Overexploitation occurs when a resource is consumed at an unsustainable rate. Agriculture in the state is characterised by low productivity and unsustainable farm practices. Renewable resources can also be depleted if extracted at unsustainable rates over extended periods. The whole book is based on Marx's view that capitalism is inherently unsustainable. Peru's guano islands experienced severe ecological effects as a result of unsustainable mining. Its very slow growth makes the traditional practice of harvesting it for fuel highly unsustainable. The aquifer is being depleted at a rate unsustainable over the long term. Associated ecotourism has grown rapidly to unsustainable levels. As a result of unsustainable harvesting, many species yielding ebony are now considered threatened. They argue that this results in unsustainable development and perpetual underdevelopment. Hypercompetition is rapid and dynamic competition characterized by unsustainable advantage. Bernstein and Krugman assessed the concentration of income as variously "unsustainable" and "incompatible" with democracy. Redeploy capital from lines where margins are unsustainable. Steven Best argues is "completely unsustainable". Almost half of the stocks are fished at biologically unsustainable levels.