There is a template in economics that deals with tragedy of the commons: permits.
And this is how it looks like when applied to replenishable commodity like fishes, graphically:
This is exactly the case in the rationale behind the proposed legalization of turtle eggs collection.
I myself learned about the model at Michigan to solve scarcity issue faced by the fishing industry in northwestern US; the Pacific. In fact, the graph is a reproduction of the original diagram I learned during a cold fall day in Ann Arbor.
For water scarcity faced by the states along the Colorado River, the same idea of introducing tradable permits to combat tragedy of the commons is used. In the NYT a few days ago, the fishery model was cited as a solution to combat another tragedy of the commons; the climate:
Later today, Mr. Festa is going to release a fascinating study about the fishing business that on its face has nothing to do with global warming, and yet has everything to do with a solution. At dozens of the nation’s fisheries, the fish population is in danger because fishermen have no incentive not to take everything out of the water that they can. But 10 fisheries, stretching from the halibut fishery off Alaska to the surf clam industry in New England, have tried a different route. [Earth’s Climate Needs the Help of Incentives. NYT. March 28 2007.]
Tradable carbon credits, which is essentially tradable permits, is part of the Kyoto Protocol.
