How climate change threatens South Africa’s wine industry

While warmer weather might seem beneficial for crops like grapes, which can thrive in higher temperatures, the implications are more complex. Archive photo supplied.

• Climate change with higher temperatures poses numerous challenges for the South African wine industry.
• These include earlier harvests, less predictability, more pests, and higher sugar and alcohol levels that change the flavour profiles of wines.
• The export wine industry generated about R10-billion in 2023.

South Africa’s wine industry enjoys domestic and international acclaim. The country produced 934-million litres of wine in 2023, of which 306-million were exported, generating approximately R10-billion.

The wine industry supports numerous jobs and extensive infrastructure. It has knock-on benefits for tourism, making it a source of pride and revenue for the country. But climate change poses serious threats to agricultural productivity and the socioeconomic stability of those dependent on it.

Climate change, often simplified to “global warming”, refers to the rising temperatures caused by increased carbon dioxide levels in the atmosphere. While warmer weather might seem beneficial for crops like grapes, which can thrive in higher temperatures, the implications are more complex.

Research from France indicates that higher temperatures lead to earlier grape ripening — harvests now occur two to three weeks earlier than they did 40 years ago. This shift could significantly disrupt seasonal labour patterns, which rely heavily on migrant workers.

Climate change is expected to make rainfall patterns more erratic, leading to increased occurrences of droughts and floods. Such volatility not only results in diminished yields and crop losses but also threatens predictability – and farmers rely on predictability to plan planting and harvesting. Grapes are particularly susceptible to environmental changes, and the marketability of wine is highly sensitive to tiny differences in flavour profile.

Furthermore, warmer conditions allow new pests and diseases to flourish; for example, the spread of Xylella fastidiosa, a bacterium spread by insects, which causes Pierce’s disease in grapevines, has been facilitated by rising temperatures.

Last year farm workers in Paarl protested against hazardous pesticides. An uptick in pest activity will likely exacerbate this, forcing wine producers to increase pesticide use rather than reduce it.

Rising temperatures can also increase the alcohol content of wines. Warmer temperatures accelerate the ripening of grapes, increasing their sugar content, which in turn raises alcohol levels during fermentation. Research shows that for every 1°C increase in temperature, grapes can gain about 12 grams of sugar per litre, which can translate to an increase of approximately 0.66% in alcohol content, though this is limited by the alcohol tolerance of the yeast used in fermentation.

Even small changes in alcohol can significantly affect the wine’s taste and mouthfeel. Higher alcohol wines can possess a taste that overwhelms subtler flavours, presenting a challenge for winemakers striving to maintain delicate profiles.

There are techniques that winemakers can adopt to manage rising alcohol levels. “Watering back” or adding water during fermentation can help balance the wine’s alcohol content but at the expense of the intensity of other flavours. (Watering-back is a tightly-regulated practice globally, and not currently practiced in South Africa.) Early harvesting, picking grapes before full ripeness, is another method to mitigate sugar accumulation, but exacerbates the issue of early ripening due to climate change. Winemakers can also utilise yeast strains with lower ethanol tolerance, allowing for better control over alcohol levels without sacrificing quality, but this leaves more residual, unfermented sugar.

The impacts of climate change on South Africa’s wine industry are multifaceted and profound. For those whose livelihoods depend on the wine industry, those affected by its crop spraying, and for enjoyers of South African wines, the effects of climate change may leave a sour taste in the mouth.

Potgieter and de Lange are Biomedical Engineering students at Wits, and Stacey is a lecturer in Chemical Engineering at Wits.

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