At a conference near Istanbul last June, the chimpanzee expert Jane Goodall spoke about the endangered habitat of what she called “our closest relatives.” Underlining the evolutionary link, she described her encounter with a senior male ape who had a “beautiful white beard.”

With a smile, she turned to the 72-year-old man in the front row and added, “Very much like yours.”

The man with the long white beard was Ecumenical Patriarch Bartholomew I of Constantinople, the spiritual leader of the world’s Orthodox Christians. Fortunately, he is known for his easy, affable manner, and he joined the laughter that followed.

But his commitment to environmental activism is deeply serious, earning him the nickname the Green Patriarch. He has preached that caring for the environment is a religious imperative, and for more than a decade, he has made a point of bringing together theologians and scientists like Dr. Goodall for debates and briefings.

This year’s reports of record melting of the earth’s ice sheets and extreme droughts have given a new urgency to Bartholomew’s messages about the degrading natural world. While economists and politicians prescribe more growth and consumption to overcome economic crises, the patriarch insists that the real crisis is cultural and spiritual, and can be overcome only by moving away from rampant materialism.