Winetech Technical Yearbook 2022

OCTOBER

High altitude vineyards CLIMATE CHANGE AFFECTS CROP PRODUCTION IN MANY WAYS. IN PARTS OF THE WORLD, PRODUCERS ARE SHIFTING NEW PLANTINGS TO HIGHER ALTITUDES TO MITIGATE THESE EFFECTS. THIS ARTICLE (BASED ON A SCIENTIFIC REVIEW ARTICLE) TAKES A LOOK AT HOW CLIMATE CHANGE AFFECTS GRAPEVINES AND EXPLORES THE ADVANTAGES AND CHALLENGES OF MANAGING VINEYARDS LOCATED AT HIGH ALTITUDE SITES. H increases. This does, however, depend on how much water is available for the plant. Grape biochemistry Climate change leads to earlier onset of veraison and higher total soluble solids, together with a decrease in the anthocyanin to sugar ratio in grape berries. Furthermore, warming temperatures and advanced phenology leads to increased sugars and a decrease in organic acids, particularly due to malic acid breakdown, along with a shift in the composition of secondary metabolites and aro ma precursors. The extent of these effects vary between cultivars. CHANGE IN SUITABILITY OF SITES FOR WINE GRAPE PRODUCTION As climate changes, altering temperatures and rainfall, it could mean that certain areas that were renowned for producing quality grapes could become less suitable. On the other hand, regions where grapes were never grown before, could possibly become prime spots. Vineyards located at higher altitude or elevation are known for shorter growing seasons and lower summer tempera tures. These areas are expected to become warmer over time, which could allow for a wider variety of cultivars to be grown successfully in these sites. BY LUCINDA HEYNS

HOW IS OUR CLIMATE CHANGING? Climate change leads to long-term shifts in temperature and weather patterns. Consequences further include extreme weather events, such as droughts, rising sea levels, raging fires and dev astating storms. According to the sixth assessment report of the Intergovernmental Panel on Climate Change (IPCC), the last four decades have been sequentially warmer than any other decade since 1850. Particularly, land surface temperature in the first two decades of the 21st century was 1,59°C higher than 1850 - 1900. Atmospheric carbon dioxide (CO 2 ) levels have continued to in crease since 1750, and will still be around for a long time, even if we were to stop our carbon emissions. Local research indicates that the climate in South Africa is also changing, but how it changes varies between regions. For exam ple, in the Breede River region, rainfall is increasing, and while maximum temperatures are increasing, minimum temperatures are decreasing, leading to more spring frost events. Conversely, the Coastal region is becoming drier, while both maximum and Research in southern Australia indicated that warming average temperatures during the growing season advanced harvest by four to 11 days. Other research indicated that elevated temperatures cause all phenological stages to advance and shortened the time needed for grapes to reach optimal ripeness. It is expected that a reduction in available water could exacerbate these effects. Physiology Studies show that increasing CO 2 levels result in a decrease in stomatal conductance. Higher levels of CO 2 do, however, contrib ute to increasing biomass as the effectiveness of carbon fixation minimum temperatures are rising in this region. HOW DOES CLIMATE CHANGE AFFECT THE GRAPEVINE? Phenology

In other places where wine grapes are currently produced, average temperatures can increase, and water availability de crease to the point where it becomes detrimental to quality wine grape production. Research in various countries using different bioclimatic indices and climatic models to simulate predictions in climate change scenarios, indicate there will be shifts in the suitability of sites for viticulture in the face of a changing climate. MOVING UP Moving grapevine production to higher altitudes could be an adaptive strategy, in certain areas, to mitigate the effects of cli mate change in order to maintain quality. Maize farmers in North ern Equadorian highlands have been following this approach for the last two decades. Although temperatures are lower at higher elevation, one should keep in mind that other factors are also at play. With altitude, thermal amplitude (difference between maximum and minimum temperatures), net global radiation exchange and UV-B radiation increase too. These variables have a great impact on phenological stages, as well as on its duration. HOW DOES ALTITUDE AFFECT THE GRAPEVINE? Altitude and phenology Research has shown that worldwide an increase in altitude causes a delay in the timing and duration of phenological stages. A study in Italy evaluated the statistical correlation between altitude and the timing of budbreak, harvest and the length of budbreak to harvest interval. Five varieties, namely Pinot noir, Sauvignon blanc, Chardonnay, Merlot and Pinot gris were included in the

35

WINETECH TECHNICAL YEARBOOK 2022