(Halifax) The trees’ usual vibrant reds, oranges and yellows, marking the arrival of fall, sometimes appeared early this year, and in other cases not at all.
Dramatic summer weather, which brought wildfires in some parts of the country and heavy rains in others, is reflected in fall colors across Canada, researchers say.
In Nova Scotia, where summer began with wildfires and ended with thunderstorms, dull brown replaced the vibrant hues usually seen this time of year in much of the province.
Mason MacDonald, assistant professor of environmental sciences and agriculture at Dalhousie University, said the colors he’s seen so far this fall don’t compare to the brilliant reds and oranges Nova Scotians are accustomed to .
“You’ve probably seen a lot of really dull colors this year. Even reds are probably duller, darker or rust-colored, Professor MacDonald said in a recent interview. A lot of people have talked to me about it this year, especially people from southern Nova Scotia.”
As nights get longer in the fall, trees receive less direct sunlight and chlorophyll, which trees use to absorb sunlight during photosynthesis, begins to break down, revealing the natural pigments present in the leaves.
One of these pigments – anthocyanins – creates the red hue of leaves and requires constant sunlight until late summer to be produced. A drop in anthocyanins is not harmful to a tree, MacDonald said, adding that if next summer is sunnier, those vibrant reds will likely come back in force.
“This year we have had more rain than usual, and at the same time we have had a whole series of dark, gray and cloudy days. That’s what happened. We didn’t get the sunshine we normally would have. So they can’t create those colors,” MacDonald said.
Early Colors in Ontario
In contrast, Ontario trees began showing their natural pigments earlier than usual.
PHOTO CHRIS YOUNG, THE CANADIAN PRESS
University of Toronto forest ecology professor Sean Thomas says there is anecdotal evidence to suggest smoke from wildfires in northern Ontario this summer may have prompted trees to prematurely reveal their colors.
“Smoke from forest fires is a kind of chemical cocktail,” Thomas said.
This cocktail of carbon dioxide, ozone, sulfur dioxide, carbon monoxide and particulate matter “contains traces of chemicals that play a sort of hormonal role with plants,” he explained, which which can cause trees to lose their leaves prematurely.
“In our case, we experienced these acute smoke effects earlier in the summer, but this could be partly responsible for the earlier autumn colouration,” Professor Thomas said.
He found there was a lot of color across much of Ontario this season. He said he had reason to believe the continued impacts of climate change would see autumn colors diminish in coming years.
There is good reason to believe that climate change will disrupt the normal leaf coloring we see.
Sean Thomas, professor of forest ecology at the University of Toronto
He thinks the combination of warmer temperatures and delayed first frosts could lead to duller fall colors.
He estimates that this effect will likely be more acute in large cities, which are generally warmer than rural areas due to the urban heat island effect, when structures such as roads and buildings absorb and re-emit heat. heat from the sun.
If climate change delays the onset of longer, colder nights in places like Toronto, “that’s a recipe that will likely result in a lot less fall coloring in the city, and that will be exacerbated by climate change,” he said. Mr. Thomas said.
In Cape Breton, where the Celtic Colors International Festival takes place, a spokesperson for the event said in an interview Thursday that trees in the region were starting to change color. Dave Mahalik heard the colors were less vibrant in parts of Nova Scotia this year, and it made him wonder how they’re going to get through this.
“But I’m in Sydney and there are trees here that are starting to grow, and they look like they usually look,” he said.
His colleagues told him the colors seemed vibrant elsewhere on the island, which bodes well for the festival which hosts about 50 concerts in Cape Breton communities.
“I’m very excited and I’m sure the colors will still be as vibrant as ever,” he said.
— With information from Fakiha Baig in Toronto