Global demand for agricultural products such as food, feed, and fuel is now a major driver of cropland and pasture expansion across much of the developing world. Whether these new agricultural lands replace forests, degraded forests, or grasslands greatly influences the environmental consequences of expansion. Although the general pattern is known, there still is no definitive quantification of these land-cover changes. Here we analyze the rich, pan-tropical database of classified Landsat scenes created by the Food and Agricultural Organization of the United Nations to examine pathways of agricultural expansion across the major tropical forest regions in the 1980s and 1990s and use this information to highlight the future land conversions that probably will be needed to meet mounting demand for agricultural products. Across the tropics, we find that between 1980 and 2000 more than 55% of new agricultural land came at the expense of intact forests, and another 28% came from disturbed forests. This study underscores the potential consequences of unabated agricultural expansion for forest conservation and carbon emissions.
A new issue brief by Scott Rozelle and fellow
researchers Jinxia Wang and Jikun Huang concludes that climate change will have
a significant effect on China's crop yields and impact its economy,
including the grain trade. It concludes that China's government is responsible
for responding in ways that will help the country adapt to and mitigate the effects
of climate change. The issue brief was jointly published by the International
Centre for Trade and Sustainable Development and the International Food and
Agricultural Trade Policy Council.
Tropical forests store more than 340 billion tons of carbon, which is 40 times the total current worldwide annual fossil fuel emissions. This has huge implications for global warming, if we continue to expand our farmland into tropical forests at such high rates- Holly Gibbs
Providing food security for a world that will be warmer, more populous, and continually developing requires the implementation of sound policies that enhance food and agricultural consumption, production, incomes, and trade. FSE is in the midst of hosting a two-year, 12-lecture symposium series on Global Food Policy and Food Security.
Is it possible to combine modern tropical agriculture with environmental conservation? Brazilian agriculture offers encouraging examples that achieve high production together with adequate environmental protection. However, these effective practices may soon lose ground to the conventional custom of resource overexploitation and environmental degradation.
A revision to the Forest Act, the main Brazilian environmental legislation on private land, has just been submitted to Congress, and there is a strong chance that it will be approved. The proposed revision raises serious concerns in the Brazilian scientific community, which was largely ignored during its elaboration. The new rules will benefit sectors that depend on expanding frontiers by clear-cutting forests and savannas and will reduce mandatory restoration of native vegetation illegally cleared since 1965. If approved, CO2 emissions may increase substantially, instead of being reduced as was recently pledged in Copenhagen. Simple species-area relationship analyses also project the extinction of more than 100,000 species, a massive loss that will invalidate any commitment to biodiversity conservation. Proponents of the new law, with well-known ties to specific agribusiness groups, claim an alleged shortage of land for agricultural expansion, and accuse the current legislation of being overprotective of the environment in response to foreign interests fronted by green nongovernmental organizations. However, recent studies show that, without further conversion of natural vegetation, crop production can be increased by converting suitable pastures to agriculture and intensifying livestock production on the remaining pasture. Brazil has a high potential for achieving sustainable development and thereby conserving its unique biological heritage. Although opposed by the Ministry of the Environment and most scientists, the combination of traditional politicians, opportunistic economic groups, and powerful landowners may be hard to resist. The situation is delicate and serious. Under the new Forest Act, Brazil risks suffering its worst environmental setback in half a century, with critical and irreversible consequences beyond its borders.
FSE director Roz Naylor discusses the stresses that climate change and a greater world population will have on our food supply in an interview with Smithsonian Magazine. An economist by training, Rosamond L. Naylor studies the world food economy and sustainable agriculture. Though she says she is deeply worried about climate change and population growth, she described herself as "optimistic" in a conversation with Smithsonian's Amanda Bensen.
Henning Steinfeld is head of the livestock sector analysis and policy branch at the Food and Agriculture Organization of the UN in Rome, Italy. He has been working on agricultural and livestock policy for the last 15 years, in particular focusing on environmental issues, poverty and public health protection. Prior to that, he has worked in agricultural development project in different African countries.
Dr Steinfeld is an agricultural economist and graduated from the Technical University of Berlin, Germany (now Humboldt University).
As efforts to mitigate climate change increase, there is a need to identify cost-effective ways to avoid emissions of greenhouse gases (GHGs). Agriculture is rightly recognized as a source of considerable emissions, with concomitant opportunities for mitigation. Although future agricultural productivity is critical, as it will shape emissions from conversion of native landscapes to food and biofuel crops, investment in agricultural research is rarely mentioned as a mitigation strategy. Here we estimate the net effect on GHG emissions of historical agricultural intensification between 1961 and 2005. We find that while emissions from factors such as fertilizer production and application have increased, the net effect of higher yields has avoided emissions of up to 161 gigatons of carbon (GtC) (590 GtCO2e) since 1961. We estimate that each dollar invested in agricultural yields has resulted in 68 fewer kgC (249 kgCO2e) emissions relative to 1961 technology ($14.74/tC, or ~$4/tCO2e), avoiding 3.6 GtC (13.1 GtCO2e) per year. Our analysis indicates that investment in yield improvements compares favorably with other commonly proposed mitigation strategies. Further yield improvements should therefore be prominent among efforts to reduce future GHG emissions.
