Our Burning Planet


Heat stress on livestock threatens to end cattle farming in tropical regions

Heat stress on livestock threatens to end cattle farming in tropical regions
Not only has the impact of heatwaves on humans been intensifying because of the climate crisis, but now the animals that feed us are also at risk from heat stress. (Photo: Stijn te Strake / Unsplash)

There is no shortage of literature on the impact of climate change-induced heatwaves on human lives across the globe, but it’s also having a major impact on our food and livestock with more than 1 billion cows set to experience heat stress by the end of the century globally.

If you consume beef or drink cow’s milk, and are involved in agriculture or cattle farming this is a study you should be reading and be concerned about as the findings indicate how extreme heat harms cattle in many different ways, especially when combined with high humidity. 

New research published in the September edition of IOP Publishing’s journal, Environmental Research Letters, “Global risk of heat stress to cattle from climate change” looks at the impacts of climate change on livestock. 

According to the research, livestock farming is set to become increasingly difficult in many tropical countries if emissions remain high, particularly those in Central America, tropical South America, Equatorial Africa, and South and Southeast Asia — meaning that cattle farming would face potentially lethal heat stress in much of the world.

Researchers from the University of Cape Town (UCT), University of KwaZulu-Natal (UKZN), and University of Chicago analysed the current heat and humidity conditions around the world and calculated how this is affecting and will affect cattle in future decades, depending on different levels of emissions and forms of land use. 

Read more in Daily Maverick: How rising temperatures threaten farmworkers in Northern Cape, South Africa’s sunniest province

The researchers state that if carbon emissions remain high and environmental protection low, global heat stress will reduce fertility, affect the growth of calves, and can result in increased deaths. In dairy cows, it will also result in reduced milk production. 

The research found that rapidly reducing greenhouse gas emissions, as well as keeping cattle production close to current levels, would reduce these impacts by at least 50% in Asia, 63% in South America, and 84% in Africa.

However, if future carbon emissions remain high, the researchers project that 9 in 10 cows around the world will experience 30 or more days of heat stress per year, and more than 3 in 10 will experience it all year round by the end of the century.

Speaking to the Daily Maverick, lead author Dr Michelle North, veterinarian and UKZN researcher said that:

  • Cattle today in many parts of the world are already experiencing heat stress, and farmers need to implement management strategies and technologies to reduce the amount of heat stress their animals experience, to improve the animals’ welfare, and also their productivity, and thus the farmers’ bottom line.
  • Heat stress for cattle will increase in the future with climate change, and in scenarios with high greenhouse gas emissions from deforestation and burning fossil fuels, the increase in heat stress will be much worse.
  • While heat will increase, with some areas more impacted than others, a very important determinant of how many cows are exposed to this heat is decisions about land-use change, especially the expansion of livestock farming in the tropics. The researchers caution that deforestation of tropical forests for livestock expansion is not a viable development future.

North states that this is “yet another reason why it is critical that we rapidly reduce the use of fossil fuels — oil, coal, and gas — to ensure a liveable future for all people, and the systems we rely on for food.”

Cutting back meat consumption

The study also highlights how societal choices that expand cattle production in tropical forest regions are unsustainable, both worsening climate change and exposing hundreds of millions more cattle to large increases in severe, year-round heat stress. 

“Societal choices refer to choices about diet and land use and protecting ecosystems. So, people are shifting to more plant-based proteins in diets and consuming less beef, not expanding cattle farming, and taking action to protect forests from destruction. This would also include choices to invest in adaptation, including existing commercial farmers, pastoralists and small-scale/subsistence livestock keepers,” said North. 

Livestock at risk

Dr Christopher Trisos, ecologist and UCT climate change researcher urged that decisions made today will be crucial for the coming decades. 

Trisos said, “We’ve seen the deadly impacts for humans of climate change intensifying heatwaves, but the animals that feed us are also at severe risk from heat. We need to act now to limit the risk.”

Although not touched on in this paper, the researchers urge that more government regulation and support services are needed for smallholder farmers and pastoralists to adapt their livelihoods to the changing climate conditions. This is particularly as farmers of more informal, subsistence style agriculture or livestock keeping will be heavily impacted by climate hazards. 

“A lot more work needs to be done with these people, using consultative methods to engage them to identify their needs, motivations, and try work to find mutually acceptable solutions. This is an important area for future research,” North said.

Rising temperatures and humidity will force farmers to adapt to these new conditions with increasingly expensive measures such as ventilation or even air conditioning for the animals or switching to heat-adapted cattle breeds. This will not be possible in all regions, meaning cattle farming could no longer be viable in places where it is currently a major occupation. 

How the study was conducted 

The researchers conducted a global synthesis of documented heat stress for cattle using 164 records to identify temperature-humidity conditions associated with decreased production and increased mortality, then projected how future greenhouse gas emissions and land-use decisions will limit or exacerbate heat stress, and mapped this globally. 

The median threshold for the onset of negative impacts on cattle was a temperature-humidity index of 68.8 (95% C.I.: 67.3–70.7). 

The study found that currently, almost 80% of cattle globally are exposed to conditions exceeding this threshold for at least 30 days a year. For global warming above 4°C, heat stress of over 180 days per year emerges in temperate regions, and year-round heat stress expands across all tropical regions by 2100. 

Limiting global warming to 2°C, limits expansion of 180 days of heat stress to subtropical regions. In all scenarios, they found the severity of heat stress increases most in tropical regions.

North worked together with Trisos, ecologist and climate change researcher at the University of Cape Town, on the Intergovernmental Panel on Climate Change’s (IPCC) Working Group II which assessed the vulnerability of socio-economic and natural systems to climate change, negative and positive consequences of climate change and options for adapting to it.

This is what set the stage for this paper. 

As part of this work, the author team had to read hundreds of research paper abstracts to identify which papers were relevant and could be included in the study, and conducted this work while also juggling IPCC commitments and deadlines, other research and work obligations, and during Covid-19. DM

Absa OBP

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