Tracking the ecological overshoot of the human economy

Abstract

Sustainability requires living within the regenerative capacity of the biosphere. In an attempt to measure the extent to which humanity satisfies this requirement, we use existing data to translate human demand on the environment into the area required for the production of food and other goods, together with the absorption of wastes. Our accounts indicate that human demand may well have exceeded the biosphere's regenerative capacity since the 1980s. According to this preliminary and exploratory assessment, humanity's load corresponded to 70% of the capacity of the global biosphere in 1961, and grew to 120% in 1999.

Figure 1

Time trend of humanity's ecological demand. This graph shows human demand over the last 40 years as compared with the earth's ecological capacity for each year. One vertical unit in the graph corresponds to the entire regenerative capacity of the earth in a given year. Human demand exceeds nature's total supply from the 1980s onwards, overshooting it by 20% in 1999. If 12% of the bioproductive area were set aside to protect other species, the demand line crosses the supply line in the early 1970s rather than the 1980s.

Figure 2

Global ecological demand over time, in global hectares. This graph documents humanity's area demand in six different categories. The six categories are shown on top of each other, demonstrating a total area demand of over 13 billion global hectares in 1999. Global hectares represent biologically productive hectares with global average bioproductivity in that year.