November 02, 2010
"Tropical forests store a tremendous amount of carbon, and when a forest is cleared, not only do you lose more carbon, but crop yields are not nearly as high as they are in temperate areas," explains lead author Paul C. West, a graduate student at the University of Wisconsin-Madison, in a press release.
The researchers found that one ton of food emitted approximately over 75 tons of carbon in the tropics, whereas a ton of food grown in temperate regions released just less than 27 tons of carbon.
The tradeoffs between the release of carbon to the atmosphere and agricultural production are markedly different between the world's temperate and tropical regions. In this representation, for each hectare of land cleared for agriculture, each rail car is equivalent to 68 tons of carbon released to the atmosphere and each bushel represents 3.9 tons of maize produced. Image courtesy of Paul West, University of Wisconsin-Madison Center for Sustainability and the Global Environment and University of Wisconsin-Madison Center for Limnology.
Rising human population, increasing consumption of meat (which requires more grain per area), the demand for biofuels, high commodity prices, and economic development plans have pushed many tropical nations to pursue large-scale agriculture over forest protection. However, the authors say the realities of carbon loss in the tropics makes a strong argument for intensifying agriculture on already cleared land, rather than more deforestation.
"Our results corroborate recommendations to concentrate reforestation and avoid deforestation in the tropics to have the greatest worldwide impact," the authors write.
But, West admits, "the realty is there will be some of both [agriculture intensification and deforestation]."
The authors explain in the paper that "despite the clear benefits of concentrating reforestation and forest conservation efforts in the tropics, several local and regional factors influence implementation. […] Choices are made locally and are influenced by local and regional food security, transportation costs, labor, poverty, and technology rather than global atmospheric carbon. Thus, local and global outcomes must be coupled to manage ecosystem services and assess their tradeoffs."
The study also highlight that agriculture comes with additional tradeoffs on top of carbon including impacting ecosystem services such as "soil and groundwater recharge, runoff, and nutrient regulation as well as ecosystems, species, and genome diversity of landscapes."
The broad study looked at 175 different crops worldwide using government data and satellite imagery.
"We have a very fine resolution of both what the carbon stocks and the yields are globally," says West. "Spatially, it is much more explicit than anything that has been produced before."
Approximately 20% of the temperate region is used for crops, as opposed to 10.5% of the tropics. In all, deforestation contributes more greenhouse gases to the atmosphere than global transportation: 12-20% of the total greenhouse gas emissions are due to the loss of forests. Scientists say that such emissions are driving global climate change.
CITATION: Paul C. West, Holly K. Gibbs, Chad Monfreda, John Wagner, Carol C. Barford, Stephen R. Carpenter, and Jonathan A. Foley. Trading carbon for food: Global comparison of carbon stocks vs. crop yields on agricultural land. PNAS. DOI: 10.1073/pnas.1011078107.
Crop types and yields between 1998 and 2002. Highest crop yields are in temperate regions of Western Europe and North America. Map courtesy of Paul West, University of Wisconsin-Madison Center for Sustainability and the Global Environment and University of Wisconsin-Madison Center for Limnology. Click to enlarge.
Map shows changes in carbon stocks due to cropland conversion. Blue is less carbon emissions due to land conversion, while red is more. Tropical areas with high conversion of croplands, such as Southeast Asia, have the highest emissions due to land conversion. Map courtesy of Paul West, University of Wisconsin-Madison Center for Sustainability and the Global Environment and University of Wisconsin-Madison Center for Limnology.Click to enlarge.
Combining cropland distribution and changes in carbon stocks due to crop expansion into native ecosystems shows that carbon loss per ton of annual crop yield is nearly three times as high in the tropics compared to temperate regions. Map courtesy of Paul West, University of Wisconsin-Madison Center for Sustainability and the Global Environment and University of Wisconsin-Madison Center for Limnology.Click to enlarge.
80% of tropical agricultural expansion between 1980-2000 came at expense of forests
(09/02/2010) More than 80 percent of agricultural expansion in the tropics between 1980 and 2000 came at the expense of forests, reports research published last week in the early online edition of the Proceedings of the National Academy of Sciences (PNAS). The study, based on analysis satellite images collected by the United Nations Food and Agricultural Organization (FAO) and led by Holly Gibbs of Stanford University, found that 55 percent of new agricultural land came at the expense of intact forests, while 28 percent came from disturbed forests. Another six percent came from shrub lands.
Will it be possible to feed nine billion people sustainably?
