Canada seems set for a debate — let’s hope a polite one — about immigration. Oh, super.

This was probably inevitable. The generally favourable liberal-democratic view of immigration is under pressure all across the Western world. It’s not a mystery why. Europe has experienced a huge surge in migrants and refugees arriving from Africa and the Middle East as conflicts in those regions set people on the move. The U.S. has long had problems with illegal immigration on its southern border — and in Washington, where successive administrations failed to do much about it but kick the can down the road in hopes that someone else would fix it later.

Things that can’t last forever don’t last forever. The public in both Europe and the United States has had enough. At least enough for members of the public, at any rate, to turn immigration into hot political issues.

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Canada, though, has largely been spared this, at least until now — and it’s clear why. Our geopolitical circumstances are different. Our success at assimilating immigrants into a broader Canadian identity is internationally recognized. Immigration has worked here. It’s still working.

But there are signs — early ones, I admit, but still — that Canadian attitudes on immigration are also hardening. Earlier this week, a poll by Angus Reid found a break from a long-standing trend in Canada. For the first time in 40 years, more Canadians want to see fewer immigrants than want to see more or a stable number. It’s always been close — immigration is divisive in Canada as much as anywhere — but this is the first time in decades that Angus Reid has found that our attitudes are, on balance, negative.

READ MORE: Ottawa to scrap controversial immigration lottery system for families

This isn’t good. Immigration is essential to this country. I’m not making an emotional appeal here. This isn’t a “diversity is our strength” moment. It’s just math. We don’t have enough babies in this country to sustain our population through natural growth alone. We wouldn’t even be holding the line — we’d be shrinking. Our entire social welfare framework depends on a growing population. If we shrink, we’re in trouble with our budgets fast, and then we end up where Japan has: abandoned towns and home-care robots.

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If Canadians were holding the line on population just via baby making, we’d be able to have a different conversation on immigration. We could decide we’d had enough and slam the doors shut. We could decide to get pickier. We could let in more. It wouldn’t matter — we’d be making the decision from an enviable position of being able to view immigration as an opportunity, maybe even a luxury, but not as a necessity.

But that’s not our position. Right now, we need immigration. Lots of it. To my mind, this is good — my life is personally richer for immigration, and I think Canada is, too. But let’s not kid ourselves. We need immigrants; that’s not the debate.

The debate is what kind of system of immigration we’re going to use to get them — what it will prioritize, where it will seek them, and how many we want. Tweet This

That hasn’t been a problem. As said above, we’re good at this. We have been for decades. And despite all the feel-good rhetoric Canadians from the Prime Minister on down like to hurl about regarding diversity, the reality of our system has often been that it’s brutally rational — sometimes too much so. Canadians may wax poetic about diversity but we’re ruthless about picking which people we want to be Canadians. Sometimes that leads to decisions that seem heartless, because they are. They’re calculating and harsh.

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And that’s OK. That’s the system we built: Canadians have supported immigration because they know the system is fair but tough.

What’s changing?

Some of it is probably just Canadians not being immune from reality. Anti-immigration sentiment is rising in the countries that are the most like us, our closest allies. Why would we assume it wouldn’t here? But there’s also the issue of the ongoing migration issue/crisis/event/thing/whatever along our own border.

READ MORE: Asylum seekers sit in state of limbo as they wait for refugee claims to be heard in Canada

More than 30,000 people have crossed into Canada illegally from the United States to seek asylum here. They have that right legally, even if the border crossing is illegal, but while these people are waiting for their hearings — the waitlists are long and growing alarmingly — their care has overwhelmed social services in Quebec and now Toronto. The federal government hasn’t yet been able to solve this problem.

There’s a big debate unfolding about whether we’re allowed to call this a “crisis.” I’ll leave that to one side for now. But whatever you may think of Canada’s ability to absorb tens of thousands of asylum seekers — most of whom won’t be allowed to stay at the end of their process — if the border situation begins to turn public attitudes against immigration in a country with a low fertility rate, guess what? That’s a crisis.

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Watch: Global News coverage on asylum seekers

And it has been from the beginning. Some of us have been saying so. Finding people a bed to sleep in today won’t do much good in the long run if Canada’s long-standing pro-immigration slant is derailed by what’s viewed, fairly or not, as government incompetence on the border.

Matt Gurney is host of The Exchange with Matt Gurney on Global News Radio 640 Toronto and a columnist for Global News.