The world may be at greater risk of infectious diseases from wildlife as humans increasingly encroach on natural habitats in the tropics to graze livestock and hunt wild animals. Devastating pandemics like HIV/AIDS, Ebola, and COVID-19 likely originated in the wild, a reminder of how environmental destruction and infectious disease are intertwined. Deforestation and overfishing are also at the root of global warming and mass extinctions.
All these events show that what we choose to eat has a fundamental impact on our health and the health of the planet.
We recently conducted a review of the scientific literature to examine how wildlife disease, global warming, and mass extinctions are linked to the global food system. Our second goal was to explore restorative actions that governments, NGOs, and each of us can take.
From the perspective of individual consumers, to prevent human encroachment on desert tropics, the world’s population must shift to diets low in animal-derived foods. Second, there is a need to limit the demand for wild meat in tropical cities.
Eat less food from livestock
Biodiversity gets richer as you get closer to the equator. These tropical regions are rich in wildlife and carbon, historically less developed and usually stored in the form of abundant vegetation. However, in recent decades, the frontiers of agriculture have rapidly expanded into tropical forests. This unprecedented expansion of arable land for grazing and forage production may increase contact between wildlife, humans, and livestock, making it more likely that pathogens will be transferred from one to the other.
Such habitat destruction also negatively affects large herbivores and predators, as they lose food sources and breeding grounds. This may lead to an increase in common species of rodents, bats, birds, and primates that are better adapted to thrive in human-altered landscapes. Some of these species are known reservoirs for infectious diseases of livestock and humans. For example, the white-footed mouse (Peromyscus leucopus) is a reservoir host for bacteria Borrelia burgdorferi, It causes Lyme disease, some fruit bats (family Pteropodidae) are reservoirs for Nipah virus and possibly Ebola virus. Intensive animal husbandry increases the likelihood that domesticated animals can act as intermediate hosts for wildlife-borne diseases, thereby increasing the risk of human infection. (See illustration on page 10.)
Flexitarian diets can feed a growing world population without further expanding arable land into tropical deserts and reducing greenhouse gas emissions.
Furthermore, if human populations continue to grow and consume diets rich in animal-derived nutrients, it is unlikely that global warming can be kept well below 2°C and the rate of species extinction slowed. This is because livestock production has the largest ecological footprint of all food production systems in terms of land and water use, greenhouse gas emissions, and pollution of land and water systems.
Asking everyone to become vegan is not realistic or even desirable. But flexible diets can feed a growing world population without further expanding arable land into tropical deserts and reducing greenhouse gas emissions. These diets contain large amounts of plant-based foods, including plant-based proteins such as legumes, nuts, and seeds; small amounts of fish, poultry, eggs and dairy products; small amounts of red meat and processed animal proteins.
Diets low in livestock-derived foods, combined with conversion to environmentally friendly or organic farming and reduction of food loss and waste, are key components of a sustainable global food system. Such a dietary change would also have other public health benefits, such as reducing overweight and obesity, diabetes, heart disease, and colorectal cancer.
Actions available to governments, civil society and businesses to promote healthier and more sustainable levels of consumption of livestock-derived foods include education in schools, training of doctors and paediatricians, eco-labels on food packaging, taxation of meat and dairy products, retail and hospitality sectors legal duty for, food supply for workplaces, schools and hospitals.
Governments tend to shy away from such interventions for fear of public backlash. However, the public tends to expect government leadership to solve such a complex problem.
Limiting demand for wild meat in tropical cities
In the rainforests of Africa, Asia and South America, hunting pressure to supply nearby cities has increased dramatically over the past 30 years. In addition to endangering vulnerable animal populations, the robust wild meat trade can increase the risk of zoonotic disease transmission.
But in the absence of effective state law enforcement and sustained campaigns to reduce consumer demand, bans do not work. In fact, consumers’ strong preference for wild meat means they may continue to buy it despite the price increases caused by the ban, fueling black markets. In the case of “luxury meat,” increasing price and rarity may even lead to increased demand. Bans may also shift the wild meat trade into illegal, unregulated channels, where less emphasis is placed on the biosecurity measures necessary to prevent wildlife-borne diseases.
Outright bans can have other unintended effects. Although pulses, fish and livestock proteins are readily available at reasonable prices in most major cities, there are local people and rural communities who rely on hunted meat for vital food and income. Their right to sustainable self-sufficiency within their traditional territories must be protected.
An ideal course of action would be to limit the hunting and trade of tropical wild meat by curbing demand in urban areas and production areas, supporting hunting rights and biosecurity measures among remote communities.
Avoiding the biohazards of animal foods
Interventions in rural communities should train poachers, traders and butchers on low-cost biosecurity measures they can easily adopt to avoid exposure to wild animals. Biosecurity measures should also apply to livestock and wildlife farms, slaughterhouses, food markets and restaurants. These measures include wearing protective clothing when handling wild animals, wrapping carcasses to prevent blood from human skin cuts, and cooking wild meat thoroughly before eating.
Other physical distancing measures should be taken on farms, pastures and livestock markets. These include fencing and reducing stocking density to minimize contact with wild herbivores, planting fruit trees frequented by bats far from breeding sites, and limiting the number of animals for sale in live bird markets.
Different strategies in different regions
Consumption levels of animal foods and the degree to which human communities depend on animal proteins vary dramatically. Efforts to reduce livestock production should focus on curbing overconsumption in wealthier countries and expanding metropolises in less developed and developing economies. In poorer rural areas of resource-limited countries, home gardening as well as smallholder livestock development programs can help reduce malnutrition with limited environmental and public health impacts.
Pastoralist communities in arid grasslands and hunter-gatherer communities in tropical rainforests and arctic areas unsuitable for crop production will instead continue to rely on animals for sustenance. Nevertheless, the impact of their lifestyle on the small environment cannot be compared to that of dense and better-off urban populations.
Our future depends on urgent changes
The incidence of infectious diseases in wild animals is high and may increase. This may be yet another warning signal that the degradation of our ecosystems is undermining planet Earth’s ability to sustain human health and well-being.
Shifting the diet away from livestock-derived foods and reducing the demand for tropical urban wild meat is also critical to protecting the environment, protecting vulnerable resource-limited communities, and reducing the risk of subsequent disease outbreaks and pandemics. We all share the responsibility to act now to prevent the ever-increasing prevalence of pollution, floods, droughts, famines and epidemics.
Giulia Wegner He is a socio-ecological researcher at the Wildlife Conservation Research Unit (WildCRU) at the University of Oxford, UK. Chris Murray He is Associate Professor in Environment and Health at the MRC Unit Gambia and the MRC Center for Global Infectious Disease Analysis at Imperial College London. Murray receives funding from the UK Medical Research Council, The Wellcome Trust and the UK Global Challenges Research Foundation. He currently serves as a scientific advisor/board member for the Soulsby Foundation and the Regenerative Society Foundation.