Many pundits agree that if we don’t heed the warnings all around us, the barriers we put up to protect ourselves against nature may well turn out to be our self-inflicted weapons of mass destruction.

I have long believed that these bastions we erect will be our undoing. Like the hapless people inside a besieged fortress in the Dark Ages, we are gradually walling ourselves off from the sources that sustain us. Eventually our supplies will run out. Since we can’t see the walls that we build, we...