The sign with the radiation symbol still stands there, yellow, dirty, planted in the tall grass like a warning that no one needs to read twice anymore. Around us, however, the scene has taken a turn that no emergency manual would have been able to predict: trees inside buildings, roads crumbling in the woods, cemeteries devoured by bushes, houses with no more voices and paws passing where previously tractors, buses, children, soldiers, technicians, employees, entire families passed.
On April 26, 1986, the explosion of reactor 4 of the Chernobyl nuclear power plant, in what was then Soviet Ukraine, caused an unprecedented release of radioactive material and prompted the evacuation of over 100,000 people in 1986 alone, followed by the relocation of another 200,000 from Ukraine, Belarus and Russia. The contamination reached several European countries and transformed a huge portion of territory into a place designed above all to remain empty.
Forty years later, the Chernobyl exclusion zone, or Chornobyl according to the Ukrainian transliteration, remains a complicated, controlled place, at times still too dangerous for a stable human presence. But the void left by men has been filled by something else. The fauna of Chernobyl took space with an almost irritating naturalness, as if nature had found an opening and entered without asking permission.
After the evacuation
The Ukrainian exclusion zone covers around 2,800 square kilometers in the north of the country, an area larger than Luxembourg and has become one of the largest inadvertent rewilding experiments in Europe. Lynx, deer, bison, elk, wild boar, wolves and other animals have returned here to find dense forests, abandoned fields and very little human pressure.
The Chernobyl radiological and ecological reserve describes this territory as a place still unsuitable for ordinary human life, yet rich in thousands of plant and animal species. Among the most recognizable inhabitants are the Przewalski’s horse, various ungulates, wolves, lynxes and even the brown bear, which has returned to a landscape that for decades had been described almost only as a scar.
The most effective phrase was used by Denys Vyshnevskyi, a nature scientist in the area: nature has done a kind of “factory reset”. It almost sounds too clean, said in front of a place full of radioactive dust, slanted crosses and military concrete. But it gives a good idea. Where before there was agriculture, cities, infrastructure and continuous presence, today there are tracks, dens, herds, young trees and animals that cross Soviet buildings as if they were any rocks.
Przewalski’s horses use empty houses for shelter
Of all of them, Przewalski’s horses seem the most out of place and the most suitable together. They are short, stocky, sandy-colored, with a short, dark mane that gives them a prehistoric look. They come from Mongolia, where they are also known as takhi, a word associated with the spirit or the sacred in local traditions. They have 66 chromosomes, compared to 64 for domestic horses, and this difference makes them a distinct line, far from the idea of the domesticated horse we have in our heads.
In the Chernobyl area they were introduced in 1998 as an ecological experiment, a sort of substitute for the wild horse that once inhabited those areas. The Przewalski’s horse is a rare species, protected by both the IUCN Red List and the Ukrainian Red Book, and its free presence in Ukraine is considered a small positive anomaly in a place born from an industrial tragedy.
The global recovery of the species is a story of farms, reserves, zoos and reintroductions. The last sighting in the wild, in Mongolia, dates back to 1969; today we are talking about around 3,000 living specimens, all descendants of a very small number of founders captured in the last century. The species remains fragile, far from full safety, but it demonstrates a very concrete thing: an animal kept in captivity, with serious preparation and long periods of time, can recover the social and ecological behaviors necessary for free life.
In Chernobyl these horses learned to use the ruins with the pragmatism of abusive roommates. Camera traps set up near abandoned buildings have recorded them entering old agricultural structures, houses and crumbling shelters, using them against the cold, insects and bad weather. In winter they were detected in 9 out of 10 monitored facilities; in summer in all 8 structures observed. Not poetry, survival.
They live in small social groups, often with a stallion, a few females and their young, while young males form separate bands. At first many specimens died, then part of the population adapted. The fascinating fact lies right here: a species born for open landscapes has managed to move even in an environment that is now partly forested, made up of clearings, ruins, broken roads, fields invaded by shrubs.
The most unlikely refuge in Europe also remains one of the most fragile places
The rebirth of Chernobyl’s fauna must be handled without sugar on top. The animals are back, yes and the area is full of life. This does not erase the radiation, nor does it turn the disaster into a fairy tale about the triumph of nature. Scientists have observed more subtle effects in several species. A study of wild birds in the region found a higher incidence of cataracts in areas with higher levels of background radiation, potentially impacting survival and breeding populations.
The frogs also told a strange story, much less immediate to see than a herd of horses on an empty road. Eastern tree frogs in the area in several cases show darker coloration, a trait linked to melanin, a pigment that may play a role in protecting against cell damage. Chernobyl research remains full of margins, differences between species and results that need to be treated with caution. Here life has returned, but it has paid and continues to pay a price.
Then came the war. In 2022, Russian forces occupied the plant and the surrounding area in the early stages of the invasion of Ukraine. Staff remained under pressure for weeks, rotations were blocked or reduced, communications compromised, some equipment damaged or stolen. The International Atomic Energy Agency also recorded local increases in gamma rates attributed to ground movement by heavy vehicles, although it assessed those levels as low and without radiological danger to the public.
Within this already crooked picture, fires are a serious threat. Contaminated forests can recirculate radioactive particles deposited since 1986. During the 2020 fires in the exclusion zone, several studies observed the return of radionuclides to the atmosphere and a temporary increase in concentrations measured in various areas, although the doses estimated for the population of Kyiv were extremely low compared to annual limits.
Today the Chernobyl landscape is also a military corridor. Concrete barriers, barbed wire, checkpoints, mined areas. Staff come and go in shifts designed to limit exposure. Firefighters must travel kilometers to reach fires caused or worsened by conflict, often in areas where any intervention requires time, caution and strong nerves. A downed drone, a fallen tree, a poorly dug fortification: here even the consequences have a long tail.
The power station, meanwhile, remains a material reminder. In February 2025, an explosion attributed to a Russian drone was reported in the area of the New Safe Confinement, the large structure built to enclose Reactor 4 and the old sarcophagus. Even without significant radioactive release, the damage was a reminder of how fragile the very idea of ”securing” a disaster is when a war is overtaking it.
Chernobyl therefore remains this: a place forbidden to humans and full of life, a reserve created by mistake, a laboratory without walls, a wound that has begun to cast shadows and leaves. The horses graze, the wolves move, the lynxes appear in the camera traps, the bears cross woods that no one cultivates anymore. Nature has regained its space. The sign remains there, reminding us who must stay out.
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