When I founded Argos Analytics in 2011, people I spoke to, including some in the wine industry, frequently dismissed climate change as a serious threat to their businesses. Happily, that’s much less common today as the result of visible changes in the weather and the many extreme weather events during the last decade. From the outset, I believed winegrowers would have a high level of interest in tools to help them deal with climate change since they think in terms of decades, or even generations, and wine grapes are the agricultural product most sensitive to climate. It was also clear that, while they would certainly have an interest in understanding the outlook for their region, their main focus would be on their own vineyards, which meant Argos had to develop tools, which are described later in this article, with that level of granularity.
In recent years, the wine industry has become increasingly focused on sustainability and the need to reduce its carbon footprint throughout its value chain from vineyard to winery to the consumer, with the Porto Protocol playing an important leadership role. There has also been a growing awareness of the need to adapt to the changes in the climate that are already inevitable due to accumulated past carbon emissions. It takes the climate several decades to respond to changes in emissions so the positive effects of current efforts to limit future climate change won’t be seen until mid-century and beyond.
Broadly speaking, wine regions around the world will continue getting warmer, but not at the same rate. In general, the more continental the climate the more rapid the warming will be, while the greater the marine influence the slower it will be. Over time, as temperatures continue to rise, some varieties may no longer be suitable in regions where they have been grown for centuries, while new wine regions farther north (farther south in the Southern Hemisphere), or at higher elevations, will blossom. Depending on the latitude, average annual rainfall may decrease, stay the same, or increase, while year to year variability will become greater. Weather extremes such as heat waves, droughts and heavy rain will become more frequent, long lasting and intense, while there will be fewer frost days following bud break as temperatures rise and less preharvest rainfall as harvest dates advance.
The ability to plan and implement effective climate adaptation measures depends on understanding how climatic conditions will evolve over time. This is especially challenging at the vineyard level since, as every winegrower knows, there can be a great diversity of microclimates within a single wine region and most of the scientific studies of wine and the changing climate have focused on the regional level. Fortunately, there are tools that make it possible to take a closer look. While global climate models have spatial resolutions of one hundred kilometers or more, downscaled projections of daily high and low temperatures and rainfall with resolutions as fine as several kilometers that are derived from the global projections are now widely available.
Even these downscaled projections need to be further localized for a specific vineyard. This is done by taking site specific factors such as elevation, slope, aspect, surrounding terrain and soil into account. It’s also important to consider local weather patterns at the vineyard, including marine influence and wind, that may not be fully reflected in data from weather stations in the region and, consequently, in the projections.
Like the weather, the climate is a chaotic system meaning that small differences in initial conditions can result in large differences in outcomes, sometimes referred to as the butterfly effect, which is why weather forecasts more than a week or so ahead have such limited skill. And, since climate is basically the statistics of weather, climate projections are not forecasts of the future climate but the statistics derived from them represent possible future climate scenarios. Generally, multiple projections, referred to as an ensemble, are used in order to get a clearer picture of the range of possible future climatic conditions. This is similar to the way in which modern weather forecasts are generated with an ensemble of weather projections being used to calculate, for example, the likelihood of rain.
While it’s important to know how climatic conditions will change in a vineyard, the real question is what effect those changes will have on the grapes, such as how rapidly bud break and maturity will advance over the next few decades. Fortunately, there are existing phenological models that can address that question based on the projected changes in temperatures.
Equally important, of course, is how the higher temperatures due to the combination of warming and earlier maturity will affect the grapes as they ripen. For example, there are different ranges for the optimum ripening temperature, the mean temperature during the thirty days prior to harvest, depending on the intended wine style. In addition, prolonged heat waves and excessive rainfall between veraison and harvest can affect both the yield of the grapes and the quality of the wine made from them. Future ripening temperatures can be derived from the climate projections and the phenological model for maturity date, as can the future occurrence and characteristics of preharvest heat waves and rainfall.
Water scarcity is another looming issue for winegrowers. Even if average annual rainfall remains the same, or even increases, extended periods of drought will become more frequent. In addition, evapotranspiration rates will climb as temperatures do. As a result, there will be greater demand for water in regions where irrigation is practiced, while greater water stress on the vines in much of the growing season can be expected where it is not.
The insights these projections provide regarding future climatic conditions, and their effects on the grapes, can be used for adaptation planning in existing vineyards, the design of new or redeveloped vineyards and strategically managing a vineyard portfolio. In existing vineyards, pruning, canopy management, crop load and cover crops can influence the rate at which the vines develop. In addition, anticipatory irrigation, shade cloth, kaolin spray and misters can help to mitigate the effects of heat waves. All of these measures are also applicable to new or redeveloped vineyards. In addition, varieties, or clones, and rootstock that are more heat and drought tolerant as well as changes in row orientation and spacing and trellising systems that reduce cluster exposure to the sun can also be considered. For those winegrowers who own multiple vineyards, especially in more than one wine region, the projections provide a way to assess the long term viability of current properties and evaluate potential acquisitions.
Winegrowers all over the world have been seeing the effects of a warming climate with earlier bud break and harvest dates, higher levels of sugar and lower levels of acidity. Many are already working to adapt their cultural practices to higher temperatures and considering more heat tolerant varieties when they replant. The projections Argos Analytics provides of future climatic conditions in individual vineyards, and the implications for the grapes being grown in them, are a valuable tool for winegrowers as they deal with a climate that will continue to change.
By Robert Dickinson
President of Argos Analytics, LLC
15 Junho, 2020