(Halifax) The usual bright reds, oranges and yellows of trees that mark the arrival of fall sometimes appeared early this year, and in other cases not at all.
Published at 12:44 p.m.
Lyndsay Armstrong The Canadian Press
Dramatic summer weather that led to wildfires in some parts of the country and heavy rains in others is being reflected in fall colors across Canada, researchers say.
In Nova Scotia, where summer began with wildfires and ended with thunderstorms, dull brown replaced the rich hues common across much of the province this time of year.
Mason MacDonald, assistant professor of environmental science and agriculture at Dalhousie University, said the colors he’s seen so far this fall don’t compare to the bright reds and oranges that Nova Scotians are used to.
“You’ve probably seen a lot of really boring colors this year. Even reds are likely to be 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 the nights grow 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 – provides the red hue of the leaves and requires constant sunlight until late summer for its production. A decline in anthocyanins is not harmful to a tree, MacDonald said, adding that the bright reds will likely come back in full force if next summer is sunnier.
“We had more rain than usual this year and at the same time a whole series of dark, gray and cloudy days. That’s what happened. We didn’t have the sunshine we normally would have. So you can’t create those colors,” MacDonald said.
Early Colors in Ontario
In contrast, trees in Ontario showed their natural pigments earlier than usual.
PHOTO CHRIS YOUNG, THE CANADIAN PRESS
Sean Thomas, a professor of forest ecology at the University of Toronto, says there is anecdotal evidence that smoke from wildfires in northern Ontario this summer may have caused trees to reveal their colors prematurely.
“Wildfire smoke is a kind of chemical cocktail,” Thomas said.
This cocktail of carbon dioxide, ozone, sulfur dioxide, carbon monoxide and particulate matter “contains trace amounts of chemicals that play some kind of hormonal role in plants,” he explained, 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 color,” 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 ongoing effects of climate change would cause fall colors to decline in coming years.
There is good reason to believe that climate change will disrupt the normal leaf coloration we see.
Sean Thomas, professor of forest ecology at the University of Toronto
He believes the combination of warmer temperatures and delayed first frosts could result in duller fall colors.
He estimates that this effect will likely be stronger in large cities, which are generally warmer than rural areas due to the urban heat island effect, as structures such as roads and buildings absorb and re-emit solar heat.
If climate change delays the onset of longer, colder nights in places like Toronto, “that’s a recipe that will likely result in much lower fall color 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 is taking place, a spokesman for the event said in an interview Thursday that trees in the area began to change color. Dave Mahalik heard the colors were less bright in parts of Nova Scotia this year and wondered how they’ll get through it.
“But I’m in Sydney and there are trees here that are starting to grow and they look like they normally look,” he said.
His colleagues told him that the colors looked vibrant elsewhere on the island, which boded well for the festival, which features about 50 concerts in Cape Breton communities.
“I am very excited and am sure the colors will still be as vibrant as ever,” he said.
– With information from Fakiha Baig in Toronto