Thought this was a great comprehensive article on the many facets of ecopsychology, and the overlay with transpersonal psychology and non-duality specifically:

"The Transpersonal Dimensions of Ecopsychology: Nature, Nonduality, and Spiritual Practice" ~ John Davis, Ph.D., Naropa University, Boulder Colorado and School of Lost Borders, Big Pine, California

(Published in The Humanistic Psychologist, 1998 (Spring/Summer/Autumn), vol 26 (numbers 1-3), pages 60-100. Special issue on Humanistic Psychology and Ecopsychology (Elizabeth Roberts, Guest Editor) )