The awards jury said her many books and articles make her a leading figure in the debate on sustainable development and the environment, with a special ability to translate science into practical recommendations.
"Gretchen C. Daily develops economic arguments for protecting biological diversity and ecosystems. She builds bridges between theory and practice," said Norwegian Environment Minister Erik Solheim, who presented the prize at a ceremony in Oslo.
The jury said an example of that was her 2002 book "The New Economy of Nature: The Quest to make Conservation Profitable," in which she explains the economic value of the world's natural resources and the potential profits of protecting them.
The prize was created in 1997 by Norwegian author Jostein Gaarder and his wife, Siri Dannevig, and named after Gaarder's surprise international best-seller "Sophie's World," a novel based on philosophy for young people.
Last year's prize went to former Swedish Prime Minister Goran Persson for his efforts to draw attention to the dangers of global warming.
