The Pope began weighing in on environmental themes in 2006. His strong defence of the Amazon’s fragile ecology, his appeals for safe water and his warnings on pollution’s burden on the poor all received general acclamation.

When he approved the installation of solar panels on several Vatican buildings and funded tree-planting in Hungary, the Vatican drew praise. But lately, the Pope’s words on ecology have raised eyebrows and even objections.

In a speech Jan. 11 to the diplomatic corps, the Pope extended the discussion of “human ecology” to same-sex marriage.

“Creatures differ from one another and can be protected, or endangered, in different ways, as we know from daily experience. One such attack comes from laws or proposals which, in the name of fighting discrimination, strike at the biological basis of the difference between the sexes,” he said.

That prompted protests from activists, including the head of an Italian gay organization, who said the Pope’s linkage of gay marriage and ecological irresponsibility was “almost comical.”

Benedict, however, was not trying to score a cheap political point. His argument touched on what might be called the leitmotif of his pontificate: man is not God, and man’s actions should correspond to God’s plan.

In 2004, in a major doctrinal document on the relationship of men and women, then-Cardinal Joseph Ratzinger said “obscuring of the difference or duality of the sexes” was part of a misguided effort to free the human being from biological conditioning.

Addressing the diplomats, the Pope said he was thinking of legislative initiatives in countries in Europe, North America and South America. Three days earlier, the Parliament in heavily Catholic Portugal was the latest to legalize same-sex marriage.

The Pope underlined that protecting the environment makes no sense unless it begins with protecting human life, including the life of the unborn. Here, too, the Pope was emphasizing that the church’s green philosophy always puts the human at the center, because humans are made in God’s image.

The Pope’s analysis of morality and ecology went in several other directions. One of his strongest points to the diplomats was that protecting creation demands a re-allocation of resources away from military spending and the development of nuclear weapons. It echoed an appeal for disarmament in his World Peace Day message Jan. 1, which was dedicated to the environment. The Pope said continued existence of nuclear weapons “threatens the life of the planet and the ongoing integral development of the present generation and of generations yet to come.”

The Pope noted many current conflicts around the world arose from a struggle for natural resources, and in turn inflict immense harm on the environment. He looked at the connection between environmental destruction and migration, and pointed to the drug trade in places like Afghanistan, where agriculture is largely dedicated to the production of narcotics. “If we want peace, we need to preserve creation by rechanneling these activities,” he said.

In short, the Pope’s analysis is not a simple one, nor is it easily categorized. His environmental “position” touches on climate change (he urged an international agreement, warning that the future of some island nations is at stake) and the global economic crisis (which he blames in part on the selfish activities of the investment industry).

He sees the ecological crisis as part of a wider moral crisis, and the common denominator is what he calls a “self-centered and materialistic way of thinking which fails to acknowledge the limitations inherent in every creature.”