Are cattle in the U.S. causing an increase in global warming?

Cows: Problem or solution? ( FJ )

Over the past decade, we have seen the media place blame for our changing climate on cattle. Scientific evidence does not support this claim though for cattle in the United States.  

Cattle produce a lot of methane gas, primarily through enteric fermentation and fermentation of their manure. Methane is a powerful greenhouse gas that, along with nitrous oxide, carbon dioxide and some other compounds in the atmosphere, create a blanket around our planet. This is good; without this atmospheric blanket, the earth would be too cold for us to survive. The current problem is that concentrations of these gases in the atmosphere are increasing, which is thickening our blanket.

Greenhouse gases and the atmosphere

The methane that cattle produce is part of a natural carbon cycle that has been happening since the beginning of life on our planet. Through photosynthesis, carbon dioxide is extracted from the atmosphere and fixed as carbohydrates in plant material. Cattle consume and digest these carbohydrates, where some of the carbon is transformed to carbon dioxide and methane gases that are respired back to the atmosphere. This methane is oxidized in the atmosphere through a series of reactions, transforming that carbon back to where it started as carbon dioxide in the atmosphere.

In contrast, when we burn fossil fuels, we are taking carbon that has been stored in the earth since pre-historic times and converting it to “new” carbon dioxide released to the atmosphere. For every gallon of fuel consumed, about 20 pounds of carbon dioxide are created and released to the atmosphere. We are releasing this gas more rapidly than it can be absorbed in our oceans and soils. Thus, we are observing a rather rapid increase in atmospheric carbon dioxide concentration, and the effect of this change will be with us for 1000s of years. Whereas cattle are part of a natural cycle with short-term impact, burning of fossil fuels has a more permanent impact.

Cattle numbers and greenhouse gas emissions

We must also consider the number of cattle and their productivity. Cattle numbers in the United States have been stable or declining for many years. Beef cow numbers peaked in 1975, and the current number is similar to that maintained in the early 1960s. Dairy cow numbers are the lowest they have been in over 100 years.

We also have to consider that modern cattle are getting larger and more productive. They consume more feed and produce more methane per animal, but they are also more efficient producing more meat or milk per unit of feed consumed. Considering cattle numbers and these increases in productivity and efficiency, methane emission from cattle in the United States has not increased over the past 50 years.

This is recent history; what if we look further back? Ruminant wildlife were prevalent in North America before European settlement. Although there are not accurate numbers for the buffalo, elk, deer, and other ruminants on the continent at that time, estimates are available. Based upon those estimates, these animals produced methane in the range of 50% less to 25% more than the current population of cattle, other farm ruminants and wildlife. This indicates that cattle today are not contributing a substantial increase in the methane emissions from U.S. lands compared to pre-settlement times.

So what might be increasing methane concentration in the atmosphere? Global cattle numbers are increasing. Methane is also released during the extraction, refining, and transport of fossil fuels. This methane also oxidizes in the atmosphere to form carbon dioxide, but this is not part of a natural cycle. Like the combustion of fuels, this removes carbon stored in the earth to create new carbon dioxide in the atmosphere with very long-term effects.

Can cattle be part of the solution?

The fact remains that cattle produce a lot of methane. This methane is essentially wasted energy escaping the rumen. Reducing this waste by increasing the efficiency of the rumen may provide a substantial benefit by producing more meat or milk with less feed consumed. Dietary changes can reduce enteric methane production, and feed supplements are being explored to improve feed efficiency and reduce emissions.

Depending upon the cost of dietary changes and supplements, these interventions may provide economic benefit to the producer. In addition, there is the possibility of claiming carbon credits for this reduction. Companies and other institutions desiring to reduce their carbon footprint may be willing to pay cattle producers to use these mitigation practices. This is largely in the future for now.

So, although cattle in the United States are not causing an increase in global warming and related climate change, they may become part of the solution. Reducing any source of greenhouse gas emission will benefit our planet.

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