The five senses of spring: How climate change is shaping our experience of the season

Singing frogs are looking for love. Sweet sap is flowing from the maple trees. Striking migratory birds are returning to their northerly nests.

Spring is about transformation, a season often marked by its dynamic sights, smells, sounds and tastes. As humans change the climate, our experience of the season is changing, too.

Here are just a few of the ways that climate change, driven by the burning of fossil fuels, is transforming our spring senses.

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HEARING: A quieter chorus

It sounds a bit like a finger running over a fine-tooth comb, but it’s about as loud as a lawn mower.

It’s hard to spot — at only 2.5 centimetres long — but when the chorus frog emerges in early spring its mating call can be heard from a kilometre away.

To Jeffrey Ethier, it’s the most iconic sound of spring’s arrival.

“You can kind of feel your eardrums vibrating,” said Ethier, a PhD candidate at the University of Ottawa who specializes in recording and studying their calls.

But that iconic sound is in trouble.

In Quebec, where the chorus frog is listed as a vulnerable species, the population has declined at an estimated rate of 37 per cent a decade since the 1950s and it only lives in about 10 per cent of its former range.

Rapid habitat loss is considered the major driver behind the population declines, but climate change is piling on to that threat, said Ethier.

The chorus frog is highly sensitive to temperature change, breeding at some of the earliest signs of spring. As climate change increases the risks of extreme weather, including brief spates of unseasonably warm, above-zero temperatures in late winter or early spring, it could prompt the frogs to breed too early, Ethier said.

If their spring breeding ponds freeze over again, the frogs’ eggs could die off. Alternatively, early-season warm spells could risk drying out those ponds quicker than before, Ethier said.

Losing the sound of the chorus frogs altogether no longer feels like a remote possibility, especially for the Quebec and eastern Ontario populations, Ethier said.

“It would be like losing a loved one. Here’s something that was so familiar, and so iconic and such a big part of spring. To lose that sound would be losing someone that’s in your family and no longer being able to hear their voice every day.”

Globally, about 40 per cent of amphibian species are at risk of extinction and climate change has been the most common driver of their deteriorating status since 2004.

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TOUCH: A worsening allergy season

For Dr. Adam Byrne’s patients, the physical feeling of spring can come with itchy eyes and noses, rashes and eczema flare-ups. They are among the roughly one in four Canadians who suffer from seasonal allergies, often triggered by tree and grass pollen.

“We talk a lot as a society about coming changes in climate change and what’s on the way. And I think from an allergy perspective, the changes are here, we’re already seeing it,” said Byrne, an Ottawa-based allergist and clinical immunologist at the Children’s Hospital of Eastern Ontario.

“We’re a little bit of the canary in the coal mine.”

Human-caused climate change drives warmer temperatures, allowing plants to grow earlier in the season, and cranks up CO2 levels, which promote pollen growth. Generally, that means there’s more pollen in the air for a longer period of time during spring, Byrne said.

In Canada, the average growing season starts about six days earlier than it did in the mid-20th century, federal data indicate. Average North American pollen concentrations, meanwhile, are up 20 per cent over the past three decades, a 2020 study found.

In spring, tree pollen is a common allergy trigger. But grass season, which typically peaks in late spring or early summer, is starting to creep forward too. People who have both tree and grass allergies are starting to get “really hammered” when the two overlap, Byrne said.

“Our immune systems are just not used to seeing things at that level for that long,” he said.

Meanwhile, as some of Canada’s trees extend their range to previously inhospitable latitudes, northerly communities could see a rise in allergies as they contend with more oak, birch, maple and other pollens, Byrne said.

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TASTE: Finding the sweet spot

One of Canada’s most iconic spring tastes may be getting a little less sweet.

Studies have indicated sap sugar content may decline slightly for each degree of warming in the previous growing season.

Consumers may not notice the difference, said Josh Rapp, a U.S. researcher who co-authored a 2019 study on maple syrup and climate change. But it could mean producers have to use more sap to find the syrupy sweet spot.

“That means your costs are going to go up a little bit,” said Rapp, a senior forest ecologist at Mass Audubon, a nature protection non-profit.

