The group behind the model found that a possible decline in milk production due to climate change will vary across the U.S., since there are significant differences in humidity and will be impacted by how much the temperature swings between night and day across the country. The humidity and hot nights make the Southeast the most unfriendly place in the US for dairy cows right now. That's not new, scientists and obviously farmers have long known about and studied the impact of heat stress on cows' milk production.
But if you read TIME or the Associated Press, local heat waves are here to stay and what was once called climate instability is now a runaway global warming trend, so the Northeast will see dropping milk production. Or you can read science and not scare journalism designed to generate pageviews, like here.
The new study combined high-resolution climate data and county-level dairy industry data with a numerical model to estimate how weather affects milk production. The result, they say, is a more detailed report than previous studies and includes a county-by-county assessment that will be available to farmers and projects the impact climate change will have on Holstein milk production in the U.S. through 2080.
They say previous research into how climate affects cow milk production in the U.S. was either limited in geographic scope or was too simplistic, ignoring the impact of humidity, for instance. By using detailed climate data covering night and day across the entire country, the researchers made some interesting discoveries. In Tillamook, Oregon, where the climate is humid and the nighttime temperature doesn't change much, milk production begins to drop at a much lower temperature than in the dry Arizona climate - Tillamook cows became less productive starting at around 59 F, while those in Maricopa, Arizona, start making less milk at around 77 F. In humid Okeechobee, Florida, cows become less productive at about the same temperature but losses increase at a much faster rate than in Arizona.
Cows in Tillamook aren't sweating it, though. The temperature doesn't stray upward often and so actual milk losses are negligible but in Maricopa the mean daily losses in summer reach nearly 50 percent. Dairy farmers knew this. They have always clustered in the most comfortable areas for cows, such as the cool coastal counties of Washington state.
But the outlook isn't good for areas in areas where cows are already less productive in the heat of the summer.
"Perhaps most significantly, those regions that are currently experiencing the greatest losses are also the most susceptible: they are projected to be impacted the most by climate change," the researchers wrote in the paper. It's not all doom and gloom. While the researchers project that dairy production averaged across the U.S. will be about 6 percent lower in the 2080s than at the start of the century, other factors are likely to actually boost milk production even more.
"Management practices and breeding are on track to double milk production in Holsteins in the next 30 or 50 years," said Guillaume Mauger, a postdoctoral researcher in the University of Washington's Climate Impacts Group and co-author of the paper. "So while a 6 percent drop is not negligible, it's small compared to other positive influences."
The researchers hope next to look at the impact climate has on other barnyard animals, such as pigs, and other effects, such as mortality rate, that rising temperature might have on cows.
Yoram Bauman of the Sightline Institute, one of the co-authors, will present the findings during this week's Conference on Climate Change at the University of Washington campus.