Speakers - AFHWC2025

Abstract

The objective of this research is to estimate the contemporaneous and delayed impacts of humid heat on milk yield. In addition to contributing new evidence on the impacts of humid heat on milk production, our work makes methodological contributions to the literature. The existing empirical literature on the impacts of climate change on agriculture has addressed counts of extreme heat events, but not how these are spread across time, e.g., the potential of a non-linear cumulative effect during hot spells, or how they interact with high levels of humidity. In addition, we conduct novel estimations of the effectiveness of adaptation strategies, and discuss how our estimates can be used to project the impact of climate change on milk production.

We use daily data on the milk production of 130,000 cows over 12 years in Israel. The data include the total daily amount of milk produced by each cow, as well as the start date of the given lactation cycle, the number of calvings - which is a reliable proxy for the cow’s age

- and the number of milkings per day. We construct two separate weather datasets of hourly temperature and relative humidity at the location of each farm, for the full period 2009-2020. In 2020-21, we attempted to survey all dairy farms in Israel in order to collect information about their basic operational characteristics, and in particular, the type of cooling technologies, if any, that they use to deal with heat stress, when they had installed them, and why. We also asked about additional adaptation strategies.

The analysis reveals nonlinear negative effects of humid heat on milk production, reaching a 10% decrease on extreme days, that persist for 10 days after direct exposure. Effects are stronger when cows are at more productive stages, suggesting a productivity- resilience trade-off. Cooling infrastructure and management adjustments were widely adopted over the preceding two decades, but only partially mitigate these losses, reducing them by less than half. Still, it is worth it to install cooling equipment, with farmers able to recoup the costs of installing the equipment in about a year and a half. Due to climate change, the top 10 milk-producing countries could see average daily milk output decline by 4 percent without cooling. With cooling, the five largest producers still see losses between 1.5 percent and 2.7 percent per cow per day.

Since the range of temperatures in the sample is representative of the largest milk- producing countries, and given the technological advancement and long-standing exposure to heat of the Israeli dairy sector, the results suggest that common adaptation strategies may hold limited potential to avert the global impacts of climate change on this nutritionally and economically important sector.