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solutions, we hope to reinforce the idea that maximizing future biodiversity will require a plurality of approaches in creative admixtures that are tailored to local realities. Each place needs a different mixture.


Into a Less Peopled, Less Hostile Planet

The human impact on biodiversity is a product of three root factors, summarized in the heuristic I=PAT identity (Ehrlich and Holdren, 1971). The overall Impact (encompassing all of the drivers of biodiversity loss discussed above) is the product of Population size, per capita Affluence, and the Technologies (and socioeconomic–political systems) used to generate affluence. “Affluence” in this context is simply per capita consumption, and “socioeconomic–political systems” refer to the strictures that regulate technology use.

Tangible steps to reduce any of these factors will lessen their product and help produce a more hospitable future for biodiversity. A current example that integrates all three factors is the drive to produce biofuel (T) to satisfy the expanding energy consumption (A) of a growing population (P). Unchecked biofuel production has the potential to destroy all moist-tropical biodiversity that lacks conservation status. Biologically impoverished monocultures of oil palm, soybeans, and sugarcane for biodiesel and ethanol are devouring swaths of Brazilian Amazon and Cerrado, Indonesian, and Malaysian tropical rainforests and other vast reservoirs of biodiversity (Fearnside, 2001; Klink and Machado, 2005). However, the production of biofuels from native grassland perennials on agriculturally degraded lands has the potential to reduce carbon emissions without displacing food production or converting native habitats (Tilman et al., 2006). In this case, an innovative Technological adjustment would reduce overall Impact. Likewise, simple shifts in socioeconomic–political systems—instituting high-occupancy vehicle lanes to reduce carbon emissions, for example, or demanding high-seas ballast water exchange for cargo ships to reduce species introductions—would do a great deal.

Although population growth has slowed or is slowing in many developed countries, it remains high in many developing regions. Much is known about how to hasten the transition to a stable and then declining world population. Education and employment—for women especially—along with access to contraception and safe abortions are the most important components (Rindfuss et al., 1980). Less is known about how to prevent overconsumption of natural resources (Ehrlich and Goulder, 2007). Mass media are a powerful tool for raising environmental aware-

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