Greenmuseum is a virtual space for environmental art with a lot of useful material. Among the featured artists is Agnes Denes, who is probably still best known for ploughing two acres of Manhattan with wheat in her 1982 work Wheatfield – A Confrontation (see above). A year later she designed Tree Mountain-Proposal for a Forest, a work that remained conceptual until the Finnish government announced at the 1992 Earth Summit that it would build the mountain. It would include 11,000 trees, planted by volunteers from around the world. Construction was finished in 1996, but of course the work continues to change: the site is legally protected for four hundred years. Each tree is owned by the person who planted it and their descendents, which means that ownership of an art work is also custodianship of nature. Whilst the trees will outlive their current owners and change hands, the forest itself cannot be owned by anyone. Images from the construction of TreeMountain are available here and there are more recent photographs of the project illustrating a short essay by Agnes Denes, ‘What it Means to Plant a Forest’.