This article traces global ideas of nature in Islam and analyses local developments in environmentalism in Indonesia, the most populous Muslim country. Based on theological considerations of cosmos, earth and humans, it investigates how religious scholars (ulama) of the Muslim world argue for environmentalism. Moreover, since Muslim actors in environmental debates have a tendency to differentiate from the West and resort to Islamic norms and values, this essay addresses the question of how Muslim authorities, from international as well as national Indonesian backgrounds, articulate cultural and religious identities. In this context, the issue addressed is how classical literary sources and traditional cultural elements are used in controversial debates on environmentalism. Furthermore, this paper analyses how the largest Indonesian Muslim welfare organisation, Nahdlatul Ulama, and its affiliated Islamic boarding schools (pesantren), have been responding to environmental challenges.