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Emergence of social inequality in the spatial harvesting of renewable public goods

Fig 5

Maximum sustainable resource extraction occurs for mobile consumers at the ‘edge of inequality’.

(A) Average per capita resource extraction rate (expressed as a fraction of the yield-maximizing extraction rate) and (B) amount of resource left in the environment (expressed as a fraction of the system’s carrying capacity), depending on the unit benefit bH and cost cH of harvesting. The sedentary regime, labeled ‘S,’ is equitable, but inefficient: the resource extraction is far less than optimal, despite the ample amounts of resource left in the environment. The mobile regime, labeled ‘M,’ is both equitable and efficient: the total resource extraction rate resulting from the evolved resource-consumption strategies reaches its maximum in this regime. However, for high unit benefits and costs of harvesting (or equivalently, for low unit costs of dispersal), the tragedy of the commons can occur also in this regime. The coexistence regime, labeled ‘S & M,’ is neither equitable nor efficient: the resource extraction rate is far less than optimal, and overexploitation by mobile consumers results in the tragedy of the commons. Parameter values are as in Fig 4.

Fig 5