The Sihl forest, a regional nature park of national importance, is the first nature reserve in Switzerland to be awarded the Naturerlebnispark (Nature Discovery Park) label and certified as such. The Sihl forest has been left to its own devices since 2000 and nature allowed to take its course undisturbed. A wilderness is in the course of being created. There is a large amount of deadwood in the natural forest reserve due to fallen trees being left to decay where they fall. The Wildnispark Zurich Foundation enforces the cantonal protection ordinance for the Sihl forest on behalf of Canton Zurich. The foundation is sponsored by the City of Zurich, Canton Zurich, the Horgen district municipalities and Pro Natura Zurich. See www.wildnispark.ch for further information.