Vineyard adaptation to climate change is one of the biggest challenges for viticulture. Wine quality is closely linked to the concept of “terroir” that suggests matching agro-climatic conditions with growing practices. Logically the increasing temperature and the change in rainfall pattern, expected in the next decades, should bring changes in wine-making practices. In the Mediterranean region, this is even more problematic as the climate conditions already lead to more concentrated wine with high alcohol content. Modelling enables to better assess the impact of climate change on wine production. As an example, the itk Company carries out a study on the effect of climate change on water deficit of representative vineyards located in Costières during a 150 year period (1955-2100).
This study is based on simulations carried out with itkVigne software developed within a collaborative project involving INRA, CIRAD, IRSTEA, Languedoc wine-growers’ cooperatives, the chamber of agriculture and the climate association of Hérault. Currently used in Europe and California, this software defines the optimal irrigation need through the modeling of vine water deficit. The retrospective part of the study (1955-2014) has been presented during the Climate-Smart Agriculture Conference in Montpellier, 2015. The results make clear that the management mode prescribed by the specifications of “Costières de Nimes” appellations well matched for wine production without irrigation under the climate conditions of 1955-1975. However, climate shift then led to an increasing water deficit justifying the use of precision irrigation. The study was pursued in order to assess the evolution prospects until 2100. Otherwise, the evolution of the cool night index (CNI) was investigated the month preceding vine-harvest. This index is related to the aromatic potential of wine and may evolve in the next decades under the combined effect of global warming and earliest harvest date. This evolution of CNI might be problematic to maintain wine typicality in Languedoc. Therefore, the evolution of water deficit and CNI until 2100 was investigated according to 3 climatic scenarios defined by IPCC. In accordance with retrospective results, the prospective study underlines a significant increase of irrigation needs whatever the scenario considered. This confirms that the traditional management mode gradually becomes obsolete due to the steady increase of water deficit (Figure 1). Irrigation represents a solution to counter this evolution however remains controversial due to the conflict of use of water resources. In this context, itkVigne proposes to estimate vine water needs at daily time step in order to better control water consumption whilst complying with the specifications obligations. The predictions are nevertheless alarmist as they show that production objectives should require doubling water input until 2100 (Figure 2). Otherwise, earliest grape harvest dates (about 1 month) are expected in parallel. This shift combined with the increasing temperature should significantly alter the CNI and ultimately compromises quality objectives. This might be problematic for wine quality and difficult to counter except by using late varieties.
These results already show that itkVigne is a relevant tool to quantify the effect of climate change on potential wine quality and its interaction with vineyard’s management. In this domain, mechanistic models have decisive advantages compared to physical measurements as they deliver a continuous follow up of base water potential. It can be used for longer-term impact studies.
Predict and Decide