A carpet of ferns, grasses, herbs and microorganisms is being transplanted into areas near Sudbury, Ont., that were once stripped bare by pollution.

The City of Sudbury and local mining companies have spent $25 million to plant nine million trees over former mining industry sites in the area since the 1970s, but a major part of the ecosystem is still missing.

Millions of trees have been replanted in the Sudbury area, but many plants, insects and other organisms from the forest floor have not come back to areas damaged by pollution. Now, they are being transplanted in from other forests, one square at a time. Megan Thomas/CBC"We have all the trees now, but there's no forest floor," said Evan Urso, part of the City of Sudbury crew that is transplanting square mats of vegetation from older forests to the reforested sites.

Many of the plants, insects and microorganisms that used to live in or near the forest floor were decimated by sulphur dioxide emissions from nearby smokestacks that made the soil acidic, said Tina McCaffrey, supervisor of the City of Sudbury regreening project that the transplant is a part of. The smoke also deposited heavy metals that are toxic to living things, she added.

McCaffrey said it's unlikely the forest undergrowth would have returned on its own, even now that the trees are back, because there are no sources of seeds for forest floor plants nearby.

But she said the project is intent on reintroducing that kind of biodiversity: "There's more to a forest than just trees."

Crews are cutting out and rescuing square mats of vegetation from a site where a new four-lane highway will soon be built. The forest above them has already been cleared, leaving the forest floor without a roof over its head.

Squares of the forest floor are being rescued from an area where trees have been cleared to make way for a new four-lane highway. Megan Thomas/CBC

Now the undergrowth — including all the insects, microorganisms and other living things on board — is being placed in bread trays and transported by ATV to its new home.

"It's bringing the entire package," McCaffrey said.

Last summer, the city moved an area of forest mats equivalent to the size of a football field. Some of the plants have already begun spreading outside the area where they were replanted, McCaffrey said.

This year, the city crews will continue their work until the end of the summer, transplanting another football field-sized plot of forest floor.

McCaffrey said that while similar projects have taken place in other parts of Canada, Sudbury's is the largest of its kind.

With files from Megan Thomas