British Columbia scientists see recovery but fear more heat domes could alter ecosystems forever

VANCOUVER – A year after the heat dome event that killed billions of plants and animals in British Columbia, scientists say ecosystems are recovering, but could be changed forever if such events become more frequent .

Cold-water marine species could be replaced by warm-water organisms, triggering cascading effects in the environment, said University of British Columbia zoology professor Christopher Harley.

“If we had another heat wave this summer, that would be a problem,” he said. “An ecosystem may be able to handle a big heat wave once every few decades – there’s plenty of time to recover – but if it starts hitting every four or five years, the species we’re used to simply cannot persist any longer.”

Dozens of temperature records were set during the heat dome. The high-pressure system settled over western Canada, acting as a lid to trap a layer of warm air that grew progressively warmer for about a week. Three successive Canadian records have been set in the town of Lytton, where the temperature peaked at 49.6°C on June 30, the day before a fire destroyed most of the village.

The heat caused more than 600 human deaths, the BC Coroners Service reported. It has also led to mass mortalities of marine life, reduced crop yields and contributed to forest fires, which then caused devastating landslides last fall.

Diane Srivastava, director of the Canadian Institute for Ecology and Evolution, organized a group of scientists currently working to understand the impact of the heat dome on species and ecosystems. She said some were “immediate and obvious”, but several years of data are needed to “get a full picture of longer-term effects”.

Group member Harley said the heat wave caught researchers off guard and they were now “trying to figure out” what it would mean for the ocean ecosystem.

“I’m a little embarrassed to say we don’t know (the ecological consequences) because it hadn’t occurred to us to ask what would happen if it got hot enough to kill billions of animals. sailors,” he said. “This heat dome was so outside of what everyone expected.”

Scientists initially estimated that more than a billion marine animals had died along the Pacific coast. Harley, who has been studying West Coast shorelines since 1995, said that’s an underestimate.

“Many billions of animals died easily,” he said. “It was a perfect storm of a few different things. It was obviously much, much warmer than usual and these high temperatures coincided with very low tides.

Mobile species had a higher survival rate than those that anchored to rocks in shallow water, he explained.

“The mussels aren’t back yet and some of the common algae aren’t, but the baby barnacles are having a blast. They are everywhere and the first step in recovery is (when) they arrive,” he said. “The foundation is now laid.”

Adam Ford, assistant professor and Canada Research Chair in Wildlife Restoration Ecology at the University of British Columbia, said the large mammals he studies were much less affected by heat than ocean life.

“We have a few years of data under our belt and there hasn’t been a spike in mortality or anything during that time.”

He said that’s because large mammals are homeothermic, meaning they can regulate their body temperature and may have moved to cooler areas to avoid direct heat.

Karen Hodges, professor of conservation ecology at the University of British Columbia, said most mobile animals and those that burrow into the ground probably fared better during the wildfires that followed the heat dome than those unable to flee quickly. She said it was difficult to estimate the total number of deaths because it would require “many assumptions about animal densities” before the fires.

The speed at which an area’s ecosystem recovers depends on environmental aspects such as soil moisture, but depends on fire management practices and the response to climate change, Hodges said.

“The answer to what comes back becomes a question of what humans will do with these landscapes over the next decade, two decades if you want to be generous, because we could either create the conditions for low levels of frequent small fires. , or we could put in place conditions that allow for the repetition of these massive fires,” she said. “It’s a pivotal time.”

Ford echoed the call for better wildfire practices to lessen the impacts of intense heat.

“We already know that climate change and poor management practices, like fire suppression, over the past 50 to 70 years have really degraded the health of our forests. So if you put those two things together, we have a recipe for catastrophic failures that have impacted all sorts of areas of society, including biodiversity,” he said.

“We need to understand how we are putting fire back into the landscape with a quantity and intensity that restores habitat for wildlife and humans.”

Wildfires are a natural part of the forest ecosystem and are important for maintaining forest health and diversity, says Natural Resources Canada on its website.

“Prescribed fires provide a valuable resource management tool to improve ecological conditions and eliminate excess fuel buildup,” the website states.

For decades, British Columbia scientists have called for the use of low-intensity fires to “maintain” forest health by creating firebreaks. Hodges said fire suppression efforts to protect communities have eliminated many of these natural breaks, allowing fires to spread more easily.

She said the provincial report following the historic 2003 wildfires in British Columbia, which forced the evacuation of more than 45,000 people from the interior of the province, was a watershed moment.

“This report is full of advice on letting certain fires burn, on FireSmart communities and on prescribed fires and all kinds of things that the province has hardly done, but that advice has been in the hands of the government for at least minus this report,” she said. said.

Hodges said large fires can also worsen weather events linked to climate change, such as the catastrophic flooding that took place in British Columbia last fall. She said the fires that kill thousands of trees affect the composition of the soil and can make it hydrophobic, meaning it repels water. Then, when heavy rains occur, the water is not absorbed by the ground, causing landslides.

“Things like this are much more common after these large, deadly fires than after the ordinary small fires we’ve had in our history,” she said.

The Ministry of Forests said in a statement that it uses prescribed burning as “one of many fuel management tools and techniques to help reduce the intensity of natural wildfires while restoring an integral process in the forest.” ‘ecosystem”.

Rachel White, the lead author of a report on the widespread ecological impacts of the 2021 heat wave currently undergoing peer review, said the lack of synthesized data has been a major hurdle for scientists .

“We’re going to have more frequent and hotter heat waves, and that’s going to impact the whole ecology. In order to monitor this, we need data,” she said.

“We need this data to really understand what the impacts are and once we know how the systems are reacting now, it gives us more information to say how they will react in the future if the climate continues to warm. due to human actions. ”

Harley, the zoology professor, and his team are working to better understand what makes an ecosystem more or less susceptible to a heat wave.

“There may be small changes we can make to make ecosystems more resilient to something like a big heat wave or a big drought,” he said.

Srivastava said the Institute for Ecology and Evolution is advocating for a provincial biodiversity monitoring network.

“Events like this highlight the need to have such a biodiversity monitoring network already in place, which would allow us to have long-term monitoring of many populations,” she said. “Instead, we have to bring together data from many different sources to try to see the immediate effects and then the long-term effects.”

She said developing a network is “a recent and ongoing topic of conversation” with provincial and federal governments.

The British Columbia Ministry of Environment has confirmed that it is working to synthesize ecological research and climate change data as part of its new Climate Change Preparedness and Adaptation Strategy.

“Understanding how climate disruptions will affect ecosystems is essential to responding to climate change,” he said in a statement. “The Province is supporting the creation of an Ecosystem Prediction Center within the Ministry of Forests to build the expertise and resources needed to translate technical projections of climate change into predictions of ecosystem change in British Columbia.

This report from The Canadian Press was first published on June 27, 2022.

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