By the 1990s, many scholars of religion had entered the debate and begun to generate a substantial body of literature discussing and analyzing how nature is valued in the world's various religious systems. A landmark event was a series of ten conferences on Religion and Ecology organized by Yale University professors Mary Evelyn Tucker and John Grim and held at the Harvard University Center for the Study of World Religions from 1996 to 1998. More than 800 international scholars, religious leaders, and environmentalists participated in the conference series. The conferences concluded at the United Nations and at the American Museum of Natural History with more than 1,000 people in attendance. Papers from the conferences were published in a series of ten books (The Religions of the World and Ecology Book Series), one for each of the world's major religious traditions.