- Author: Mary Burich, CLEAR Center
Are cattle a secret weapon for taking on California wildfires?
California's cattle ranchers contribute a significant amount to the region's culture, economy and food supply, but do they also inadvertently help to temper the wildfires that have been plaguing the state? And if so, is it a better alternative – environmentally speaking – to letting grasslands burn?
A new study published in the journal Sustainability delves into the topic, weighing the advantages – and disadvantages – grazing cattle bring to the table. Researchers, including scientists from University of California, Davis and UC Agriculture and Natural Resources, set out to calculate the greenhouse gas emissions of cows consuming vegetation that would otherwise burn in wildfires. Then they estimated the GHG emissions that would result should that forage be untouched and therefore, consumed by fire, eventually comparing the two.
Feeling the burn
Given the severity of California's recent wildfires and the belief they will continue and even escalate in the near future, it's a discussion worth having, said Frank Mitloehner, an expert in animal agriculture and air quality from UC Davis, director of the CLEAR Center and one of the researchers who contributed to the peer-reviewed article.
“Each year from 2010 to 2020, California lost on average 89,000 acres of grassland to wildfires,” said Mitloehner, who is also a Cooperative Extension specialist. “In addition to the obvious disruption and devastation they caused, the fires spewed greenhouse gases and harmful particulate matter such as black carbon into the air and into our atmosphere. Those alone threaten climate health and human well-being.”
A fast and furious gas
Cattle are adept at eliminating herbaceous fuel as they graze. However, at the same time, their specialized digestive system produces methane that is expelled most often in the form of enteric emissions … more commonly known as belches. By way of background, methane is a potent greenhouse gas that warms the atmosphere at 25 times the rate of carbon dioxide over 100 years. But it's only in the atmosphere for 10 to 12 years after it's emitted. Following that, it's broken down into carbon dioxide and water vapor.
For that reason, Mitloehner refers to methane as a “fast and furious” gas. Furious because it warms with a vengeance and fast because it does so for only a short time, especially when compared to carbon dioxide. Furthermore, because of the biogenic carbon cycle, whereby plants extract carbon dioxide from the atmosphere for photosynthesis, the warming of methane and its byproducts can end entirely when it's hydrolyzed and used by plants.
How researchers calculated emissions
In order to determine if grazing, methane-emitting cattle are better for the atmosphere than burning grasslands, Mitloehner and the other researchers employed a method known as “Monte Carlo simulation,” a mathematical technique used by scientists to predict outcomes of an uncertain event.
Looking exclusively at methane emissions, they found it's better to have cows eat vegetation than to have wildfires burn it. Granted, it's only marginally better, but when one considers other advantages of animal agriculture and conversely, other disadvantages of widespread, uncontrolled fire, the conversation suddenly shifts.
“Even if cattle provided no other benefit to us, which certainly is not true, we can now make the case that they are helpful to us in yet another way,” Mitloehner said.
Friends or foes?
It goes without saying that one would be hard pressed to find much good to say about wildfires, but that doesn't hold true for animal agriculture. The industry provides jobs and supports the economy in other ways as well. Plus, it is a major source of protein-rich food that is in increasing demand as the world's population continues on a trajectory toward 10 billion people by the year 2050.
Where global warming is concerned, the industry is in the unique position of being able to reach net-zero warming, also known as climate neutrality, if it continues to aggressively chip away at its methane emissions, which Mitloehner asserts is of critical importance to the planet. “Few other sectors can reduce its warming to net zero and still be of service to society, but agriculture can because of the way methane behaves in the atmosphere,” he said.
To be clear, grazing cows are no match for wildfires. Yet, in addition to everything else the sector does for us, slowing the burn and keeping relatively more methane from entering the atmosphere are not nothing.
In addition to Mitloehner, authors of the study are Cooperative Extension advisors Sheila Barry, Devii Rao and Theresa Becchetti; Rowan Peterson, Ermias Kebreab and Minju Jung of UC Davis; and Felix Ratcliff and Kaveh Motamed of LD Ford.
This article was first published on the website of the CLEAR (Clarity and Leadership for Environmental Awareness and Research) Center at UC Davis.
