The animals whose future we do worry about -- whales and elephants, for example -- are not typically subject to ownership. It's the tragedy of the commons.

Elephants are endangered because in much of Africa, poachers kill them for their tusks. Poachers have no incentive to expand herds, and neither does anyone else. Governments outlawed hunting and the ivory trade, but that hasn't stopped the loss of elephants. The plain is too vast to police it all.

Yet, where the property principle has been applied -- however imperfectly -- the fate of the elephants has been reversed. Villagers in Zimbabwe earn income by permitting hunting. In effect, the villagers have property rights in the herds. That changes attitudes. They'd be poorer if they let the elephants be hunted to extinction.

The result? "To say that we have too many elephants would be an understatement," Zimbabwe Department of National Parks and Wildlife Management acting director E.W. Kanhanga said in 2001.

The system is not perfect because individual property rights -- which would create a stronger sense of responsibility -- are not allowed. Moreover, the system has come under suspicion because cronies of Zimbabwe's despicable dictator, Robert Mugabe, are said to be killing elephants in game parks.

Nevertheless, Zimbabwe tried property rights. Kenya tried prohibition. Kenya lost elephants while Zimbabwe gained them. [http://tinyurl.com/22xdrp].

The pattern is clear. Property equals responsibility equals prosperity.