Global risk of heat stress to cattle from climate change

Abstract

Cattle farming is a major source of global food production and livelihoods that is being impacted by climate change. However, despite numerous studies reporting local-scale heat impacts, quantifying the global risk of heat stress to cattle from climate change remains challenging. We 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). 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 sub-tropical regions. In all scenarios, severity of heat stress increases most in tropical regions, reducing global milk yields. Future land-use decisions are an important driver of risk. Under a low environmental protection scenario (SSP3-RCP7.0), the greatest expansion of cattle farming is projected for tropical regions (especially Amazon, Congo Basin, and India), where heat stress is projected to increase the most. This would expose over 500 million more cattle in these regions to severe heat risk by 2090 compared to 2010. A less resource-intensive and higher environmental protection scenario (SSP1-RCP2.6) reduces heat risk for cattle by at least 50% in Asia, 63% in South America, and 84% in Africa. These results highlight 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.

Content Analysis of International News About the Heat Waves in India

“…Zander et al (2023) analyze Twitter conversations about heat waves, revealing high public awareness about heat impacts and the influence of scientists and respected media. North et al (2023) examine the global risk of heat stress for livestock due to climate change, suggesting that livestock management practices will need significant adaptation to cope with the increasing effects of extreme heat. "The criteria for declaring a heat wave in India requires the maximum temperature to be 4.5 to 6.4 degrees Celsius (40.1 to 43.52 degrees Fahrenheit) higher than usual.…”

Gene Editing Cattle for Enhancing Heat Tolerance: A Welfare Review of the “PRLR-SLICK Cattle” Case

“…Regarding cattle, North et al [33] conducted a study on the correlation between future climate projections and the impact of heat stress on cattle mortality, fertility, and production. In particular, they estimated that "77% of cows are already exposed to climate conditions likely to cause heat stress for at least 30 days each year, with 20% of cattle (those in the tropics) exposed to heat stress conditions yearround" ( [33], p. 5), and that by 2100 "these percentages are projected to increase to 90% of cows exposed for at least 30 days each year, and 34% experiencing year-round heat stress" ( [33], p. 5).…”

“…Another possible welfare risk, and one that also relates to the way SLICK cattle are used in the production sector, concerns negligence. Since SLICK cattle cope better with heat, farmers could take advantage of them and economise on strategies usually adopted to keep herds cool [33]. How far, however, could such negligence extend before the cattle are harmed?…”

Hypothalamic Neuromodulation and Control of the Dermal Surface Temperature of Livestock during Hyperthermia

“…Exposure to high ambient temperatures can be implicit inside production systems due to the design of the units or the geographical location of farms, making livestock susceptible to heat stress and hyperthermia [ 1 , 2 ]. Moreover, climate change and global warming are current challenges for farm animals [ 3 , 4 ]. Preventing increases in core body temperature is essential because several physiological and behavioral mechanisms are activated when animals are under thermal stress [ 5 ].…”