Robert Nelson at the top of Mount Kilimanjaro in 2002. (Family photo)

Robert H. Nelson, a professor at the University of Maryland and an author who wrote about belief systems and policies often thought to be in conflict, died Dec. 15 at a hotel in Helsinki, where he was attending a conference. He was 74.

The cause was acute appendicitis, said his wife, Jill Nelson.

Dr. Nelson joined the staff at U-Md.’s School of Public Policy in 1993 after 18 years as an Interior Department policy analyst. He trained as an economist but branched into other fields, including climate change and theology.

He wrote about the theological bases of economic theory in a 2001 book, “Economics as Religion,” and again in 2010 in “The New Holy Wars: Economic Religion vs. Environmental Religion in Contemporary America,” which explored not just the science behind environmentalism, but also the moral implications.

“Environmentalists see humans engaged in acts of vast hubris, remaking the future ecosystems of the Earth,” he wrote in an essay published in the Atlanta Journal-Constitution in 2010. “By playing ‘God’ with the Earth, humans seek to become as God themselves. The Bible’s book of Deuteronomy reveals dire consequences for those who try 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.’ ”

“It is no mere coincidence,” he continued, “that contemporary environmentalism prophesies virtually the same set of calamities resulting from the warming of the earth — rising seas, famine, drought, pestilence, hurricanes and other natural disasters. Even without realizing it, environmentalism is recasting ancient biblical messages to a new secular vocabulary.”

Robert Henry Nelson was born in Brockton, Mass., on Sept. 29, 1944. He graduated in 1966 from Brandeis University and received a doctorate in economics at Princeton University in 1971.

He taught at City College of New York before moving to the Washington area in 1975.

His books included “Zoning and Property Rights” (1977) and “God? Very Probably: Five Rational Ways of Thinking About the Question of a God” (2015).

Survivors include his wife of 47 years, Jill Wechsler Nelson of Chevy Chase, Md.; two children, Fred Nelson of Underhill, Vt., and Martha I. Nelson of Washington; and three grandchildren.