Advances in high-yield agriculture achieved during the so-called Green Revolution have not only helped feed the planet, but also have helped slow the pace of global warming by cutting the amount of biomass burned - and the resulting greenhouse gas emissions - when forests or grasslands are cleared for farming. Stanford researchers estimate those emissions have been trimmed by over half a trillion tons of carbon dioxide. The paper is being released this week in the Proceedings of the National Academy of Sciences.
Advances in high-yield agriculture over the latter part of the 20th century have prevented massive amounts of greenhouse gases from entering the atmosphere - the equivalent of 590 billion metric tons of carbon dioxide - according to a new study led by two Stanford Earth scientists.
The yield improvements reduced the need to convert forests to farmland, a process that typically involves burning of trees and other plants, which generates carbon dioxide and other greenhouse gases.
The researchers estimate that if not for increased yields, additional greenhouse gas emissions from clearing land for farming would have been equal to as much as a third of the world's total output of greenhouse gases since the dawn of the Industrial Revolution in 1850.
The researchers also calculated that for every dollar spent on agricultural research and development since 1961, emissions of the three principal greenhouse gases - methane, nitrous oxide and carbon dioxide - were reduced by the equivalent of about a quarter of a ton of carbon dioxide - a high rate of financial return compared to other approaches to reducing the gases.
"Our results dispel the notion that modern intensive agriculture is inherently worse for the environment than a more 'old-fashioned' way of doing things," said Jennifer Burney, lead author of a paper describing the study that will be published online by the Proceedings of the National Academy of Sciences.
Adding up the impact
The researchers calculated emissions of carbon dioxide, methane and nitrous oxide, converting the amounts of the latter two gases into the quantities of carbon dioxide that would have an equivalent impact on the atmosphere, to facilitate comparison of total greenhouse gas outputs.
Burney, a postdoctoral researcher with the Program on Food Security and the Environment at Stanford, said agriculture currently accounts for about 12 percent of human-caused greenhouse gas emissions. Although greenhouse gas emissions from the production and use of fertilizer have increased with agricultural intensification, those emissions are far outstripped by the emissions that would have been generated in converting additional forest and grassland to farmland.
"Every time forest or shrub land is cleared for farming, the carbon that was tied up in the biomass is released and rapidly makes its way into the atmosphere - usually by being burned," she said. "Yield intensification has lessened the pressure to clear land and reduced emissions by up to 13 billion tons of carbon dioxide a year."
"When we look at the costs of the research and development that went into these improvements, we find that funding agricultural research ranks among the cheapest ways to prevent greenhouse gas emissions," said Steven Davis, a co-author of the paper and a postdoctoral researcher at the Carnegie Institution at Stanford.
To evaluate the impact of yield intensification on climate change, the researchers compared actual agricultural production between 1961 and 2005 with hypothetical scenarios in which the world's increasing food needs were met by expanding the amount of farmland rather than by the boost in yields produced by the Green Revolution.
"Even without higher yields, population and food demand would likely have climbed to levels close to what they are today," said David Lobell, also a coauthor and assistant professor of environmental Earth system science at Stanford.
"Lower yields per acre would likely have meant more starvation and death, but the population would still have increased because of much higher birth rates," he said. "People tend to have more children when survival of those children is less certain."
Avoiding the need for more farmland
The researchers found that without the advances in high-yield agriculture, several billion additional acres of cropland would have been needed.
Comparing emissions in the theoretical scenarios with real-world emissions from 1961 to 2005, the researchers estimated that the actual improvements in crop yields probably kept greenhouse gas emissions equivalent to at least 317 billion tons of carbon dioxide out of the atmosphere, and perhaps as much as 590 billion tons.
Without the emission reductions from yield improvements, the total amount of greenhouse gas pumped into the atmosphere over the preceding 155 years would have been between 18 and 34 percent greater than it has been, they said.
To calculate how much money was spent on research for each ton of avoided emissions, the researchers calculated the total amount of agricultural research funding related to yield improvements since 1961 through 2005. That produced a price between approximately $4 and $7.50 for each ton of carbon dioxide that was not emitted.
"The size and cost-effectiveness of this carbon reduction is striking when compared with proposed mitigation options in other sectors," said Lobell. "For example, strategies proposed to reduce emissions related to construction would cut emissions by a little less than half the amount that we estimate has been achieved by yield improvements and would cost close to $20 per ton."
The authors also note that raising yields alone won't guarantee lower emissions from land use change.
"It has been shown in several contexts that yield gains alone do not necessarily stop expansion of cropland," Lobell said. "That suggests that intensification must be coupled with conservation and development efforts.
"In certain cases, when yields go up in an area, it increases the profitability of farming there and gives people more incentive to expand their farm. But in general, high yields keep prices low, which reduces the incentive to expand."
The researchers concluded that improvement of crop yields should be prominent among a portfolio of strategies to reduce global greenhouse gases emissions.
"The striking thing is that all of these climate benefits were not the explicit intention of historical investments in agriculture. This was simply a side benefit of efforts to feed the world," Burney noted. "If climate policy intentionally rewarded these kinds of efforts, that could make an even bigger difference. The question going forward is how climate policy might be designed to achieve that."
