In April, the government of Premier Jean Charest introduced a bill in the Quebec National Assembly that seeks to protect nearly 150 million acres — half of northern Quebec, an area the size of France — from industrial development, including logging, mining and petroleum exploration. The bill matters, not just to Canada but to the world: The boreal forests and tundra of northern Canada remain a relatively intact ecosystem, absorbing more carbon than the world’s tropical forests and providing a vital buffer against global warming. Industrial development would weaken that buffer, and, as things stand now, there is almost nothing to prevent it.

As envisioned by Mr. Charest, the bill would have made a firm commitment to prevent all industrial activity. As revised by government bureaucrats, the latest version promises only that, at some future point, steps will be taken to “protect the environment, maintain biodiversity, enhance the natural heritage and promote the sustainable use of resources.” Mr. Charest is the leader of a majority government, so the bill will almost certainly pass. Before it does, it needs to be strengthened to prohibit even piecemeal development in this sensitive region.

Mr. Charest is not against development. Last year, he proposed Plan Nord, to manage the public lands of northern Quebec in a way that balances exploitation and conservation. Permanently setting aside 150 million acres would still leave plenty of room for economic development in northern Quebec, and it would set a remarkable precedent for sustainable use. It will take years of planning before these new protections come into force. But this bill will lay the groundwork for one of the largest land conservation initiatives in history.