Posted: Jul 17, 2019
In the past decade, there have been a number of stories written on the connection between climate change and wine. Climate change is already one of the greatest challenges our planet is facing. Its effect will continue to take hold and shake up countless aspects of our lives. As a scientist who studies the connection between climate and agriculture with a focus on viticulture, I’m asked routinely – is climate change good, or bad, for wine? – which is a fair question. Perhaps better put: If the world is on fire, will there be Merlot?
It depends, in part, on if you are a wineglass half-empty, or half-full kind of person. And in part on other factors, like terroir.
Lightning wine 101 lesson
The concept of terroir is central to winemaking. Terroir, or the characteristics of the land where grapes are grown, is made up of four components:
Soils are important for vine growth and fruit quality. Soils control factors like water and nutrient availability, drainage and pH. Topography is also critical, as even a slight slope to the land can have a large influence in vineyard management. Tradition and grape variety are tied more to the history and types of wine produced in a region. These are all significant variables that explain why one area may be famous for an expensive delicate white wine that one would pair with a heavenly seafood meal and another region may be famous for a bold red that you picked at the store for $6 that’s going to go great with that $4 frozen pizza* you also bought. These components change over space, but they stay relatively static over time. The fourth component, climate, changes over space too.
*This is a judgement free zone here
Different wine-grape varieties thrive in different climates. Climate change will greatly influence regional, and global, wine trends. Click to enlarge.
The fact that climates changes over space is important because it helps establish the types of wine-grape variety grown in the major production regions of the world. Each variety has an optimal temperature threshold, thus growers traditionally pair their location’s climate with a certain type of grape. We have warm-climate regions like Sicily, Spain, Southern France, the Murray-Darling region in Australia, or the Central Valley in California which produce red wines; we have cool-climate regions that produce lighter reds and numerous white wines like Germany, Northern France, Oregon, or New Zealand; and we have many places in between. This concept of climate changing over space allows for thousands of varieties of wine-grapes to grow on six continents.
However, climate also changes over time. This can mean two things: 1.) year-to-year climates vary such that no two growing seasons are ever the same for one location, and 2.) large-scale climate change greatly influences regional, and global, wine trends. For now, let’s focus on the second aspect because the first feature is worth an entire blog post of its own.
A brief history of climate change and wine
Climate change is directly connected to wine throughout history. It is written in to the DNA of Vitis vinifera and its thousands of varieties. Even for times before there were reliable temperature or rainfall measurements, historians can estimate regional climate fluctuations via records of grape and wine production, wine quality, and even pricing. We have reliable historic records that tell us that when the world warms up (Medieval Warm Period, approximately 900 to 1250), wine production moves poleward. When the world cools down, production shifts equatorward (Little Ice Age, mid-1600s). We know where people were growing winegrapes, and we get a picture of their success – and the climates they were experiencing – on a year-by-year basis. This is incontrovertible data that bears no ability to be twisted to conform to an ideological thought process. Simply put, you can’t argue with it.
In modern times, we’ve seen warming of nearly 1?C (>1.5°F), and we now have a robust, reliable network of weather measurements for entire planet. The change we see now is different than what we have seen in the past, and that change is yet again being reflected in the vines. Most of the world’s major producing regions have seen significant warming, particularly in the last few decades. This has sped up the cycles of fruit maturation, changed fruit biochemistry, introducing new pressures to these regions. Growers have methods for counter-acting some of these issues, but most problems do not have simple solutions. For example, increased water stress coupled with a rise in the cost of water, is one of several issues that warmer regions will need to contend with more and more.
Maybe that glass of Merlot is starting to look half-empty.
Michigan Pinot Noir grapes undergoing full fall colors.
Or is it? Warmer global temperatures allow for production to move poleward which can introduce winegrapes to regions that could not previously accommodate production. My research, across four peer–reviewed papers, looked at one such region: Michigan. Before the late 1960s, there were virtually no Vitis vinifera varieties of grapes growing in the state. The growing season was too short and not reliably warm enough to sustain winegrapes. Additionally, brutal winter temperatures would drop below the threshold for traditional winegrape varieties. A few enterprising growers attempted some plantings, and after a few rough years, they managed to survive. By the mid-2010s, there were nearly 3000 acres of more than a dozen varieties of vinifera. So what happened?
Michigan, in particular the SW corner of the state along the shores of Lake Michigan, has experienced a rise in temperature of at least 0.55°C since 1950. Using seasonal Growing Degree Days (a measure of thermal time that allows one to compare how much heat “accumulated” over time), we found that the region had warmed significantly since the 1950s. Average growing season temperatures had increased, and, perhaps most importantly the growing season increased by 28.8 days from 1971 to 2011. That is nearly an entire month more of proper growing conditions that allow for growers to harvest when they want to, rather than when they need to. This reliability, particularly since 1980, saw an explosion of vinifera acreage that continues in to the present. There are, of course, challenges. Inconsistent late frosts, pest pressures, and severe weather still make Michigan a challenging location for expansion, but the opportunity is alluring.
As the climate changes, so will our wine
Currently, there are several “Michigans” across the globe which are emerging as viable winegrape producing regions. As global temperatures very likely will continue their rise, these regions will also grow in reputation, size, and number. At the moment, it’s a waiting game.
To recap: climate change is happening. And one place to see, or taste, it is a glass of Michigan Riesling or a snifter of Oloroso Sherry. Climate change has impacted global winegrape production in the past, it is having an impact in the present, and will almost certainly continue to do so in to the near and foreseeable future. For the warm wine producing regions of the world, it is already becoming more difficult and new vineyard management strategies will be needed. But, there are many areas that are now gaining the ability to produce winegrapes, like Michigan. Those places are not without difficulties, but as these regions continue to warm up, new varieties and methods will almost certainly bring them to the forefront of global wine production.
Ultimately, it largely depends on if you are a wineglass half-empty, or half-full kind of person.
By Steven R. Schultze
UCS SCIENCE NETWORK, UCS
July 16, 2019
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