Charitable and voluntary organisations also have important roles to play. The National Trust for Scotland is the conservation charity that protects and promotes Scotland's natural and cultural heritage. With more than 270,000 members it is the largest conservation charity in Scotland. The Scottish Wildlife Trust is a leading voluntary conservation organisation, working to protect Scotland's natural environment. The Royal Zoological Society of Scotland is a learned society and registered charity that maintains Edinburgh Zoo and the Highland Wildlife Park (a safari park and zoo near Kingussie, which specialises in native fauna). The Society is also involved in various conservation programs around Scotland and the world. The Royal Society for the Protection of Birds promotes conservation of birds and other wildlife through the protection and re-creation of habitats. The John Muir Trust is a charity whose main role is as a guardian of wild land and wildlife, through the ownership of land and the promotion of education and conservation. The trust owns and manages estates in locations including Knoydart and Assynt, and on the isle of Skye. It has links with the Sierra Club in the United States, which also celebrates the legacy of Dunbar-born John Muir. Trees for Life is a charity that aims to restore a "wild forest" in the Northwest Highlands and Grampian Mountains.