(01/28/2010) Sometime around 2050 researchers estimate that the global population will level-out at nine billion people, adding over two billion more people to the planet. Since, one billion of the world's population (more than one in seven) are currently going hungry—the largest number in all of history—scientists are struggling with how, not only to feed those who are hungry today, but also the additional two billion that will soon grace our planet. In a new paper in Science researchers make recommendations on how the world may one day feed nine billion people—sustainably.
Farms in the sky, an interview with Dickson Despommier
(10/12/2010) To solve today's environmental crises—climate change, deforestation, mass extinction, and marine degradation—while feeding a growing population (on its way to 9 billion) will require not only thinking outside the box, but a "new box altogether" according to Dr. Dickson Despommier, author of the new book, The Vertical Farm. Exciting policy-makers and environmentalists, Despommier's bold idea for skyscrapers devoted to agriculture is certainly thinking outside the box.
Nearly half of the world's wetlands used for crops
(09/27/2010) Wetlands used for crops have expanded significantly over the past eighty years. According to a new study in the open-access journal Tropical Conservation Science, wetlands being utilized for crop production has jumped from 25 percent in 1926 to 43 percent in 2006 of the world's wetlands as identified by the Ramsar Convention on Wetlands.
Indonesia's forest conservation plan may not sufficiently reduce emissions
(08/25/2010) One third of Indonesia's greenhouse gas emissions from deforestation originate from areas not officially defined as 'forest' suggesting that efforts to reduce emissions from deforestation and degradation (REDD+) may fail unless they account for carbon across the country's entire landscape, warns a new report published by the World Agroforestry Centre (CGIAR). The policy brief finds that up to 600 million tons of Indonesia's carbon emissions 'occur outside institutionally defined forests' and are therefore not accounted for under the current national REDD+ policy, which, if implemented, would enable Indonesia to win compensation from industrialized countries for protecting its carbon-dense forests and peatlands as a climate change mechanism.
Could biochar save the world?
(08/16/2010) Biochar—the agricultural application of charcoal produced from burning biomass—may be one of this century's most important social and environmental revolutions. This seemingly humble practice—a technology that goes back thousands of years—has the potential to help mitigate a number of entrenched global problems: desperate hunger, lack of soil fertility in the tropics, rainforest destruction due to slash-and-burn agriculture, and even climate change. "Biochar is a recalcitrant form of carbon that will stay almost entirely unaltered in soils for very long periods of time. So you can sequester carbon in a simple, durable and safe way by putting the char in the soil. Other types of carbon in soils rapidly turn into carbon dioxide. Char doesn't," managing director of the Biochar Fund, Laurens Rademakers, told mongabay.com in a recent interview.
Ending deforestation could boost Brazilian agriculture
(06/26/2010) Ending Amazon deforestation could boost the fortunes of the Brazilian agricultural sector by $145-306 billion, estimates a new analysis issued by Avoided Deforestation Partners, a group pushing for U.S. climate legislation that includes a strong role for forest conservation. The analysis, which follows on the heels of a report that forecast large gains for U.S. farmers from progress in gradually stopping overseas deforestation by 2030, estimates that existing Brazilian farmers could see around $100 billion from higher commodity prices and improved access to markets. Meanwhile landholders in the Brazilian Amazon—including ranchers and farmers—could see $50-202 billion from carbon payments for forest protection.
UN warns food prices could rise by 40 percent
(06/17/2010) Some staple food prices could rise by as much as 40 percent in the next decade, according to a new report by the UN's Food and Agriculture Organization (FAO).
How an agricultural revolution could save the world's biodiversity, an interview with Ivette Perfecto
(05/04/2010) Most people who are trying to change the world stick to one area, for example they might either work to preserve biodiversity in rainforests or do social justice with poor farmers. But Dr. Ivette Perfecto was never satisfied with having to choose between helping people or preserving nature. Professor of Ecology and Natural Resources at the University of Michigan and co-author of the recent book Nature’s Matrix: The Link between Agriculture, Conservation and Food Sovereignty, Perfecto has, as she says, "combined her passions" to understand how agriculture can benefit both farmers and biodiversity—if done right.
Just how bad is meat-eating for the environment?
(03/28/2010) Meat is booming. In the past thirty years, livestock production has increased threefold. In many parts of the world where incomes are expanding, meat, once a delicacy, is now eaten regularly and voraciously. But what are the environmental impacts of this 'livestock revolution'? Two recent studies look at the global impact of the livestock industry, one alleges that its environmental impacts in relation to greenhouse gas emissions has been overestimated, while the other takes a holistic view of the industry's environmental impact.