The Chernobyl fallout offered the possibility to test new monitoring methods and better understand the behaviour of radionuclides in natural and semi-natural environments. The research started after the Chernobyl accident confirmed previous knowledge, yet producing new information on the radioecology of forested ecosystems. Biological indicators were used with success to establish a relationship between ground deposition and radioactive transfer to wildlife and to evaluate the biological effects of ionizing radiations at low doses.