T U R N I N G T H E T I D E : T O W A R D S S U S TA I N A B I L I T Y 30 per cent would reach 100 per cent in the 2030s even if recent increases in agricultural yields continue. This means that biological capacity equal to two planet Earths would be required to keep up with humanity’s resource demands and waste production. This business-as-usual scenario is conservative as it assumes no unpleasant surprises: no biocapacity losses due to freshwater shortages, no feedback loops that cause a changing climate to reach tipping points, no damage by pollution, and no other factors that could cause biocapacity to decrease. But there are hints that such assumptions should not be taken for granted; for example, the current devastation of bee populations could cause worldwide declines of crops that require pollination.
If overshoot continues to increase, what will the future hold? Under assumptions of rapid global economic growth and a shift to a balanced mix of energy sources, the Intergovernmental Panel on Climate Change projects that annual carbon emissions will more than double by 2050. Moderate United Nations estimates show global population growing to 9 billion over the same period, while FAO projections show increasing consumption of food, fibre and forest products. Furthermore, if present management schemes persist, fisheries are projected to decline by more than 90 per cent by 2050. Figure 31 shows the implications of these scenarios for humanity’s footprint through to mid-century. The 2005 overshoot of
Fig. 31: BUSINESS-AS-USUAL SCENARIO AND ECOLOGICAL DEBT
The longer that overshoot persists, the greater the pressure on ecological services, increasing the risk of ecosystem collapse, with potentially permanent losses of productivity. Scientists cannot accurately predict the tipping point at which an ecosystem decline may suddenly accelerate, or cause a failure that cascades across other ecosystems. Most would agree, however, that ending overshoot as quickly as possible will reduce this risk, and will allow degraded ecosystems to begin their recovery. Fortunately, humanity can change course. Instead of continuing business-as-usual, we should strive to end overshoot by midcentury. WWF is promoting this change through its various sustainability and market transformation activities, as well as by
Fig. 32: RETURN TO SUSTAINABILITY
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tackling energy use as the root cause of climate change. Figure 32 shows how a rapid transition out of overshoot would significantly shrink the magnitude and duration of ecological debt that will otherwise accrue. Such a path reduces the risk of ecosystem degradation and increases the probability that human well-being can be maintained or improved. It could also reduce and perhaps even reverse the current rapid rate at which biodiversity is being lost. Ending overshoot means closing the gap between humanity’s footprint and available biocapacity. Five factors determine the size of this gap (Figure 33). On the demand side, the footprint is a function of population size, the goods and services each person consumes, and the
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