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California has established aggressive world-leading targets (SB 1383 [Lara 2016]) for reducing methane from dairy and other livestock (primarily beef cattle) sectors by 2040.

As the California Air Resources Board's Analysis of Progress report correctly concludes, no single livestock methane reduction action can achieve the targeted reductions. Achieving the state’s targeted reductions requires a coordinated, comprehensive approach involving continued efficiency (fewer cows), methane avoidance, methane capture and utilization, as well as enteric methane reduction activities. Ongoing research is also important as we seek to identify, implement, and verify cost-effective enteric and other reduction strategies.

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Efficiency and Attrition

Producing more milk with fewer cows greatly reduces the carbon intensity of milk production. After a period of rapid herd growth in California between 1980 and 2008, the number of cows in California has steadily declined from 1.885 million milk cows in 2008 to 1.688 million in 2022, according to the United State Department of Agriculture (USDA)'s most recent Census of Agriculture (2017-2022). This herd attrition has already accounted for approximately 2 million metric tons of CO2e reduction from the state’s dairy sector (a roughly 10% decrease). Continued and likely accelerated attrition will lead to an estimated additional 1 MMT CO2e reduction by 2030, or a total of approximately 3 million metric tons.

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Fewer Cows Since 2008


Over the past 50-plus years, California dairy production has undergone significant advancement, including advanced nutrition, improved animal care and welfare, breeding practices, as well as overall feed crop production efficiency.

According to research published in the Journal of Dairy Science, the climate footprint of milk production in California has been significantly reduced over the past 50 years (1964 to 2014). Scientists at the University of California, Davis conducted a life cycle environmental assessment (cradle to farm gate) of California dairy farm production, using the latest scientific models and international research standards.

“The study documents the productivity, efficiency, and overall sustainability of milk production in California and the critical role dairy cows play in regenerative agricultural practices and sustainable food systems,” said Dr. Ermias Kebreab, Professor at UC Davis and Sesnon Endowed Chair, who led graduate student Anna Naranjo in completing the research project.

The study’s key findings include:

  • The amount of greenhouse gas emissions per each unit of milk (e.g. glass or gallon) produced has decreased more than 45 percent, due to increased milk production efficiency, including improved reproductive efficiency, nutrition, comfort, and overall management.

  • The amount of water used per unit of milk produced has decreased more than 88 percent, primarily due to improved feed crop production and water use efficiency.

  • Dramatically improved feed crop production and utilization of agricultural byproducts have led to significant reductions in the amount of natural resources used to produce each unit of milk, including, land, water, fossil fuels, pesticides and energy.

As the study documents, more than 40 percent of dairy feed ingredients in California are byproducts of other agricultural and food production processes, such as almond hulls, citrus and tomato pulp, culled carrots and other similar products that are not suited for human consumption but make healthy, nutritious feed for cattle. As a result, nearly half of the feed needed to produce California milk—which represents about 20 percent of all U.S. milk—is being provided without a single drop of additional water. Dairy cows are efficient recyclers, making use of food and agricultural byproducts that are either indigestible or undesirable for humans and avoiding the need to landfill or otherwise dispose of these materials.


The study shows that California's dairy farm families are producing milk more efficiently and sustainably, minimizing their climate footprint in the process. While there is always more work to be done, the findings show a significant overall improvement in environmental performance, producing more wholesome, nutritious milk and dairy products with fewer natural resources, less water, less energy, and fewer fossil fuels.

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Click here to read the full summary about California's comprehensive approach to methane reduction.

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