The age of the forest and the range of habitats it contains make it a valuable area for wildlife, and it is designated as a Site of Special Scientific Interest. Its former status as a working or pasture forest has had a great effect on its ecology. This is particularly evident with the pollarded trees, which, as they have not been cut since the passing of the Epping Forest Act, have now grown massive crowns of thick, trunk-like branches with correspondingly large boles. This gives the trees an unusual appearance, uncommon in other forests. Often the weight of the branches cannot be supported by the parent tree, and the large amount of dead wood in the forest supports numerous rare species of fungi and invertebrates. Epping Forest has 55,000 ancient trees, more than any other single site in the United Kingdom.