Vulnerabilities

Growing season length and temperatures are critical aspects that have to be taken into consideration to maximize a style of wine and its quality (2). The dynamics of grape ripening of early-, medium late-, and late-ripening vine varieties in the Slovenian Styria wine-growing region in North East Slovenia has been studied for the period 1980 to 2009 and interpreted in relation to the trend of changes in temperature from 1950 to 2009. This is the first national study of the impact of climate change on wine grape quality aimed at establishing the response of studied varieties (White Riesling, Sauvignon Blanc, Welschriesling, and Bouvier varieties) to increasing temperatures (1).

Slovenia is a viticultural world in miniature, including all of the world’s important wine grape varieties for the production of quality wine. The region of Styria is the most extensive wine-growing region in the country (4).

In general, temperature changes were more signifi­cant since 1980 than between 1950 and 1979. The mean annual and seasonal temperature significantly increased, i.e. 0.06°C per year. The growing season was shortened in all studied varieties by 15 to 27 days. Trends showed significantly decreasing content of total acidity, which can be considered explicitly as a consequence of higher tem­peratures during the growth period and ripening of grape berries. Grapes now ripen at temperatures which are ap­proximately by 2°C higher than 30 years ago. Regarding the total acidity content of the late-ripening varieties, the influence of higher temperatures is positive. Minor changes were found in precipitations rates (1).

Estimation of the impact of climate change on the growth cycle of the grapevine has shown a significant impact on harvest timing and season duration. Grape maturity was shown to occur 4−8 days per decade earlier since the 1980s when compared to previous decades for all varieties studied, and harvest was advanced into a warmer part of the season (4).

In general, the quality of Slovenian wine increased after 1970, due to higher temperatures, but also due to modernization in both the vineyard and winery. However, if the trend in regional warming continues as predicted by climate models, or continues at the same rate as it has been occurring in the past 30 yr, the Slovenian Styria wine region will likely see lower quality vintages, mainly because of low acid content, very high alcohol, and other less desirable wine characteristics (4).

Negatives effects of climate change on viniculture include an increase of soil erosion, particularly in vineyards on steep slopes (1), greater pest and disease pressure due to the milder winters (5), a higher likelihood of diseases such as botrytis due to earlier grape ripening, and changes in the physiology of the vine and grape composition due to an increase in ultraviolet-B (UV-B) radiation on the soil surface (4).

Adaptation strategies

Some adaptations in existing vineyard management practices are necessary to preserve certain specific characteristics of the wines produced in this wine region, especially the technique of arrangement and care of vineyards and management (3). In specific situations the early varieties will be suitable for the location less exposed to the sun. In this wine region, this is pos­sible because the majority of vineyards are on steep slopes with different sun exposures. More negative influences of climate change can be expected in the case of early-ripe and aromatic varieties (lower acid, bitter substances, atypical aromas, and wine aging, etc.), whereas the growing season in the case of late varieties may be shortened (1).

A more long-term measure is the replacement of varieties, because the wine laws allow the planting of only certain varieties in certain regions of Europe. Therefore, the use of drought-tolerant rootstocks is a reasonable adaptation (4).

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Slovenia.

1. Vršič and Vodovnik (2012)
2. Jones et al. (2005), in: Vršič and Vodovnik (2012)
3. Vršič et al. (2011), in: Vršič and Vodovnik (2012)
4. Vršič et al. (2014)
5. Schultz (2000); Tate (2001), both in: Vršič et al. (2014)