On April 26, 1986, the worst radiation disaster in history shook what is now northern Ukraine. As a result of design flaws and human errors, a catastrophic explosion occurred in the core of a nuclear reactor.
Radioactive contamination in the form of streams of steam and smoke from the damaged reactor was about 400 times larger than the atomic bombing of Hiroshima. Three months after the disaster, 30 employees and firefighters of the nuclear power plant died as a result of severe radioactive contamination. More than 100 thousand residents were evacuated: they were forced to abandon their houses, apartments, cars, photographs and toys, affected by radioactive fallout.
People are gradually returning to the area around the Chernobyl nuclear power plant. A government team, large enough to comply with the rules of work in the field of contamination, monitors the state of the reactor and the level of radiation in this area. Brave tourists are increasingly venturing to visit the nearby city of Pripyat: they inspect abandoned buildings and try to imagine life in Ukraine during the Soviet period. But it's not just tourists who show curiosity.
The contaminated soil of the Chernobyl Exclusion Zone, a no-man's land that is comparable in size to Yosemite National Park, is ripe for scientific research there. The destruction of the reactor created the conditions for the largest natural experiment on the planet in the field of nuclear safety. By observing the changes taking place - declining radioactive levels, declining populations, cancers among survivors, the slow destruction of abandoned towns and villages in the area - we can learn a lot about how wildlife copes with low levels of radioactive contamination, as well as others. long-term impacts after incidents at nuclear power plants.
Grasshoppers and "comets"
The new study, led by ecologist Andrea Bonisoli-Alquati at the University of North Carolina, used the common garden experiment to take this a step further, as well as fewer swamp grasshoppers (Chorthippus albomarginatus) caught in the Chernobyl exclusive zone and brought to the laboratory. The controlled situation in the laboratory allowed team members to investigate the effects of parental radiation contamination without worrying about the direct effects of radiation on the offspring.
To do this, they bred grasshoppers and watched the development of their offspring. Since radiation destroys DNA, breaks it apart, the researchers also measured the integrity of hemolymph (insect blood) with a new technique called comet assay. They placed the resulting DNA samples on a glass surface and exposed them to an electric current. Since DNA has a negative charge, its elements began to move towards the positive end. And in the case of damaged DNA, the smaller, destroyed parts moved farther than the heavier, preserved spirals. Scientists use the size of this part - the comet's tail - to determine the amount of damaged DNA in a sample.
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Based on the radiation exposure of the parent grasshoppers, it was impossible to predict what the DNA damage would be in their offspring. Those grasshoppers whose parents received high doses of radiation - 50.05 microsilberts per hour or the equivalent of three chest x-rays - received the same DNA destruction as those grasshoppers whose parents had a low level of infection - 0.02 microsilberts per hour (this is less than the amount of radiation emitted by a banana).
Perhaps they were helped by highly charged defense mechanisms that limit the effects of radiation. For example, grasshoppers from highly contaminated areas may experience less DNA damage because they have more antioxidants; or because they have more efficient proteins that can repair broken DNA strands.
This kind of defense mechanisms can provide an answer to the question of why the offspring of grasshoppers from more contaminated areas survive better, and this is due to the fact that more severe DNA damage weakens the cell's functions and its health.
The case of the grasshoppers is a small illustration of how mother nature finds a way to step back from the brink, make the necessary changes, and repair human damage. After the disaster in the spring of 1986, the remainder of the year was difficult for plants and animals in the area. Many of them have since been able to recover, and in 2015 the number of mammals in the Chernobyl zone was comparable to their number in neighboring areas that were not affected by radiation.
This resilience is remarkable, given that most of the contaminated area will not be safe for humans to live in for 20,000 years. The number of people in the Chernobyl exclusion zone is 200 (these are elderly self-settlers), and they were eventually allowed to stay there, so the forests around Chernobyl are now de facto a wildlife sanctuary. In other words, humans seem to pose a greater danger to animals than fallout.
Auricularia mushrooms, wolves and lynxes
Years of research work show that this exclusive zone is far from being a wasteland, as it is often tried to present to us in apocalyptic pictures of a nuclear winter after the third world war. Recent calculations based on observation from helicopters and the study of animal tracks have shown that there are seven times more wolves in the Chernobyl special zone than in neighboring regions. The installed traps with video and cameras suggest that such rare species as the elusive Eurasian lynx (last seen in this place more than a century ago) began to appear in this special zone.
During the turbulent 1990s, when poverty in the countryside increased and no one was involved in wildlife conservation, many tetrapods fell into the risk zone, and the Chernobyl zone turned out to be one of the few places in the former USSR where there was no sharp decline in the population of elk and wild boars. Some animal species have even learned to take advantage of the unique situation in which they find themselves: black fungus have been spotted in the reactor core. When curious scientists brought these mushrooms to the laboratory and exposed them to radiation, it turned out that they grow faster under such conditions, and it seemed that the mushrooms had adapted to the ionized radiation that the reactor emits to generate energy.
This does not mean that wildlife has escaped the devastating impact of the Chernobyl disaster. Some researchers generally doubt that there has been an increase in the animal population in the exclusion zone. Many invertebrates, including butterflies and spiders, are rarely seen in the most infested areas. Unlike roaming wolves and deer, invertebrates live and feed in a very limited space, and therefore they are forced to stay in highly infected places.
The swallows there were found to have a smaller brain and beak deformities. The reason for this kind of mutations is considered to be radioactive contamination, while other experts believe that the reason for this may actually be a decrease in human activity (swallows, like pigeons, coexist well with humans). Since the increase in radiation levels occurred at the same moment when people left the Chernobyl zone, it is difficult to say which factor - the absence of a person or prolonged exposure to radiation - caused these changes.
Mixed effects of this kind are often noted in observations and natural experiments, which make up the majority of the scientific literature on the Chernobyl disaster, and there are not so many data that can help solve existing problems. So, for example, we know very little about cancer diseases, about generic effects, genetic mutations (all this occurs as a result of long-term, classical exposure to radiation) in wildlife in the Chernobyl zone.
The history of the Chernobyl exclusion zone after the disaster seems to be rather complicated, but the situation there is not as grim as many predicted in the late 1980s. Wildlife has a tremendous capacity to absorb and respond to a disaster.
However, this remarkable ability has its drawbacks. Not a single ecosystem has been able to fully recover from a disaster comparable in scale to the Chernobyl one. Instead, a process of change and adaptation takes place. Human impact and climate change, two major new environmental challenges of our time, are likely to have impacts that are similar in complexity and unpredictability.
Some species, including rats and swallows, will be able to adapt, they will be fine, and even thrive. While others, such as elephants and bison, will not be able to adapt or will cease to exist altogether. We don't have enough knowledge to protect most species in one way or another. The amazing second chance at life for animals in the Chernobyl exclusion zone is a testament to how unpredictable evolution can be.
Brittney Borowiec