Over the past several years, most of the discussion of the likely impacts on agriculture from climate change have focused on the crop sector. I’ve been somewhat guilty of that myself, although I did write a blog in January 2018 about the steps that livestock producers could take to reduce their emissions of greenhouse gases. In this blog, I will explore some of the likely impacts on livestock from the higher temperatures and more variable precipitation expected from climate change, both direct and indirect.
The most vulnerable livestock species will be those that spend most of their lives grazing in the open, especially in developing countries, such as cattle, sheep, and goats. For such animals, numbering roughly one billion around the world, the direct impacts will result from greater heat stress and susceptibility to animal diseases getting footholds in new regions of the world due to climate change.
The optimal environmental conditions for livestock production include temperatures and other conditions for which animals do not need to significantly alter behavior or physiological functions to maintain relatively constant core body temperature. Optimum animal core body temperature is often maintained within a relatively narrow 4°F to 5°F range, while deviations from this range, above or below, can cause animals to become stressed. This stress can disrupt performance, production, and fertility, limiting the animals’ ability to produce meat, milk, or eggs. In many species, deviations in core body temperature in excess of 4°F to 5°F cause significant reductions in productive performance, while deviations of 9°F to 12.6°F often result in death. For cattle that breed during spring and summer, exposure to high temperatures reduces conception rates. Livestock and dairy production are more affected by the number of days of extreme heat than by increases in average temperature.
A report prepared under the U.S. Global Change Research Program found that in 2010, heat stress caused $1.2 billion in losses to the U.S. dairy industry alone. Based on that study, it is likely that annual economic losses to global animal agriculture due to heat stress already surpass tens of billions of dollars.
Livestock raised in developing countries are likely to experience greater effects of climate change for a number of reasons. A majority of human and animal populations lie in warm tropical and sub-tropical areas and those regions will be greatly affected by rising temperatures. Strategies such as zone-cooling (air-conditioning), and shades with insulated roofing are not cost efficient on a large scale and systems using extensive water or electricity may not be practical or sustainable in many areas.
Climatic restrictions on disease vectors, environmental habits and disease-causing agents are important for keeping animal diseases under control. Climatic changes may influence livestock health through a number of factors, including the range and abundance of vectors and wildlife reservoirs, the survival of pathogens in the environment, and farming practice. Alterations in temperature and rainfall may result in the spread of disease and parasites into new regions or produce an increase in the incidence to which a particular disease is already prevalent, which will lead to a decrease in animal productivity and increase in animal mortality.
Examples of animal diseases that could become more problematic in the face of climate change include anthrax, which is a serious bacterial infection caused by Bacillus anthracis that occurs primarily in animals. Cattle, sheep, horses, mules, and some wild animals are highly susceptible. Extreme weather events, such as droughts or floods, can expose bacteria spore resident in the soil that lead to anthrax, according to agricultural experts and animal industry trade reports.
Hog farmers in China and elsewhere in Asia are already experiencing the impact of the spread of African Swine Fever (ASF), which until last year had rarely been a problem outside of the African continent. African Swine Fever (AFS) is a highly contagious hemorrhagic disease of pigs, warthogs, European wild boar and American wild pigs. All age groups are equally susceptible. With high virulence forms of the virus, ASF is characterized by high fever, loss of appetite, hemorrhages in the skin and internal organs, and death in 2-10 days on average. Mortality rates may be as high as 100 percent. ASF is spread primarily by ticks or shipments of contaminated meat products. It is believed that higher temperatures and humidity will allow infected ticks to live longer, enabling more rapid dissemination.
Official Chinese estimates place hog losses at between 15 and 25 percent of the country’s herd due to either deaths from the disease itself or culling interventions (amounting to 50 to 90 million animals), while outside analysts believe that the final toll could be much higher, easily into hundreds of millions. Since ASF first was detected in China in August 2018, it has also spread to Cambodia, Laos, Mongolia, North Korea, and Vietnam.
In many countries, livestock other than cattle are increasingly raised in confined feeding facilities nearly all their lives. According to estimates from the United Nations Food and Agriculture Organization (FAO), globally, such animals account for:
• 72 percent of all poultry produced
• 43 percent of all eggs produced
• 55 percent of all hogs produced
Livestock production systems that provide partial or total shelter to reduce thermal environmental challenges can reduce the risk and vulnerability associated with extreme heat. In general, livestock such as poultry and swine are managed in housed systems where airflow can be controlled and housing temperature modified to minimize or buffer against adverse environmental conditions. However, management and energy costs associated with increased temperature regulation will increase for confined production enterprises and may require modification of shelter and increased water use for cooling. Such operations will also likely face higher feed costs, as models project that climate-induced reductions in crop yield will increase prices for corn and soybeans by as much as 20 percent by 2100, depending on the extent to which U.S. crop producers adjust their practices to the new conditions.