Sunday, April 28, 2013

Wine-ing about climate change

If you like wine, particularly Old World wines, a recent paper by Lee Hannah et al (PNAS 2013), suggests that climate change is going to put a dent in your drinking habits. One way of communicating the ecosystem and economic effects of global warming has been to relate them to products or factors that affect the general population directly (an approach which has had mixed success). Wine (from Vitis vinifera grapes) is a great focal product - the success and quality of winemaking depends on terroir, which results from local temperatures and soil moisture. Changes in climate suitability for grapes reflects changes in suitability for many other agricultural and native species. Also, the motivations behind examining the effects of climate change on vineyards is more than economic – viticulture particularly thrives in Mediterranean-type ecosystems (France, Spain, Italy, California, Chile, South Africa, and Australia), which are areas with particularly high biodiversity and endemism. Vineyards use large amounts of fresh water and house low numbers of native species – so changes in their location and size may have contrasting effects on native biodiversity, local economies, and water supplies.

Given these relationships, the authors suggest that modeling regional changes in viticulture suitability provides insight into changes in ecosystem services and diversity. They examined 17 possible climate  models (GCMs) to look at how appropriate conditions for viticulture might shift by 2050. More than 50% of the models predicted that traditional wine producing regions (Bordeaux and Rhône valley regions in France and Tuscany in Italy) will decline greatly. However, regions farther north in Europe may become increasingly suitable. 
From Hannah et al. 2013. PNAS. The percentage of GCMs supporting a prediction reflects the degree of certainty behind it. Click for larger image.
New World vineyards receive a less dire forecast – some areas in Australia, Chile, California, and South Africa will remain suitable for viticulture in the future and new areas to the north are likely to become available. According to model predictions, New Zealand may one day produce many times more wine than it does currently. Such predicted increases in wine production in novel regions may be accompanied by viticulture’s increased ecological footprint. Some shifts take advantage of high elevations with cooler temperatures, leading to the development of areas that are currently relatively preserved. Water usage demands are likely to be problematic in the future: for example, vineyards in Chile’s Maipo Valley rely on runoff mountain basins that are vulnerable to warming conditions.
From Hannah et al. 2013. PNAS. (CA, California floristic province; CFR, Cape floristic region (South Africa); CHL, Chile; MedAus, Mediterranean-climate Australia; MedEur, Mediterranean-climate Europe; NEur, Northern Europe; NMAus, non–Mediterranean-climate Australia; NZL, New Zealand; WNAm, western North America).

Wine is a useful focal point for another reason - it exemplifies the complicated nature of most predictions related to climate change: positive outcomes (increased wine production in NZ) may be linked to negative changes (threatened water supply and native diversity in these new areas). Wine producers in a number of regions have recognized the possible impacts of vineyards, and groups such as the Biodiversity and Wine Initiative in the Cape Floristic Region of South Africa, and the Wine, Climate Change and Biodiversity Program in Chile exist to reconcile conflicting interests. There may be ways to mediate the effects of changing climate on viticulture, including developing tolerant varieties, changing methodologies, or the separation of varieties from their traditional regions. 

Making predictions about how ecosystems will change in the future is still difficult. However, the climate envelope model approach is actually well suited for situations like human agriculture, where dispersal limitation, competition, and non-equilibrium conditions are unlikely to be an issue. Cultivated crops are limited mostly by human/economic motivation. The results across most models strongly support the idea that Mediterranean climate growing regions will experience decreased viticultural suitability. It is likely more difficult on a fine scale to determine which regions will become more suitable in the future (i.e. probably don’t invest in land in New Zealand, assuming you can start a vineyard there in 50 years) but the strong agreement between models suggests that you should enjoy some French or Italian wine sooner rather than later.

1 comment:

south africa news online said...

This is interesting info about the climate change. I think that it can also be a reason of climate change in South Africa and other countries around it.