Stop clear-cutting and protect BC forests to manage flooding: UBC study

Researchers say decades of hydrological studies ‘seriously and consistently underestimated’ the impact of forest cover on flood risk

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BC must protect its forests to manage flood risk and shift to more sustainable forestry practices, UBC Faculty of Forestry researchers say.

That means the government must end the practice of clear-cutting, according to a recent study published in the journal Total Environmental Science.

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The need to stop this practice is “urgent,” said Younes Alila, a hydrologist and professor at the Faculty of Forestry, due to the growing problems caused by human-caused climate change, such as droughts, floods and forest fires.

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“When replanted with monoculture, the forest grows very dense and is not diverse. It is not fire resistant. In fact, it spreads fire faster than you think. Trees grow very slowly. And now with the drought these trees are going to have more difficulties growing,” he said on Tuesday.

“The practice of clear-cutting is increasing the severity and frequency of forest fires. Everything is related”.

Alila and her graduate student Henry Pham analyzed decades of hydrology studies, which “severely and consistently underestimated” the impact of forest cover on flood risk.

This led to forest management policies and practices that were flawed or poorly informed by outdated scientific data, Alila said.

“This is because the system is not designed to indicate how forest clearing changes or increases in frequency,” Alila said. “They focused on assessing the effects on severity, but were silent on how logging may be making these events more frequent.”

Communities such as Grand Forks, Cache Creek, Merritt and Williams Lake that have experienced severe flooding are located in areas where logging continues, he said.

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“These areas have been flooded time and time again. And then you run into these basins that flow into areas that have been flooded and have been completely cleared of trees,” he said.

Aerial view of old-growth logging in the Klanawa Valley on southwest Vancouver Island. Photo by TJ Watt/Ancient Forest Alliance /PNG

“It used to be once every 100 years and now it’s every two years…increases in the magnitude, duration and frequency of flooding have important consequences on infrastructure, fish and water quality.”

In an emailed statement Tuesday, British Columbia’s Ministry of Forests acknowledged that climate change is impacting forests, causing flooding, increased insect infestations and hotter, drier summers that lead to droughts and wildfires.

The statement says British Columbia forestry scientists and professionals always consult significant amounts of data, review topographic maps, surface geology maps and detailed ground stability maps, and consider these factors when developing recommendations for silvicultural systems and harvest limits .

The ministry said it is developing alternatives to clear-cutting practices, such as selective harvesting techniques, that support forest resilience, ecosystem health and climate adaptation, including a new $10 million forestry program at the Bulkley Valley Research Centre.

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“Any science and research, including this new UBC paper, that can help improve forestry practices is a welcome addition to a field of study that is always changing,” the ministry said.

Alia said, “It is recording and speaking. “I would like it to be implemented as soon as possible because we are running out of time and trees.”

A study published last year by UBC forestry researchers, including Alila, found that when 21 per cent of trees were removed through clear-cutting, the average flood size increased by 38 per cent in the Deadman River watershed and 84 percent at Joe Ross Creek. area, both regions north of Kamloops.

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—with files from The Canadian Press

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