Projections of Future Climate from the GCMs

A Broader Perspective on the Fruit Industry

(slide #1) The role Michigan plays in the U.S. fruit industry. In apple production we´re either second or third, New York and Michigan have about identical size industries. Washington is number one. Michigan is number one in production of tart cherries, producing 75%-80% of the US total. In cultivated blueberries, Michigan is also the leader, with about a third of the production. In sweet cherries, we´re generally 3rd or 4th. The bottom line is, it´s a fairly significant industry. (slide #2)

The largest fruit producing counties are along the western coast of the state. The other states that produce deciduous fruits, Washington, Oregon, California, New York, all of them have a large body of water beside them, which moderates the climate.

Climate plays a very significant role in fruit production. It is very dramatic.

(slide #3) In Traverse City, they keep track of when the bay freezes and if it freezes going back to 1851. Plotted by decade, the years that it frozeÑgenerally 8-10 years out of a decade it would freeze—until we get into the last 20 years we´ve really had a drop off in the number of years the bay has frozen. It froze 3 years in the last decade. The bay has not frozen in 2001 or 2002. This is a graphic description of how are winter climate is behaving.

(slide #4) The big lake (Lake Michigan) helps fruit production in some critical ways. It reduces our winter injury by moderating the climate. It delays spring bud development and that is critical in all of our fruit crops. It reduces the risk of late spring frost. The Lake also cools us in the summer, important for some crops more than others. Reduces risk ? Fall for us. It gives us lake-effect snow, which helps us overwinter some of our crops.

What is Critical in terms of Different Times of the Year

Whether or not the bay freezes is a function of the amount of cold accumulation during the winter. We´re getting less and less cold accumulation, one would assume that we would have less winter injury and hence could raise more winter-tender crops. That is possible, but a perennial crop accumulates the ability to withstand cold temperature. This is influenced by the climate. One of the reasons we can grow winter-tender crops is because we get cold and (the temperatures) stay there. In the most extreme case, the coldest temperature we ever recorded in Traverse City was in the winter of 1977-1978, February 21, it was -36°F. At many of our fruit sites the temperature was -24°F. We had peaches, a crop that´s very tender—some literature says it can´t tolerate below 10°F—survived -24°F because we had not had an hour above 32°F since sometime early in December and this was late February. The trees were so well acclimated they were able to tolerate incredibly cold conditions.

(slide #5) Winters like this past year, where we have a very slow onset of winter with many more temperatures above freezing, we are much more prone to winter damage. It comes back to the issue of extreme events or variability. If the probability of getting cold extreme events also reduces as the average temperature increases, then we should be in good shape. If, however, we reduce our ability to tolerate the cold and the very cold temperature events occur, it could be more damaging. It´s more complex than that. There are issues of onset of winter hardiness, mid-winter and late-winter hardiness factors.

Most prone to problems of winter injury would be wine grapes, peaches, and sweet cherries. Those are the crops that are most sensitive to wintertime temperature.

(slide #6) What is the effect on spring bud development? Fruit buds become susceptible to cold injury relatively early in the spring. This is the time of year when, probably of any single factor, most commonly determines what our crop is going to be. There will be some influence from the crop size the year before. Bud development is a very critical period.

What we´re seeing in a trend, what we would expect to see with a warming trend is the beginning of bud development earlier. That means we get to a susceptible stage earlier. Twenty six years ago, in Leelanau County, the growers used to say, "You can pretty well set your calendar by bloom in tart cherries, it will occur May 21 in east Leeland." Where our research station is it would bloom two or three days before that, 18th or 19th of May. In the last four years we´ve bloomed four weeks ahead of that. We´ve bloomed between May 3 and May 5. Fourteen days is a huge advance.

The question is, and the thing that could stand some good research from climatologists, is what is going to be the potential effect of variability or extremes? If the probability for those negative temperatures declines at the same rate that the season advances, then there will be no effect. But, if in fact we develop earlier, and still get cold events then we´re going to be in worse shape. Most susceptible to spring bud injury are tart cherries, sweet cherries, and apricots; but all of our fruit crops to some extent.

(slide #7) The next issue is the summer issue. One thing that we can certainly predict for our crops is that as temperatures go up, we´re going to need more water. One possible scenario is that summer rainfall increases. If we get enough increased rainfall, then that could offset this increased need for water. The negatives of increased rainfall would hurt the sweet cherry industry more than any other because sweet cherries are very prone to a problem with cracking if it rains at the wrong time. During the 90´s we´ve had an exceptional amount of loss of sweet cherries to cracking, much more so than in prior decades. Disease pressure will also increase if precipitation increases.

(slide #8) Another possible scenario related to the variability issue, is that while rainfall may go up, if we see greater extremes, and then if heats going up, transpiration is going up—evapotranspiration—we´re going to need more moisture. If we don´t get the offsetting rain, I see an increased need for irrigation. A great example occurred this past summer, where we had a year where the average precipitation is average or above for our area, all in the spring and fall, we actually had the worst drought in NW Michigan in 26 years. This was significantly worse than the 1988 drought. The reason is that we had less than 1/4 inch of rain from the 20th of June to about the 8th of August; right during the heat of summer. In 1988 the drought was more in May and June and we got some summer rains during that critical time. How that precipitation is spread out is a critical issue because we know we´re going to need more water for the plant.

Increased need for irrigation is a likely outcome if for nothing else than this kind of an event happening.

There would be some good things about that. We´d have decreased disease pressure and sweet cherry growers would hate to see rain come along just as sweet cherries are about to mature.

(slide #9) It´s so hard to predict what will happen. If I was reading it, probably the most likely winner is wine grapes. There we are really pressing the northern end of the limit for them. We often produce some of our best wines in some of the warmer years. Increased heat probably helps the Michigan wine industry.

If I were going to guess what crop would be the most likely loser, it would be tart cherries. They really love our cool climate. There is a reason we produce 75%-80% of the US production. They love that cool weather and they´re very prone to spring bud damage. If we get advanced bud development, we might see a greater likelihood of loss of that crop or reduced crops due to bud damage.

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