Climate Change: The New Normal In Fruit Growing
Bring up topics like global warming and climate change, and more than likely you are going to raise a few eyebrows. There seems to be endless debate over whether or not global warming is real and a legitimate concern, and if it is, whether it’s man-made or natural and if humans have any control over preventing it.
However, if you cast aside this discussion and step into the reality of an apple orchard in Michigan or a vineyard in California, you’re going to find some real and valid concerns. In 2012, the effects of an early heat wave followed by multiple spring freeze events in the Northeast brought devastation to many tree fruit farms, both in the crop and in the bank accounts of farm owners who were left without much of a product to sell. While 2013 is shaping up to be more of a “normal” year — if that word even applies anymore — the data presented by weather experts at grower meetings this past year indicates an overall trend of earlier bloom dates. The major question is, what does this mean for you, and is there anything you can do to counteract the effects of this trend?
During the Great Lakes Fruit, Vegetable, and Farm Market Expo in Grand Rapids, MI, in December 2012, Jeff Andresen, in the Department of Geography at Michigan State University (MSU), addressed the extreme spring weather events earlier in the year. “Perennial and overwintering annual crops in the region emerged from their protective dormant states much earlier than normal in 2012 due to an unprecedented heat wave during the middle of March,” he said. “At its peak during the third week of March, daily mean temperatures soared to 30°F to 40°F above normal, and minimum temperatures exceeded the normal maximum temperatures by more than 10°F.”
The heat wave led to rapid early growth and development of crops across the region, at least four weeks ahead of normal in most regions. However, following the late March upper air pattern change, more than 15 freeze events (including at least five with minimums below 28°F) occurred across the region, which is “climatologically greater than normal,” according to Andresen.
It wasn’t just the freezes that caused problems, either. Following relatively normal weather in late April and early May, a large upper air ridge of high pressure developed across the center of North America and led to persistent hot and dry weather across large portions of the Midwest. The unusually dry conditions led to rapid use of soil moisture reserves and ultimately to water stress in many unirrigated crops. In terms of crop water needs, not only were soils generally not able to supply sufficient water to meet crop needs, due to the extended dryness, but rates of potential evapotranspiration “based on atmospheric conditions were significantly greater than normal this year, which exacerbated the impacts of the drought.”
The concern expressed by growers in the region, says Andresen, is whether the year’s highly abnormal weather was the result of simple weather variability or part of a longer-term trend. “The initial response is that it was simply a part of short term ‘weather’ variability,” says Andresen. “However, there is some evidence to suggest the root cause is not so straightforward.” He notes that the early warm-up fits with a trend toward earlier onset of spring. More troubling, the number of days between first green and the last spring freeze has been increasing.
“Given how unusual this year has been and assuming relatively slow trends in climate over time, one would not expect to see anything like it in many years,” says Andresen. “While we can expect a more normal, (and hopefully) less stressful growing season in 2013, one can’t completely count out the possibility of yet another weather-related challenge or two.”
In California, Calanit Bar-Am and Daniel Sumner with the University of California Agricultural Issues Center are in the middle of a research project on the economic effects of climate change on the California wine industry. “Climate and soil affect the yield and quality of grapes,” says Bar-Am. “Temperatures above certain levels may reduce the quality of some varieties and may make them unsuitable for some wine regions.”
Previous studies have found that quality and yield of grapes depends on the interaction among soil, typography, and climate. As a result, high sensitivity to quality of grapes can affect wine prices. In a region where average winegrape prices can reach as much as $3,000 per ton, there is a lot at stake, says Bar-Am.
Bar-Am and his team are looking to estimate a relationship between climate and quality of extra-premium wines in several top wine regions around the world, including Napa, CA, and Bordeaux, France. They also want to estimate the share of high-rated wines out of total wines produced in each region as a function of weather variables by using cross sections of historical data. “By doing this, we can draw implications for wine and grape prices, and quantity and producer surpluses.”
What You Can Do
Whether or not the previously addressed weather problems are isolated one-off events or a sign of a larger trend, the question becomes, is there anything a grower can do in response? At the same Great Lakes event where Andresen presented his findings, Robert Evans, a retired research agricultural engineer from Washington State University, offered several tips on how to best use frost protection methods in tree fruit. (Evans’ and Andresen’s presentation are available on the Great Lakes Expo web site) “The questions of how, where, and when to protect a crop must be addressed by each grower after considering crop value, markets, expenses, cultural management practices, and historic frequency and intensity of cold temperature events,” says Evans. “The implementation of frost protection strategies must be balanced against risk assessments of both the probabilities of annual and longer-term costs of lost production and possible long-term tree or vine damage.”
In addition, several land grant universities offer local online resources. Many of them are designed to serve as pest management tools, but certainly have weather pattern applications as well.
• Enviro-Weather, Michigan State University
• Network for Environment and Weather Applications, Cornell University (www.newa.cornell.edu)
• Northeast Regional Climate Center (www.nrcc.cornell.edu)
Jim Flore, a professor in the Department of Horticulture at MSU, says any efforts to help delay bloom will be critical, whether this means using plant growth regulators, cultural practices, or mist coolers. One system in development that may prove to be a valuable resource is the solid set canopy delivery system, the subject of American/Western Fruit Grower’s February cover story.
Going back to California, Bar-Am notes that premium wines such as Cabernet Sauvignon and Pinot Noir are grown in the optimal climate range required for achieving high quality. “An increase of average, minimum, and maximum temperatures across winegrape growing regions may reduce the suitability of growing these varieties in regions that have grown them for decades.” Coupled with this, a study published in the “Proceedings of the National Academy of Sciences” asserts that global warming will reduce viable winegrape acreage by 70% or more, “making it impossible to grow high-quality winegrapes in many of the outstanding wine regions of the world.”
So does this really mean winegrape production in Napa Valley will soon be headed north? Not so fast, says Napa Valley Vintners, a trade association representing more than 450 wineries. “Climate change can and will affect all fine wine-growing regions worldwide, but the results will not necessarily be a blanket effect,” says the group. “This is a very long-term issue which vintners and growers around the world need to pay attention to and be directly involved with.”