Agriculture has a huge impact on the environment. Food production takes up more than one-third of Earth’s land, is responsible for one-third of humanity’s greenhouse gas emissions and is the largest cause of deforestation on Earth. But agriculture does not only have a greenhouse gas footprint – it has a disease footprint.
With the outbreak of Covid-19, global attention became focused on the causes of “zoonotic” diseases – those that begin in animals before crossing over into humans. Research suggests that Covid most likely emerged from the wild animal trade, but wildlife trafficking is not the only cause of zoonotic diseases.
Many of the disturbances that humans inflict on the environment can increase the rates of disease emergence and spread by changing delicate relationships that animals have with each other. A newly fractured ecosystem can cause diseases that would normally be suppressed in otherwise healthy populations of animals to rapidly mutate and spread.
Both deforestation and climate change allow new diseases to emerge and flourish. Major public health and environmental institutions expect diseases in the future to emerge and spread more rapidly with continued climate change and habitat loss.
In this context, research has emphasised the importance of addressing agriculture’s outsized environmental impacts.
For example, improving agricultural efficiency, a process called “intensification”, allows humans to produce more food on the same amount of land. This can, in turn, reduce the massive amount of land – and deforestation – that agriculture requires, as well as reducing emissions from land-use change and other sources such as cattle belches, manure and feed production. So one might expect that intensification would also lower the risk of potential pandemics.
However, this is not necessarily the case when it comes to meat production. My recent research suggests that while intensification produces short-terms gains in carbon efficiency, it comes at the cost of heightening longer-term risks for disease outbreaks.
One major way that producers intensify animal agriculture is by confining animals. These intensively confined animals gain weight more quickly than their free-roaming counterparts. Because animals in intensive facilities are sedentary, rather than grazing on open land, this lowers their feed requirements – and, therefore, their land-use and greenhouse gas emissions.
Lower feed requirements could indeed decrease deforestation, thereby helping to maintain wild animal habitats and providing a buffer against diseases that come from those wild animals by keeping them far from regular human contact.
But intensification can accelerate the emergence and spread of diseases that come from domestically farmed animals. This is because intensive production facilities confine animals close to each other – and to their own wastes. This confinement, which is most typically used for pigs and chickens, allows diseases to quickly spread and mutate rapidly between the many thousands of animals kept in a single facility.
In order to control bacteria outbreaks between these confined animals and their wastes, intensive farming involves giving antibiotics to animals. Producers add them to feed routinely, even before an outbreak occurs. In humans, doing this is a recipe for creating antibiotic-resistant bugs and infections that become impervious to the drugs meant to kill them.
With animal agriculture, it is no different. We’ve already seen outbreaks of MRSA, an antibiotic-resistant strain of staph infection, as well as urinary tract infections from resistant E. coli. Both of these superbugs have been traced to chicken production in the US and increasingly in developing countries.
Swapping beef with chicken
Chicken is a relatively low-carbon meat. In fact, many scientists and advocates have recommended swapping out beef for chicken in order to reduce the environmental impact of dietary choices.
Greenhouse gas emissions from chicken production are as much as 10 times less than those from beef – although both still have higher emissions than plant protein sources, such as beans, nuts and soy.
But these recommendations ignore disease risks. On average, chickens are fed three times more antibiotics than cattle in order to produce the same weight of meat. And it takes 170 chickens to produce the weight of meat of one cow. Every individual chicken is another potential vector for diseases, such as highly pathogenic avian influenza, which is more commonly known as “bird flu”.
In its latest climate pledge under the Paris Agreement, Ethiopia pledged to shift 30% of its beef production to chicken in order to limit warming, but chickens require more intensive confinement, higher antibiotic use and larger numbers of animals than beef production. Swapping beef for chicken could, therefore, hasten the spread of costly, potentially pandemic diseases.
The figure below shows the requirements in high-income countries for producing one tonne of meat from cattle (orange), pigs (pink) and chickens (yellow) in terms of deforestation footprint (top left), antibiotic usage (bottom left) and number of animals (right).
During COP27, all manner of food-system solutions to climate change were suggested, including “agroecology” and “net-zero dairy”. But squarely focusing on improving carbon emissions could lead us into a disease “trap”. Intensification and swapping out beef for chicken would undoubtedly reduce climate emissions. But doing so may be a zero-sum game, trading reduced climate emissions with the risks of hastening the next pandemic.
Furthermore, there is not enough land on Earth to raise all livestock animals for meat in a free-range manner. There are now more than 40bn farmed animals on Earth. Taking animals – whether chickens or cattle – from these intensive systems and spreading them out on pasture takes far more land.
So are we stuck having to choose between reducing climate impacts on one hand, or reducing disease risks on the other? How do we get out of the trap of combined disease and climate risks from animal agriculture?
Mitigating climate and pandemics risks in tandem
Research is clear that eating less meat would reduce the total number of animals farmed, reduce greenhouse gases, and free up land for other uses, including carbon sequestration and biodiversity conservation and restoration.
Research also shows that governments in high- and middle-income countries could take several steps to encourage less overall meat consumption among middle-class populations, from monitoring and gentle nudges to changing government price supports, such as subsidies and buy-back programmes.
Conservation laws and bilateral agreements to protect forests in the countries that are most at risk of losing them can also be implemented and improved. Along with preserving forests, this would also protect the vast carbon stores and populations of wild animals within.
Finally, not all intensification is equally harmful. There are some win-win forms of intensification that could improve livestock production in low-income countries that currently have the lowest forms of productivity. This includes better veterinary services, vaccines and pasture management.
These “win-win” forms of intensification – called “pastoral intensification” – do not require confinement. While this cannot meet all of the world’s high – and continually rising – demand for meat, it can make a big difference to the world’s poorest producers by protecting local environments and improving their food security and income.
The figure below shows a proposed “three-pillar” approach to balancing climate mitigation with disease prevention in the context of food systems.
Together, a coordinated three-pronged approach of sustainable plant-rich diets, protecting forests and improving productivity in lower-income parts of the world without resorting to confinement can reduce climate emissions and reduce the risk of the next pandemic.
Hayek, M. (2022) The infectious disease trap of animal agriculture, Science Advances, doi:10.1126/sciadv.add6681.
Guest post: Intensive, lower-carbon animal farming could raise pandemic risks