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In doing this they challenge the conventional wisdom that a tragedy of the commons will be the result unless farmers cooperate. They show that a tragedy might be exacerbated due to ecosystem dynamics and also show cases where a non-cooperative regime actually might under-exploit the grassland.
Their results show that all the parts of the model are important: the choice of how to model cattle response to grass availability, the choice of parameter values and the choice of initial conditions.
Grasslands increasingly degreading
Overgrazing occurs when grasses are exposed to livestock grazing for extended periods of time, or without sufficient recovery periods. It reduces the flow of ecosystem services from the land and often cause problems as desertification and soil erosion.
Today grasslands cover some 40 % of the earth´s surface and are found in every region of the world, except from Greenland and Antarctica.
Unfortunately, 50 % of the grasslands in the developing world, where people are directly dependent on them as a resource and have few opportunities for other livelihoods, are degraded today.
Source: Crépin, A-S, Lindahl, T. 2009. Grazing Games: Sharing Common Property Resources with Complex Dynamics. Environmental and Resource Economics, Published online 09 January, 2009.