Fifty years ago, China was in the midst of a cultural revolution. Called the Great Leap Forward, it was a massive series of plans set in motion by the government with the intention that China would catch up with the rest of the civilized world. Before that time, China had been a mostly agrarian society; Chairman Mao wanted them to become a superpower, and he was going to accomplish this by undertaking the biggest communist experiment in history.

One of the major complaints of farmers was that the sparrows, plentiful in the countryside, were eating all of their seeds and hurting the crop. So among the first plans of the Great Leap Forward was something called the Great Sparrow Campaign, in which the government called for the elimination of sparrows by whatever means possible. Nests were destroyed and chicks were killed. As for the grown sparrows, people would bang pots and pans to scare flocks into the sky; as soon as they’d land, someone else would scare them back up. Without anywhere to land, the sparrows died of exhaustion. All in all, over 4 million sparrows were killed in China that year.

The crop the next year was plentiful. Since there were few sparrows to eat the seeds, the farmers could plant their fields uninterrupted. But before they could harvest, swarms of locusts invaded and ate everything. It wasn’t until later that the Chinese researchers realized that sparrows also eat locusts; without a predator, the locust population flourished and swept across the farmland. This plague, along with a concurrent drought, caused a mass starvation in China that lasted until 1962 and killed 38 million people. Instead of the Great Leap Forward, those years became known to the Chinese as the Three Bitter Years.

There is a consequence for every decision we make. It may be a good consequence or a bad one; it may be immediate or it may not happen in our lifetime, but there is a consequence.

The bluefin tuna is considered a delicacy in sushi. When it comes to delicacies, people tend to spare no expense; in a Tokyo fish market, an enterprising fisherman can sell a bluefin tuna for between $60,000 and $100,000. This is because there are just 22,000 bluefin tuna left in the world due to severe overfishing. Thirty years ago, there were ten times that amount.

But look at it from the fisherman’s perspective. Honestly, what difference does it make if there are 22,000 bluefins or 21,999? And he’s $100,000 richer. The decision is rational and easily justified. It’s a lot of money. And then another few legions of fishermen make the same rational decision and the bluefin tuna are gone.

Individually harmless choices are often collectively destructive. People choose to do things in their own interest, believing that it doesn’t really make a difference in the grand scheme of things, and something that was nice is now ruined.

There is always a consequence.

UPDATE 1/6/2009: A timely article from the Wall Street Journal about bluefins in Japan.