Thermal stress can affect cows in the Amazon and in the world – 08/25/2023 – Environment

By the end of the century, it is estimated that more than a billion cows on the planet could suffer from heat stress if global warming continues unabated, threatening their fertility, milk production and lives.

Nearly eight out of ten cows across the planet already have excessively high body temperatures, accelerated breathing rates, heads down, and panting—symptoms associated with severe heat stress.

In tropical climates, 20% of cattle have these symptoms throughout the year. These numbers are expected to increase if livestock farming continues to expand in the Amazon and Congo basins, where temperatures are on track to rise faster than the global average, according to research published Thursday. , at Environmental Research Letters.

If greenhouse gas emissions that cause global warming continue to rise, the study predicts that heat stress will become a year-round problem in Brazil, southern Africa, northern India, northern Australia and Central America by 2100.

“A very important determinant of how many cows are exposed to this heat is land-use change decisions,” said study lead author Michelle North of the University of KwaZulu-Natal in South Africa.

“Deforestation of tropical forests for the expansion of livestock is not a viable development future, because it exacerbates climate change and will expose hundreds of millions more head of livestock to severe heat stress,” he added.

The study concluded that, in the worst-case scenario, livestock farming will nearly double in Asia and Latin America and more than fourfold in Africa.

Scientists’ projections indicate that development pathways that increase cattle numbers in India and expand cattle production in the Congo Basin and the Peruvian and Brazilian Amazon could expose more than 537 million head of cattle to heat-stressed conditions by 2090, compared to the number of cattle in 2010.

loss of livelihood

If greenhouse gases are sufficiently controlled—mainly by reducing the use of fossil fuels and limiting the expansion of livestock—the number of cows suffering could be cut in half in Asia and by four-fifths in Africa.

Commercial ranchers can lose a lot of money from heat stress. In the United States alone, the problem already costs up to US$ 1.7 billion annually. But these breeders usually have insurance, good relationships with banks and the ability to borrow to help them recover from heat-related losses, North said.

However, when heat or other weather catastrophes hit small farmers, “they can literally lose their livelihoods, even if the net losses may seem ‘negligible,'” she details.

Michelle North and her team found that the global milk supply could be reduced by 11 million tons per year by 2050, in a scenario of high greenhouse gas emissions. If emissions are aggressively reduced, nearly half of that amount would still be lost, particularly in Asia and Africa, where milk supplies are already low.

In the short term, to reduce the consequences of overheating cows, the researchers suggest providing access to shade and fans, in addition to feeding early in the day.

(With AFP)