/h3>/h3>/h3>/h3>/h3>- Author: Frank M Mitloehner
Frank Mitloehner, Professor & Air Quality Specialist
Department of Animal Science, University of California, Davis
As the November 2015 Global Climate Change Conference COP21 concluded in Paris, 196 countries reached agreement on the reduction of fossil fuel use and emissions in the production and consumption of energy, even to the extent of potentially phasing out fossil fuels entirely. Both globally and in the U.S., energy production and use, as well as the transportation sectors, are the largest anthropogenic contributors of greenhouse gasses (GHG), which are believed to drive climate change. While there is scientific consensus regarding the relative importance of fossil fuel use, anti-animal agriculture advocates, portray the idea that livestock is to blame for a lion's share of the contributions to total GHG emissions.
One argument often made is U.S. livestock GHG emissions from cows, pigs, sheep and chickens are comparable to all transportation sectors from sources such as cars, trucks, planes, trains, etc. The argument suggests the solution of limiting meat consumption, starting with “Meatless Mondays,” will show a significant impact on total emissions.
When divorcing political fiction from scientific facts around the quantification of GHG from all sectors of society, one finds a different picture. Leading scientists throughout the U.S., as well as the U.S. Environmental Protection Agency (EPA) have quantified the impacts of livestock production in the U.S., which accounts for 4.2% of all GHG emissions, very far from the 18% to 51% range that advocates often cite. Comparing the 4.2% GHG contribution from livestock to the 27% from the transportation sector, or 31% from the energy sector in the U.S.brings all contributions to GHG into perspective. Rightfully so, the attention at COP21 was focused on the combined sectors consuming fossil fuels as they contribute more than half of all GHG in the U.S.
Breaking down the 4.2% EPA figure for livestock by animal species, shows the following contributors: beef cattle 2.2%, dairy cattle 1.37%, swine 0.47%, poultry 0.08%, sheep 0.03%, goats 0.01% and other (horses, etc.) 0.04%. It is sometimes difficult to put these percentages in perspective, however; if all U.S. Americans practiced Meatless Mondays, we would reduce the U.S. national GHG emissions by 0.6%. A beefless Monday per week would cut total emissions by 0.3% annually. One certainly cannot neglect emissions from the livestock sector but to compare them to the main emission sources would put us on a wrong path to solutions, namely to significantly reduce our anthropogenic carbon footprint to reduce climate change.
In spite of the relatively low contributions to total GHG emissions, the U.S. livestock sector has shown considerable progress during the last six plus decades, and commitment into the future, to continually reduce its environmental footprint, while providing food security at home and abroad. These environmental advances have been the result of continued research and advances in animal genetics, precision nutrition, as well as animal care and health.
1950 | 2015 | |
Total Dairy Cows: | 22 million dairy cows | 9 million dairy cows (-59%) |
Milk Production: | 117 billion pounds | 209 billion pounds (+79%) |
Carbon Footprint: | 1/3 that of 1950 | |
1970 | 2015 | |
Total Beef Cattle: | 140 million head | 90 million head |
Beef Production: | 24 billion pounds | 24 billion pounds (-36%) |
Globally, the U.S. livestock sector is the country with the relatively lowest carbon footprint per unit of livestock product produced (i.e. meat, milk, or egg). The reason for this achievement largely lies in the production efficiencies of these commodities, whereby fewer animals are needed to produce a given quantity of animal protein food, as the following milk production example demonstrates: the average dairy cow in the U.S. produces 22,248 lbs. milk/cow/year. In comparison, the average dairy cow in Mexico produces 10,500 lbs. milk/cow/year, thus it requires 2-plus cows in Mexico to produce the same amount of milk as one cow in the U.S. India's average milk production per cow is 2,500 lbs. milk/cow/year, increasing the methane and manure production by a factor of 9 times compared to the U.S. cow. As a result, the GHG production for that same amount of milk is much lower for the U.S. versus the Mexican or Indian cow. Production efficiency is a critical factor in sustainable animal protein production and it varies drastically by region.
Improvements in livestock production efficiencies are directly related to reductions of the environmental impact. Production efficiencies and GHG emissions are inversely related—when the one rises, the other falls.
