How Luxembourg vineyards adapt to climate change

Higher temperatures, cold snaps, fungal diseases and droughts: climate change has been bringing a whole set of challenges to Luxembourg’s vineyards, with producers relying on science, innovation and history to continue wine production.  

“Starting in 2003, we had the first really, really hot summers, which produced wines in Luxembourg with lots of sun and heat,” Marc Fiedler, head of the viticulture section at Luxembourg’s Wine Institute (Institut d’état Viti-Vinicole, IVV), told Virgule in an interview.

The results of these increasingly hot summers are dense wines, with a high sugar content and therefore higher alcohol percentage, that end up resembling Mediterranean wines. “We are not a region of overly alcoholic wines, which are typical of the south,” Fiedler said, explaining that Luxembourg wines risk “losing their typical character”.

Very early harvests

Harvests are also profoundly affected by the rise in temperatures.

“The average temperature, which has risen linearly over the last few decades, is higher throughout the vegetation cycle, particularly during the flowering and ripening phases of the vine,” said Fiedler.

As a result, these harvests are taking place much earlier than a few decades ago. Whereas in the 70s and 80s, harvests always took place during or even at the end of October, without even a guarantee that all the grapes had reached maturity, they now take place towards the beginning of September, with the ripening phase now taking place as early as August.

Increase in fungal diseases

Another consequence of rising temperatures is that, by causing more evaporation, they increase the frequency and intensity of heavy rainfall, which can cause serious damage to the vines.

Higher humidity levels, coupled with a warmer climate, also create a more favourable environment for the proliferation of fungi and hence fungal diseases.

This year, with its heavy rainfall, was a perfect example of this scenario.  

“Fungi really like these conditions of humidity and high temperatures, which we experienced during this vintage,” said Fiedler. “This created a lot of problems with fungi, such as botrytis, but especially peronospora and powdery mildew.”

Reducing foliage to bring more air

Winemakers can initially implement short-term solutions to prevent fungal diseases from spreading. One of these is to aerate the foliage by removing excess leaves from the vines, thereby reducing the risk. But this requires painstaking work in the field on the part of the winegrowers.

Other more sophisticated methods, aimed more at solving problems over the long term, are being developed as part of research work involving the IVV, whose mission is to advise winegrowers and transfer research knowledge, and the Luxembourg Institute of Science and Technology (LIST).

New varieties to delay ripening

Other solutions involve planting other varieties more adapted to the change in climate.

“In recent years, we have been testing varieties that ripen later, with very good results,” explained Fiedler. However, the aim remains to avoid borrowing varieties that are more resistant to current and future climatic conditions, but which would distort the typical character of Luxembourg wines.

To maintain the Luxembourg taste profile, the IVV and LIST have been studying Piwi, from the German ‘Pilzwiderstandsfähig’, since the early 1990s. Piwi are interspecific grape varieties, crosses that have developed resistance to fungal diseases and have the great advantage of reducing the use of phytosanitary products.

“We have around twenty Piwi varieties that we are studying and which are very promising,” said Fiedler. Among the best-known names are Cabernet blanc, Satin noir, Bronner and Johanniter.

These Piwis can themselves be grafted onto rootstocks – the base of the vine that will develop the root – that have developed adequate resistance.

This is not a new technique for planting vines: it was used at the beginning of the 20th century, when phylloxera-resistant rootstocks were imported from America to help European vineyards survive the ravages of the epidemic.

A new generation of rootstocks

This technique is once again proving its effectiveness in the face of climate change.

“Grafting can also be a solution,” said Fiedler. “There are different types of rootstock. They carry resistance to phylloxera, but we can add other resistances, to heat for example, or to drought and water stress. Research is working hard on this.”

While research is going well, climate change continues to intensify, creating new challenges as the older ones are being solved.

“LIST projections predict an increase in average annual temperature of around 2°C between now and 2100, but the increase during the vegetation period and the maturity phase could be of the order of twice that,” said Fiedler, adding that this was a “rather perplexing” scenario.

“We are continuing to study this development by launching new research projects,” said Fiedler.

More experiments are already in preparation: to improve the water balance on farms, while creating shade and new income for winegrowers, plant trees will be planted in vineyards, with the idea of exploiting their potential synergy with vines.

Solar installations

In the same vein, ‘vitivoltaic’ installations could emerge within vineyards, with solar panels installed above the vines. There are a number of advantages to these panels: they create shade, protect the harvest from heat and excessive solar radiation, but also from excessive rain or hail, while allowing the plants to breathe thanks to the inclination of the panels.

“These installations can create a better, more moderate microclimate,” said Fiedler. “And they can also delay the ripening period. With the possibility of producing not only wine but also energy.”

For Fiedler, “the big challenge for Luxembourg is really to keep the typicality of the white wines we grow here, the Riesling, Rivaner, Auxerrois and Pinot, which we want to drink with freshness and acidity”.

(This article was originally published by Virgule. Translation, editing and adaptation by Tracy Heindrichs)