Do Cows Cause Climate Change?
Methane gas is mostly released by dairy cow belches and manure decomposition rather than farts. There’s a hypothesis, then, that may sound logical to some: Eliminate U.S. dairy cows and you’ll lessen climate issues.
But does that hypothesis stand up to sound science?
Will Removing Dairy Cows Help Stop Climate Change?
A team of researchers from Virginia Tech and U.S. Department of Agriculture recently put it to the test and found that if the dairy herd were somehow removed from the U.S., greenhouse gas emissions (GHG) would only be reduced by about 0.7%, while seriously reducing the supply of various essential nutrients that milk provides.
“This idea of removing animal agriculture is being overly simplified in many ways, as well as the assumption that nutrients can be easily replaced,” said Juan Tricarico, Ph.D., vice president for sustainability research at the Innovation Center for U.S. Dairy, which supported the research. “It’s a story that on the surface may sound compelling, but you have to remember that the truth is usually much deeper in terms of all the factors that contribute to an outcome. And, all those factors cannot be understood until they are tested, as this study did.”
Milk production only contributes approximately 1.3% of all U.S. GHG emissions, the researchers say. (By comparison, transportation as an industry in the U.S. accounts for 28% of GHG emissions.) While proponents of the cow elimination hypothesis might suggest plant-based alternatives as an environmentally friendly option to dairy, those foods also generate emissions and come with their own footprint. For example, reallocating land currently used for dairy cow feed to grow fruits and vegetables instead resulted in increased GHG emissions and reduced supply of calcium, vitamins D and B12, riboflavin and alpha-linolenic acid. Growing nuts and pulses reduced emissions but resulted in similar nutrient supply shortages.
Affordable dairy for accessible nutrients
Eliminate the cows to reduce emissions and you also eliminate a great source of accessible, affordable and nutrient-rich dairy foods. Americans get more than half of their calcium and vitamin D from milk, cheese and yogurt. Different researchers found that it is not a simple task to obtain essential nutrients found in milk from another single food source, or even many foods, without increasing daily calories – and cost.
“The efficiency through which dairy provides us these nutrients would not be possible without cows,” said Katie Brown, EdD, RDN, senior vice president, scientific affairs and outreach for National Dairy Council. “This study indicates that without cows, there would be a minimal impact to greenhouse gas emissions and a significant impact to the availability of essential nutrients needed for human health, such as calcium, vitamin D and vitamin B12.”
The researchers also examined what they call the “downstream” effects of eliminating dairy cows, including land use and sourcing of fertilizers. Pastures used for dairy cows would no longer be used for that purpose. The same goes for cropland that farmers use to produce nutritious feed for their cattle. Under some simulated scenarios, synthetic fertilizer production and associated GHG emissions would increase, offsetting the GHG reduction expectations related to the dairy herd elimination.
Tricarico cites the continuous improvements made by the U.S. dairy industry as an example of its environmental stewardship. On the farm, the environmental impact of producing a gallon of milk in 2017 shrunk significantly from 2007, requiring 30% less water, 21% less land and a 19% smaller carbon footprint.
He credits the cows’ ability for consuming plants and byproducts not fit for human consumption to produce nutrient-rich milk. And he credits dairy farmers for effectively managing cow manure, such as using it as a natural fertilizer or as a source of energy.
“The strength of the study is its focus on the trade-off between GHG emissions and supplying nutrients people need to be healthy and lead quality lives. Milk continues to provide a valuable bundle of nutrients while farmers keep reducing GHG emissions per pound of milk produced,” Tricarico said. “It’s the realization that dairy cows convert feed resources unavailable to people into nutritious milk while continuously improving the efficiency of use of natural resources with the goal to become carbon neutral or better.”