I'd been invited to lunch with a group of fellow enviros at a posh downtown restaurant. The atmosphere started out casual and friendly. There was no indication from the topics under discussion – the usual banter on overpopulation, global warming, resource depletion and mass extinctions – that things might get ugly. As I recall, it was about the time we started ordering from the menu that the group’s good mood began to subtly change.

“Let’s see… you know, I haven’t had a good steak in a long time,” said the Sierra Club member at the end of the table. “I’ll have the eight-ounce sirloin.”

“Surely you jest!” I blurted in spite of myself. “You could serve up to 50 people each a cup of cooked cereal from the feed cost of your eight-ouncer. It’s right here on page 14 of Diet for a Small Planet.”

“I guess you’re right,” he muttered. “I’ll just have a hamburger.” Then he turned and whispered something to the Earth First! person on his left. I’m not sure, but I think it was, “Who invited this guy?”

Unfazed by his rudeness, I tried as best I could to hold up my end of the conversation. “If you really believe that more of Central and South America’s precious rain forests should be converted to rangeland just so you can buy a cheap hamburger, go ahead – enjoy,” I said. “Just remember that with every bite there will be less diversity of fauna and flora on this planet.”

I never did get to hear what the Sierra beefeater said. I was much too busy listening to what the Greenpeacer next to me was ordering.

“Waiter, I’ll have the swordfish. It’s not often you find grilled swordfish at this price.”

“If we keep on over-fishing the oceans, pretty soon you won’t be able to find swordfish at any price,” I scolded, pointing my breadstick at him. “With the world fish catch already estimated to be at or beyond its maximum sustainable level, and with world population still increasing, the per capita fish catch is actually going down. And, meanwhile, the number of commercially extinct species of fish continues to grow.”

Parrying my breadstick with his own, the Greenpeacer tried to shut me up and take the higher moral ground with a quick switch to fettuccini, but it was too late.

“And what about biological magnification?” I continued in high spirits, trying to remember the last time I had so thoroughly enjoyed a conversation. “You know as well as I do how dangerous pollutants like mercury can become increasingly concentrated as they are passed through higher levels of the ocean food chain to predatory fish such as tuna and swordfish. Have you had your daily dose of mercury today?”

“I’ll just have an omelet,” said the Audubon woman to my right. Then she slowly turned toward me and asked with totally uncalled-for sarcasm, “I presume eggs are all right?”

“Hey, it’s all right with me,” I said, “… if you want to squander energy. Kilogram for kilogram, it takes almost 12 times as much energy to produce eggs as it does to produce soybeans. Not to mention, of course, the ethical dimensions of keeping all those poor birds locked up in tiny cages.”

“Oh, for Pete’s sake – let’s just all go have the salad bar,” growled the Sierra Club member. “I’m so hungry I could eat a … oops, sorry. Wild horses must be on your list, too.” He glared at me in a way that only a man deprived of his steak could glare. In fact, the whole group was now glaring at me and seemed strangely poised for my next reply.

“Well, what are you all waiting for?” I asked. “I’m sure the salad bar is just great. I wonder, though … do you know if it's organic produce? One cannot be too cautious, these days, what with pesticide residues and …”

It was precisely at this point that my formerly friendly associates all grabbed their knives and forks and began advancing toward me in menacing fashion. Leaving behind my precious underlined copy of Diet for a Small Planet, I made a hasty, somewhat undignified retreat through the back door of the restaurant.

All I can say is, Barry Commoner was right. There is no such thing as a free lunch.