Far be it from me to try to steal some of the thunder of Pope Francis, but he has plenty of thunder to spare and is generous enough not to begrudge such efforts. I will therefore venture to suggest, amidst the increasing media hoopla over his encyclical on ecology--to be released tomorrow--that what he says is almost certainly going to be far from revolutionary or even very original in some respects. (This is as it should be for, as Fr. John Hunwicke rightly and repeatedly says, the job of the pope is to be a remora or a breakwater against innovation.) By that I mean that other Christian leaders, pre-eminent among them the Ecumenical ("Green") Patriarch Bartholomew, have been writing on ecological themes for decades, a fact that seems to have been acknowledged by the pope in having Met. John Zizioulas be one of the people involved with the official presentation of the encyclical on Thursday--and a fact, moreover, acknowledged in the text if the leaked draft's footnotes are anything to go by. Though one should not expect the dim and highly selective cheerleaders in the media to know this history of Eastern Christian theologizing about ecology, I drew attention to such Eastern Christian publications most recently in 2015. For earlier publications, see here but also here in 2014, and in 2011 here. (None of this, nota bene, is to gainsay what the pope will say, which deserves careful and respectful attention.)
In addition, for those seeking practical advice, His All-Holiness Bartholomew has written a preface to Greening the Orthodox Parish: A Handbook for Christian Ecological Practice.
Other Orthodox scholars have written on the topic, including Elizabeth Theokritoff, Living in God's Creation: Orthodox Perspectives on Ecology (SVS Press, 2009), 266pp.
The Orthodox scholar John Chryssavgiss has also edited a hefty collection, Toward an Ecology of Transfiguration: Orthodox Christian Perspectives on Environment, Nature, and Creation (Fordham University Press, 2013), 508pp.
Chryssavgiss also authored an informative piece here on how the Ecumenical Patriarch came to be know as the "Green Patriarch." And he edited another important collection: In the World, Yet Not of the World: Social and Global Initiatives of Ecumenical Patriarch Bartholomew.