Lichens, mosses, higher plants: Following the reactor accident in Chernobyl, the radiocesium ( 137Cs ) activity in the lichen Pseudevernia furfuracea rose to over 50 000 Bq kg-1 d. w. from an initial value of approximately 400 Bq. The biological half-life of 137Cs in lichens and mosses was two to three years. The biological half-life of 90Sr was shorter than that of 137Cs, between 1.2 and 1.6 years. The biological half-life is not a constant value, it is increasing with time. The 137Cs concentrations in higher plants from forests (altitude approximately 1000 m) and pastures in the Styrian Koralpe were found to be still high today, 16 years after the Chernobyl accident. This is not the case for higher plants around Graz.