GEOSCIENCE CANADA 1 PAPER 4 FROM THE “TERROIR,GEOLOGY AND WINE:A TRIBUTE TO SIMON J. HAYNES”SESSION HELD AT THE GEOLOGICAL SOCIETY OF AMERICAN ANNUAL MEETING,SEATTLE,WASHINGTON,NOVEMBER 2, 2003 for threshold issues in which too much Earth- and human-based systems. From warming will potentially alter traditional controlling vegetation patterns and geo- wine styles and/or varieties planted, and logical weathering characteristics, to likely bring about spatial shifts in viticul- influencing water resources and agricul- tural viability. tural productivity, climate is at the heart of the delicate equilibrium that exists on SUMMAIRE Earth. Climate is a wide-ranging factor Cet élément du concept de terroir qu'est in virtually all forms of agriculture, from le climat détermine la viabilité d'une influencing spatial variations of crop région à permettre le mûrissement d'une viability to largely determining year-to- variété définie de raisin ainsi que l'élabo- year yield variability; climate is an impor- Climate and Terroir: Impacts ration du style du vin qu'on en tire. La tant issue in determining where and how variabilité et le changement du climat crops are grown. Climate-related impacts of Climate Variability and affectent toute forme d'agriculture, mais on agriculture are generally related to cli- Change on Wine les effets sont rarement plus évidents mate variability over the short term (i.e., que sur la production de grands vins où intra-annual and inter-annual) and cli- Gregory V. Jones l'optimisation de la qualité nécessite une mate change over the long term (i.e., Department of Geography, Southern Oregon viticulture en des zones climatiques aux decades to centuries or longer). University, 1250 Siskiyou Blvd, Ashland, conditions très circonscrites, d'où les Understanding such relationships is sel- Oregon 97520, U.S.A., [email protected] risques. Bien que les climats aient dom more important than today, as vari- changé dramatiquement dans l'histoire ations and/or changes in climate can SUMMARY de la culture des vignes vinicoles, les greatly impact the ability to produce a As part of the concept of terroir, cli- changements climatiques récents ainsi given crop. mate is a factor that influences both the que les changements projetés dans un general viability of a region to ripen a avenir rapproché ont été beaucoup The Climate Component of Terroir specific variety of grapes and the result- étudiés en fonction de leurs impacts sur Grapevines are some of the oldest culti- ing wine style. Climate variability and l'actuelle industrie vinicole. Les compte vated plants and have been historically change affect every form of agriculture rendus des recherches montrent que les associated with Mediterranean climates and are seldom more evident than with changements climatiques, tant à courts et (e.g., Italy). Today, however, grapevines the production of high quality wines qu'à longs termes, ont amené des saisons for wine production (note that all occur- where narrow climate zones for opti- viticoles plus chaudes et plus longues rences of grapes or grapevines refer to mum quality place them particularly at comportant moins de risques de gel, et grapes for wine production, unless stat- risk. While climates have changed dra- cela dans nombres des meilleures ed otherwise) are grown in many types matically during the history of the culti- régions vinicoles du monde. Bien que of climates throughout the mid lati- vation of grapes for wine, the changes ces changements aient été associés à une tudes: Mediterranean, marine west coast in the recent past and those projected in amélioration de la production et de la (e.g., Oregon), humid subtropical (e.g., the near future have received a great deal qualité, les projections climatiques mon- eastern Australia), and semi-arid conti- of attention for their potential impacts trent qu'il est possible qu'un seuil soit nental climates (e.g., eastern Washington on today’s wine industry. Research has atteint, au-delà duquel ce réchauffement state) (Fig. 1). The climates of these shown that both recent short and long- pourrait altérer le style les vins tradition- regions are an integral part of the term climate changes have resulted in nels et/ou les variétés utilisées, entraî- notion of terroir, the French concept in generally warmer and longer growing nant des changements spatiaux proba- which a complex interplay of physical seasons with less frost risk in many of bles de la viabilité viticole. factors (Wilson, 1998; Haynes, 1999; the world’s best wine regions. While Meinert and Busacca, 2000) and cultural these changes have been related to INTRODUCTION influences (Vaudour, 2000) interact to greater production and quality, future cli- Climate is a very complex, highly vari- define the wine styles and