Leaves on trees not changing colour due to Climate Change, experts say

It’s almost the fall season in Calgary, and the trees, leaves, bushes, and everything is still green. Should people be concerned?

Biological experts like Dr. Samuel Yeaman, an associate professor of biological sciences at the University of Calgary, say these changing patterns are one of the various factors that scientists are noticing as part of climate change.

“The delayed changing of colors that we see in the fall when there has been a warm summer is absolutely consistent with what we expect,” Yeaman said.

“As climate change results in higher temperatures in the summer. It would make sense that we start to see shifts in leaf change to a little bit later in the Fall.

But that said there are a lot of other factors that modify it. So things like precipitation, [and] how much rain there is over the summer can also change it. And they found in some places pollution levels decreased and solar radiation increased. They found that it would also change the trees’ timing of when they change color.”

“This is one of [the] hundreds and hundreds of wake-up calls that we should be paying attention to,” Yeaman said.

Similar to the effect on leaves, a warm and extended summer can increase the population of wasps.

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In Calgary, wasps are a common insect that can be dangerous because of their stinging habits and venom. There are 13 species of yellow jackets and paper wasps that make bigger colonies in Alberta. Only three of these continue building their colonies past September.

“If we are having longer Falls, warmer Falls; that plays into bigger populations. Which can mean they will produce more queens that will hibernate. And if it stays warmer in the winters and drier as well, it means there will be less fungi that will kill those hibernating queens. So that’s why we could start to see if climate change continues as what we are seeing, that could lead to higher populations,” said John Swann, an entomologist at the University of Calgary.

“Calgary has got very erratic weather already, relative to many places in Canada. And yeah people are generally expecting [the] weather to be changing a little more erratically,” said Yeaman. 

“I don’t think this is a severe one that is going to affect livelihoods in a big way but it’s one of many signs that we can see our world is changing,” said Yeaman.