Once the votes have been counted, Americans will either have elected a new president with by far the most ambitious climate-change plan of anyone who has held the office, or re-elected a climate-change denier.

Never mind the caveats. Sure, Democratic nominee Joe Biden probably won’t be able to implement his entire $2-trillion climate plan if he wins. Yes, despite Donald Trump’s obstructionism, subnational governments and the private sector will take some strides toward decarbonization even if he prevails.

It is still impossible to overstate this unresolved election’s stakes for the planet’s future. As the clock runs down to avert environmental catastrophe, the United States will reassume its global leadership role, or keep retreating from it.

And there is also no escaping that the leadership of Canada’s behemoth neighbour will help shape this country’s role in that fight.

While Prime Minister Justin Trudeau kept quiet on his U.S. election preferences, it’s a safe assumption that he would welcome a continental ally who shares his view that climate is a top priority.

But both potential outcomes stand to pose new climate-related challenges for Canadian policy makers, alongside new opportunities. What’s in question is whether that will require Canada striking out on its own in a way it hasn’t to date, if Mr. Trump wins; or scrambling to keep up, alongside Mr. Biden.

The climate-related peril for Canada if Mr. Trump is re-elected is certainly more obvious.

If Canada is serious about trying to exceed its Paris Agreement commitments, it would have to break from its biggest trading partner in risky ways.

The best example involves road transportation. Canadians and Americans drive unusually gas-guzzling vehicles relative to elsewhere, and a way to address that is through fuel-efficiency rules. But Mr. Trump scrapped Barack Obama’s ramping up of those standards. If he gets another four years, Mr. Trudeau’s government may be compelled to break with the decades-long practice of aligning Canadian standards with the American ones – and face warnings about costing jobs in an integrated auto sector dominated by the U.S.

Even with regulations that are less directly correlated, there will be questions about how much Canada can afford to move in isolation from its neighbour; about whether raising carbon prices or imposing stricter rules around oil extraction makes sense competitively.

A sense of futility could be disincentive to take such risks, or spend large sums on climate mitigation. The opposition Conservatives have at times argued Canada’s climate ambition should be tempered by its small share of total global emissions, despite its per capita emissions being among the highest. That could get more traction if it will be at least four more years before there is national effort in the U.S.

At the same time, there is potential competitive advantage in Ottawa taking the clean-economy transition more seriously than Washington. Attempts to help boost Canadian clean-technology sectors could be more successful if the U.S. isn’t doing the same. More traditional sectors could benefit if Canada outflanks the U.S. on climate-risk disclosure requirements, as markets prioritize sustainable finance.

And as a matter of politics, if not the planet’s well-being, there is some comfort for Mr. Trudeau in helming North America’s greenest national government by default. It makes relatively mild action look progressive.

If Mr. Biden prevails, and has a chance to implement a climate agenda aimed at net-zero emissions by 2050, it will be almost exactly the other way around. Canada will be less isolated, better able to meet climate targets – and less comfortable in its relative virtue, pressured to move more aggressively in ways that could cause domestic strain.

On some fronts, Canada will return to moving in lockstep with the U.S. That will include the fuel-efficiency standards, mentioned explicitly in Mr. Biden’s platform. There might be greater harmony on regulation of other industries, including fossil fuels, through measures such as newly ambitious continental targets for reducing methane emissions.

Where policies don’t line up exactly, aims will be close enough for Canada to not be out on a limb. If Mr. Biden doesn’t get some form of carbon pricing through Congress, his rebuild of environmental regulations scrapped by Mr. Trump could add up to a similar push to decarbonize industry. His promised investment in green infrastructure should help create economies of scale, enabling more efficient spending in both countries.

But it’s also possible that Mr. Biden, whose platform pledged to push allies to set emissions targets “beyond the commitments they have already made,” will go further than Canadian leaders are prepared for.

Although Mr. Biden did not say he would immediately do away with U.S. fracking as Mr. Trump falsely claimed, he does intend to challenge the oil and gas industry in ways that – particularly if Ottawa is seen to be aligned with him – could exacerbate frustrations in Alberta and Saskatchewan. While planning to cancel the permit for the Keystone XL pipeline, he has vowed to “demand a worldwide ban on fossil fuel subsidies.” If he succeeds in dramatically expediting the U.S. transition away from fossil-fuel usage, the Canadian sector’s decline will hasten.

And although massive U.S. public investment in climate mitigation could create new sales opportunities for Canadian cleantech, Mr. Biden will be more aggressive than Mr. Trump in using subsidies and procurement policies to get low-emissions products made in America. Mr. Trudeau’s government will likely need to boost its own supports if it wants to compete.

If there is a constant between these two scenarios, it’s that once this election is done, Canada will be compelled to up its game.

The Globe and Mail, November 3, 2020