Switch to Corn Promotes Amazon Deforestation

Corn ethanol has many flaws and is, at best, not a substantial climate solution, as we’ve seen. Now Science magazine has published a letter from William F. Laurance of the Smithsonian Tropical Research Institute casting yet more doubt on our corn ethanol strategy. I reprint it here in its entirety, with references and notes:

The United States is the world’s leading producer of soy. However, many U.S. farmers are shifting from soy to corn (maize) in order to qualify for generous government subsidies intended to promote biofuel production (1); since 2006, U.S. corn production has risen 19% while soy production has fallen by 15% (2). This in turn is helping to drive a major increase in global soy prices (3), which have nearly doubled in the past 14 months.

The rising price for soy has important consequences for Amazonian forests and savanna-woodlands (4). In Brazil, the world’s second-leading soy producer, deforestation rates (5) and especially fire incidence (6) have increased sharply in recent months in the main soy- and beef-producing states in Amazonia (and not in states with little soy production). Although dry weather is a contributing factor, these increases are widely attributed to rising soy and beef prices (5, 7), and studies suggest a strong link between Amazonian deforestation and soy demand (8, 9).

Some Amazonian forests are directly cleared for soy farms (8). Farmers also purchase large expanses of cattle pasture for soy production, effectively pushing the ranchers farther into the Amazonian frontier or onto lands unsuitable for soy production (9). In addition, higher soy costs tend to raise global beef prices because soy-based livestock feeds become more expensive (10), creating an indirect incentive for forest conversion to pasture. Finally, the powerful Brazilian soy lobby is a key driving force behind initiatives to expand Amazonian highways and transportation networks in order to transport soybeans to market, and this is greatly increasing access to forests for ranchers, loggers, and land speculators (11, 12).

In a globalized world, the impacts of local decisions about crop preferences can have far-reaching implications. As illustrated by an apparent “corn connection” to Amazonian deforestation, the environmental benefits of corn-based biofuel might be considerably reduced when its full and indirect costs are considered.

William F. Laurance
Smithsonian Tropical Research Institute
Apartado 0843-03092, Balboa, Anc³n, Panama

References and Notes

  1. P. C. Westcott, “U.S. ethanol expansion driving changes throughout the agricultural sector” (
  2. National Agricultural Statistics Service Acreage Report, U.S. Department of Agriculture (
  3. USDA-ERS ( Growing global demands for soy for edible oil, livestock feed, and biodiesel are also contributing to high soy prices.
  4. The corn-soy-deforestation link was evidently first noted by D. C. Nepstad et al., The Amazon in a Changing Climate: Large-Scale Reductions of Carbon Emissions from Deforestation and Forest Impoverishment [Amazon Institute for Environmental Research (IPAM), 2006].
  5. C. Angelo, Desmatamento cresce 8% na Amazonia, Folha de S¤o Paulo Online (
  6. ImazonGeo (
  7. R. A. Butler, “Is the Amazon more valuable for carbon offsets than cattle or soy?” (, 17 October 2007);
  8. D. C. Morton et al., Proc. Nat. Acad. Sci. U.S.A. 103, 14637 (2006).
  9. D. C. Nepstad et al., Conserv. Biol. 20, 1595 (2006).
  10. D. L. Hard, in Protein Sources for the Animal Feed Industry (Animal and Production Health Proceedings, FAO, Rome, 2002), pp. 125-140.
  11. W. F. Laurance et al., Science 291, 438 (2001).
  12. P. M. Fearnside, Environ. Conserv. 28, 23 (2001).

And yet the recent energy bill will more than double corn ethanol production from current levels! We have a long ways to go before we are truly serious about fighting global warming.

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