Restoring the Sudbury Basin to its original state
Delegates to the 6th Mining and Environment International Conference in Sudbury June 20 to 25 received an update on the Sudbury Regreening Program and were able to see for themselves the steady progress the city has made in reversing the devastating effects of early mining activity in the region.
For the first few decades of the program, regreening activity focused on the liming of barren lands, seeding them with a grass and legume mixture and planting a limited variety of trees.
However, a major rethink and broadening of the program was triggered by the release of the Sudbury Soil Study’s ecological risk assessment in 2009, noted Stephen Monet, manager of environmental planning initiatives for the City of Greater Sudbury.
“The ecological risk assessment basically told us that we still had a lot of work to do and that there were still a lot of biologically impoverished areas. That led Vale, Sudbury Integrated Nickel Operations and the City to move forward with a Biodiversity Action Plan.”
The objective was to diversify the vegetation with species native to the region and restore the land to something more closely approximating its original state.
The choice of grass and legume seeds was one example of the rethink.
“Initially, the idea was to lime the area to counteract the acidity of the soil and to create a situation that would allow the metals in the soil to bind more tightly with the soil particles and make it more difficult for the plants to absorb them,” said Monet. “The grass and legume seed mixtures we used were the typical species you’d find in an agricultural setting. They weren’t necessarily native species, but they created a quick ground cover. The following year, we went in and planted pine seedlings.”
The formula worked well for a number of years, but as the trees grew, the grass died because of the shade, while in unshaded areas, the grass grew aggressively, preventing other vegetation from coming in.
“We have now changed to a more native seed mix, so the grass that develops is supposed to be there and is not as aggressive as the agricultural grasses,” said Monet.
“We have also collected local seeds from a plant called Poverty Oak Grass which grows on very rocky and sandy soils. We found some in Hanmer (north of the city). We collected the seed and spread it by hand and were very excited to see it flourishing this year. That will be another species we’ll add to the seed mix.”
The Biodiversity Plan also impacted the species of trees chosen for planting.
“In the early years,” said Monet, “almost 95 per cent of the tree seedlings planted were of four species: white spruce, jack pine, red pine and white pine. They were chosen because they were readily available. They’re easy to plant, they’re inexpensive and they’re produced in the millions for the forest industry. They were also among the species that were knocked back quite hard by the sulphur dioxide fumigations.”
As a result of the Biodiversity Plan, dozens of other species, including deciduous species, are now being planted.
Forest floor transplants began on a trial basis in 2006 and expanded in 2010 as a major component of the regreening program.
“An area came open to us as a result of the widening of Highway 69 between Sudbury and the French River,” said Monet. “We harvested quite a bit of material from there. Since that time, we have planted the equivalent of one and a half football fields of material in four metre by four metre plots.
The plots – 250 of them were transplanted in the first year – were laid out precisely and marked with string and steel pins at the corners to allow researchers in future years to measure their expansion.
In the five years since the plots were planted, the vegetation has spread as much as three metres from the confines of the original four-by-four metre plots.
The Biodiversity Plan has also focused on bringing lichens back to the Sudbury Basin.
Lichens are composite organisms made up of a fungus and a photosynthetic symbiant – usually a green algae or a blue-green algae – really “two organisms in one,” explained Monet. Because they are ultra sensitive to sulphur dioxide, the Sudbury Basin was considered a lichen desert until the Superstack began dissipating acidity over a wider area.
Lichens were collected, crushed, dumped into the hoppers of Vale planes and air dropped as little propagules.
Field reconnaissance confirms they are adhering to the substrate.
Lichens are important because they are “pioneers, or colonizers on bare rock,” explained Monet. “They trap dust, soil particles and organic matter. They retain moisture and reflect light, which keeps the rock cooler. They also attract other vegetation and organisms, including mosses, arthopods and voles, which set in motion a whole chain of recovery.”
The area damaged by early mining activity in the Sudbury area has been estimated at 80,000 hectares, or close to 200,000 acres. The area limed and seeded by crews to date encompasses only 3,450 hectares, but that doesn’t include the areas not limed but planted with tree seedlings or the 100 to 150 hectares per year that Vale treats by dropping lime, seed and fertilizer from the air.
Since 1978, between 13 and 15 million trees have been planted in the Sudbury area.
The program traces its roots to the establishment of the Vegetation Enhancement Technical Advisory Committee in 1973 and the commencement of land reclamation efforts in 1978.
Regreening activity, funded by Vale, Sudbury Integrated Nickel Operations and the City continued this summer with a crew of 25 and will likely continue for many more years, but the City is already beginning to give some thought to developing completion criteria – in essence, the conditions “telling us for a given area everything that needs to be done or can be done has been done, at which point we give the keys over to Mother Nature,” said Monet.