Whether you love Lagers or extra bitter IPAs, you love alpha acids and just don’t know it. These are the compounds in hops that give them their bitter taste, which can be subtle or intense depending on the variety. For centuries, farmers growing hops for traditional European beer production – particularly in Germany, the Czech Republic and Slovenia – have refined this alpha acid content. More recently, farmers in the U.S. Pacific Northwest have made their own refinement, producing hops with the distinctive flavors that make West Coast IPAs citrusy and juicy.
But now climate change is taking a serious toll on hops. Droughts and extreme heat have already led to a decline in yields and alpha acid content of hops grown in Europe. And new modeling, published last week in Nature communicationestimates that Europe’s hop growers will see a further 4 to 18 percent decline in yields and a 20 to 31 percent decline in alpha acid content by 2050. “What we are seeing with climate change is a combination of more droughts, which will affect crop yield unless irrigation is supplemented,” says bioclimatologist Mirek Trnka of the Czech Academy of Sciences, co-author of the new paper. “At the same time, higher temperatures are not conducive to high alpha acid content.”
Lower yields and a decline in acidity could become a compounding threat, says hop chemist and brewing scientist Tom Shellhammer of Oregon State University, who was not involved in the new paper. If the hops are harvested with 30 percent less alpha acid content, “that means you have to use 30 percent or more of those hops,” Shellhammer says. “If the actual yield achieved on the farm goes down,” he adds, “then there is simply less of it available in the industry.” So the brewery would have to use more of it. This then leads to a supply problem.”
In general, brewers and farmers – be it for hops, barley or malt – are still analyzing how beer is changing due to climate change. There are overlapping factors. In addition to rising global temperatures and worsening droughts leading to water shortages, there are also more extreme heatwaves and associated problems such as major wildfires that can cause smoke to ruin crops. (The wine industry faces similar problems with grape production.) “We still don’t fully understand what impacts climate change might have, particularly on smaller components that contribute to flavor,” says Glen Patrick Fox, who studies brewing and beer quality the University of California, Davis. “This will be a case where the industry needs to measure things over a longer period of time to really understand how this will happen.”
Grown on a trellis system, hop plants can reach 20 feet tall and produce the cones that add complex flavors and bitterness to beer. However, higher temperatures reduce alpha acid production in these cones. The reason is not yet clear, but it could be a result of their development at the start of the season. In Europe they are now appearing about three weeks earlier than in 1994. Higher temperatures lead to a similar acceleration of development in cereal plants.
“They simply don’t have enough time to produce all the valuable chemicals – or, in the case of grains, to make enough starch,” says Trnka. “This could be a mechanism for hops, or it could be another mechanism linked to a certain biochemistry. But we don’t know that yet. It was pretty hard to grasp.”