Four decades after reactor number four at the Chernobyl nuclear power plant exploded on April 26, 1986, the exclusion zone surrounding the site remains one of the most closely studied landscapes in the world for understanding how wildlife responds to long-term radioactive contamination.The explosion, regarded as the world’s worst nuclear disaster, released radioactive material across large parts of Europe.

Winds carried radioactive dust as far as the United Kingdom, Norway and parts of North Africa. The immediate area surrounding the plant in northern Ukraine received the heaviest contamination, prompting the evacuation of tens of thousands of residents and the establishment of a 60-kilometre-wide exclusion zone where human activity sharply declined.

In the decades since, scientists have documented a landscape transformed not only by radiation but also by the near-total absence of people. Wolves, bears, bison, deer, wild boar and elk now move through forests and abandoned settlements that were once heavily populated.

Yet researchers say the question of whether radiation itself has changed wildlife through adaptation, mutation or selective survival remains unresolved.Pablo Burraco, an evolutionary biologist at Doñana Biological Station, part of Spain’s National Research Council, has spent years studying tree frogs in and around Chernobyl.

During his first field trip in 2016, he captured a male tree frog near the abandoned reactor site and noticed it was darker in colour than similar frogs found farther from the exclusion zone.That observation led to broader fieldwork involving more than 250 tree frogs.

In 2022, Burraco and his colleagues published findings showing that frogs inside the exclusion zone were, on average, darker than those outside it, particularly in areas that experienced the highest radiation exposure immediately after the 1986 accident.

The researchers proposed that the darker colour, linked to higher levels of melanin, may offer some protective advantage against ionising radiation. Melanin is known to play protective biological roles in many organisms, and the team suggested that darker frogs may have had better survival rates after the disaster.

Burraco has stressed that this remains a hypothesis rather than established proof. He argues that radiation levels today differ significantly from those immediately after the explosion, and that the frogs were sampled across habitats that were otherwise comparable.

Timothy Mousseau, a biologist at the University of South Carolina who has conducted extensive research in Chernobyl, has questioned the strength of that conclusion. He argues that the frog sampling was not broad enough to establish a clear distinction between frogs inside and outside the exclusion zone and says melanisation does not clearly correlate with present-day radiation levels.

Carmel Mothersill, professor emeritus of radiobiology at McMaster University, described the 2022 study as methodologically sound and noted that its authors were careful not to overstate their conclusions. She said the disagreement reflects a broader scientific challenge in Chernobyl research: separating the direct effects of radiation from other environmental pressures.

Heavy metals and other pollutants also remain present in the area, complicating efforts to isolate radiation as the sole cause of unusual biological traits. Similar debates surround studies of feral dogs living near Chernobyl, where researchers have observed genetic differences but have not established definitive evidence linking those changes directly to radiation exposure.

Bank voles have also become a focus of study. Research has shown that voles living in contaminated areas carry higher levels of genetic diversity in their mitochondria compared with those from uncontaminated regions. Scientists say these differences may reflect mutations caused by radiation exposure, though other ecological factors may also contribute.

Mothersill notes that the landscape itself changed dramatically after the accident. Pine forests, which are highly sensitive to radiation, suffered extensive die-off following fallout exposure. In some areas, birch trees replaced them, creating different habitats and altering the ecological balance.

“It’s teeming with trees and wildlife but it’s not the same as it was before the accident,” she has said, arguing that species responses may reflect habitat transformation as much as radiation exposure.The absence of people has also played a major role.

Species that were once rare or absent have returned. Brown bears, not recorded in the region for more than a century, were captured on camera traps inside the exclusion zone in 2014. Eurasian lynx have reappeared after disappearing long before the nuclear disaster.Wolf populations are estimated to be significantly higher inside the exclusion zone than in nearby protected reserves, likely supported by abundant prey and reduced human disturbance.

Groups of dogs descended from pets abandoned during the evacuation also continue to live in the area, often cared for informally by security personnel stationed around the zone.The question of whether some organisms have evolved true adaptations to survive radiation remains one of the most contested areas of research.

