In a sequel to The Limits to Growth two decades later the same principal authors refined their original systems dynamics model and fed in much-improved data. Beyond the Limits (Meadows et al., 1992) argued that the 1972 warnings were broadly correct, that some of the limits have already been exceeded, and that, if current trends continue, there is virtually certain to be global collapse within the lifetime of children alive today. They argue that it is possible to have ‘overshoot but not collapse’, and to achieve the goal of sustainable development in spite of excessive population growth in the short term, provided demands are cut and there is an increase in efficiency of materials and energy use soon. Beyond the Limits threw down an urgent challenge to environmental management and indicated an approximate timescale for action.