Fig. 1. The human ecological footprint from 1961 to 2005 (Ewing et al. 2008). The Ecological Footprint is a measure of the demand human activity puts on the biosphere, or Biocapacity (the capacity of an area to provide resources and absorb wastes), in global hectares (ascending red line). In 1986, humanity's consumption began its overshoot with respect to the reference biocapacity of 1961, which has not remained constant but has declined (descending green line), corresponding to its lowered productivity potential relative to its original natural capital. Note that for some commodities the yield (quantity) has remained relatively constant but changed in composition due to technical advances in harvesting that have large unaccounted costs to the environment.