Animal Radioecology in the Exclusion Zone Since the Chernobyl Catastrophe

We review 20 year long investigations by the Schmalhausen Institute of Zoology on radioecological and ecological consequences of the Chernobyl catastrophe for wild animals in the Exclusion Zone (EZ) around the nuclear plant. Using previous observations on bird migrations through Ukraine, we assessed the ¹³⁷ Cs and ⁹⁰ Sr carry-out with migrants from the EZ. In addition, we selected animal species as standard indicators of the state of the environment to map: 1) contamination of vertebrates with 137 Cs in the EZ and 2) beta-activity of mollusc shells indicating ⁹⁰ Sr, in the whole Dnieper drainage area, in the Kiev Administrative Region, and in the EZ. We revealed regular seasonal and long-term trends, relative radionuclide accumulation by different species, transfer and accumulation factors, and used these measurements to diminish the enormous variation and complexity of the data. Secondary ecological changes in forest, devastated by direct irradiation, were caused by the crash of trophic chains and an outbreak of insect pests on dead or sick trees. Ninety-nine percent of the EZ area was not affected directly by irradiation. Ecological changes in this area have been caused by evacuation of the public, cessation of agriculture and forest management, and decontamination on a large scale. After initial changes, animal density and distribution have been stabilized at a limit restricted by natural resources, predators and poachers. A herd of Przewalski horses was successfully introduced into the EZ years ago. We renewed the protected state of nature reserved sites, which existed before, and proposed to expand the area of nature reservation.