This article explores the growing movement of environmentally activist Roman Catholic women religious in North America and the implications of this movement for theorizing new directions in religion and culture. Sisters' creative efforts to conserve traditional religious and cultural forms while opening up these forms to "greener" (ecologically-minded) interpretations reveals the very protean process of religious meaning-making. It also subsequently challenges more static and conventional theoretical models of religion. In particular, the author documents and analyzes the intertwining of bioregional philosophies of "reinhabitation," expressions of American Catholic religious life, and manifestations of "green culture." Integrating geographic, ethnographic, and historical methodologies, the author argues that when researchers approach the study of religion as "biogeographers," they discover complex levels of religious understanding and expression that are otherwise overlooked. Significantly, it is these frequently-missed dimensions of the religious landscape that more accurately reflect the "living and lived" quality of religion.