Heterotrophic organisms live on accumulated plant and animal biomass. By harvesting the output of a land area that exceeds their coverage of the Earth's surface they attain consumption rates (per unit coverage by the organism) that exceed by several orders of magnitude the rate of production of vegetation (per unit Earth surface area). This occurs as a result of the fact that organisms move over the area they utilize due to the accumulation of production as biomass. Plants use photons, which have zero rest mass. Photons cannot be stored so that plants cannot increase their utilization of photons by moving about. For this reason, plants are stationary and the area they utilize coincides with the Earth surface area that they cover. Under natural conditions, approximately 90\% of the vegetation is consumed by immobile microscopic organisms, for which the rate of consumption equals the rate of production of vegetation. As organisms become larger, their rates of consumption increase and the fraction of the production of vegetation that they consume decreases. (All vertebrates in the wild consume about 1\% of the vegetation produced.) This results in a rapid increase in the area utilized as the size of the animal increases and increases the energy expended on grazing, which limits the increase in size. Man falls into the class of large organisms and under natural conditions must expend a large amount of energy on locomotion, which leads to all of his energy problems. When man learned how to combust the products of the biosphere and the fossil fuels outside the body and how to use this energy for locomotion, he became a more competitive mammal and he was able to increase his share of the total consumption in the biosphere to 25\% of the vegetation produced on land by displacing the natural consumers. Such a high anthropogenic share of the total consumption in the biosphere can only be achieved through the use of nonrenewable energy resources.