Technical Yearbook 2023

JUNE

Chenin blanc (Ina Smith, WoSA Library)

This article is based on a joint presentation by the three authors at the 2nd Chenin Blanc International Congress in Stellenbosch, 1 - 3 November 2022. Background The supreme adaptability of Chenin blanc to diverse regions makes it a very interesting case study for exploring the future of wine under a changing climate. Production regions in both France and South Africa are already undergoing climatic shifts linked to warming and changing rainfall patterns. In the Western Cape Province of South Africa, Chenin blanc is successfully produced in widely ranging climates. With climate change, the shifting mosaics of micro climates will play an important role in vineyard decision-making for the future. Approach and case study sites This study was structured around three components: • The latest climate change science – recent trends and modelled future projections – for the Western Cape Chenin blanc – the versatile variety By Rosa Kruger, Stephanie Midgley & Tara Southey New ways and new sites to plant Chenin blanc in years to come in the quest to deal with climate change.

(for details of methods and results, see Jack and other authors, 2022); • The finer-scaled web-based spatial tools provided by TerraClim that can aid climate-adaptive decision making at farm and vineyard level (www.terraclim.co.za); and • Practical experience in vineyard

during autumn and spring, especially in the interior, higher-lying areas (figure 2). Daytime warming has been more muted in summer and winter. Trends in seasonal mean annual rainfall (1982 - 2020) indicate significant drying during autumn across all the sites (figure 3). Trends in core winter (June - August) rainfall are mixed and demonstrate a dipole from the northwest towards the southeast, from drying to apparent wetting. Potential evapotranspiration (PET) has consistently increased across all sites in all seasons, although more strongly in spring and summer, and on the southwestern and southern coastal plains. Future-modelled climate projections (to the mid-century) suggest a further drying associated with hemispheric climatic processes, including a poleward displacement of the westerly wind belts and storm tracks during the winter rainfall period. Projected changes in annual total rainfall show drying of up to 40 - 80 mm per year, or up to around 30% in some production regions, but for most regions, the

planning and management for long-term vine resilience and climate adaptability (www. oldvineproject.co.za).

We chose six Chenin blanc vineyards in the Western Cape as case studies, spanning the range of distribution from north to south along strong climatic gradients (figure 1, table 1). Climate change trends and future projections Trends in daily minimum temperature (1902 - 2020) show strong increases in autumn and spring along the West Coast, but moderate warming for the two southernmost sites, and across the whole region in summer and winter (figure 2). Increasing trends in daily maximum temperature are greatest

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TECHNICAL YEARBOOK 2023