On April 26, 1986, in Chernobyl (Ukraine), the largest and most serious nuclear accident in history took place , above the one that happened in Fukushima. The nuclear power plant suffered a core meltdown, which caused a large hydrogen explosion that blew off the reactor lid. A radioactive cloud of 162,000 square kilometers spread across Europe and reached North America.
This accident represents the largest release of radioactive material into the environment in history , with a volume 500 times greater than that of the Hiroshima atomic bomb.
In order to reduce human exposure to this source of radiation, after the accident, the area was evacuated and an exclusion zone of 30 kilometers in radius was established around the plant, in which the presence of settlements and activities was prohibited.
However, the wildlife was still there. And he suffered the consequences of the accident.
Life after the catastrophe
The intense ionizing radiation caused widespread damage to the DNA of living beings exposed to it and, with it, biodiversity was reduced. However, not all living things suffered negative consequences . Certain populations have recovered from the disaster, and there are signs of adaptation to radiation. The scientific debate about the long-term effects of exposure to moderate levels of ionizing radiation continues.
In communities of microorganisms , no change in the diversity of bacteria is observed between areas with high and low levels of radiation. However, the species composition does change. Radiation-resistant bacteria and archaea have been found in the exclusion zone, which are poorly or not represented in the cleaner zones. Some species capable of reducing uranium stand out.
Plants: Adaptable Survivors
The plants were the ones that retained the largest amount of radioactive fallout from the beginning; between 60 and 90 % of the radioactive isotopes were initially intercepted by the dense canopy of pine trees . The first signs of injury were yellowing and death of the needles, which began two weeks after the accident. As they ended up falling to the ground, most of the isotopes migrated to the litter in less than two months, and remained there for 7 years.
Four zones of vegetation affected in different ways were observed. On the one hand, the radiation was lethal in an area of 600 hectares. In an area of 3,800 hectares there was a partial mortality — between half and three quarters of the trees withered — and those that remained alive stopped growing and reproducing for more than 5 years. A third area of 11,900 hectares suffered moderate damage, with growth failure and partial female sterility. The area that suffered the least damage covered the rest of the forest in the exclusion zone, and although there was also growth inhibition, it was observed that reproduction continued.
Herbaceous plants, meanwhile, received less radiation and more gradually, which allowed them to adapt to radiation. Still, during the first year, flowering and reproduction were severely affected.
In general, there was a higher rate of mutations in the plant cover , which caused growth deformities. Stem branching, duplication of clusters, changes in color and size of leaves and flowers, and gigantism were observed.
Animals: mutation or extinction
Mutations were also abundant among animals. Many caused their death and serious damage to their populations. But life makes its way, and a disturbance can open new doors to the evolutionary process .
An independent recent evolutionary history has been found in some surviving frog populations compared to other European populations. A high rate of mitochondrial mutation has been observed in these frogs. It is thought that they were able to offset the impact of harmful mutations by having huge clutches full of eggs. Selective pressure would act strongly on them, hence the populations have few highly mutated individuals.
Mutations have also been observed in birds. In the barn swallow, cases of partial albinism and asymmetry in the feathers have been detected . These mutations, very rare in nature, have increased fivefold in the exclusion area.
Most of the mammals that suffered the accident did not live long. However, the area was soon colonized again by rodents, wolves, roe deer, elk, wild boar and deer , coming from nearby less affected areas.
In the vicinity of Chernobyl, rodents are currently the most abundant group of mammals. The high speed of reproduction and the very numerous litters make them very apt to withstand the effects of chronic radiation.
However, that did not make them immune to mutations. more than 20 % of northern voles (Microtus oeconomus ) in the region suffer from hyperchromic anemia . Liver, endocrine and kidney problems have also been observed.
nature moves on
The effects of mutations and alterations in animals, plants and microorganisms are reflected in the ecosystem. The role of the evolutionary processes triggered by the Chernobyl disaster 36 years ago is still not fully understood, and more long-term observations will be needed to understand the resulting ecological dynamics.
Large-scale studies have, however, provided unique insights into nature’s responses at different levels of biological organization—from the molecular to the ecosystem level—and under conditions of changing radioactive contamination, from virtually zero to lethal levels. .
This information makes it possible to understand the environmental risks of ionizing radiation . In this sense, Chernobyl has become a unique test site in the world.
Meanwhile, in the exclusion zone, life makes its way, developing unique ecosystems, adapted to the chronic presence of this radiation.
REFERENCES:
Geras’kin, S. A. et al. 2008. Effects of non-human species irradiation after the Chernobyl NPP accident. Environment International, 34(6), 880-897. DOI: 10.1016/j.envint.2007.12.012IAEA. 2016, noviembre 7. Frequently Asked Chernobyl Questions [Text].International Atomic Energy Agency; IAEA.Moller, A. et al. 2006. Biological consequences of Chernobyl: 20 years on. Trends inEcology & Evolution, 21(4), 200-207. DOI: 10.1016/j.tree.2006.01.008Videvall, E. et al. 2022. Impact of ionizing radiation on the environmentalmicrobiomes of Chernobyl wetlands [Preprint]. Ecology. DOI: 10.1101/2022.01.17.476627
