Vulnerability of US dairy farms to extreme heat

Livestock agriculture, and dairy more specifically, is threatened by climate change as extreme weather conditions become more frequent. When temperature and humidity increase above critical levels, dairy cows become heat-stressed and experience a drop in milk production. We quantify the impact of heat stress on the dairy industry throughout the Midwestern and Eastern United States in the years 2012–2016 using animal-level production data. We estimate that 1% of total annual yield is lost to heat stress, and losses are predicted to increase about 30% by 2050 on average under various climate scenarios. We provide three new insights compared to previous estimates with aggregated data. (1) Heat stress disproportionately affects milk quality, having larger impacts on farm income and nutritional value than previously estimated. (2) Small farms experience the largest losses to heat stress, suggesting they face barriers to adaptation. (3) Cows in the highest-yield production stage are the most vulnerable to heat stress in both relative and absolute terms. Our results have global implications given the prevalence of dairy as a source of income and nutrition in high- and low-income contexts. We outline ways that funds for climate-smart agriculture could be used to increase climate resilience in the dairy industry.