Features

How the Rheingau is keeping ahead of the climate curve

Winemakers and university professors in the Rheingau are conducting vineyard experiments to prepare for the effects of a changing climate on viticulture. Jim Clarke hears how and why this cool-climate appellation has become the wine world's trailblazing research region

Words by Jim Clarke

Rheingau lead
Theresa Breuer, winemaker at Georg Breuer, has embraced a new type of vineyard terracing following a recent research project

As winegrowing moves further and further north – witness the booming English wine scene – it seems natural to assume that wine industries in the hottest regions should be leading the way in researching ways to adapt to the changing climate. In fact, it’s in Germany – a classic cool-climate winegrowing country – where you’ll find a region at the top of the class, conducting detailed, long-term research on how to cope with climate change.

‘We wanted to look at climate change not only because of the higher temperatures but also because of the extreme situations,’ says Ralf Bengel, CEO at Schloss Vollrads. The area has grown drier overall but when precipitation has come it has been more intense, with brief, powerful, even torrential, storms becoming more common.

 

The Rheingau is top of the class, conducting detailed, long-term research on how to cope with climate change

Schloss Vollrads is in the Rheingau, one of Germany’s most prestigious growing regions and one dedicated to Riesling; the grape makes up 75% of the region’s plantings. In 2015, Schloss Vollrads invested in a large-scale project to determine what Riesling clones would suit the Rheingau’s changing conditions, planting 49 different clones in an experimental vineyard. Cuttings were sourced from all over Germany, as well as from Alsace and even Australia.

Two clones have emerged as winners. ‘They are clones from Geisenheim,’ Bengel says. ‘We expect clone number 355 will work very well; they [its grapes] stay healthy when its wet but also work very well during dry periods.’ One of 355’s virtues is longer, looser clusters of grapes; during wet periods these allow better airflow amongst the berries, making rot less likely. Selecta is almost seedless, with only one or two pips, making for a small berry and looser clusters as well.

The ‘Geisenheim’ Bengel mentions is Geisenheim University, just a few kilometers away; it’s one of the world’s leading wine research and educational institutions. The university’s researchers collaborated with Schloss Vollrads on the research; they work with many wineries in addition to conducting experiments in their own vineyards and facilities. The university had been tracking climate data for the past 130 years and began its first research into the impact of climate change in the 1990s, under the direction of today’s University President, Dr. Hans Schulz.

Domain Assmanshausen vineyards
The fall line and terraced vineyards of Domain Assmanshausen, one of the steepest sites in the Rheingau

Visitors to the Mosel and Rhine River wine regions will be familiar with the dramatic hillside vineyards – a 45-degree slope is typical and some are even steeper. One of the university’s most ambitious projects may dramatically change the appearance of these vineyards. In the 1960s, the small, step-like terraces of Germany’s steep-slope vineyards were removed and replanted with rows of vines running vertically down the slope. Theresa Breuer, fourth-generation owner of the Georg Breuer winery, says the restructuring improved access to the vineyards, saved money on labour and made modern vineyard management practices possible. ‘But the big advantage back then was that it was important to get water out of the vineyard as soon as possible.’ Terraces retained the water; the vertical ‘fall line’ rows allowed water to drain freely. But with drier conditions, water-holding terraces are due for a return.

‘Not the little balconies like it was before,’ Breuer says. ‘Now it’s a shape that follows the contour of the slope and it’s always just one row of vines [per terrace], which makes it easier to work.’ The new terraces feature embankments rather than stone walls and are long and wide enough to allow modern machinery into the vineyards, reducing labour costs.

Installing solar cells over vines to simulate a total absence of frost is one of Geisenheim's current research projects

While they help keep water in the vineyards in drier conditions, they also cope with the more intense storms that climate change has made much more common in the area. ‘A major advantage we have in the new terraced vineyards is much better erosion control,’ says Geisenheim Professor Dr. Ilona Leyer. ‘In fall-line vineyards, the water and all the sediments go straight downhill and into the river. We saw this in 2018. We had three newly established terraced vineyards and in close vicinity, some young wines planted in fall-line vineyards. On the ninth of June, we had huge precipitation like we’ve never measured before – 70 millimeters per square meter within three hours. In the fall line we had 100% damage. The sediments were all over the roads. And in our terraced vineyards we had zero damage.’

The university is able to embark on expensive, long-term projects independent of the annual cashflow demands of a wine producer

Not all of Geisenheim’s research is so immediate in its impact; the university is able to embark on expensive, long-term projects independent of the annual cashflow demands of a wine producer. ‘This is the most expensive vineyard on earth,’ says Professor Dr. Manfred Stoll, waving his hand at six large rings interspersed amongst rows of Riesling and Cabernet Sauvignon vines. These rings, and the carbon dioxide they disperse, are the expensive part. Each ring has sensors monitoring the wind and air; the ring itself is dotted with pumps that release CO2 as dictated by the sensors to maintain the levels expected in the vineyard by 2050. The experiment sets aside questions of temperature and climate and instead looks at how vines will respond to an increase in the key fuel of photosynthesis.

The Free Air Carbon Dioxide Enrichment (FACE) project started in 2014 with newly planted vines. Results so far suggest that vines in a more CO2-rich future will produce more plant mass and use more water to do so. The number of grape bunches won’t change but the individual berries will be larger and therefore more tightly packed. This could increase the risk of disease, as will the impact on insect life, which in these conditions propagate themselves a whole extra generation each season.

Professor Dr. Manfred Stoll
Professor Dr. Manfred Stoll leads a project looking at how vines will respond to the predicted increase in carbon dioxide

Other current projects examine the impact of placing solar cells over and amongst vine rows or using heating wires to prevent frost – another growing, climate change-related problem. Maintaining the long-term programmes is a challenge, as grants for research tend work in two-or three-year cycles; at ten years of age, the FACE program has already been through three grant application periods, with the fourth already approved. But Stoll says long-term projects bring insights that would be impossible otherwise. ‘A good example is our trial comparing conventional, organic and biodynamic farming. It ran for almost 15 years, with organic and biodynamic always showing a reduction in crop yield. And then we had hot and dry summer conditions in ‘18, ’19, ’20 and ‘22, and in those years, organic and biodynamic actually did not show any difference in crop yield. They were cropping to the same extent as the conventional vines or probably even better.’ A short-term project would never have exposed that difference, nor can we hope for short-term answers to the long-term impact of climate change.