Will the climate crisis create a global milk shortage?

Israeli-American study reveals that an extremely hot day reduces milk yield by up to 10% and that cooling technologies only partially compensate for the damage

A new and comprehensive study by Israeli and American researchers Prof. Eyal Kimchi from the Faculty of Agriculture at the Hebrew University and Vice President of the Shoresh Institute for Socio-Economic Research, was recently published in the journal Science Advances  And found that a single day of extreme heat can reduce milk yield by up to 10%. Furthermore, the impact of a single hot day lasts for over ten days, and cooling technologies are not sufficient to overcome the impact.

While previous studies have shown that climate change will hurt crop yields, few studies have examined its impact on livestock. Dairy farmers already know that their cows are sensitive to heat – but what will happen when the heat gets even hotter?

"Climate change will have a wide-ranging impact on what we eat and drink – including a cold glass of milk," says Dr. Eyal Frank, one of the study's lead authors and a faculty member at the Harris School of Public Policy at the University of Chicago"Our research has shown that extreme heat is causing significant and lasting damage to milk supplies, and even the most advanced farms – equipped with technology and resources – are failing to keep up with the pace of climate change."

The researchers studied dairy farms in Israel, which are considered among the most advanced in the world. They analyzed detailed, local weather data to assess the impact of humid heat measured using bulb temperatures  law on more than 130,000 cows over 12 years. They also surveyed over 300 dairy farmers to test the effectiveness of cooling technologies.

"The dairy industry in Israel constitutes an ideal experimental population, as dairy farms are scattered throughout the country and are subject to a wide range of temperatures and humidity - similar to the conditions prevailing in the world's leading dairy producing countries," Says Prof. Ram Fishman of Tel Aviv University. "Almost all dairy farmers have already adopted ventilation and spraying systems, and dairy farms in Israel are among the most advanced in the world – so any impact identified here is likely to be even more severe elsewhere."

The researchers found that milk yield drops significantly on hot, humid days – by up to 10% when the wet bulb temperature exceeds 26 degrees Celsius. This temperature takes into account both the dry bulb temperature and humidity, and better reflects the degree of thermal stress. Cows, like humans, feel heat differently on dry days than on humid days. When cows are exposed to such “steam heat,” it takes more than XNUMX days for production to recover to normal levels.

Although almost all dairy farms used cooling technologies, the use of the technology was only able to offset about half of the loss on 20°C days. When the temperature rises to 24°C, the offset drops to only 40% of the loss. However, the researchers emphasize that the investment in cooling equipment is worthwhile – according to the data, the return on investment comes within a year and a half.

"Farmers are well aware of the negative effects of heat stress on their herds, and they are taking a variety of adaptation measures," Says Prof. Eyal Kimchi of the Faculty of Agriculture at the Hebrew University and Vice President of the Shoresh Institute for Socio-Economic Research"Adaptation costs money, and farmers need to weigh the cost against the benefit. That's why we're seeing some investment in refrigeration – but not complete isolation of cows from the environment, which is too expensive to implement."

Using data from Israel, the researchers model how climate change will affect global milk production by mid-century. They found that without refrigeration, the top ten milk-producing countries could suffer an average drop of up to 4% in daily output, with particularly severe impacts in India, Pakistan and Brazil – between 3.5% and 4% per cow per day. Even with refrigeration, the top countries – including the US and China – are expected to lose between 1.5% and 2.7%.”

"Our research highlights both the value and limitations of cooling technologies and other climate change adaptation measures," concludes Dr. Claire Flanders, Principal Investigator"Policymakers should also consider other ways to reduce stress – such as reducing crowding and separating calves – as stressors make cows more sensitive to heat and less resilient."

The study was conducted by Prof. Eyal Kimchi of the Faculty of Agriculture at the Hebrew University and Vice President of the Shoresh Institute for Socio-Economic Research; Dr. Claire Flanders and Dr. Eyal Frank of the Harris School of Public Policy at the University of Chicago; Prof. Ram Fishman of Tel Aviv University; Dr. Yaniv Lavon and Ephraim Ezra of the Dairy Producers Association.

for the scientific article

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