The 2050 challenge to feeding the globe is real: throughout our lifetime, the global human population will have tripled from three to more than nine billion people without concurrent increases of natural resources to produce more food. Our natural resources of land, water and minerals (fertilizer) necessary for agricultural production, have not grown but in fact decreased. As a result, agriculture will have to become much more efficient worldwide and engage in an efficient path similar to the one it has traveled down in U.S. livestock production in recent decades.
How can emissions accurately and fairly be assessed to lay ground for a path for solutions?
In its quest to identify a sustainable, scientific path toward fulfilling the future global food demand, the Food and Agriculture Organization of the United Nations (FAO) has formed an international partnership project to develop and adopt a “gold standard” life cycle assessment (LCA) methodology for each livestock specie and the feed sector. The ‘Livestock Environmental Assessment and Performance Partnership' (LEAP), engaged with more than 300 scientists from the world's most prestigious academic institutions in developing this unprecedented effort in developing a global benchmarking methodology. The first three-year phase project was finalized in December 2015 with six publicly available LCA guidelines. This globally harmonized quantification methodology will not only allow the accurate measurement by livestock species and production regions across the globe today, but will also identify opportunities for improvement and the ability to measure that progress in each region going forward.
Summary
Addressing the 2050 challenge of supplying food to a drastically growing human population can sustainably be achieved through intensification of livestock production. Indeed, intensification provides large opportunities for climate change mitigation and can reduce associated land use changes such as deforestation. Production efficiencies reduce environmental pollution per unit of product.
The livestock sector is committed to continuous improvement of their environmental impact in North America, and to doing its part in transferring knowledge, technologies and best practices to enhance global environmental livestock impact by region. Now is the time to end the rhetoric and separate facts from fiction around the numerous sectors that contribute emissions and to identify solutions for the global food supply that allow us to reduce our impact on the planet and its resources.
Last updated 06-28-16
- Author: Yoni Cooperman
- Contributor: Jordon Wade
A variety of cover crops exist, way too many to be fully covered in this blog post. Generally speaking, cover crops tend to be grasses or legumes, and many growers utilize mixes to achieve targeted results. Legumes can be a source of N fertilization, though they can also contribute to N pollution if N levels exceed crop needs. Grasses have the potential to hold on to excess soil N and limit losses through nitrate leaching. Mixes of multiple cover crop types with different uses are used to maximize inputs of organic matter in hopes of building soil carbon.
While cover crops can have many potential benefits, like any other management decision tradeoffs are involved. While competition for soil water and nutrients can be used to control vigor, under certain conditions this can be harmful for vine development. Another possible downside to using cover crops, their potential to increase the production of greenhouse gas emissions, was the focus of our study conducted in a three year old Merlot vineyard in Lodi, CA. The vineyard soil is classified as a Devries sandy loam.
In our two year study, we compared rates of greenhouse gas (GHG) emissions from vineyard alleyway soil grown under three different cover crop mixes: a legume mix, a “soil builder” mix, and a ryegrass treatment all planted at 100 lbs/ac.
These three treatments were chosen to represent three reasons growers might utilize cover crops in a vineyard. The legume mix was chosen to be a “green manure” and increase soil nitrogen. The “soil builder” mix was meant to maximize plant biomass and increase soil organic matter. The ryegrass was chosen as a “catch crop” that can take up large amounts of soil N, limiting N losses through nitrate leaching.
After our two year monitoring period, we found that cover crops had little effect on soil N2O emissions, while they increased soil CO2 emissions. While CO2 emissions were higher when cover crops were used, there were no differences between the different cover crop types. These findings suggest that during drought years, growers are free to choose the cover crop mixes they think will best serve their needs, without being overly concerned about excess N2O emissions stimulated by cover cropping. However, the legume mix did result in higher levels of soil N and the ryegrass treatment did decrease leachable soil nitrate. It is unclear if the "soil builder" mix resulted in increased soil organic matter, although that is to be expected, considering it takes several years to substantially increase soil organic matter content.
For more information about utilizing cover crops visit the Solutions Center for Nutrient Management page on cover crops.