With its vast expanses of forest, Canada has the most “certified” sustainable timber operations of any nation, according to the nonprofit organizations that attest to the environmental soundness of logging practices.

Such forestry-standards groups were born in the 1990s out of rage over tropical rainforest destruction. Today, they put their leafy seals of approval on toilet paper, two-by-fours and other wood and paper goods to assure eco-conscious consumers and investors they were responsibly produced.

Yet research shows Canadian forests have seen some of the world’s largest declines in ecologically critical primary and old-growth woodlands over the last two decades, even as sustainability-certification programs grew to include nearly all of Canada’s logging.

To track destruction of older woodlands in these certified zones, Reuters analyzed forestry data in Ontario, a major logging province. The analysis found that about 30% of the certified boreal forests harvested from 2016 to 2020 were at least 100 years old. That resulted in the loss of 377 square miles of these older forests, an area the size of New York City and Washington D.C. combined, the analysis found.

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