Predicting peak cropland

Can we control our destiny? by Liza Lester, ESA communications officer Population by Total Fertility (millions). The United Nations predicts 10.1 billion living humans will inhabit the Earth by 2100. Source: United Nations, Department of Economic and Social Affairs, Population Division (2011): World Population Prospects: The 2010 Revision. New York. Joe Fargione, lead scientist for The Nature Conservancy’s North American Region, wants to know how to feed 10 billion people. More specifically, he wants to know how much of the Earth’s land we will need to devote to crops to feed us all in the foreseeable future, for values of “foreseeable” converging on about one century hence. Ten billion and growing is the most recent UN global population projection for the year 2100. Fargione is a little more optimistic about reaching a population peak before the end of the century. Population has an intimate, complicated relationship to land use, and sparing wildlands from the plough is, of course, a topic close to TNC’s heart. “We currently crop an area equivalent to all of South America,” (about 1.5 billion hectares) Fargione said, explaining his (as yet unpublished, as far as I can discover) efforts to model “peak cropland” at World Wildlife Fund headquarters in Washington, D.C., on February 28. “We don’t have another South America to put into production.” As the human population continues to grow, and grow wealthier, more land will be converted to agriculture. But how much more, and when will it stop? Predicting peak cropland, the year when the greatest extent of Earth’s lands will be sown in crops, requires a metaprojection interpolating growth in population, food consumption, wealth, technology, and efficiency with the uncertain effects of a changing climate.  How many humans we will be, and how much and what kinds of food we will eat? Will we grow until we reach carrying capacity and world population is checked by the hard limits of starvation, or can we control our destiny? Fargione thinks it doesn’t have to come down to a Malthusian equation. He’s using predictions of a demographic transition from exponential population growth to static, stable numbers in the 21st century, counting on the non-compulsory drop in fertility observed in relatively wealthy nations to spread throughout the world. Japan and several European nations are currently below replacement rate (approximately 2.1 children per woman). Associated with the demographic transition is an uncertain tangle of influences: wealth, security, urbanization, and the education of girls. That last bit, the education of girls, is an angle Fargione thinks has been under appreciated and under emphasized by conservationists. A projection of straight numbers of humans is not sufficient to predict...

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