Missionaries to the planet.

Green Sisters: A Spiritual Ecology, by Sarah McFarland Taylor. Harvard University Press.

Call them what you will--"green nuns," "eco-nuns," or "green sisters"--but across the country Roman Catholic vowed women are actively engaged in tending and healing the earth. Their grassroots movement is growing in numbers and influence. When Sarah McFarland Taylor, now an assistant professor of religion at Northwestern University, began her research back in 1995, she was able to identify only about a dozen "ecological learning centers" run by Catholic sisters in North America. By 2006 she could document at least 50 such ministries, and she notes that today there are now "green sisters'" involved in eco-justice ministries all over the world.

Neither Catholic nor a member of a religious community, Taylor offers the perspective of an "intimate outsider," and in this absorbing and comprehensive study of the "greening of religion" in Catholic religious communities, she takes the reader on a tour of everything from a biodynamic farm in New Jersey to a community garden in inner-city Detroit that replaced a burned-down crack house. Although this is a work of extensive academic research and scholarship, the narrative reflects the author's hands-on contact with her subject, and so we join her in peering into the geothermal tank in the basement of a motherhouse in Indiana, in shucking garlic on the porch of an old Victorian main house in Ohio, and in interpreting--and recovering from--a particularly intense retreat experience at a Sisters of Earth conference in Holyoke, Massachusetts.

Along the way Taylor gives a stirring account of how Catholic religious communities long committed to social justice and peace have come to connect with environmental concerns and ecological activism. She offers a very helpful critique of agribusiness that monopolizes seed distribution worldwide and of the bioengineering that renders seeds sterile, and she describes the myriad ways in which these sisters are confronting our planetary crisis--from "greening" their vows to speaking out at a General Electric shareholders meeting.

THE TEXT MAY be packed with facts and footnotes, but its author--and the women she quotes--are clearly passionate about their convictions, and sometimes funny. To cite just one example, Sister Miriam MacGillis, cofounder of Genesis Farm in New Jersey, is quoted as proclaiming, "If we truly saw the Divine in a potato, we could not turn potatoes into Pringles! It would be sacrilege to do so."

Taylor is particularly compelling when she discusses the different ways these religious communities understand themselves as being caretakers of the deep core of their Catholic heritage, even as they push Christianity to enter what theologian Mary Evelyn Tucker has called its "ecological phase." These Catholic "missionaries to the planet" live in some tension not only with mainstream American capitalist culture but also with Catholic doctrines and practices as conventionally understood. "Green sisters" are sometimes accused of being New Age pantheists and nature worshippers, and Taylor provides a thoughtful account of some of the charges and how the sisters have replied.

This intriguing book will raise provocative questions for the Christian reader. What are the risks and rewards of replacing distinctly Christian language with the language of contemporary cosmological physics as interpreted by Thomas Berry? Are solstice and equinox rituals necessarily a sign of "paganism" or "neo-paganism," or can they be integrated into a specifically Christian life of prayer? Is it theologically sound to argue that the "passion of the earth" is an extension of Christ's passion? How does it affect our prayer and our community life when walking "stations of the earth" replaces walking the Stations of the Cross? Are Christian symbols and rituals being emptied of their distinctly Christian content, or is their meaning being wonderfully deepened and expanded?

Whatever the reader may decide about such questions, Taylor is convincing in her claim that religion is as dynamic as any other living system and is in a perpetual process of change and creative redefinition. She is also persuasive when she portrays these religious women's communities as active participants in shaping the next chapter of Christian theology and practice.

If there is anyone out there who is still laboring under the illusion that environmental issues have no connection to, and are secondary to, issues of social justice, this book should help put that fond belief to rest. As one sister who works with the poor succinctly puts it, "If we look out for the earth, we're looking out for each other."

Green Sisters is an academic work of wide-ranging research and scholarship, but it should appeal to any reader who is interested in environmental activism, nature mysticism, social justice, feminism, Catholicism, or monasticism. Green Sisters makes an important contribution both to contemporary American religious history and to women's religious history.

Margaret Bullitt-Jonas is an Episcopal priest and serves on the leadership council of the interfaith network Religious Witness for the Earth.