New Worldwatch Institute study examines the
agricultural sector's impact on global greenhouse gas emissions
Washington, D.C.---Global greenhouse gas emissions from the agricultural sector totaled 4.69 billion tons of carbon dioxide (CO2) equivalent in 2010 (the most recent year for which data are available), an increase of 13 percent over 1990 emissions. By comparison, global carbon dioxide emissions from transport totaled 6.76 billion tons that year, and emissions from electricity and heat production reached 12.48 billion tons, according to Worldwatch Institute's Vital Signs Online service (www.worldwatch.org).
Growth in agricultural production between 1990 and 2010 outpaced growth in emissions by a factor of 1.6, demonstrating increased energy efficiency in the agriculture sector.
The three most common gases emitted in agriculture are nitrous oxide, CO2, and methane. Methane is generally produced when organic materials----such as crops, livestock feed, or manure----decompose anaerobically (without oxygen). Methane accounts for around 50 percent of total agricultural emissions. Enteric fermentation----the digestion of organic materials by livestock----is the largest source of methane emissions and of agricultural emissions overall.
Nitrous oxide is a by-product generated by the microbial breakdown of nitrogen in soils and manures. Nitrous oxide production is particularly high in cases where the nitrogen available in soils exceeds that required by plants to grow, which often occurs when nitrogen-rich synthetic fertilizers are applied. Nitrous oxide is responsible for around 36 percent of agricultural greenhouse gas emissions.
Finally, carbon dioxide is released from soils when organic matter decomposes aerobically (with oxygen). The largest source of CO2 emissions within agriculture is the drainage and cultivation of "organic soils"----soils in wetlands, peatlands, bogs, or fens with high organic material. When these areas are drained for cultivation, organic matter within the soil decomposes at a rapid rate, releasing CO2. This process accounts for around 14 percent of total agricultural greenhouse gas emissions.
Emissions from enteric fermentation rose by 7.6 percent worldwide between 1990 and 2010, but regional variation was high. At 51.4 percent and 28.1 percent, respectively, Africa and Asia saw their emissions increase, while emissions in Europe and Oceania fell by 48.1 percent and 16.1 percent. Europe's significant reduction in emissions parallels the decline in its beef production between 1990 and 2010, but it may also reflect increased use of grains and oils in cattle feed instead of grasses.
"Adding oils or oilseeds to feed can help with digestion and reduce methane emissions. But a shift from a grass-based to a grain- and oilseeds-based diet often accompanies a shift from pastures to concentrated feedlots, which has a range of negative consequences such as water pollution and high fossil fuel consumption," said Laura Reynolds, Worldwatch Food and Agriculture Researcher and the study's author. "Aside from reducing livestock populations, there is no other clear pathway to climate-friendly meat production from livestock."
Manure that is deposited and left on pastures contributes to global nitrous oxide emissions because of its high nitrogen content. When more nitrogen is added to soil than is needed, soil bacteria convert the extra nitrogen into nitrous oxide and emit it into the atmosphere----a process called nitrification. Emissions from manure on pasture were highest in Asia, Africa, and South America, accounting for a combined 81 percent of global emissions from this source.
These data indicate the huge share of global emissions that is attributable to livestock production. While reducing livestock populations is one way to reduce global emissions from agriculture, farmers and landowners have numerous other opportunities for mitigation, many of which offer environmental and even economic co-benefits. For instance, growing trees and woody perennials on land can sequester carbon while simultaneously helping to restore soils, reduce water contamination, and provide beneficial wildlife habitat. Reducing soil tillage can rebuild soils while lowering greenhouse gas emissions. Some practices can even result in increased income for farmers----"cap-and-trade" programs allow farmers to monetize certain sequestration practices and sell them, while government programs like the U.S. Conservation Reserve Program pay farmers to set aside some of their land for long-term restoration.
Further highlights from the report:
About the Worldwatch Institute:
Worldwatch is an independent research organization based in Washington, D.C. that works on energy, resource, and environmental issues. The Institute's State of the World report is published annually in more than a dozen languages. For more information, visit www.worldwatch.org.
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NERRS Grant Funds Research into Roles Salt Marshes Play in Sequestering Greenhouse Gases, Will Link Salt Marsh Restoration to Carbon Markets
(WASHINGTON)-The Waquoit Bay National Estuarine Research Reserve (WBNERR) has been awarded a $1.3 million grant by the National Estuarine Research Reserve System (NERRS) Science Collaborative to examine the role that salt marshes play in climate change and the effect that nitrogen pollution has on that role. The three-year project will quantify how much carbon in the form of greenhouse gases (GHG) is stored and emitted from coastal wetlands, and how increases in nitrogen and changes in climate and sea level affect their ability to store that carbon.
Heading the study will be Dr. Kevin Kroeger of USGS, Dr. Jianwu Tang of the MBL, and Dr. Serena Moseman-Valtierra of URI. The NERRS Science Collaborative is administered by the University of New Hampshire through a cooperative agreement with the National Oceanic and Atmospheric Administration. The research will also be supported by USGS Coastal and Marine Geology Program.
