Precipitation intensity under a warming climate is threatening some Italian premium wines

Highlights

• Global warming is recorded also locally and is impacting grapevine phenology.

• Harvest date of premium wine analysed with local meteorological data shows the role of climate change.

• Increase of Precipitation intensity exacerbate the influence of the temperature rise on grapevine.

• Short intense precipitations are not beneficial for grapevine.

• Keeping the high quality of wine using unchanged cultivation technique is becoming harder.

Abstract

Changes in regional climate are causing disruptions in global agriculture, including wineries that produce premium wines. Temperature is the key factor influencing the growth stages of wine grapes worldwide and its recent increase is causing early harvests, affecting the quality and quantity of premium wine. Water availability is the other important element: during the growing season the crop yield benefits of constant moderate rains, whereas this positive effect would be reversed if the same precipitation amounts fell in short periods of time. Climate change may alter the characteristics of precipitation such as intensity, duration and frequency of rain even if it does not alter the total amount of precipitation. Although the impact of precipitation amount and drought on wine grape phenology have been investigated, knowledge of the role of precipitation characteristics is very limited. Here we show that the precipitation intensity, which is the precipitation amount divided by the number of the rainy days (NRD), has also caused early grape harvest dates for one grape varietal. Using the harvest dates (1820–2012) of a premium wine made by a winery that has kept the cultivation methods and practices unchanged since 1650, we found that for growing seasons since 1960, annual harvest dates have been getting early as temperature increases (−5.92 days °C⁻¹) and more intense precipitation events occur (−1.51 days/(mm/NRD)). Our results are consistent with the hypothesis that the increasing tendency of precipitation intensity could exacerbate the effect of global warming on some premium wines that have been produced for >400 years.

Introduction

The wine industry has had cultural and economic importance in Europe for centuries and now may be threatened by climate change (Cook and Wolkovich, 2016; Fu et al., 2014; Sherry et al., 2007; Cleland et al., 2007). Europe is the largest global producer, with 56.3% of the total in 2017, and Italy produces more wine than any other country, accounting for >30% of the European volume (EU Wine Market Data Portal, 2018). In the past fifteen years, European wine production has shifted from cask and low-cost bottle wine toward premium wines, with 82% of the EU wine grape area now used in quality, premium wines (Agriculture, forestry and fishery statistics, 2017). In Italy, as well as other wine-growing countries, premium wines have been produced for centuries. Several studies have shown that premium wine production and climate are linked (White et al., 2006; Jones et al., 2005).

Premium wines can provide a good indicator of climate change for several reasons. First, the premium wine grapes are sensitive to climate changes, requiring a narrow climate range that excludes both extreme heat and extreme cold (White et al., 2006). Second, some premium wines have been produced the same way in the same location for centuries (White et al., 2006; Chuine et al., 2004). Third, some vintners have kept long-term records of annual wine production (Meier et al., 2007; Jones and Davis, 2000). One of the most well-documented aspect of premium wine production is the grape harvest date (GHD), which is tightly linked to grape maturation (Meier et al., 2007; Sun et al., 2018). The strong connection between GHD and temperature serves as a proxy to reconstruct past climate (Meier et al., 2007; Sun et al., 2018) as well as a predictor of the impact of climate change on wine quality and a guide for adapting wine production to a warmer climate (White et al., 2006; Wolkovich et al., 2018). Early GHD is always associated with temperature increases during the growing season, whereas more precipitation, in terms of the total amount of rain or the average rain measured in a certain period, generally delay harvest (Cook and Wolkovich, 2016; Fu et al., 2014; Sun et al., 2018). Thus precipitation must be considered as well as temperature when analysing these long-term records of a premium wine GHD (Ciais, 2005). Although the impact of precipitation amount and drought on wine grape phenology have been investigated, knowledge of the role of precipitation characteristics is very limited (Cook and Wolkovich, 2016; Wolkovich et al., 2018).

Precipitation can be characterized for a growing season as total amount of rainfall, number of the rainy days (NRD), which is the number of days with precipitation equal or above 1 mm, or precipitation intensity, which is the total amount of precipitation divided by the NRD. These characteristics can vary from region to region and can respond differently to climate change (Allan and Soden, 2008; IPCC, 2013; Trenberth, 2011; Giorgi et al., 2014). However, there is a general consensus that the annual precipitation (mm/yr) has changed little or not at all for 76% of the global land surface (IPCC, 2013; Trenberth, 2011). In contrast, observations confirm that the number of heavy precipitation events has increased over much of the global land surface (Fischer and Knutti, 2016; Trenberth, 2011; Hannah et al., 2013; van den Besselaar et al., 2013). Model simulations for future scenarios of global warming predict that heavy precipitation events will become more frequent and more intense (Donat et al., 2016; Trenberth, 2011; Giorgi et al., 2014; Rajczak and Schär, 2017). Severe precipitation causes flooding, landslides, agricultural damage and loss, including vineyard damage and loss.

Several previous studies of the relationship between climate and wine production have used multiple grape varietals. However, each varietal can have different quality standards, resulting in grape harvest dates at different levels of maturation from year to year, and a different response to climate stresses. In addition, over the years, many vineyards have changed their cultivation techniques, such as using irrigation and fertilizers, and these changes could alter the GHD (Webb et al., 2012; Thorne and Vose, 2010). Finally, some of these studies use global meteorological data, which may not accurately represent the climate at the vineyards (Thorne and Vose, 2010). All of these issues can mask a possible correlation between GHD and climate change. We address these issues by analysing the GHD of a premium white wine (Trebbiano d'Abruzzo) from a single vineyard. This wine won the best wine of Italy award in 2012 (Xoplaki et al., 2003) and has been constantly ranked in the top 10 of Italian wines for the past decade. The winery has used the same cultivation practices since 1650, with no irrigation or fertilization, and has a long-term record of GHD. As a result, it should be possible to determine the climate sensitivity of the GHD for this wine without biases due to changes in cultivation practices or grape varietals. The goal of this work is to explore if the advance of the recorded GHD is triggered by the observed changes of climatological parameters. In particular which of the different meteorological parameters and climatological indexes can be used to describe the GHD changes. Considering the observed and predicted increase for the future of severe precipitation events, we introduce another parameter (precipitation intensity) among those usually considered to drive GHD, to assess if this characteristic of precipitation plays a role in the advance of GHD.