among those suffering lower reproductive success due to “sperm abnormalities, oxidative stress and reduced antioxidant levels”. Other studies have documented increased mutation rates, chromosomal aberrations and developmental abnormalities in birds and amphibians. Gennady Laptev of the Ukrainian Hydrometeorological Centre, who has conducted many years of research in Chornobyl, said he had not seen any visual evidence of mutations, but it was difficult to assert conclusively that the ecosystem was better than before the accident. “This is a complex question. In my opinion, if the wild animals are in abundance, it means it is OK with them,” he said.
Smith, who began his career as an opponent of nuclear power but has become a cautious supporter, acknowledged that radiation damages DNA and estimated there have been about 15,000 extra cancer deaths in Europe as a result of the Chornobyl accident. He argued, however, that this is likely dwarfed by mortality caused by air pollution or by the atmospheric nuclear bomb tests the US and Russia conducted in the 1950s and 1960s. “Since the 1990s, many scientists have been frustrated about how we failed to get the message across about what the important thing at Chornobyl is,” Smith said, adding that evacuations had also carried a heavy psychological and economic cost.
The nuclear debate intensifies
The political implications of these scientific debates are immense. The Trump administration is trying to weaken safety regulations to allow the construction of nuclear power plants in suburban areas, partly to alleviate the extra demand for energy from datacentres. In Europe, Ursula von der Leyen, President of the European Commission, said that the continent’s turn away from nuclear power had been a “strategic mistake” because it had made countries more dependent on expensive and volatile imports, a view amplified by the US-Israeli attack on Iran, which has inflated oil prices. Twenty countries recently attended a summit in France on civil nuclear power’s potential to become “the sector of the future”. In the UK, the nuclear industry has intensified its lobbying, particularly in Scotland, to counter opposition to new reactors; groups such as the UK Nuclear Industry Association advocate for nuclear power to be central to Scotland’s “clean energy” future.
To have any chance of revival, supporters must persuade the world that nuclear is safe and affordable. But anti-nuclear campaigners argue that will be difficult while Russia deliberately targets Chornobyl and Japan discharges radioactive water from Fukushima into the Pacific Ocean. Shaun Burnie of Greenpeace Ukraine said any attempt to revive the sector was a dangerous distraction by a nuclear industry fighting for its existence. “In contrast to the hype and misinformation, the probability of another severe accident remains. Unlike those in the Kremlin and the White House, who together promote nuclear power, these risks remain too great to ignore – while nuclear power remains massively uncompetitive financially.”
Burnie works with scientists and engineers in Chornobyl, where he has encountered wild elk on the roads, heard Russian drones flying overhead on their way to targets in Ukraine, and made three visits inside the New Safe Confinement where radiation levels remain high. “The nuclear industry will grab on to anything – like the Middle East crisis – to try to revive its fortunes, but the future in terms of energy security and decarbonisation is renewables,” he said. “After more than eight decades of massive subsidies and multiple nuclear disasters, including Chornobyl, nuclear power produces less than 10% of global electricity and 4% of global energy. That is not a track record to be proud of. What it remains very good at is what it was originally designed for: producing plutonium for nuclear weapons.”
