# A Review of the Potential Climate Change Impacts and Adaptation Options for European Viticulture
## 5 Climate Change Adaptation Strategies
### Long-Term Adaptation Strategies
#### 5.2.2 Varietal/Clonal and Rootstock Selection  
Because the suitability for the successful cultivation of different varieties is largely temperature dependent, long-term adaptation strategies may consist of changes in the varietal spectrum [12]. A recent study postulated dramatic changes in arable viticultural land under strong warming, showing that in situ varietal selection may provide important climate change adaptation potential under moderate climate change scenarios [217]. Cooler northern European winemaking regions may benefit from a wide range of varieties from southern Europe [114], whereas southern Europe will be limited to varieties well adapted to very dry and warm climates. Some heat-tolerant varieties, such as Cabernet Franc, Cabernet Sauvignon, Malbec, Merlot, Syrah, or Tempranillo, have already been identified [32]. Hence, grapevine breeding should be focused on the development of heat-tolerant vine varieties [106]. A framework for genetic breeding of new varieties that will be more adapted to future climates has already been proposed [218]. The selection of appropriate varieties might be guided by mid-term climate change projections and bioclimatic indices describing the thermal demand of specific cultivars, such as the Huglin heliothermic index [77] or the average growing season temperature [56]. However, it needs to be kept in mind that these indices describe the lower temperature threshold for a variety, whereas the upper threshold is mostly unknown. This has previously led to substantial misconceptions concerning the prediction of future suitability of grape-growing regions [113; 210]. Therefore, preserving the existing biodiversity of autochthonous grapevine varieties is vital, as some varieties may thrive in future climates and may thereby open new adaptation opportunities [219; 220]. Because most of the sensory properties and the fame of many terrorir wines rely on specific varieties [12], their replacement with more resistant ones is challenging in viticulture [12], as immediate varietal changes may cause economic losses. Accordingly, to fully exploit the potential of varietal selection, the preference of retailers and consumers for specific varieties needs to be changed, for instance by marketing wine from better-adapted varieties under a specific climate change adaptation label. The clonal selection has also a very important adaptation potential, as different clones from a given variety are more resilient to future abiotic and biotic stresses, at the same time contributing to the maintenance of local or regional wine typicity. Rootstocks can also confer plant resistance, particularly to soil-borne pests and pathogens, but they also differ with regards to their resistance to abiotic stress. Planting new vineyards on rootstocks with enhanced resistance towards the primary abiotic stresses, present in a particular region or predicted to become the dominant stresses, can become a key element in adaptation [221]. More adapted rootstocks will be beneficial to yield, quality, and other vine physiological parameters [222; 223]. Many studies have been performed to assess rootstock effects under different soil water conditions [223; 224; 225]. Rootstocks may present the single most effective cultural strategy to find a long-term solution concerning water availability, without tapping into the public water supply in the form of irrigation. However, to achieve this, the genetic potential of _Vitis_ germplasm needs to be further explored in order to enhance water use efficiency and maintain yield and quality [226]. Grafting _Vitis vinifera_ scions to phylloxera-resistant American _Vitis_ rootstocks is commonly used in (Western) European countries, where hybrids (or interspecific hybrids) are generally not yet accepted for \"quality wine\" production [227]. However, the use of hybrids has increased worldwide in recent years (e.g., Brazil, China, and the USA).