Restore America's Estuaries (RAE), a national alliance of 11 regional, coastal conservation organizations, was heavily involved in development of the proposal, and will play an essential role in "translating" the science into products that will be used by the coastal management community.
Among RAE's goals is the creation of a national greenhouse gas offset protocol for coastal tidal wetlands. Such a protocol would help bring coastal wetlands into international carbon markets, providing new opportunities and incentives for private and public investment in the restoration and preservation of vital tidal wetlands.
Carbon dioxide, nitrous oxide and methane are potent greenhouse gases (GHG), which contribute to global warming by trapping heat in the atmosphere.
While it is well known that forest ecosystems store large amounts of GHG carbon-a process popularly known as "Green Carbon"-and help reduce global warming, new research is focusing on so-called "Blue Carbon" in coastal wetland ecosystems such as mangroves, seagrasses, and salt marshes. Recent findings suggest that coastal wetlands may sequester and store carbon at rates 3-5 times greater than temperate forests, making them efficient-and essential-carbon "sinks," as world temperatures rise.
But data indicate that when nitrogen from sources such as septic systems, stormwater discharges, fertilizer runoff, and airborne pollution is added to coastal marshes, their ability to store carbon may be substantially reduced. In extreme cases, coastal wetlands may even become net "sources" of GHG and thus contribute to climate change.
"This long-term study offers researchers a real-world 'laboratory' to test if excess nitrogen produces the same type and volume of GHG emissions that we have observed in shorter-term experiments," says Moseman-Valtierra. If data from the three-year study bears this out, it would strengthen incentives for reducing the amount of nitrogen pollution flowing into coastal ecosystems.
A large focus of the NERRS Science Collaborative is to link scientists with "end-users," who will apply the science to better manage the coast.
"The idea is to foster research that has direct, relevant, and significant applications for communities locally and across the nation," said Alison Leschen, WBNERR Reserve Manager, and Project Manager for the grant.
To further this goal, the collaborative project requires that end-users-coastal habitat restoration practitioners-be involved in project development, and that the research is a high priority for at least one of the 28 NOAA NERRs located around the U.S. coast.
"We know that coastal tidal wetlands sequester greenhouse gases like carbon dioxide at impressive rates," said Steve Emmett-Mattox, Senior Director of Strategic Planning and Programs for Restore America's Estuaries. "The GHG quantification model that will be developed under this project will help refine wetlands GHG methodologies."
As part of the collaborative project, the Manomet Center for Conservation Sciences in Plymouth will conduct an economic analysis of the potentially deleterious effect that nitrogen has on the "value" of a salt marsh for storing GHGs. If the effect is significant, carbon markets may provide one economic incentive for towns to remove nitrogen, helping defray the costs of additional sewers, storm drains, and other expensive and infrastructure-heavy mitigation strategies.
Using study data, a user-friendly model will be developed by a modeler from Florida International University that will enable towns to evaluate this potential. Such a model could also be used by land trusts and others to provide another way to "measure" land restored or preserved besides number of acres. As an example, The Nature Conservancy or Massachusetts Division of Ecological Restoration, which both supported the grant proposal, could state that a land purchase or restoration project contributed "X" tons of GHG storage.
WBNERR is particularly interested in the project because it addresses two of the most significant issues facing coastal communities today -climate change and nitrogen pollution.
"We are very excited to be part of this incredibly talented team doing cutting-edge research that has local, national, and even global applications," said Leschen.
Most of the field work will take place at the Reserve's salt marsh at South Cape Beach in Mashpee, which is being set up with infrastructure to measure sea level rise and its effect on this important ecosystem as part of a NERRS-wide "bio-monitoring" project.
"The two projects meshed so well - our hope is that by establishing that area as an observatory for all types of research on climate change, we will create a real synergy between projects, enabling scientists to feed off each others' findings," said Leschen.
WBNERR is one of 28 NOAA National Estuarine Research Reserves around the U.S. coast, whose goal is to improve coastal stewardship through research, education, and demonstration. They translate science conducted on the Reserve and elsewhere to coastal managers, school classes, and community members to foster understanding about the importance of coastal ecosystems and how what people do on land affects the water. WBNERR is a federal/state partnership and is also part of the Massachusetts Department of Conservation and Recreation.
Founded in 1995, Restore America's Estuaries is a national alliance of 11 regional, coastal conservation organizations with more than 250,000 volunteer-members dedicated to preserving our nation's estuaries. RAE members include: the American Littoral Society, Chesapeake Bay Foundation, Conservation Law Foundation, Coalition to Restore Coastal Louisiana, Galveston Bay Foundation, North Carolina Coastal Federation, People for Puget Sound, Save The Bay-Narragansett Bay, Save The Bay-San Francisco, Save The Sound-a program of the Connecticut Fund for the Environment, and Tampa Bay Watch.