Soil degradation is caused by geological, climatic and biological factors, as well as human activities. One kind of degradation involves loss of soil biodiversity as a result of global environmental changes. A study on earthworms was carried out near Ustrzyki Górne in the Bieszczady Mts (Poland), on a monthly basis, in 1986–1987 and 2009–2010 at various sites within the Carpathian beech forests (Fagetum carpaticum). During the years 1986–1987, a total of 13 species of earthworms were found: 6 species on site I, 8 species on site II, and 9 species were recorded within the site III. The highest abundance, i.e. 11 species was found on site IV. The study, which revisited the same locations in 2009–2010, identified only 10 species. In sites I, II and III, 7 earthworm species were found in each, and in site IV –10 species. The authors also investigated the factors endangering the fauna of earthworms in the Bieszczady Mountains, and following the example set by other countries which had made attempts to introduce earthworms into the red lists of the threatened species, it was proposed that such a procedure should be adopted for the endemic species O. transpadanus. It was also observed that specimens of L. terrestris had penetrated the natural areas of the National Park.