Polanski Log, a forest area extending between Mala Polana, Brezovica and Nedelica, is the largest black alder site in Europe. The alder needs a lot of water to grow. It survived here because groundwater remained on the surface in the forest throughout the year. Today the alder is under threat as a result of regulation work and decreasing rainfall, and alder forests are disappearing from our environment. Polanski Log is one of the rare surviving complete ecosystems in which besides the black alder many other endangered plant and animal species have their home.