In the wake of COVID-19, many have pointed to modern factory farms with tightly packed livestock as potential hothouses for new pandemics caused by “zoonotic” diseases: those transmitted from animals to humans.
However, researchers now say the free-range alternative, which requires far more land, would increase encroachment on natural habitats and create increasing risks for diseases carried by wild animals to come into contact with wild animals. humans and cross the species barrier.
In a article in the Royal Society Open Science, a team of scientists led by the University of Cambridge found a lack of sufficient evidence to conclude which method of farming is the least risky, and say there is evidence that abandoning intensive farming could in increases the risk of a pandemic. They call for more research to be done before changing policies or encouraging a particular type of agriculture.
“High-yield or ‘intensive’ livestock farming is blamed for pandemics, but those who call for a move away from intensive farming often fail to consider the counterfactual – the pandemic risk of less intensive farming and in particular the implications for land use,” the leader said. author Harriet Bartlett, a doctoral student in the Department of Zoology at Cambridge.
“Low-yielding farms need a lot more land to produce the same amount of food as high-yielding farms. A widespread shift 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 well harbor the next pandemic virus and increasing contact between wildlife, humans and livestock,” Bartlett said.
The researchers point out that globally, we produce four times more meat today than in the 1960s. Most of our meat, eggs and dairy products now come from intensive farming, but these flocks are considered risky due to their overcrowded conditions which increase the risk of diseases “taking off” and spreading rapidly.
However, intensive farms need less land than extensive, or “open-air” farms to produce the same amount of food – both to grow their food and to raise their animals.
According to the researchers, the growing demand for livestock products has caused dramatic habitat loss, meaning we now farm in places where livestock and people frequently come into contact with wildlife. They say this contact with increasingly disturbed, stressed and infected wildlife makes it more likely that zoonotic viruses will spread to people or livestock.
“If we were to move from the current system to one based on extensive agriculture, we would need a lot more land to meet demand, which would result in the conversion of habitats roughly the size of Brazil and India between 2009 and 2050,” the newspaper said. author, Professor Andrew Balmford. “This could increase contact between people, livestock and stressed wildlife – including wildlife that may well harbor the next pandemic virus.”
“Intensive farms may have a greater risk of take-off, but extensive farms may have a greater risk of spillover,” he said.
Worryingly, the researchers say, we simply don’t know which risk is most important to preventing future pandemics, and so it’s currently impossible to determine which types of farms pose the least risk overall.
Bartlett added: “COVID-19 has demonstrated the enormous potential impact of zoonotic diseases, and this study underscores that more research is urgently needed to identify how we minimize the risk of another pandemic.”
Bartlett H, Holmes MA, Petrovan SO, Williams DR, Wood JLN, Balmford A. 2022 Understanding the relative risks of zoonotic disease emergence under contrasting approaches to meeting the demand for livestock products. R. Soc. Open SCI. 9:211573. https://doi.org/10.1098/rsos.211573
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