The trees are blooming
Early – again. Mid-march buds are starting to be a trend.
There are sooty mounds of snow and garbage, swooping pigeons and a dead squirrel. Homeless men crouch nearby, picnicking on bread from Dollarama.
Not idyllic conditions for a scientific experiment.
But on this glorious March day, David Greene has stopped by this shady spot off St. Mathieu behind the Faubourg Ste. Catherine, where a stand of silver maples has Montreal’s pollen season off to an even swifter start than usual.
Greene is a forestry ecologist in Concordia University’s geography department, where he studies pollination and seed production for a living.
On the morning walk from his toddler’s daycare to his office, he’s been keeping informal track of those silver maples – Acer saccharium – the first genus of trees to flower and seed in our region.
As a scientist – and yes, an allergy sufferer – Greene can’t help noticing how over the last 15 years, the trees have been blooming as much as two weeks earlier than they used to, observations backed up by data collected by the Aerobiology Research Laboratories.
“It tended to be late March or early April. And now it is starting to be, with some consistency, mid-march,” said Greene. “That is nothing to sneeze at. Two weeks in 15 years in an enormous change.
“In the long history of plants on this planet, you can have periods where over 15 years things got really warm or things got really cold. If this was not tied in to a much larger argument about global warming, it would not be worth talking about. It would just be another of those statistical blips.
“I am not saying anything earth-shaking. If the weather keeps getting warmer, then trees like this will flower sooner.
“The odds of this trend just being a coincidence are incredibly tiny.”
So what happens to those new buds if – be brave now, Montreal, it could happen –it gets cold again?
“That depends on how cold,” says Greene. “Inside the bud, they are armoured. They are safe. It’s not just that bud scales are wrapped tightly around them, they have what amounts to an antifreeze.”
Once the blossoms emerge, those feathery tendrils are as vulnerable to the elements as a college student in a T-shirt and cargo shorts.
“If it were to get incredibly cold for a while, below freezing with the wind whipping through, I would presume that huge numbers of these flowers would die and therefore this species would put out very few seeds in late May.
“At this stage to have sustained, truly cold weather this late in the game is really not likely. What are the odds that it suddenly gets to minus 10 and stays that way for a couple of days?”
He suggests there’s something almost philosophical about the way trees and other woody plants take advantage of the first hot weather to sprout and germinate.
“There is a danger for these guys. What if it gets as cold as can be in the next two weeks? The answer to that would be ‘I live a long time. If I screw up this year, I live a long time. Yes, all my progeny this year are screwed, but I’ll have many more. … I’m not going to waste any time worrying about that,” he said.
“Plants are pretty neat. They can’t walk around, they can’t run away. They can’t do anything, but they hang in there. It’s hard not to admire them.”
Greene had been studying seeds long before pollen forced its way into his head.
“I clearly had trouble with grasses. I was out in Calgary and I got a job in Montreal. I thought, ‘At least I am away from grasses. As long I stay in the city I am fine.’ Then, there was ragweed.”
On advice from friends, Greene went to the hospital for allergy tests.
“The woman was so fast, she goes jab, jab, jab. Every needle has different pollen or spores.
“So there is this little orchard on your arm. Everything is just different levels of inflammation. The one that is ragweed is huge. It is taking over my arm. The grasses are big. All are inflamed. And there was one that wasn’t. I said, ‘At least I am not allergic to that.’ And she said ‘That’s the control.’ That’s when I thought I needed to start taking pollen seriously.”
Greene is quick to say he’s not an expert in phenology, the study of plant and animal cycles events and what they may tell us about climate change. Indeed, he said, it wasn’t until recently that people, even in the scientific community, really began paying attention.
“No one could imagine that the climate could change this fast. We forget but it is really just in the last 15 years that people have started to say, ‘My God, the climate isn’t just warming up, we expect it to warm up very fast. So what are the consequences?’ ”
What, for instance, might the impact be for plant species which, unlike maple trees that use the wind to pollinate, depend on the graces of birds, bees and insects to spread their seeds.
He said woody plants appear to respond to heat sums, the gradual warming of the Earth, and it appears that animals do the same.
“They need to be cued too. Somebody has to tell them it’s time to wake up. It would appear heat sums do it for them as well.”
But what happens if plants and insects are out of sync?
“Maybe they end up being off by a week. That can make a hell of a difference in reproductive success of these species.”