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Climate change isn't the only thing threatening maple trees

  • Oct 14, 2014
  • 710 words
  • 3 minutes
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Climate change is creating extreme weather, but it may also be having an effect on what you put on your pancakes. Researchers from Memorial University of Newfoundland have found that sugar maples may have more trouble responding to warming temperatures than originally thought.

“We would expect the whole species distribution to shift northward,” says Carissa Brown, an assistant professor of biogeography. But Brown and her team have found that factors other than climate are affecting sugar maple’s ability to “migrate” in response to climate change.

In a series of what Brown described as “character building” experiments, her team lugged about 800 litres of earth up and down the kilometre high Mont-Megantic in southern Quebec. Doing so allowed the team to simulate northward migration by simply changing elevation. Instead of moving the soil to higher latitude, they took it up the mountain where the temperatures were comparably cool.

To ensure their results were being determined by factors other than climate, they brought soil from high on the mountain, outside the sugar maple’s range, down to the heart of the tree’s range and planted the winged seeds kids often call “helicopters.”

They found that even in the best climatic conditions, planting seed in soil from outside the tree’s range resulted in less seedlings taking root, meaning trees would naturally have problems expanding their range. But the real surprise was waiting for the scientists at the top of the mountain, where they’d transported the good soil.

“We came to our pots and instead of finding seedlings we found the seed wing, but instead of a seed attached to it, we found little bite marks,” Brown says.

Whatever was eating the seeds was stifling the sugar maples’ range expansion more than other factors such as soil quality. To prove it they ran another series of experiments using cages to protect some seeds, and found that when protected and planted in good soil, the seeds would germinate at high elevation.

Brown says the research shows that the idea that trees and plants will simply move north as the climate warms is too simple. And that there will probably be a time when sugar maple range is squished between a warmer climate to the south and obstacles such as seed predation or soil quality to the north. Nicely described

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(Photo: Carissa Brown)

So what’s next for the $300 million maple industry?

As director of the University of Vermont’s Proctor Maple Research Center, Timothy Perkins researches climate change and sap production in sugar maples. He says maple syrup is made from harvesting sugar maple sap, which flows when there is a cycle of cold nights and warm days.

“Maple season is starting considerably earlier than it did 40 to 50 years ago, and also ending correspondingly earlier,” Perkins says, adding that the two ends of the season aren’t moving together. Much like the maple being squished between mysterious seed-eaters and increasingly warm weather, sap season is getting squished between its start and end date.

“In the very long term, if we continue to see this shortening of the duration, we are likely to experience reductions in syrup production,” Perkins says. There are, however, a few beacons of hope for syrup lovers. Perkins says new harvesting technology is actually increasing yields despite a shorter season, and Perkins’ research is finding that there’s a fall sap season that has gone largely untapped.

Back in Canada, Caroline Cyr from the Federation of Quebec Syrup Producers says Canada’s biggest network of maple syrup producers isn’t concerned about climate change right now. Cyr says the 2014 season was their second biggest with about 51 million kilograms of maple syrup produced, just shy of the 2013 record of about 54 million kilograms.

“We never know when a season will be good or bad,” she says, adding that the effect of climate change on the industry is impossible to predict.

Meanwhile Brown says her team is continuing to try to tease out factors that could be hampering sugar maple’s ability to shift north. She says the surprise of seeds being eaten at a higher rate at high elevations underscores the complexity of our ecosystems.

As for your syrupy pancakes, they’re safe for now.


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