Juliana Ranches drove to work in eastern Oregon in early September through wildfire smoke so thick that, for a moment, she thought it was just a grey, foggy day and it would soon start to rain. Ranches is a livestock researcher relatively new to living in the area, and the conditions were unlike anything she had experienced before, leading her to ask questions about the animals that spend their summers in the smoke. Eastern Oregon has this year experienced regular wildfires since early July. “We know there is a negative effect,” Ranches said, referring to the cows grazing outside in some of the most polluted air in the US. The area registered 160 on the air quality index (AQI) in early September after reports of a large number of wildfires, a level that can put human health at risk. “There is a little bit of work out of California with [dairy and beef] producers and indirect impacts, reporting lower conception rates and birthrates, but we cannot say for sure because there are no studies in a controlled environment looking into that.” Research into the impact on livestock bred for human consumption is limited, although it is known that particulate matter from the smoke is a significant health threat, especially when exposure is long-term. According to new preliminary research from the University of Idaho, a sample of dairy cattle exposed to poor air quality and heat stress produced less milk – about 1.3 litres less than normal (just over two UK pints) – a day than average. Some cows had not fully recovered two weeks after the air quality improved. But because this observation was based on just one herd, the data does not yet translate into solid recommendations for ranchers and farmers. The work must be scaled up to explore larger patterns. It is why Ranches, along with her colleague Jenifer Cruickshank, who specialises in dairy management, has begun a three-year study to collect more data on cows and the effects of wildfire and smoke, as part of which they have put nearly 30 cows out to pasture. “I call them my smoke cows,” said Cruickshank. During a wildfire event that results in an AQI measure over 50, she takes daily milk samples and blood tests, which will be analysed as stress markers. The cows’ respiratory rate and body temperatures are also documented. “We’re getting a finer-grained picture of what these cows are experiencing, through poor air quality associated with wildfires – a better understanding of the physiological effects on them, like is it mild? Is it severe? Is there diversity among the response in the cows? With that information, we can start to look at the negative effects and minimise the damage,” she said. Cruickshank lives in western Oregon, which has some of the highest concentrations of dairy herds in the state. Tillamook, a community with a nationally recognised creamery, has 80 dairy farms and nearly 30,000 cows. Historically, the cows there were not exposed to wildfire risks like their counterparts on the dry eastern side of the state. But as summers become hotter and drier, alongside anomalous wind events, the lush forests along the Oregon coast are also burning. Farmers like Derrick Josi, whose family has farmed in Tillamook for generations, have become increasingly aware of the risks. With resources strained in response to megafires on the other side of the Cascade mountain range, sometimes they have to pitch in to help tackle the fires. “We did have a little wildfire last year,” said Josi. A small team of forestry firefighters responded, but some equipment was lacking. “There were farmers up there to get water to people. The [feed] tankers all have vacuum pumps, and they needed water. So, we sent the tractors and tanker wagons up into the woods.” While wildfires are a threat, the more consistent issue on the coast is the hotter summers and the smoke – both of which are worsening. In some so-called smoke storms, ash will fall from the sky, which isn’t only a respiratory concern, but potentially an issue for still water in troughs. Also, most coastal farm facilities are not equipped to provide shelter from severe smoke and prolonged heat. “Usually, we have an upper valley, east or west wind, and as long as you have a wind, cows handle heat fairly well. But this time [over the summer] it was over 100 degrees, no wind, and a cow’s natural reaction when it gets hot is to find shade,” Josi said. “So then they all ran into the barn, but you get them inside a barn with a metal roof, and that kind of heat, and then, all of a sudden, they crowd around water troughs. So then you have lots of cows in a small, confined space, and it just compounds the issue. In that type of heat, nobody does well.” In places that deal with extreme heat regularly, facilities are built to respond. In the midwest, for example, climate-controlled barns the size of a large supermarket help circulate air, and misters are installed along feed bunks to cool the cows. In traditionally cool, coastal Oregon, most barns are naturally ventilated, and that means finding a solution to changing weather patterns will be challenging and costly. “It would be expensive,” said Josi. “It would be a rethink of how you design barns, for sure.” A comparison of seven ventilation systems by the Journal of Dairy Science found that annual costs ranged between $246 and $318 a stall. With most dairy farms in Oregon averaging about 400 cows, that cost quickly rises to hundreds of thousands of dollars, and construction is just the start. Mechanical systems cost twice as much to operate as natural systems, with costs in hotter US climates double those in milder climates. Tami Kerr, executive director of the Oregon Dairy Farmers Association, is confident that farmers will be able to keep their livestock safe. Many across the state have already installed fans and misters in their barns, and she said they will do whatever it takes in difficult circumstances to take care of their animals. “The top priority of every dairy farmer is cow care and cow comfort. Healthy, happy cows produce high-quality milk, and Oregon is a national leader in milk quality, which reflects well on the care our farmers provide to their animals,” Kerr said. “Our producers are creative and will explore more options to keep their workforce, as well as their cows, as safe and comfortable as possible.”