<P> The application of the concept of carrying capacity for the human population has been criticized for not successfully capturing the multi-layered processes between humans and the environment, which have a nature of fluidity and non-equilibrium, and for sometimes being employed in a blame - the - victim framework . </P> <P> Supporters of the concept argue that the idea of a limited carrying capacity is just as valid applied to humans as when applied to any other species . Animal population size, living standards, and resource depletion vary, but the concept of carrying capacity still applies . The number of people is not the only factor in the carrying capacity of Earth . Waste and over-consumption, especially by wealthy and near - wealthy people and nations, are also putting significant strain on the environment together with human overpopulation . Population and consumption together appear to be at the core of many human problems . Some of these issues have been studied by computer simulation models such as World3 . When scientists talk of global change today, they are usually referring to human - caused changes in the environment of sufficient magnitude eventually to reduce the carrying capacity of much of Earth (as opposed to local or regional areas) to support organisms, especially Homo sapiens . </P> <P> Some aspects of a system's carrying capacity may involve matters such as available supplies of food, water, raw materials, and / or other similar resources . In addition, there are other factors that govern carrying capacity which may be less instinctive or less intuitive in nature, such as ever - increasing and / or ever - accumulating levels of wastes, damage, and / or eradication of essential components of any complex functioning system . Eradication of, for example, large or critical portions of any complex system (envision a space vehicle, for instance, or an airplane, or an automobile, or computer code, or the body components of a living vertebrate) can interrupt essential processes and dynamics in ways that induce systems failures or unexpected collapse . (As an example of these latter factors, the "carrying capacity" of a complex system such an airplane is more than a matter of available food, or water, or available seating, but also reflects total weight carried and presumes that its passengers do not damage, destroy, or eradicate parts, doors, windows, wings, engine parts, fuel, and oil, and so forth .) Thus, on a global scale, food and similar resources may affect planetary carrying capacity to some extent so long as Earth's human passengers do not dismantle, eradicate, or otherwise destroy critical biospheric life - support capacities for essential processes of self - maintenance, self - perpetuation, and self - repair . </P> <P> Thus, carrying capacity interpretations that focus solely on resource limitations alone (such as food) may neglect wider functional factors . If the humans neither gain nor lose weight in the long - term, the calculation is fairly accurate . If the quantity of food is invariably equal to the "Y" amount, carrying capacity has been reached . Humans, with the need to enhance their reproductive success (see Richard Dawkins' The Selfish Gene), understand that food supply can vary and also that other factors in the environment can alter humans' need for food . A house, for example, might mean that one does not need to eat as much to stay warm as one otherwise would . Over time, monetary transactions have replaced barter and local production, and consequently modified local human carrying capacity . However, purchases also impact regions thousands of miles away . For example, carbon dioxide from an automobile travels to the upper atmosphere . This led Paul R. Ehrlich to develop the I = PAT equation . </P>

Available raw materials are one of the limiting factors regulating carrying capacity