36 years later, how did nature regain its rights?

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[EN VIDÉO] Return to Chernobyl 30 years after the disaster
In 1986, an unprecedented accident occurred at the Chernobyl reactor in Ukraine, and then in the USSR. During the exercises, the power of reactor No. 4 was increased until an explosion occurred. Discovery Science Channel returns to this tragedy in a documentary that airs Tuesday, April 26, 2016 at 7:50 pm, an excerpt from which is reproduced here.

After the overclocking of reactor No. 4 of the Chernobyl nuclear power plant on April 26, 1986, the spread of radioactivity throughout Europe, even in Francebut especially in what is called Exclusion Zone, a perimeter of 30 kilometers around the plant. Various types of radiation were emitted and then absorbed by the environment, causing many changes that scientists have been trying to understand ever since.

To do this, not one, but several different methods are used, which are based on the same principle: the collection and analysis of field data. Population counting, footprints in the snow to determine the number of people, absorbed dose reconstruction: every detail counts. Combined with knowledge radiobiologyField observations allow researchers to recreate the evolution of populations in Chernobyl, whether in terms of numbers or even characteristics, and draw conclusions about the real consequences of this. accident on the biodiversity.

Fauna and flora adapted to radioactivity

Since radioactivity causes changes genetic different depending on the individual. The term “radioactivity” can also refer to different types of elements: atoms in the so-called unstable statewhich will gradually decrease according to their duration life, or gamma radiation which come from nuclear reactions. During such reactions, other radiations are also emitted, but they can only travel short distances, less than one centimeter, for example alpha and beta particles. But how then these radiations scattered then absorbed? In its report, the IRSN describes pollution environment: through water, through plants, through animals, radiation penetrates everywhere, and then remains mainly in the ground, hence the concern that follows Russian occupation Online.

In plants, if during the accident the radioactive elements are mainly absorbed by the leaves, after this first phase everything is transferred by the roots: there is no more radioactivity in the leaves.airso all pollution is internal. The radioactivity then gradually decreases as the plants grow and according to the progressive decay of each element: for example,iodine 131 quickly disappears until cesium 137 rest.

The researchers focused in particular on Japanese pines growing on Fukushima websitea variety very radiosensitive also present near the Chernobyl nuclear power plant. On this last site they noted in particular the death of 90% trees within a radius of ten kilometers around the reactors, creating “red forest”, gradually replaced by other species, such as birch or other shrubs. As for the rest of the pines, whether in Fukushima or Chernobyl, the observation was the same: they had undergone genetic modification. Them morphology changed from a main axis, a trunk, with branches growing on both sides, to a more bushy appearance. More precisely, we found “disappearance of the upper bud in favor of the lateral buds”explains IRSN in the report.

The entire food chain has been affected.

But, of course, not only plants suffered. If today many animals repopulate the exclusion zone, then immediately after the accident this was not the case: according to the study, the number of large animals has decreased by 60%. mammals a 10-fold increase in dose was observed in the most contaminated environments. Today they have returned and are descended from previous generations affected by the accident. Studies agree on this: these species have more genetic diversity than is normal among individuals due to multiple genetic mutations caused by radioactivity surrounding.

In several species of birds, researchers have found population declines in response to radiation exposure through reduced fertility, a well-known consequence of radiation exposure to living beings. They measured the speed fertility only 25% in the area of ​​infection, which led to a rapid decline in the number of birds. In particular, swallows have a high levelanomalies morphological, such as malformations beakfrom tumorsfrom’albinism partial observed. Finally, for all bird species, size reduction brain was observed, on average, by 5% compared with control zones devoid of radioactivity.

Few studies manage to draw conclusions about the entire ecosystem.

But if these studies were carried out on fauna and flora, ecosystem much more: it does not take into account the interaction between each species in a given location. For example, in the most polluted areas, there is a decrease in the number of birds and pollinating insects. Or, more precisely, calculated on the basis of real observations on the ground: a decrease in the number of fruit trees. Because these trees depend on insects for pollen dispersal and birds for seed dispersal, their evolution and that of the two species are closely related. These are what researchers call indirect effects.

Today, more than thirty-five years after the accident, most species have returned, but the radioactivity persists thanks to elements that slowly decay and accumulate in the earth. in cesium 137, for example, has a period half life about 30 years, decreased by just over 50%. The site remains accessible and much less dangerous, but caution is required.

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