Now, its really without question that Ratzinger is a smart man, but I too found these comments to be ill-conceived.
What I imagine he was trying to do was to draw a parallel to the environmental crisis and the moral crisis Catholics see originating in the popular departure from natural law and perhaps the total abolition of "nature" as a moral category.
I think the observation is that, at a certain point, human beings conceived of civilization in a certain way that forgot nature, and the result is the present crisis where nature is being corrupted and becoming inhospitable for us because we have forced crude desires for efficiency, prosperity and its material pleasures over-top the natural rhythms and 'institutions' of the earth, violated their intrinsic laws, and are reaping the tragic and violent results. Likewise, there is a certain parallel here in a conceptualization of human sexuality that sees it without reference to those laws which arise out of nature itself- in this case its intrinsic link to procreation, and furthermore, the metaphysics which underlay "man and woman".
I think the Pope sees, in the calls to re-make much of society's industrial workings consonant with the regenerating laws of nature, a shift that points us towards moral considerations like that of homosexuality. I think there is real wisdom in this connection, as he says
"We need something like human ecology, meant in the right way."
Human sexuality is a more sublime sphere to be sure, but the Pope's point is that the question of man's "inner life" as well as his relationships with others are also called to be in accordance with certain laws of nature (in the philosophical sense), and that to ignore these moral questions is to make the error that gave rise to the present crisis on another plane of human existence that is, possibly, even more dear to us.