Toronto’s urban forest has never faced an environmental assault as great as the recent ice storm, according to climatologist Dave Phillips.

“No question about it. I can’t think, of all the 170 years of weather observations that we have in Toronto, that I would have seen events that would have been more devastating (to trees),” said Phillips, senior climatologist for Environment Canada.

The city announced Thursday that it will spend $25 million cleaning up debris from the ice storm and an additional $50 million repairing the damage to the canopy after an ice storm pulled down branches and limbs across Toronto. The costs are on top of the estimated $1 million per day spent by Toronto Hydro to reconnect power.

The forestry price tag speaks to the extent of the damage and the complex work required to mend wounded trees. Limbs that fall from a canopy are like girders being removed from a building, according to arborist Todd Irvine. Careful pruning is needed to restore stability to damaged treetops.

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“Most people think (pruning is) just like a barber, you just clip it off and it comes back. These trees are incredibly complicated dynamic systems,” said Irvine.

Crews are being dispatched to all corners of the city Friday, visiting the areas with the most complaints first. More than 600 city staff and contractors will be part of the two-month cleanup effort. Each tree will first be inspected and crews will remove any branches that are in danger of falling, according to Brian Mercer, supervisor of forest policy and standards with the city of Toronto, who also described the damage as extensive.

“I’ve been around Toronto looking after trees for 10 years now. It’s the worst I’ve seen,” said Mercer.

Branches and limbs littered the roads after an ice storm that paralyzed the city Dec. 21 and 22 and left more than 300,000 Toronto Hydro customers in the dark. The hydro company’s CEO, Anthony Haines, estimated its repair costs at around $10 million — just a fraction of what the city will spend on its forests.

The city is asking all residents to pile branches under 15 centimetres (6 inches) in diameter on their boulevards regardless of whether it’s a city tree or private. Pickup will begin on Friday but the city has said it will be flexible and attempt to pick up all the debris. Residents who miss the pickup should call 311 as soon as they realize it. Any larger chunks that are from private trees will have to be removed by a contractor.

Following the initial inspection, which focuses on safety, the city will then return to any trees that have broken branches that need removal and take other measures to protect the trees. Any that are damaged beyond repair will be replaced, said Mercer.

Deputy Mayor Norm Kelly and councillor Denzil Minnan-Wong, who chairs the city’s public works and infrastructure committee, were joined by Mayor Rob Ford at a press conference Thursday to announce the effort. Minnan-Wong indicated that the cleanup and repair bill would put pressure on the upcoming budget, and Mayor Ford said council will ask the province for help at a special council meeting Jan. 10.

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The full extent of the damage is difficult to pinpoint. Last week, city staff gave an estimate that as much as 20 per cent had been lost — something Jason Doyle, director of forestry, says may have been premature.

“We’re not exactly sure how that number was produced. I think there was an estimate provided between 5 and 20 per cent. At this point I’m reiterating — we have no clue. We do not know what the impact is,” said Doyle. He said once crews begin evaluating trees, they will have a better idea of the true amount of damage.

Tree repair is no trivial thing, says Irvine. The removal of branches destabilizes the canopy — something that can only be fixed by highly trained arborists. Even more attention will be needed in the spring when trees that lost limbs start to sprout new ones.

“Each branch break is a significant wound and the tree will respond to that wherever there’s a branch break by putting out new shoots,” said Irvine. “Those new shoots are very weakly attached and there’s way more of them than you’ll ever need.”

The new shoots need to be thinned out so that the weaker ones are removed and those with the strongest attachment to the tree are encouraged to grow. Irvine said a tree that previously required pruning every three to five years will potentially require annual attention after an injury.

“You can’t just let the trees do their own thing. The damage has altered their biomechanics permanently,” said Irvine. “If there’s hundreds, if not thousands, of trees like that you can imagine how much more pruning is required.”