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Heat-stressed larches turning golden earlier than usual, experts say

“We are starting to see some change in colour and with that comes more visitation. Fall is traditionally a busy time for visitation in Kananaskis Country.”

KANANASKIS COUNTRY – Robert Frost said it best: ‘Nothing gold can stay.’

A coniferous larch tree reaches its full autumn glory, turning from green to gold over a few weeks in what has become an increasingly popular sight to behold in parts of the Rocky Mountains before its needles drop, signifying the onset of winter.

This year, though, hot, dry conditions coupled with wildfire smoke have caused the golden larch season to start earlier, and it could last longer than usual, experts say.

“What we’ve seen here in terms of the similar progression of leaves and larches, is that it has been a bit quicker than normal,” said Michael Roycroft, regional director for Kananaskis with Alberta Parks.

“We are starting to see some change in colour and with that comes more visitation. Fall is traditionally a busy time for visitation in Kananaskis Country.”

Larch season is typically in full swing from mid-September to early October.

The provincial ministry responsible for environment and forestry confirmed it has received many reports from visitors, campers and trail users of larch trees turning earlier than normal this year.

Gerard Fournier, master arborist and landscape horticulturist instructor at Olds College, grows thousands of larches, among other species of trees, at his nursery in Didsbury.

He’s also observed early fall colours in his larches, which are watered regularly.

“What sort of precipitates fall colour in a lot of cases is drought stress,” said Fournier. “If there isn’t enough moisture, that will trigger a physiological response which we see as fall colours, which is really the plant downloading chlorophyll and turning it back into sugar.

“In the process, it unmasks other pigments that also have a similar function in the tree to capture energy from the sun and convert it into sugar.”

Heat stress from periods of warmer than average weather also plays a role in trees changing, along with wildfire smoke.

In the Bow Valley, which does not have data to date back long-term temperature averages, there were 16 days from April 29 to the end of August when temperatures broke record highs, compared to records in Banff.

“There were two in April, seven in May, five in June, one in July and one in August," said Terri Lang, Environment and Climate Change Canada meteorologist. "That tells you May and June were particularly hot.”

This year was the fifth hottest summer on average in Banff, with the warmest-ever May on record.

The Bow Valley had 9.3 millimetres of rain in May, compared to an average of 59.6 mm. In June, there was 93.3 mm, compared to an average of 61.7 mm. July had 14.6 mm compared to 54.2 mm and August had 35.8 mm compared to an average of 60 mm.

As a result of hot, dry conditions, there have been 998 wildfires, according to Alberta Wildfire, 80 of those are active.

In terms of area burned, Canada is experiencing the worst fire season in modern record.

“The summers are getting hotter and drier. There’s certainly a lot more smoke in the air, and if it’s really hazy that cuts down on trees' ability to photosynthesize,” said Fournier.

This year, the Calgary area is set to break its record for the total number of smoke hours.

According to Environment Canada, there have been 445 hours of smoke cover in the area this year due primarily to wildfires.

“That is far and above the average,” said Lang. “The last few years have been crazy with respect to the amount of smoke and Calgary is about five or six hours off from breaking the record from 2018.”

While subalpine larches are not immune to the effects of climate change, Fournier said the tree as a species is highly adaptable and has “weathered many storms.”

Subalpine larch is one of the longest-lived tree species, growing at higher elevations in the Rocky Mountains in southern B.C. and Alberta, into parts of the U.S.

Trees can survive at high altitudes and grow in a variety of soils and shade levels. A subalpine larch tree in Kananaskis discovered by a University of British Columbia researcher in the 1980s is believed to be the oldest tree in Canada at about 1,950 years old, Fournier said.

The arborist said periods of warmer than average weather in early spring also caused an earlier than usual start to the growing season for larches and other tree species this year, which plays a part in when trees enter dormancy.

“I had trees on my farm that were starting to leaf out as early as the end of April, so that means they had almost an extra month of growing season,” Fournier said. “That means they’ve done their business taking in as much energy as they can, and now they’re ready to start downloading that energy.”

If there is a trend of cooler weather while staying above freezing in September and October, the downloading process could be prolonged and extend the amount of time trees are golden, he added.

Kananaskis Country along with Banff National Park and other parts of the Rockies are hotspots for larch-lovers.

Roycroft said Alberta Parks is gearing up for the busy fall hiking season as September, for the past three years, has been the area’s busiest month in terms of visitation behind July and August.

“Virtually every weekend when the larches are in full bloom, if you will, is incredibly busy in places where you can see them,” he said.

In Kananaskis, these areas include the Highwood Pass and around Chester Lake, among others.

Roycroft said while the area has always been busy in the fall, it wasn’t until the last few years that Alberta Parks started looking at further visitor management strategies for the area, including implementing public transportation to address vehicle congestion and ongoing talks with Alberta Transportation to look at reducing the speed limit on sections of Highway 40 during larch season.

“It didn’t really rise to a point of ‘we have to do something different’ in terms of managing that visitation, until recently. It really, really did explode in terms of popularity over the last four or five years,” he said.

Roycroft believes this is likely due to a combination of the COVID-19 pandemic, which saw a record visitation of 5.4 million people to Kananaskis in 2020 and over five million in 2021, along with the influence of social media in recent years. Visitation has since returned to pre-pandemic levels at 4.2 million visitors in 2022 but is consistently rising.

While Alberta Parks has invested in building more parking space at trailheads throughout Kananaskis Country such as at Grassi Lakes and Ha Ling Peak near Canmore in response to higher visitation, there will never be enough parking stalls to accommodate the number of visitors to the area, said Roycroft.

For the upcoming larch season, Alberta Parks is planning to have contractors managing vehicle traffic in busy areas to address any public safety issues with overcrowded parking, particularly along Highway 40.

The agency is also encouraging visitors to make a plan B or a plan C if there is no safe parking at their chosen location to recreate in Kananaskis at busy times of year.

The Local Journalism Initiative is funded by the Government of Canada. The position covers Îyârhe (Stoney) Nakoda First Nation and Kananaskis Country.

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