Whether you love heavily hopped IPAs or subtle golden ales, you love alpha acids but don’t know it. These are the compounds in hops that give bitterness, which can be subtle or intense depending on the cultivar.

For many years, farmers who produce hops have been breeding varieties to enhance the alpha acid content. In particular, hop growers in the Pacific North-West of the US have done their own polishing, producing hops with the characteristic aromas that make West Coast IPAs citrusy and juicy. Growers in many parts of Europe have responded with their own high alpha, but more subtle, cultivars.

But now, new research shows climate change could put a stop to this. Droughts across the continent and extreme heat have seen reduced yields and alpha content of European hops.

New modelling in Nature Communications estimates that by the year 2050, Europe’s hop growers will see a further four to 18 per cent drop in yields and a 20-31 per cent hit to alpha acid content.

“What we are seeing under climate change is a combination of more droughts that will affect the yield of the plants, unless irrigation is supplemented,” says bioclimatologist Mirek Trnka of the Czech Academy of Sciences, a co-author of the new paper. “At the same time, higher temperatures are not conducive to high alpha acid content.”

Hotter, longer and drier summers are predicted to worsen the situation and could lead to beer becoming more expensive. The authors warn growers they will need to adapt their farming techniques to suit the changed conditions.

So, does this mean the end of the fruity flavoured hops many of us have come to love? The answer from Britain’s hop growers is a clear no.

British Hop Association and Wye Hops director Ali Capper said: “Climate change has been a consideration for British hop growers and our Wye Hops breeding programme for well over a decade. We have done work in previous years on producing new seedlings that may have the potential to cope with hotter dryer, summers and wetter milder winters.

“The UK will remain a good place to grow food and drink crops into the future and the warmer weather is likely to broaden the range we can grow. For hops the warmer weather is likely to intensify hop aromas.”

However, Capper does concede some traditional British hops may struggle in excessively hot and dry conditions so it’s important that we look for new varieties that can thrive.

“We have developed Jester, Olicana and Harlequin in recent years and all thrive in hot and dry conditions. Lots of new varieties are coming through that will thrive in the warmth and provide great flavour and aroma,” said Capper.

“Equally vernalisation is an important process in the winter months which shuts down the plant and helps it to thrive the following year. Traditionally vernalisation for hops requires 1,000-plus hours of chill units [an average 24-hour temperature below seven degrees]. Some hop varieties cope well with less chill hours, so breeding hops that can cope with milder winters will be important.

“Much work is going on in the industry to reduce reliance on fossil fuels, but we wait to see what government decisions will be made on the infrastructure required for electricity versus biofuels versus hydrogen. Each of these have the potential to power farm vehicles and dry the hops in the future.

“Water footprint is another very important consideration. Hop growers in the UK have a climate advantage on many hop-growing regions because we use more natural rainfall to grow hops, due to our maritime climate, than any other region in the world making our water footprint one of the lowest in the world.

“Carbon footprint created by the transport of hops to the brewery is an important consideration. British hops can reduce the carbon footprint for shipping to a British brewery by up to 85 per cent, simply because they have less miles to travel”, she said.

Hop supplier Charles Faram’s technical director Will Rogers said the report is perhaps a little sensationalist in focussing on some landrace varieties. A landrace is a variety of a hop species that has distinctive characteristics arising from development and adaptation over time to conditions of a geographic region.

Rogers said: “The UK is well placed to grow hops sustainably and has a promising future ahead, but growers need support from brewers to continue the good work they have been doing.

“It is some interesting research, that has garnered a lot of interest in the last week. It is focussed on aroma hops, noble, mostly landrace varieties. These landrace varieties by their definition have not moved on genetically since they were tamed.

“There are few crops that have been grown unchanged for centuries, without any breeding involved. We know that our landrace varieties are more prone to heat stress and also drought pressure, varieties with newer genetics can certainly be bred with more resistance.

“Drought causes problems for hop growers, the hop being perennial, grows from a rhizome. This rhizome has enough energy and food stored for the plant to start growing, but there comes a time when the plant needs to be fed, this food is water soluble, if there is no groundwater this food can’t be taken up by the plant.

“The UK is in an unusual position with regard to hop growing. We have a maritime climate. Even during the last few years of extremes, we have had enough rain to grow hops. Perhaps the rain hasn’t been when we would ideally like it, we need to learn to manage our water resources more effectively.

“Mainland Europe has a different climate and a far more significant issue. This means that climate change is likely to give [growers] more drought issues, and irrigation will not be an option for many of the regions growing hops.

“The US has some water issues on the horizon. The Yakima Valley, where the majority of hops are grown in the US, is a desert. Growers rely heavily on irrigation [1,600ltrs for every kilo of dried hops].

“This irrigation water comes from melting snowpack in the Cascade mountains from which the rivers have been dammed, allowing for slow release during the growing season. This snowpack is not guaranteed and has been insufficient in some years recently. There is also significant competition for this resource.

“UK growers have been supporting hop breeding and research for more than 100 years. Our unique climate has presented some issues, the same climate that now makes UK hop growing at the leading edge of sustainability.

“Hops are grown as a monoculture and are prone to fungal disease. Genetic resistance to these diseases was identified in the last century by Ernest Salmon as the key to the future of growing hops. This research and breeding is now starting to show its true value. The program run by Klara Hadju at Wye Hops is partially funded by growers, but also merchants and brewers. There is also a private breeding program run by Charles Faram which is separate, but complementary to the Wye Hops program.

“Hops can be bred to be more tolerant of heat and drought. We have some varieties in our Charles Faram breeding program which have demonstrated that breeding and selecting for disease and drought tolerance can achieve remarkable results.

“High alpha varieties like Herkules, now the largest acreage grown in Germany, tend to be more resilient to heat and drought. They are stronger plants, that grow more aggressively.

“Much of the acreage in Germany has moved from the landrace varieties, over to this variety. Now Germany leads the world in alpha production, which is mostly purchased by the large multinational brewing companies.

“The Czech Republic has not moved to high alpha varieties. It continues to focus on Saaz, a variety which is a true noble hop. Unfortunately Saaz is very prone to heat and drought stress, causing yields recently to fluctuate wildly.

“In 1978 the Czech Republic grew 10,400 hectares of hops, which produced 10,870,900kg, or 970kg/hectare. In 2022 it grew 4,943 hectares, which produced 4,452,000kg or 900kg/hectare, so seven per cent less. But in 2021 Czech Republic grew 4,971 hectares, which produced 8,306,000kg or 1,671kg/ha.

“These older varieties are more prone to significant swings in yield, climate change will continue to bring uncertainty but with high-quality packaging and storage, brewers and merchants can mitigate some of the risk, but they have to be prepared to hold stock.

“In the Czech Republic growers have been trying to breed a new Saaz, they have planted 50,000 seedlings for the last 20 years (a million plants) and are yet to find a true brewing match for Saaz.”

So, if all goes well, pints brimming with citrus flavours will be safe, however warm it gets.

For the hop research go to: https://www.nature.com/articles/s41467-023-41474-5