Replanting one type of tree is not enough to stop clearcutting harm, study finds

·3 min read
Replacing diverse Acadian forests, left, with one type of tree, right, is causing population declines of up to 70 per cent for some bird species, according to a new study. (Oregon State Univeristy/Submitted - image credit)
Replacing diverse Acadian forests, left, with one type of tree, right, is causing population declines of up to 70 per cent for some bird species, according to a new study. (Oregon State Univeristy/Submitted - image credit)

Planting trees to replace clear-cut forests is not good enough to protect the ecosystem, according to a new study.

Matt Betts, a professor of forest ecology at Oregon State University, is studying the decline of bird species caused by deforestation in the Maritimes and the replacement of diverse Acadian forests with one type of tree.

The study, which was published Thursday in Nature, Ecology and Evolution, shows some species have seen a population decline of up to 70 per cent since 1985. More common species have seen a decline of 50 per cent.

"At the very least, we need to change some of our core forestry practices, focus more on maintaining those those nice, colorful Acadian forest tree species we have," he told Shift New Brunswick.

The species most affected is a little migrant songbird with a bright orange face called the Blackburnian warbler, which has seen a 70 per cent decline.

Oregon State University/Submitted
Oregon State University/Submitted

Common species also suffering include the olive-sided flycatcher, Swainson thrush and winter wren.

Researchers in the study looked at habitat and populations of 54 bird species in New Brunswick, Nova Scotia, and Prince Edward Island. They compared satellite images with bird-counting data from 11,000 locations.

They found 28 million hectares of habitat were lost over 35 years. Betts said that's linked to the loss of 35 million to 100 million birds.

Of the 54 bird species studies, all but six per cent showed some sort of decline.

Jeff Nadler/Boreal Birds Need Half
Jeff Nadler/Boreal Birds Need Half

'Forest degradation' is the new deforestation?

Betts calls the replacement of diverse forests with one type of tree "forest degradation," and almost everyone has seen it.

"You can notice it when you drive along the highways, that often the planted forests are coniferous and the forest that's being removed is mixed, diverse, what we call Acadian forest. So red spruce and sugar maple and yellow birch," he said.

"That's a major change."

The data shows population decline followed the route of forest degradation, so more birds were lost in areas where more forests were clear cut and replaced. If there had been another factor, the pattern would not have been so clear, he said.

"This is as close as it can come to … being able to point to cause."

A canary in the coal mine

From interpreting their bones for omens in ancient Rome, to air quality measurements in coal mines, birds have been used as indicators for thousands of years. And that's still true today, he said.

"I would say that if we've got bird declines like this, it's potentially symptomatic of other problems environmentally, which we need to fix," he said.

When bird populations decline, the entire ecosystem is affected, he said. Birds eat insects that harm trees. Fewer birds mean more insects and weaker trees.

Lois Corbett, executive director, Conservation Council of New Brunswick, said this study just proves what's been anecdotally seen.

"Dr. Betts's research reinforces what a lot of citizens, scientists and groups like the Conservation Council have been saying for years: we need much more ecological forestry in New Brunswick and much less clearcutting and large-scale plantations," she said.

Betts said the good news is New Brunswick and Nova Scotia are on the cusp of major policy changes that can help bird populations.

"The number of protected areas in New Brunswick is going up," he said. "Also, we're moving more toward different forestry practices that don't involve clearcutting and replacing with conifers, but more focusing on maintaining the type of forest we've got."

He said even if forestry practices are changed fundamentally right now, populations may still decline for a while before the benefit is seen.

"We're going to keep an eye on that and keep going along with the research."

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