Background/Question/Methods Sustainability results when the removal rate of natural resources is less than or equal to the rate at which those resources are renewed by natural processes. Thus, a given rate of removal or harvest may be either sustainable or unsustainable depending on the natural rate of renewal of that resource. Renewal results from growth in population size or biomass, measured as net primary productivity in the case of plants or net secondary productivity for animals. Understanding the global distribution of net primary productivity is the key to understanding the natural constraints on sustainability.

Results/Conclusions One reason that human activities have so often been unsustainable may be that the global patterns of productivity are not understood correctly. The global distribution of marine productivity, which is highest in the high latitudes, has been well-understood for several centuries, although this has unfortunately not prevented over-fishing. The terrestrial pattern of NPP is currently thought to be the opposite of the marine pattern, being lowest at high latitudes and highest near the equator. This is almost certainly wrong. Reanalysis and reinterpretation of published data on NPP and related plant and animal properties indicate that ecologically relevant NPP, that which is available to plants and animals during the growing season, is low at the equator and increases with latitude to a maximum between 50° and 60° north or south latitude, which is the same as the marine pattern. The actual global pattern of terrestrial NPP, and thus the constraints on sustainable land use, are the opposite of what is currently believed, which will require a major re-evaluation of international development and conservation strategies, as well as a re-evaluation of much of ecological and evolutionary theory.