A new study shows that cows with stomach upsets can be a big problem for the environment. This is because cattle and other livestock with worms and other parasites produce a more powerful greenhouse gas, methane, than healthy animals. Methane is 28 to 36 times more powerful than carbon dioxide when it comes to warming the planet.
Methane from livestock and other livestock is projected to grow by 20 percent between 2017 and 2050, according to the United Nations Food and Agriculture Organization. But when parasitic worm infections are taken into account, the increase in methane could be as high as 827 percent, according to a new paper released today. Trends in Ecology and Evolution.
That’s a big discrepancy, especially given how much livestock is already contributing to climate change. About 60 percent of all mammal biomass on Earth is livestock, and the livestock industry is responsible for more than 14 percent of human-caused greenhouse gas emissions. (For comparison, aviation alone accounts for about two percent of global emissions.)
Even more worrying is that there could be a dangerous feedback loop between climate change, parasitic diseases and higher methane emissions: animals infected with parasitic worms and bacteria push more methane during their lifetimes, accelerating climate change. The parasites that infect livestock thrive in warmer temperatures, infect more animals and then the vicious cycle continues.
“It could be a really interesting phenomenon, or something important that we’re not really considering,” says Vanessa Ezenwa, a leading author of the paper at the University of Georgia and professor of ecology.
Whether infected or not, cows and other sporadic vegetables, called rumenants, are at the top of the ap throat of methane-emission. Other animals (including humans) also emit methane, but romantics cause more gas to leak out due to the wheeled stomach. They have a complete chamber for fermenting food, where ultra-microbes help them digest tough foods, which contain lots of planet-warming gases. “It’s big for them compared to us,” says Azenwa.
Parasitic infections can lead to many changes that can increase methane emissions from livestock. Animals grow more slowly, leading to more lifetime emissions, as it takes longer for them to develop enough to slaughter for meat. The infection also reduces milk production, making dairy farms less efficient. Ranchers may decide to pull and change their livestock more often, and evidence suggests that this usually leads to less animals (and more emissions).
At the extreme end of the scenario presented in the paper, if every animal fell ill, methane emissions from livestock would increase by 5 percent globally, according to the study authors. To calculate this, Azenwa and his colleagues reviewed existing research on the effects of parasitic infections on methane production in certain animals. They used these findings to figure out what the potential global impact on methane emissions is. The data from the UN Food and Agriculture Organization served as a baseline.
There are some limitations to the study, which provide estimates rather than rigorous statistics. Researchers used sliding potentially extensively because there was no real global rate for parasitic infections. The real world numbers can vary dramatically from one area to another and there are gaps in the data.
According to Ermias Cabreb, director of the World Food Center at the University of California, Davis, the results of the new study are not necessarily surprising. Cabreb was not involved in the study. “That’s common sense,” he says.
Cabreb points out that research in low- to middle-income countries may be most helpful where parasitic infections are common. Livestock productivity has increased in North America and Europe with better control of pathogens.
“This is a good article to help us remember,” says Cabreb.
The parasitic worm that causes trouble to the cows develops outside before infecting the host. According to Azenva, some of these worms require a high temperature. As such, climate change makes winters milder and in some areas longer summers, so these parasites have more time to develop and infect livestock, he says.
Ultimately, the new study highlights the need for more research to inform efforts to address the weather crisis. It can have advantages: healthy animals and a healthy world for all of us to live in.
