THERE ARE PLENTY of fish in the sea, teaches an old adage – the formulators of old adages apparently having left out of their calculations the brute reality of overfishing. Eating seafood now involves a rather complex moral calculation, as Patricia Unterman explains in a recent food column in the San Francisco Examiner. Seafood is, generally speaking, healthful, and if it is cooked right, it is often sublimely flavorful, but there is drastic variability in environmental consequences. Some seafood is abundant and carefully taken, and quite a lot isn't, and it's become increasingly difficult to ignore that divide and its serious consequences.

"Now every morning," Unterman (who owns the 25-year-old Hayes Street Grill) writes, "I have a surrealistic conversation with my fish man about what I morally can serve in the restaurant, hitting upon reproductive cycles, fishing techniques and sonar radar."

Surrealistic: that is a word from unhappy-camperdom. Unterman does not exactly say she is irritated at the duty of moral arbitration circumstances have forced upon her (can she serve this? should she serve that?), but she does remind us more than once that originally she was "driven by an esthetic, and a desire to give pleasure." Clearly she did not foresee "that the restaurant would become a battleground, an educational tool and a political platform about the ecological repercussions of what we eat."

As readers of our column the Food Snoop know, it is possible to take a full measure of satisfaction from eating while serving the cause of sustainability – sustainability being a slightly less grim term than survival. For if our kind is to survive, the biosphere that sustains us must also survive. And the greatest threat to that biosphere is, paradoxically, too much human survival.

Yes, too many mouths to feed. The real message to be gleaned from recent well-publicized battles about overfishing and genetically modified food is that there are simply far too many of us crowded onto this small planet. Hence the ever mounting strains on the world's fisheries, the ever mounting pressure to make the land yield more, until one day, as the insane television advertisement of Archer Daniels Midland suggests, all the globe will be a farm field – growing tomatoes with mouse genes.

The obvious answer to this unacknowledged crisis is that we should spend less time, money, and genius on managing the populations of other living things and more on managing our own. Yet that is not the human way; like bacteria in a comfy petri dish, we will go on blithely proliferating until all the world's a baby stroller from which will emanate yowls of hunger, because all our cupboards will be bare.