Maple syrup taps are typically still flowing by the time spring arrives in Canada, so long as temperatures still fluctuate below and above freezing between the nights and days.

Rapp and his co-authors, including those from Canada, found across the sugar maple’s North American range, climate change was expected to lead to a decline in syrup production in southern parts of Ontario and Quebec, but could increase in the north.

Luc Lagace and his team at the Quebec-based ACER Centre, which is devoted to maple syrup research, are studying this migration and where syrup production may thrive in the future.

“The main concern is about if the maple sugar makers will be able to produce it in the long term,” he said.

Near-term risks include climate-fuelled extreme weather events, from wildfire to windstorms, and insect infestations.

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SMELL: A smokier breeze

Payton Knight can smell the wildfires coming.

The campfire-like smell, at times reminiscent of burnt plastic, often lingers over her family’s working farm south of Edmonton.

“I hate it,” the 13-year-old said.

Studies indicate climate change is helping to fuel earlier wildfire seasons and more intense burns. A recent study of Canadian fires from 1981 to 2020 found some areas had seen a significant increase in the number of days conducive to highly severe wildfires, mostly in the spring and autumn.

For Knight, it means more days when she may struggle to breathe. The teenager has a severe form of asthma with multiple triggers, but wildfires are among the worst of them.

“It kind of feels like an elephant sitting on my chest,” said Knight. She put it another way: “Imagine breathing through a straw.”

When the air is clear, Knight spends her days outside, riding her beloved horse Reo and tending to the family’s goats and her baby lambs. But when the smoke arrives, she has to stay cooped up indoors and is sometimes home from school for days at a time.

Separated from the outdoors, she said she struggles to understand why anyone would choose to stay inside.

While Canada has some of the cleanest air of any country in the world, wildfires have put a dent in that reputation. Air pollution in Peace River, Alta., in May of Canada’s record-breaking 2023 wildfire season was worse than the annual average in India, the third-most polluted country, according to data compiled by the Swiss air-quality firm IQAir.

If air quality is improved, children’s lungs function better and they’re less likely to develop asthma or severe symptoms, said Anne Hicks, Knight’s doctor and an associate professor at the University of Alberta in pediatric respiratory medicine.

“If we’re degrading our air quality, whether it’s from cars or wildfires, we’re going to have a generation of kids whose lungs are going to be smaller and worse functioning,” Hicks said.

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SIGHT: Thinning migratory crowds

The sight of the first migratory birds in spring has long been therapeutic for Jody Allair – a sign of returning life and warmth after a long winter.

“But I look at spring now and I can’t help but feeling a little bit melancholic,” said Allair, a biologist based in Drumheller, Alta., and director of communications for Birds Canada.

Allair has seen the data, but he’s also seen the skies. Climate change is accelerating the decline of several bird species and thinning out the spring spectacle.

“I can feel it, I can tell there are fewer birds coming through,” he said. “You used to get big migration pushes for a whole month and now it’s just like a few days in a month.”

Shorebirds in particular, which nest as far north as the Arctic, have seen their populations decline by 42 per cent since 1980, as they contend with climate-fuelled sea-level rise and extreme weather disruptions along their lengthy flights.

Allair, to get himself excited about the spring migration push, recently updated his desktop background to a picture of the Hudsonian godwit. The shorebird with a long, slightly upturned bill and spindly legs undertakes an over 10,000 kilometre-long multiday spring migration from the tip of South America to Canada’s northern wetlands, including the Arctic Ocean and Hudson Bay.

The threatened bird’s population has rapidly declined by over 90 per cent since the 1980s, with climate change and severe weather ranked as one of its most serious threats.

The birds are struggling to adapt to the earlier start to spring, with some chicks hatching after peak insect season. Their spring migration passes through the Prairies, where wetlands are shrinking. Rising sea levels are expected to cut into its coastal foraging habitat, according to a federal assessment report.

Allair said he finds it’s hard to get people to care about declining bird populations through graphs and data. It helps to see it for yourself, he said.

“It’s about getting to know something and building those connections with nature through birds that could be the breakthrough.”

This report by The Canadian Press was first published March 22, 2025.

Jordan Omstead, The Canadian Press