Intensive Farming May Ease Climate Change

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To many people, modern required to feed today’s world S agriculture, with its industrial-scale using yesterday’s technology, the reuter farms and reliance on petroleum- researchers froze agricultural yields based fertilizers, may seem a at 1961 levels and then allowed necessary evil — one that has fed a population and living standards to . Whitaker/ . growing human population while increase apace. Although emissions p causing untold damage to the from fertilizer use were lower than environment. But the alternative in the real-world scenario, the may be worse, concludes a Stanford amount of land required to grow University study: a less-productive food expanded by nearly 1.8 billion agricultural system would destroy hectares. In a second scenario, even more wild land, drive up both the yields and the standard of greenhouse-gas emissions and Modern farming practices have led to reduced carbon dioxide emissions. living were fixed at 1961 levels; the wreak havoc on biodiversity. effects in terms of agricultural-land The study’s results suggest that further Yet the balance turns out to be favourable, conversion and greenhouse-gas emissions agricultural intensification will play a says Lobell, “and the carbon savings are were roughly half those of the first scenario critical part in addressing global warming. quite large”. All other things being equal, the but were still higher than actual impacts in In the study, researchers modelled the researchers found that agricultural advances the real-world analysis (see ‘Greenhouse-gas world as we know it, complete with the between 1961 and 2005 spared a portion of emissions’). ‘green revolution’ and modern agricultural land larger than Russia from development Finally, the team analysed the nearly practices, and two alternative realities in and reduced emissions by the equivalent of US$1.2-trillion investment in agricultural which crop yields were kept at the levels 590 gigatonnes of carbon dioxide — roughly research and development since 1961. of decades ago. Published on 14 June, the a third of the total emitted since the start of Averaged over the study period, investments results show that increased greenhouse- the Industrial Revolution. in agricultural yields reduced carbon gas emissions resulting from intensive The notion that increasing crop yields emissions at a cost of around $4 per tonne of farming are more than offset by the effects preserves forests and other native lands dates carbon dioxide equivalent, less than a quarter of land preservation, which keeps carbon back to the father of the green revolution, the of the going price for emissions permits sequestered in native soils, savannahs and late US plant scientist Norman Borlaug, and under Europe’s carbon-trading scheme. forests (J. A. Burney et al. Proc. Natl Acad. Sci. is known as the Borlaug hypothesis. Lobell’s The environmental benefits will accrue if USA doi:10.1073/pnas.0914216107; 2010). team attempted to quantify that effect yields continue to increase, say researchers. “In the beginning, we weren’t even sure and to calculate the resulting reduction in Last year, for example, a team from the Joint whether the carbon savings from land use greenhouse-gas emissions. Global Change Research Institute in College would outweigh the increased agricultural Between 1961 and 2005, the global Park, Maryland, analysed land-use scenarios emissions,” says David Lobell, an agricultural population increased by 111%, from and found that increasing yields could scientist at Stanford University in California 3.1 billion to 6.5 billion, but agricultural reduce emissions as much as could energy and a co-author on the study. After all, the yields went up by 135% over the same period, technologies such as wind and solar (M. Wise fertilizers used in intensive farming increase according to the researchers. As a result, et al. Science 324, 1183–1186; 2009). emissions of greenhouse gases. All told, global cropland increased by just 27%, from “Above all, this study underscores the agriculture was responsible for 10–12% of 960 million to around 1.2 billion hectares. purpose of agricultural research funding, global anthropogenic emissions in 2005. To work out how much land would be especially in developing countries,” says Andrew Balmford, a conservation GREENHOUSE-GAS EMISSIONS scientist at the University of Cambridge, A comparison of two model worlds with the real world suggests that intensive farming has UK. Unless the world sees a second green actually mitigated total carbon emissions from agriculture (SOL, standard of living) revolution, some 1.5 billion to 2 billion 10,000 Soil emissions 10,000 additional hectares will need to be put Fertilizer production into production by 2050 to feed a growing Rice cultivation population, according to an ongoing Land conversion analysis by David Tilman, an ecologist at 1,000 1,000 the University of Minnesota in St Paul. Fortunately, there is plenty of cleared land that is underperforming and massive 100 100 potential for boosting yields in developing

Tg C equivalent per year C equivalent Tg countries, Tilman says. “If we want to save Crop yield ﬁxed, Crop yield and the Earth, we have to feed the world,” Tilman Real world SOL increases SOL ﬁxed 10 10 adds.“And it’s these poorest countries that ■ 1970 1980 1990 2000 1970 1980 1990 2000 1970 1980 1990 2000 have the most to contribute.” Jeff Tollefson