Climate Change Threatens Milk Quality and Quantity, Cornell Study Finds

Americans drink tens of billions of pounds of milk each year to get muscle-building protein and bone-strengthening vitamin D and calcium.

But new research shows both the quality and quantity of milk production is under threat.

Heat stress due to human-caused climate change is reducing the protein and fat levels in milk, as well as impacting production, according to a study from New York’s Cornell University.

These impacts could sneakily lead to economic losses totaling millions, the school’s researchers warn, especially as years get hotter. Scientists say this year could be the hottest on record.

“The heat-induced dilution of these valuable milk components is happening a bit under the radar,” Ariel Ortiz-Bobea, an associate professor of agricultural economics at Cornell, said in a statement. “When you account for the deterioration in milk composition, the economic loss ends up being of the same order of magnitude as the yield effect, so it just basically doubles the damage.”

With just a 10-point increase on the temperature and humidity index, there’s a 1.2 percent reduction in milk yield and a 2.8 percent reduction in revenue - or a $1.65 billion loss across the industry.

The researchers tallied the toll using weather and milk data gathered from 43 states between 2007-2016

Negative effects on milk began at lower temperatures than may be considered extreme heat, increasing as the thermostat climbed.

“If it’s a day in the 60s or 70s, you don’t see any effect on yield, but the milk starts to get diluted gradually,” Ortiz-Bobea said. “Unlike the yield effect, which only happens in the summer, this is happening all the time.”

Unfortunately, there is little evidence that cows are resilient to heat, too.

Hundreds may die in a single state each summer and the cows are also susceptible to extreme cold, according to research from the National Aeronautics and Space Administration.

“These challenges have considerable economic impacts: for instance, winter cold events in the Northern Plains resulted in over $20 million in cattle losses in 2023 alone, while heat stress nationwide causes an estimated $370 million in annual losses to feedlot operations,” the space agency said last November.

The only adaptation to extreme heat has been in where the industry chooses to farm, the Cornell team noted.

“It’s another headwind for dairy farmers,” Ortiz-Bobea said. “Milk prices are low, and farmers are struggling, and that usually leads to more consolidation, which changes the landscape in rural areas, literally and economically.”

In the future, the team hopes to see if there are specific cows that are more resilient to heat than others, as well as if milk’s protein, fat and heat resilience could be traded for higher yields.

The milk industry produces 20 percent of U.S. animal products and is valued at nearly $60 billion a year.