A 2012 study found evidence that soybeans grown in contaminated parts of Chernobyl had adapted to cope better with both radioactivity and heavy metal stress. Bank voles have also shown greater resistance to DNA damage, raising the possibility of inherited protective traits.Mousseau points to the black fungus growing inside the damaged reactor building as one of the strongest examples supporting this theory.

The fungus appears to benefit from increased melanin, which may provide resistance to ionising radiation.He says this supports the idea that melanin offers biological protection, though he rejects claims made by some researchers that the fungus has evolved to use radiation itself as an energy source for growth.

Experiments conducted aboard the International Space Station have also shown that some fungi become darker in response to radiation exposure, reinforcing the idea that melanisation may be adaptive.For Mothersill, the critical issue is whether mutations triggered immediately after the disaster have persisted across generations even as environmental radiation levels declined.

A 2006 study found that chromosomal abnormalities in bank voles continued through successive generations, even after the animals were moved to contamination-free laboratory conditions for reproduction.Not all species have benefited. Recent research suggests that barn swallows living around Chernobyl face increasing strain from the combined effects of radioactive heat exposure and rising global temperatures linked to climate change, reducing their resilience.

The radioactive legacy of Chernobyl also extends far beyond Ukraine. Small amounts of radionuclides linked to the disaster have been detected in edible mushrooms in Poland, blueberries sold in the United States and firewood burned in Greece, demonstrating the long reach of contamination decades after the explosion.

Jonathon Turnbull, a geographer at Durham University, says the exclusion zone should not be viewed simply as either a thriving wildlife refuge or a damaged wasteland.

He argues that the reality is more complex, shaped by radiation, ecological succession and the disappearance of human pressure.The Chernobyl zone, he says, is not evidence that nature has fully recovered or collapsed, but a place where multiple forces continue to reshape life long after the reactor fire was extinguished.

The release, organized by the Ukrainian Center for Chiropteran Rehabilitation, drew more than 1,000 attendees on Saturday evening, including families, off-duty soldiers and wildlife enthusiasts.

The event coincided with the onset of spring following a winter marked by subzero temperatures, repeated Russian drone and missile attacks, and widespread power disruptions.Volunteers opened cloth bags at dusk, allowing the bats to take flight as onlookers observed and applauded.

Many of the animals had been rescued from eastern regions affected by fighting, where destruction of buildings has disrupted natural habitats.Anastasiia Vovk, a volunteer with the rehabilitation center, said all 28 bat species in Ukraine are listed as protected due to declining populations.

She said conservation efforts were critical, noting that the animals are included on endangered species lists.Experts say the war has compounded threats to bat populations. Explosions and structural damage have destroyed traditional roosting sites, while disturbances during winter hibernation can be fatal.

Bats reproduce slowly, typically bearing one or two offspring annually, limiting population recovery.Alona Shulenko, who led the release, said habitat loss has forced bats into urban areas, where they shelter in buildings and balconies.

Repairs or demolition of such structures can destroy entire colonies, she added.Ukraine lies along an important eastern European migratory route for bats, all of which in the country are insect-eating and legally protected.

The rehabilitation center said it has rescued more than 30,000 bats overall, including around 4,000 during the past winter.Attendees described the event as a rare opportunity for normalcy amid the conflict.

Oleksii Beliaiev, a Kyiv resident attending with his family, said the gathering provided a temporary distraction from wartime pressures, though he noted the conflict remains the central concern for most Ukrainians.

Shulenko said the organization would continue its work despite the challenges posed by the war, emphasizing that halting rescue efforts could result in significant losses to already vulnerable bat populations.

Wearing a helmet fitted with a headlamp and a protective mask, molecular biologist Raúl da Silva Armando Chomela moves through the confined, low-light interiors of cave systems in central Mozambique, examining bat populations and their byproducts as part of a broader scientific effort to understand subterranean ecosystems.

