Ostrom pointed out is that though you do see these tragedies occur, they're not nearly as common as the basic tragedy of the commons analysis would suggest. What you might think of as "traditional" or "precapitalist" societies generally manage to handle these situations sustainably without shifting to a mode of well-defined property rights. - http://www.slate.com/blogs/moneybox/2012/06/12/elinor_ostrom_first_woman_nobel_prize_winner_in_economics_dies_at_78.html