Climate change is forcing Swiss winemakers to adapt

Swiss winemakers understand a thing or two about adaptation. In the 1990s, they had to adjust their practices after state protections, long a shield against foreign competition, were lifted. Today, a warming planet is demanding the country’s vintners update their techniques again as winters grow milder and summers hotter.

The northern Swiss hamlet of Wermatswil, with 1,200 souls, sits atop an ancient moraine left by glaciers that retreated 15,000 years ago. For orientation, it’s a 45-minute drive from Zurich, or 25 minutes by train and bus. I often spend time in the nearby forest, cycling or out on an evening stroll that takes me past the village’s sun-drenched southern slopes; here, a half-hectare of vines produces a few tons of Müller-Thurgau white wine grapes annually.

After picking up a few bottles of Wermatswil wine through a village connection, I dropped a note to the master of the vines here – “der Rebmeister” -- because I wanted to learn more about how climate change was affecting his grapes and the wine he produces, and what the future holds.

This region’s inhabitants have produced wine since at least Roman times. Today, members of the Rebverein, or Vine Club, who cultivate Wermatswil’s grapes are continuing a tradition stretching back 2,000 years. The limited bottling of Müller-Thurgau wine they produce is light and fruity, with a pleasant acidity, judging from the 2022 vintage I got my hands on.

Beneficiary of change?

Previously, I’d read winemakers in Switzerland have seen harvests pushed forward significantly over the last 25 years as winters grew milder and summers warmer. I’ve even heard Swiss winemakers may be among climate change’s beneficiaries, as cold and damp summers are replaced by weather conducive to more consistent harvests, higher grape sugar levels and potentially better wines.

Switzerland is, in fact, warming. The country experienced its hottest year ever in 2022. Average summer temperatures also topped the 15 degrees Celsius threshold in 2015, 2017, 2018 and 2019. Alarmingly, the past two “catastrophic” heat years have trimmed 10 percent from glacier volume in the Swiss Alps. I’ve written before about the depressing disappearance of Switzerland’s eternal ice.

So -- is this diminutive Alpine republic, now hardly on the map of wine exporting countries, on the verge of becoming the next hot tip for oenophiles as temperatures soar? The first thing Wermatswil’s vine master, Max Koller, tells me is that my simple question has a complicated answer.

The winters have definitely gotten warmer, he said, meaning the vines begin budding earlier. And while the basic rule is “early budding, early harvest,” there are notable exceptions, he tells me. Earlier blooms can be exposed to killing frosts or to hail stones, which scientists say is on the rise as convective storms grow more intense on a warming, wetter planet.

Frost or hail damage can delay the harvest, Koller said, or wipe it out. Still, he said, climate change's impact on wine making goes beyond factors surrounding his vines’ vegetation cycle. ?“In grape cultivation,” he said, “more important things are being decisively transformed by increasingly warm temperatures.”

High volume, low quality

To understand what he means, a quick excursion back into recent Swiss wine history, and the transformation the domestic industry has been through over the past half century, is helpful.

Incongruously, in the home of fine mechanical watches and (arguably) the world’s best chocolate, the quality of Swiss grape must – the freshly pressed grape juice that’s fermented and turned into wine – actually wasn’t historically a top priority among Swiss wine growers. The aim of most winegrowers in Switzerland prior to the 1990s was to produce as much wine, as cheaply as possible.

That’s because Swiss government protections conspired to keep wine from neighboring Italy, France, Germany, and Austria out, shielding domestic winegrowers from competition from better wines from abroad. Absent competition, meeting minimum Swiss government standards was good enough; some years, winegrowers intent on high volumes filled outdoor swimming pools with their after running out of space elsewhere.

I found this snarky anecdote describing the bad old days of Swiss wine this way: “As wine lovers, people were nearly overjoyed when, like in 1983 or 1985, a significant portion of the grape harvest was lost to frost and – finally – modestly drinkable Grüner Veltliner imports from Austria were allowed as a replacement.”

Free trade, higher quality

About 30 years ago, however, the world changed for Swiss wine growers. Trade liberalization in the early 1990s opened the country’s lucrative market to foreign wines. It didn’t happen overnight, but Swiss wine makers had to shift their focus from mass production to quality - or face extinction.

As post-liberalization Müller-Thurgau vintners looked to improve their wines, they initially focused closely on the sugar content of their grape must, what the Swiss measure according to their the so-called “Oechsle value”. To achieve higher sugar levels, they left their grapes hang on the vine for longer.

For a time, at least, Koller says there was something of an “Oechsle value mania”, with winemakers grilling each other whenever they gathered about “How many Oechsle do you have?”

Leaving their grapes on the vine longer to maximize sugar content opened up another option for winemakers, as well. They were able to forego so-called biological acid reduction, the addition of bacteria to reduce the acidity of cold-climate grapes. In letting grapes ripen longer as the summer stretches on and on, malic acid is converted by grape cell metabolism into sugar when temperatures hover between 20 and 30 °C.

Hitzesommer 2003

Then, the freakishly warm summer of 2003, a harbinger of a warming climate, intervened. Locals still call it the “Hitzesommer,” or heat summer. While the grape must’s sugar content soared during that sweltering season, driving Oechsle values ever higher, dreams of a wonderful vintage nonetheless soured for many growers.

Koller says days and days of outlandishly hot, glacier-melting weather also led to extremely low acidity. This was particularly true for Müller-Thurgau wines, made from grapes naturally low in acidity. The result: much of that year’s harvest lost its acidic backbone and was unstable, he said.

The experience of 2003 forced many Swiss wine growers to again rethink their harvest strategies, to bring them into harmony with warmer temperatures. Out went the hype of the high Oechsle values in which sugar content was king. What replaced it was increasing attention paid to picking the grapes when their acidity was just right.

In other words, Koller said, Switzerland's warming climate is demanding winegrowers harvest their grapes not when sugar is at its highest, but when their acid values reach ideal levels -- even if it means removing grapes from the vines before they’ve reached their physiological ripeness. A changing climate has served to teach Swiss winemakers that a more balanced approach is needed.

In wine, truth

My takeaway: The Müller-Thurgau grapes in Wermatswil that produced the bottled sunlight I snared through my village connection remain well suited to this region, but only because winegrowers like Koller have been able to adapt to changing conditions forced upon them by a warming climate. By staying nimble, they're able to produce wines whose quality surpasses those from decades past.

In Swiss wine, we’re seeing a universal truth: Successful societies must adapt if they are to thrive despite a warming planet. The means of adaptation, of course, are distributed unevenly, meaning there will be winners and losers. Agile Swiss winemakers may belong to the beneficiaries but elsewhere – likely on a different continent, with scarcer resources to fuel their adaptation – people will struggle.

You still can’t find much Swiss wine outside the country. That’s because production costs are just too high; what’s bottled here often stays put. But the quality of many Swiss vintages is excellent, even if some of my wine-loving friends have been tough to convince. I don’t think they’ve given it a chance. This goes for the wine from Wermatswil, which my wife and I found slightly effervescent and infinitely drinkable. “Instead of the earthy, nutmeg-accented, broad Müller-Thurgau wines of the 1980s,” Koller says, “we have today’s fresh, flavourful and fruity white wines.”