Chomela, originally from the port city of Beira, has spent two years conducting research inside caves located in and around Gorongosa National Park, a 4,000 square kilometre conservation area recognized for its biodiversity.

His work focuses on bats and guano, a substance formed from accumulated bird and bat excrement that serves as a complex biological environment.“Guano is far more than just bat droppings,” Chomela said in an interview, describing it as a dynamic ecosystem.

According to his observations, guano supports a wide range of cave-dwelling organisms, including beetles, amphibians and microorganisms that have adapted to life in conditions without sunlight.

The caves in Gorongosa represent highly specialized environments. Organisms found within them have evolved to survive in stable, low-light conditions with distinct microbiomes that differ significantly from surface ecosystems.

These systems are characterized by limited external input and reliance on internal nutrient cycles, often driven by organic deposits such as guano.Chomela’s research involves entering narrow passages and descending into enclosed spaces using ropes and ladders, often without full knowledge of the terrain or species present.

According to the park’s science department, the cave networks in the region extend across approximately 183 square kilometres, forming interconnected underground systems.

More than 100 bat species have been identified in Gorongosa, although there is no precise data on how many inhabit these caves. One site, known as Tombo Aphale 5, has been extensively studied and hosts an estimated population of over 10,000 bats.

The cave is also the site of an active archaeological excavation, indicating its broader scientific relevance beyond ecological research.Gorongosa National Park was established in 1960 during Portuguese colonial administration.

Following Mozambique’s independence in 1975, conservation was not prioritized under the ruling Frelimo party. Two years later, the park became a strategic location during the country’s civil war, which involved government forces and the insurgent group Renamo.

Renamo, initially formed with support from the Rhodesian government under Ian Smith and later backed by apartheid-era South Africa, operated within the park’s terrain. During the conflict, armed groups relied on wildlife for sustenance, leading to widespread depletion of animal populations.

By the end of the war, which lasted more than 15 years, approximately 95% of the park’s wildlife had been lost, including nearly all of its estimated 5,500 hippos.The effects of the conflict extended beyond environmental damage.

Local communities experienced forced recruitment and other human rights abuses during the war, contributing to long-term social and economic challenges in the region.

In the decades since the conflict ended, Gorongosa has become the focus of sustained conservation and restoration efforts. These initiatives have involved partnerships between international institutions and Mozambican researchers, aiming to rebuild ecosystems and support local development.

One such initiative is the Paleo-Primate Project, established in 2018 as a collaboration between the University of Oxford and Gorongosa National Park. The project is led by Susana Carvalho and integrates research in archaeology, ecology and geology.

It also provides training and employment opportunities for local researchers and students.Carvalho said the broader Gorongosa Restoration Project has become a significant employer in the region, contributing to economic stability.

The project supports scientific research while also engaging local communities in conservation efforts.Chomela joined Gorongosa’s biodiversity laboratory in 2022 before becoming part of the Paleo-Primate Project in 2025.

His research spans multiple disciplines, including the use of environmental DNA to reconstruct historical ecosystems and metabarcoding techniques to analyze genetic material from bats and primates.

He is currently a first-year doctoral student at the University of Porto in Portugal, with his research based at the EO Wilson Laboratory in Chitengo, located within the park. In addition to his academic work, he leads the genetics laboratory at the facility, contributing to ongoing studies of biodiversity and ecosystem dynamics.

Chomela has also raised concerns about the potential overexploitation of guano resources. While the material is valued for its agricultural and economic uses, he noted that excessive harvesting could alter the composition of cave ecosystems.

“When they see the guano, they see money,” he said, adding that unsustainable extraction could disrupt the balance of species that depend on it.He emphasized the importance of building a scientific foundation to inform conservation practices and community engagement.

“We want a scientific base to convince the community,” he said, referring to efforts to align local economic interests with environmental sustainability.

The integration of scientific research, conservation policy and community involvement remains central to ongoing work in Gorongosa, as researchers continue to document and restore one of Africa’s most ecologically significant regions.