When the Tonga volcano erupted 18 months ago in the middle of the Pacific Ocean, it set in motion a chain of events that Maine growers and homesteaders will deal with for at least the next several years, experts say.
While climate experts are not ready to say Maine’s growing seasons are undergoing a permanent change, growing seasons are increasingly unpredictable. Growers now have to be ready to quickly adapt to extreme weather and changes within a single season.
“There have been a lot of extremes even in the past couple of months,” said Sean Birkel, state climatologist at the Climate Change Institute at the University of Maine in Orono. “Next year could bring very different weather patterns [and] based on one particularly warm year we can’t infer any long-term change.”
In other words, next year could be very different from this year’s warm, rainy summer. And this year was very different from past years. In something as weather-dependent as growing crops, it adds a layer of uncertainty to an already unpredictable practice.
“The last three years have been years of extreme droughts in Maine,” said David Handley, vegetable and small fruit specialist with the University of Maine Cooperative Extension. “It’s made more sense to only plant what you have the ability to water, and now this year it’s been quite the opposite.”
Until this season, parts or all of Maine had been under some level of drought or dry conditions since 2014. One of the rainiest Junes on record this summer broke that streak, but not before a lot of growers planted crops based on the previous year’s dry conditions.
Growers were left scrambling to manage water in fields and gardens this summer that had to be irrigated due to drought last year.
Some root crop seeds were either washed away before they had a chance to germinate or were stunted due to the soggy conditions. Pick-your-own berry farms reported good yields, but the constant rain kept pickers away. Meanwhile, the rain favored garden pests like slugs, which munched their way through gardens
Even with all that rain, parts or all of Maine could still experience drought conditions, experts say.
Month-to-month temperature extremes — July was a particularly hot month, for instance — knocked a lot of crops off schedule. Strawberry, raspberry and blueberry seasons overlapped this summer. In a more normal year, one fruit typically follows the other. Other crops like tomatoes, corn and zucchini are ripening more slowly than in past years — or not at all.
At the climate center, Birkel is tracking the far-flung events adding challenges to Maine growers.
When the Hunga Tonga-Hunga Ha’apai — Tonga for short — volcano erupted underwater in the southern Pacific Ocean in early 2022, it shot massive amounts of water vapor into the atmosphere.
The water vapor produced by the Tonga volcano was enough to warm the planet and impact weather patterns for a decade, according to a study published in Nature Climate Change.
“That single [Tonga volcano] eruption added another 10 percent of moisture to the atmosphere,” Birkel said. “That is one possible part of warming that we are seeing this summer.”
Another factor playing into Maine’s shifting weather patterns are atmospheric changes in the Pacific tropics that are happening more frequently and producing warmer or cooler than average conditions.
“The extremes we see here are connected to extremes elsewhere on the planet,” Birkel said. “Natural systems respond to those changes — like lakes [in Maine] freezing later and ice-outs coming sooner.”
That can also translate to Maine’s growing season extending — at least in the short term.
For decades, anyone who grows anything here has relied on the U.S. Department of Agriculture’s plant hardiness zone map. It shows what plants have the best chance of thriving in specific locations. It’s based on the average time between the last plant-killing frost in the spring and the first in the fall.
Last fall, the season ending frost in October was followed by a string of summer-like days in November that tricked fruiting trees and plants to come out of winter dormancy and setting them up for cold-weather damage.
A frost this past May followed a string of unusual 70-degree days in April that caused many fruiting plants and trees to blossom early. Any that were not quickly covered during the coming frost died.
There are indications that the state’s peach crop did not make it through the early warmup and following frost.
Overall, Maine winters have been slowly warming, and that has opened the door for new crop-damaging invasive pests as well. Growers are having to change pest management schedules and practices in response, Handley said, sometimes mid-growing season.
Based on climate models, there is no guarantee next year is going to look anything like this year.
“Growers are used to weather being somewhat unpredictable, but they had years of data that gave them an idea of what the summer would be like,” Handley said. “The last several years have been real outliers with events the data did not predict — adapting has to be the new strategy.”