Friday, April 22, is the 41st anniversary of Earth Day. The theme this year is “A Billion Acts of Green” and we’re asked, like recovering sinners, to reform our ways: take our baths with less water, turn off the lights, spend less time on the computer, watch less TV, reduce our toilet paper consumption, and make a donation.

Getting an early start, the Environmental Protection Agency (EPA) observed Earth Day this past weekend (April 16-17) on the National Mall, with 40 exhibits.

As all this suggests, environmentalism has become our newest religion. According to Joel Garreau, professor of law, culture and values at the Sandra Day O’Connor College of Law at Arizona State University, a religion is characterized by “a distinction between sacred and profane objects; a moral code; feelings of awe, mystery and guilt; adoration in the presence of sacred objects and during rituals; a worldview that includes a notion of where the individual fits; and a cohesive social group of the likeminded.” Environmentalism, Garreau concluded in an article last year, fits this definition of religion very well.

Environmental historian William Cronon of the University of Wisconsin, Madison—president-elect of the American Historical Association—writes of environmentalism that it has “certain landscapes—usually the wildest and most natural ones—[that] are celebrated as sacred”; it is “openly prophetic”; it develops frequent “parallels to biblical prophecy in the Hebrew and Christian traditions”; and it offers “practical moral guidance about virtually every aspect of daily life. . . . from the apocalyptic to the mundane.”

Then-Senator Al Gore, environmentalism’s leading convert, in 1992 declared in “Earth in the Balance” that “the more deeply I search for the roots of the global environmental crisis, the more I am convinced that it is an outer manifestation of an inner crisis that is, for lack of a better word, spiritual.”

As such, issues such as climate change involve more than just “science.” The Bible’s book of Deuteronomy reveals dire consequences for those who seek to “play God.” We learn that God will strike down sinners who “worship other gods,” causing them to suffer “infections, plague and war. He will blight your crops, covering them with mildew. All these devastations shall pursue you until you perish.”

Contemporary environmentalism prophesies virtually the same set of environmental calamities resulting from global warming: rising seas, famine, drought, pestilence, hurricanes and other natural disasters. Often without realizing it, environmentalism is recasting traditional biblical messages. The Endangered Species Act replaces Noah’s Ark; wilderness areas are the environmental “cathedrals”; Earth Day is the new “Easter,” a time for deep religious reflection and revival.

Environmentalism thus is literally, not simply metaphorically, a new religion.

This raises difficult constitutional and political questions that have yet to be addressed—or even recognized—in American public debate. As University of Alabama law professor Andrew Morris and co-author Benjamin Cramer ask in a pioneering 2009 article, “Disestablishing Environmentalism,” published in the journal Environmental Law, how can we reconcile the character of environmentalism as an actual religion with the constitutional principle of separation of church and state?

It is clear, for example, that environmental religion is being actively proselytized in U.S. public schools. Similar proselytizing by Jews or Christians would be strictly prohibited.

In 1961, Justice Hugo Black wrote for a unanimous U.S. Supreme Court that government was constitutionally prohibited from aiding “those religions based on a belief in the existence of God as against those religions founded on different beliefs”—the latter including “Ethical Culture” and “Secular Humanism” in the justice’s definition of religion. The obverse also must hold: nontraditional religions cannot be favored over traditional ones.

In a 1965 Court opinion dealing with conscientious objection to military service, Justice Tom Clark quoted one of the great theologians of the 20th century, Paul Tillich, to the effect that a religion necessarily involves a core “idea in which meaning within meaninglessness is affirmed.”

But, according to Tillich, this need not be “the God of traditional theism.” Indeed, not unlike Justice Black’s earlier opinion, a religion was appropriately defined as a belief system that dealt with “ultimate concerns” and that may include a concept of “the power of being, which works through those who have no name for it, not even the name God”—such as environmentalism today.

Constitutional scholars have often lamented that past Supreme Court reasoning relating to separation of church and state is far from a model of judicial clarity. But this much is clear: Government cannot officially favor one religion over another, as government is now doing in declaring Earth Day and establishing environmental religion. The solution admittedly is not so clear. Let the discussion begin.