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CU �ֲ���ý researcher Cliff Bueno de Mesquita and colleagues are showing why microbial solutions to livestock methane emissions reductions won’t stop beef and dairy’s environmental and health problems

By nature, cows are gassy creatures. But it’s not just the stink of their manure or their belches that are troublesome. The methane gas released by ruminants like cows (or bison, sheep or goats) also causes a lot of trouble for the planet.��

That’s because methane is a potent greenhouse gas with a dramatically higher global warming potential than carbon dioxide. And ruminants raised for food account for .��

Over the last decade or so scientists have been hard at work figuring out how to infuse cows’ feedstock with additives that inhibit methane-producing microbes. The process could reduce those methane emissions and potentially produce a more “climate-friendly” beef.

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Cliff Bueno de Mesquita, who studies microbial ecology of permafrost and ancient sediments in the lab of ecology and evolutionary biology Professor Noah Fierer and in the Cooperative Institute for Research in Environmental Sciences, teamed up with other microbiologists passionate about environmental issues for this perspective piece. (Photo: Cliff Bueno de Mesquita)

Sounds like a win-win, right? A new perspective piece by�� (PhDEBio'19), a research associate in the lab of ecology and evolutionary biology Professor Noah Fierer and the , says otherwise.��

“Even if you could decrease cows’ methane emissions by 100%, cows are still worse than plant-based agriculture for their land use, water use, pollution and impacts on human health,” says Bueno de Mesquita.

In��, Bueno de Mesquita and a team of microbiologist colleagues outline all the reasons that altering cows’ rumen microbes is a misdirected use of time, money and energy. “This is basically distracting from what we really need to be doing, which is reducing the ruminant population size,” he says.��

This conclusion—that reducing the numbers of ruminants raised for food is the only solution to actually reducing livestock’s impact on the planet—has already been drawn by researchers around the world.��

“There are a lot of great scientists working on this topic, with strong data sets that have been assembled with all of the evidence,” says Bueno de Mesquita.��

Bueno de Mesquita and his colleagues cited 98 studies, to be exact, in their peer-reviewed opinion piece that re-emphasizes the personal and planetary benefits of a shift to a plant-based diet—and lays out exactly why rumen microbes are not the answer.��

The problem with microbes��

Some of the literature references cited in the piece are studies that have been done on the most common feed additives that have been studied for methane inhibition: seaweed and 3-nitrooxypropanol (or Bovaer). The research shows that the demonstrated efficacy of these microbes is extremely variable, with one review reporting a range of 10–63% reduction and another review reporting a range of a 4% increase to a 97% reduction.��

Bueno de Mesquita and colleagues are also concerned that altering rumen microbes may lead to unpredictable health effects for the cattle, and may even decrease immunity to pathogens that could be detrimental to human health.��

Another reason for concern? This method favors intensive beef production, where cattle are fed in feedlots rather than on grass (as is more likely to be the case in small-holder production). Not to mention that seaweed harvesting has its own inherent carbon emissions and environmental impact.��

But Bueno de Mesquita’s team points out that even if none of these were issues, methane reduction does nothing to address potent nitrogen emissions or other emissions from the rest of the production life cycle (e.g., land use, water use, fertilizer, crop residues, manure).��

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Bueno de Mesquita and colleagues created this graphic to demonstrate how many ways livestock production can impact the environment and human health—and how only one of these impacts is reduced by trying to alter the microbes in the rumen with feed additives. (Graphic: Cliff Bueno de Mesquita and Ylenia Vimercati Molano)

Shifting people’s perspectives

The authors wrote the piece to be accessible to non-scientists in hopes of reaching as wide an audience as possible. “I want the public to be aware and to be skeptical of labels coming from the beef and dairy industry that are calling those products climate friendly,” says Bueno de Mesquita.��

Of course, he also hopes that people will consider simply shifting to a plant-based diet in order to make their meals more climate friendly. But he knows that’s easier said than done.��

“We're basically living in a ‘carnistic’ society where eating meat is perceived to be normal, natural and necessary,” says Bueno de Mesquita. “That's sort of people's default. So when they’re met with a proposal for a minor shift that challenges that, we know there's gonna be pushback.”��

Two years ago Bueno de Mesquita and his co-authors published�� documenting a push within CU �ֲ���ý’s Ecology and Evolutionary Biology department for more plant-based meals. “The PhD students were very hesitant to implement a dietary change, even though they know that it's going to be better for the environment.”

Even still, Bueno de Mesquita says the current perspective piece is getting a lot of traction. “I basically never get emails about my research papers,” he says. “But I've already gotten emails from multiple people saying that they agree.” He adds that even some leading microbiologists have posted it on social media.��

That’s key to reaching the other audience Bueno de Mesquita and colleagues wanted to address: the microbiologists actually doing the research on rumen microbes in livestock feed, usually funded by the beef and dairy industries, he says.��

“They're enabling the dairy industry to say, ‘Hey, we're doing this research. This is going to work’,” says Bueno de Mesquita. “Then the industry has an excuse to keep business as usual.”��

Instead, he hopes that microbiologists and other scientists studying climate change will step up and speak with a unified voice about what needs to be done as a society. “It's very obvious,” says Bueno de Mesquita. “If you want to reduce methane from ruminants, you need to decrease the number of ruminants.”

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