Lithuanian ecosystems include natural and semi-natural (forests, bogs, wetlands and meadows), and anthropogenic (agrarian and urban) ecosystems. Among natural ecosystems, forests are particularly important to Lithuania, covering 33% of the country's territory. Wetlands (raised bogs, fens, transitional mires, etc.) cover 7.9% of the country, with 70% of wetlands having been lost due to drainage and peat extraction between 1960 and 1980. Changes in wetland plant communities resulted in the replacement of moss and grass communities by trees and shrubs, and fens not directly affected by land reclamation have become drier as a result of a drop in the water table. There are 29,000 rivers with a total length of 64,000 km in Lithuania, the Nemunas River basin occupying 74% of the territory of the country. Due to the construction of dams, approximately 70% of spawning sites of potential catadromous fish species have disappeared. In some cases, river and lake ecosystems continue to be impacted by anthropogenic eutrophication.