In our warming world, could a California classic like Zinfandel soon be growing in Washington or British Columbia?
Some climate models predict that favorable conditions for wine grapes will shift northward in coming decades, from Spain to Sweden and, in the U.S., California to the Northwest.
Dramatic predictions like that don’t account for growers’ ability to adapt practices or plantings, according to experts who say climate changes are already reshaping how wine grapes are grown and where.
Unlike many crops which can be grown across a wide climate range, every wine grape has its own narrow niche for producing premium fruit.
“Viticulture is about a sense of place,” says Hans Schultz, president of Hochschule Geisenheim University in Germany and expert on grapevine physiology and climate. “Production systems have always been related to climate and landscape.”
Climate change is altering growing conditions of the world’s esteemed wine regions at an unprecedented pace, ushering in warmer temperatures and less predictable weather.
That poses opportunities for new growing regions as conditions warm enough for grapes, but it could also dislocate iconic varieties from the regions where they have been grown for centuries.
But beneath those broad climate trends lies a host of complexities, Schultz said in a presentation at a Washington State University symposium on climate extremes and the wine industry in March.
Average temperatures have risen in all grape growing regions in recent decades, but in Germany, for example, evapotranspiration rates are up, and in Australia, winds are slowing.
“The problem is the high spatial and temporal variability,” Schultz said, showing photos of vineyards in standing water one year and suffering from drought just a few years later.
That’s harder for growers to predict and to prepare for than a broad warming trend. Take winter injury, for example. It’s not the average winter temperatures that matter to grapevines, it’s the extremes.
“Even if it hardly happens, twice in 25 years and you are out of business,” Schultz said.
Growers are already prepared to handle a variable climate, especially in the Pacific Northwest, where ocean conditions drive long-term weather patterns such as the El Niño and Pacific Decadal Oscillation,.
“In the Pacific Northwest, we swing back and forth between warm winters and really cold ones. The issue that climate change plays on top of that is you are moving the average conditions in one direction, but you’ve still got this variability,” said Greg Jones, a climatologist at Southern Oregon University who specializes in viticulture. “If our climate modeling is precise and we’re expecting it to be 4 to 6 degrees warmer by 2050, the issue is, how does a grower respond to that?”
That’s a big increase, especially considering that a variety like Cabernet Sauvignon only has a 3.5 to 4 degrees of flexibility in terms of a suitable growing season, Jones said.
But growers at the symposium said they were more concerned about how climate change is expected to increase variability, not suitability.
“My biggest concern about climate change is not the increase in heat units, it’s the extension of the season and the increased variability in predicting our weather seasons,” said Wade Wolfe, owner of Thurston Wolfe Winery in Prosser, Washington. “Looking ahead, I see more exposure to damage from erratic weather conditions even though we are getting gradually warmer.”
What change means
For grape growers, warmer weather is often welcome because it improves fruit quality in many varieties and could expand the regions where grapes can be grown.
But while a new region might become suitable for growing grapes most of the time, that doesn’t mean it’s a good idea to plant there, said WSU viticulture professor Markus Keller.
“Vines don’t really care about averages, they care about extremes,” he said.
In particular, extreme winter lows. Which could ironically become an increasing risk to grape growers in a warming world because cold conditions cause the vines to build their protective cold hardiness.
And warming conditions drive earlier bud break, which puts vines at risk for damage from spring frost, Keller said.
He also urged growers to take broad climate change predictions — such as a 2013 study that showed the amount of land suitable for vineyards in established wine regions will decrease 25 to 75 percent by 2050 — with a grain of salt. In that case, the model didn’t consider any access to irrigation, for example.
“Vineyards exist on a meso-climate or micro-climate scale, so you have to be careful when you make these broad generalizations,” Keller said.
To stay profitable in a changing climate, choosing the right micro-climate for your vineyard is key, including the elevation, slope, soils, and proximity to a large body of water, according to a panel of growers.
“At Chateau Ste. Michelle, we grow cool weather Riesling and we grow long-season Bordeaux,” director of viticulture Russ Smithyman said. “I believe in matching sites with varieties. We still have that ability with the diversity here (in Washington).”
