Sub-Saharan Africa could lose a significant percentage of its meat and milk production to environmental stresses as climate change threatens cattle farming in poor countries.

Scientists say heat stress will become an increasingly serious challenge to cattle production systems in the lower latitudes of tropical west and east Africa as the century progresses, with the exception of the highlands of central Ethiopia and south-western Kenya.

Researchers from the International Livestock Research Institute (ILRI), the Consultative Group for International Agricultural Research (CGIAR) and Cornell University say climate change poses a potentially devastating economic threat to cattle farmers due to increasing heat stress on animals.

Depending on the breed, cattle can experience thermal stress at temperatures higher than 20 degrees Celsius.

At higher temperatures, animals reduce their feed intake by three to five percent per additional degree of temperature, reducing productivity.

Heat stress increases respiration and mortality, reduces fertility, modifies animal behaviour and suppresses the immune and endocrine system, increasing animal susceptibility to diseases. Heat stress can also reduce rumination and nutrient absorption.

These changes will affect the economic returns of dairy and beef farming, the scientists say in a paper published in the March issue of Lancet Planetary Health.

Losses in production are predicted to be most severe in Africa, especially in tropical regions.

“Some locations will become too hot and humid for animals to thrive. The same challenge faces the pastoral regions of sub-Saharan Africa, which are mostly arid-semiarid systems, and cattle often constitute one of the major assets of pastoralist people,” said the scientists.

“Globally, by the end of this century these producers may face financial loss between $15 and $40 billion annually,” the scientists warn in the paper.

Mario Herrero, professor of sustainable food systems at Cornell University, called for the creation of equitable adaptation practices that reach the vulnerable sectors of society.

“We cannot just hope that the poor will not be affected,” he said.

Adaptations required include switching to more heat-tolerant breeds or animals, crossbreeding and infrastructural investments such as provision of shade, ventilation and cooling systems, which could increase production costs in all cattle systems in the future.

“Different arrangements of shade trees in tree–livestock systems can be highly effective in reducing heat stress,” the scientists said.

Species switching is another alternative, such as switching from cattle to more heat-resistant and drought-resilient camels in pastoral systems of southern Ethiopia.

"Various options available include breeding and cross-breeding strategies. There are significant differences among breeds in ability to cope with heat stress, even among high-yielding genotypes,” they advised in the paper.

They say as in many systems in Africa, the role of livestock is heavily conditioned by socioculture rather than economic factors, and effective government policies and well-directed international finance will be needed to address these vulnerabilities, lead author Philip Thornton, of the International Livestock Research Institute and CGIAR said in a press release on Thursday last week (March 10)

“Resource-poor farmers in low-income countries depend heavily on their livestock for their livelihoods,” . “The adaptation needs are even higher in these countries, and those farmers are the ones where the hit is even more severe.”

They estimate that in high greenhouse-gas emission (GHG) scenario, cattle production losses from heat stress are estimated to be $39.94 billion annually, or 9.8percent of the value of production of meat and milk from cattle in 2005 – the scientists’ baseline year. In low-emission scenario production losses are projected at $14.9 billion annually, or 3.7 percent of the 2005 value.

The scientists say the region consistently hit the hardest, in terms of the percentage of meat and milk production potentially lost to both mid-century and end-century, according to their projections, regardless of the GHG emissions scenario, is sub-Saharan Africa.