Global warming effects on grape growing climate zones within the Rioja Appllation (DOCa Rioja) in north Spain

Aims: The aims of this work were (1) to assess the changes in some of the main bioclimatic indices used for climate viticultural zoning within the Rioja Appellation area in the north of Spain between 1950-2014 (60 years), and (2) to carry out a comprehensive sociological evaluation among grapegrowers and winemakers of this region, to better understand the impact of climate change on their activity, their degree of concern about it and the potential adaptation measures they would be willing to adopt to cope with it in future years.

Methods and Results: For the climatic evaluation, two high-resolution (5Km x 5Km) daily gridded temperature and precipitation datasets covering the years between 1950-2014 were used. Following the criterium of the World Meteorological Organization, two subperiods of 30 years were created. For the Winkler index (WI), the Huglin index (HI), the Growing Season average Temperature (GST) and the Growing Season Precipitation (GSP), the median for each subperiod was compared (at p<0.01 or p<0.05) using the Wilcolxon-Mann-Whitney test. A significant increase between 0.7 and 1.1°C of GST was found for most of the region between the two subperiods. This was reflected in changes in the WI and HI zoning within the region, with increased and predominant area in zones II and III for WI and H+1 and H-1 for HI. In terms of GSP, no significant changes were detected, but larger areas with GSP between 160 and 200 mm H₂O were observed. Regarding the sociological approach, 481 on-site surveys with 29 different questions were conducted among grapegrowers, winemakers, consultants and other wine-related stakeholders. Some of the main findings include that 64.3% of respondents have experienced some negative impact, including economical effects. The main actions taken in the last years to cope with climate change were installation of irrigation, increase of crop insurance adoption against hail and frost, and adaptation to new pests and diseases.

Conclusions: 

Global warming was significantly detected in a 60 year period in the Rioja Appellation area, which caused changes in the grapegrowing climate zoning within the region. At social level, climate change was highly perceived by viticulturists and winemakers, which had started to adopt different actions to cope with increased temperatures and strong climate events. 

Significance and Impact of the Study: This work provides a unique, high-resolution diagnosis about climate change and viticultural zoning displacement within the Rioja Appellation, which is one of the top wine regions worldwide. Likewise, the sociological study is the first one carried out in this area, and offers valuable information for policy makers to drive mitigation and adaptation policies towards global warming in future years.