Beyond geographic diversity, growers in Eastern Washington and California have a significant advantage with existing irrigation.
But climate change also poses a risk to irrigation supplies, especially in areas like Central Washington’s Yakima River Basin, which relies on the slow melting of winter snowpack for summer irrigation.
“As climate warms, of course, more of the precipitation falls as rain instead of snow so we are losing that natural reservoir,” said Steve Ghan, a climatologist for Pacific Northwest National Laboratory, a federal research laboratory in Richland, Washington.
Climate models show that the water supply in the Columbia River, the largest waterway in the Pacific Northwest, is far more resilient to that shift than tributaries like the Yakima River, where summer river flows could be cut in half by 2050.
Irrigation is a major adaption for growers but the vines themselves — as living organisms — are capable of adapting as well, although just how much and how fast remains unclear, Jones said. That’s because researchers and growers have focused on finding the optimum conditions for each variety, not the edges of its tolerance.
Another mode of adaptation is adopting new varieties or breeding new clones better suited to warmer growing conditions.
“We have untapped potential through plant breeding and genetic work to fine tune varieties to perform better in hotter, drier climates,” Jones said.
The challenge, of course, is that growers plant vineyards to meet market demands, not just Mother Nature’s. People expect to order Merlot or Cabernet Sauvignon, not Lemberger — a cold-hardy red grape from Austria that grows well in Washington but never caught on with customers.
“We have a tendency to plant the top 10-15 varieties, but there are over 500 varieties being grown in Portugal today, many of which we have no experience with in the new world,” Jones said.
Maybe there is a variety in Southern Italy or Greece that could be a perfect fit for warming conditions in the Western U.S., he mused, but growers and winemakers would have to be willing to bet on consumer acceptance. •
The adaptive vineyard
Growers in the Pacific Northwest got a preview of predicted growing conditions in coming decades during 2015.
A warm winter brought the lowest snowpack on record in the Cascade Range, where snowmelt provides irrigation through the growing season, resulting in a drought on top of a warm, early spring and prolonged summer heat wave.
“The bad news is that 2015 is your typical growing year in 2070. The good news is we survived it,” said Wade Wolfe, owner of Thurston Wolfe Winery in Prosser, Washington.
Wolfe and other growers with junior water rights in the Yakima River Basin received just half their normal water allotment that season.
Luckily, his irrigation company decided to shut off delivery for three weeks in May — a low demand time for grapes — to stretch the supply. Wolfe recommended making sure you’re not over-cropping or carrying too large of a canopy before a heat wave sets in.
That season, Sagemoor Farms learned the hard way how beneficial overhead cooling can be, with heat stress in blocks where the old cooling system had been pulled out, said vineyard manager Lacey Lybeck.
“We quickly learned that Syrah growing on a pile of sand can benefit from cooling,” she said. “It’s amazing how, by running overhead irrigation for 15 to 20 minutes, we’re able to cool the ambient air temperature and slow down the ET.” (ET refers to the evapotranspiration rate.)
Canopy training strategies also can help vineyards adapt to warmer conditions, said Russ Smithyman, director of viticulture at Ste. Michelle Wine Estates.
For example, a “ballerina” architecture in which the canopy flops down like a skirt to protect the fruiting zone, or perhaps with the “skirt” up on the morning side, works well in warmer conditions, he said.
Given all the tools growers have to adapt to warm weather, the challenge posed by climate change is more from the increased unpredictability: cold snaps during a warm winter when vines aren’t hardened off, early springs and less predictable precipitation.
Hot weather — managed right — often makes for good quality fruit.
As for longer term adaption, finding the right sites for the right varieties will continue to be critical to the industry’s success.
“Looking over the next 10 years, I would suggest that we get really good at grafting if you want to change varieties,” Smithyman said. “Grafting is less expensive than buying new vine and paying to put it in the ground. I think rootstocks might have a place going forward, but it’s certainly nice to be own-rooted.”
– by Kate Prengaman
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