This paper examines the writings of a prominent contemporary environmental activist, Julia Butterfly Hill, in light of the resonance between her own account of her two year tree-sit atop a California redwood and motifs from the history of religions. Environmentalism is often derided as a new religion. Acknowledging this critique, the paper argues that, indeed, a significant part of Hill’s public appeal lies in the religious elements in her actions and ideas. Like Byzantine Stylite saints, her charisma is indebted to her asceticism. Hill’s environmentalism is not a new religion, but it is a manifestation of overlapping environmental and religious sensibilities. This religious environmentalism or environmental religiosity may be new but it draws on very ancient religious associations between nature and the sacred. If Hill is representative of a new eco-piety, her eco-piety is informed not only by these archaic and archetypal elements, it is also derived from and influenced by Christian piety. Finally, if asceticism generates charisma, it also generates heightened awareness and sensory sensitivity—in Hill’s case, the claim to be able to listen to her tree and the message of the forest.