Of all the ‘alternate’ artists I know, Andy Goldsworthy is perhaps the most famous. I first came to know of his work during a short visit to the Museum of Modern Art store in NYC. His book ‘A Collaboration with Nature‘ was on display, and I was in awe as soon as I flipped the cover.
Andy produces site-specific sculpture and land art situated in natural and urban settings. He only uses natural and found objects to create both temporary and permanent sculptures. There is tons of info on his wikipedia page and his official website.
(The image above is embedded from Andy Goldwater’s official website)