quality that mate projections indicate the potential able, and pervasive factor in our natural come from any site or region. Climate is 2 one part of the continuum that includes 2003). While the average climate struc- Although the climate-based aspects of the physical landscape influences of soil ture is very important for grape growth terroir are related to various factors that and terrain, which in combination large- and wine quality, weather and climate operate from the macroscale to the ly determine the grape variety that can factors on daily and hourly time scales microscale, measures of temperature on be grown in a given region. Once grape are critical, and include: solar radiation, daily, weekly, monthly, and growing sea- variety-site characteristics are considered, heat accumulation, temperature extremes son time scales have most often been the remaining viticulture (the science of (including high temperatures during the employed to define the spatial differ- the cultivation of grapevines) and enolo- summer, winter freezes and spring and ences between regions. In general, grow- gy (the science of the making of wines) fall frosts), diurnal temperature ranges, ing season length and temperatures are aspects, which include regional associa- precipitation (especially during flowering critical aspects because of their major tions and cultural traditions, result in the and ripening stages), wind, and extreme influence on grape ripening and fruit defining wine style a region produces. weather events such as hail. Owing to quality, and therefore varietal adaptation Of all of the site factors, climate inadequate weather station locations, to a specific terroir. It is in its ideal cli- arguably exerts the most profound effect poor data sharing between countries, mate that a given grape variety can on the ability of a region or site to pro- and disagreement on what weather and achieve optimum ripening profiles of duce quality grapes. Worldwide, the aver- climate factors are most important, the sugar, acid, and flavour to maximize a age climatic conditions of a wine region climate component of terroir has been given style of wine and the vintage qual- determine to a large degree the grape studied largely through spatial and tem- ity. varieties that can be grown there, where- poral averaging, and by comparing new The growing season necessary as wine production and quality are wine region climates to analogous cli- for wine grapes varies from region to chiefly influenced by site-specific factors, mates in historical regions. region but averages approximately 170- husbandry decisions, and short-term cli- 190 days (Mullins et al., 1992). The mate variability (Jones and Hellman, Temperature and Growing Season length of the frost-free season is impor- Figure 1. General geographical extent of the world’s main viticulture regions (adapted from de Blij, 1983). Contours represent the mean annual 10°C and 20°C isotherms as a proxy for the latitudinal limits of the majority of the world’s grape growing areas. Neither latitude nor isotherms fully accounts for the location or quality of individual vineyard regions, however. The solid dots represent the wine regions studied by Jones et al. (2005). GEOSCIENCE CANADA 3 tant to the onset of bud break, flower- 2000 degree-days. However, this index oped a simple classification of viticultur- ing, and the timing of harvest. Prescott has been found to be less appropriate al climates that uses five dimensions of (1965) noted that in most areas suitable for determining viticultural viability out- mean temperatures, continentality for grape production the mean tempera- side of California (Gladstones, 1992; (defined as the difference between the tures of the warmest and coldest Spellman, 1999; Jones and Davis, 2000). average mean temperature of the months are more than 18.9ºC and warmest and coolest months), sunlight -1.1ºC, respectively. Winter and spring Bioclimatic Indices hours, aridity (based upon the difference temperatures are also important in that Other bioclimatic indices have been between rainfall and evaporation), and frost and low temperatures can cause used to characterize a region’s potential relative humidity. Gladstones (1992) injury to grapevines. Research has also for viticulture and are mostly developed developed a classification similar to shown that there is a minimum winter on the basis of temperature. Various Amerine and Winkler (1944) but refined temperature that the grapevines can forms of a heliothermal index (Branas, it by imposing an upper limit on mean withstand. This minimum ranges from 1974; Huglin, 1978) and a latitude-tem- temperatures, a correction factor for lati- -5ºC to -20ºC, and is chiefly controlled perature index (Jackson and Cherry tude, and a correction