Scientists review the evidence that intensive livestock farming causes pandemics and find that intensive farming may actually reduce the risk of future pandemics compared to “free-range” farming.
In the wake of COVID-19, many have pointed to modern industries with dense livestock populations as potential hothouses for further pandemics caused by “zoonotic” diseases: those transmitted from animals to humans.
However, researchers are now arguing that free-range alternatives, which require much more land, would increase encroachment on natural habitats and create ever more potential for wildlife-borne diseases to come into contact with humans and cross the species barrier.
In an article in the Royal Society Open Science, a team of scientists led by Cambridge University found a lack of sufficient evidence to conclude which type of farming is least risky, saying there is evidence that moving away from intensive farming could actually increase the risk of pandemics. They call for more research before policies are changed or incentives are introduced for any particular type of farming.
“High-yield or ‘intensive’ livestock farming has been blamed for pandemics, but those calling for a shift away from intensive farming often fail to consider the counterfactual — the pandemic risk of less-intensive farming and particularly the implications for land use,” said lead author Harriet Bartlett, a PhD student at Cambridge Zoology.
“Low-yield farms need much more space to produce the same amount of food than high-yield farms. Widespread conversion to low-yield agriculture would result in the destruction and disruption of large areas of natural habitats. This increases the risk of viral spread by disrupting wildlife that may harbor the next pandemic virus and by increasing contact between wildlife, people and livestock,” Bartlett said.
The researchers point out that we produce four times more meat worldwide today than we did in the 1960s. Most of our meat, egg, and dairy products today come from intensive farms, but such farms are considered risky due to their cramped conditions, which increase the likelihood of diseases “breaking out” and spreading quickly.
However, intensive farms require less land than extensive or free range farms to produce the same amount of food – both to grow their feed and to raise their livestock.
The growing demand for animal products has resulted in dramatic habitat loss, the researchers said, meaning we are now farming in places where livestock and humans come into frequent contact with wildlife. They say this exposure to increasingly disturbed, stressed, and infected wildlife makes zoonotic viruses more likely to spread to humans or livestock.
“If we switched from the current system to one based on extensive farming, we would need significantly more land to meet demand – resulting in a habitat conversion roughly the size of Brazil and India between 2009 and 2050 said Paper co-author Prof Andrew Balmford. “This could increase contact between humans, livestock and stressed wildlife – including wildlife that may be harboring the next pandemic virus.”
“Intensive farms may have a greater risk of starting, but extensive farms may have a greater risk of spillover,” he said.
The researchers say that, worryingly, we simply do not know which risk is more important to preventing future pandemics, and so it is currently impossible to determine which types of farms are at the lowest risk overall.
Bartlett added, “COVID-19 has highlighted the huge potential impact of zoonoses, and this study shows that more research is urgently needed to find out how we can minimize the risk of another pandemic.”
Reference: Bartlett H, Holmes MA, Petrovan SO, Williams DR, Wood JLN, Balmford A. Understanding the relative risks of zoonosis occurrence under contrasting approaches to meeting the demand for livestock products. Royal Soc Open Sci. 9(6):211573. doi:10.1098/rsos.211573
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