Canada's federal riding map is about to change — and even small shifts could have big impacts

The next federal election in Canada likely will be fought on a new political battlefield, now that a process to reshape electoral ridings is entering its final stages.

The House of Commons is expanding to 343 seats. Five new ridings are being added to keep pace with Canada's growing population.

Those five new seats — three in Alberta, one in B.C., one in Ontario — could by themselves play a role in determining who wins the next election.

But according to Michael Pal, a University of Ottawa professor and expert on electoral law, thousands of other, smaller changes to federal ridings could also help shape Canada's political future.

"A lot of ridings are very close, you know, and if you move an apartment building out that has a lot of voters that tend to vote in one direction, that can have a big impact" on who wins a seat, he told CBC's The House.

The process of altering the boundaries of federal ridings is in its final stages. A parliamentary committee is now reviewing draft maps from across the country before the final lines are drawn.

In a tight general election race, Pal, said, the coming changes could add up to big consequences.

"It has an impact," Pal said. "I mean, it's nothing like people's views on health care or the economy, or whether they think the incumbent government is doing a good job, which party leader they like ... It's more if the election happens to be close on all those other factors, then it comes down to one or two or three ridings."

The boundary changes are decided by independent commissions in each province, chaired by judges and made up of experts like political scientists. They have a mandate to draw the riding boundaries so that ridings all have roughly the same population numbers.

They're also expected to consider other factors — like the history of the riding, cultural or economic ties between communities, the size of ridings and the impact of boundary changes on Indigenous representation.

The commissions also gather feedback from the public and MPs, and several drafts of a riding map are considered before a new map is finalized. The Commons committee on procedure and House affairs is holding meetings to formally hear objections from MPs displeased by changes to their ridings.

Committee consideration is one of the last steps before a new riding map is finalized. The new riding maps will be used in the next election, as long as that campaign takes place seven months after the new maps are in place.

The redrawing process is inherently political, Pal said, but the role of partisanship is kept to a minimum.

"When the commissions draw the lines, they are not supposed to, in any way, shape or form, take into account what the partisan outcomes are going to be," he said.