Article: Asha Jhamandas
Images: Arlene and John Neilson and Jim Robertson
On the surface, peatlands don’t seem like prime real estate, especially when a hard, honest look reveals them to be acidic, oxygen-starved environments. This was indeed the prevailing opinion of the early European settlers who considered them wasted lands because they were difficult to farm. But in the 1950s, soil scientists sowed the seeds for a greenhouse revolution when they discovered that peat was an excellent potting medium. Now it seems everybody wants a piece of peat because it has become the soil of choice for an ever-growing horticulture industry that is worth approximately $170 million in Canada.
But today we also know that peatland ecosystems perform many vital functions: they are the world’s carbon stores, the only home for many species of bird and plant, they act like giant sponges to regulate water flow, and they are paleo-archives of local natural history.
These important ecological values, and the fact that peatlands take thousands of years to grow, imply a need to find alternatives to peat moss as a growing medium or at least implement and enforce sustainable harvesting practices to minimize industrial footprints.
The nature of peat
Canada has about 25 per cent of the world’s peatlands and they cover about 12 per cent of the nation’s surface area. Peatlands are very delicate, slow-growing ecosystems, composed of semi-decayed biomass that has accumulated for many thousands of years. The Ramsar Convention on Wetlands, an intergovernmental treaty promoting the wise use of wetlands, has identified peatlands as of special importance.
Sphagnum mosses dominate peatland vegetation; they have an impressive water-holding capacity and maintain the waterlogged conditions in a bog. Sphagnum also monopolizes nutrients and releases humic acid — a substance that binds heavy metals and helps nutrient uptake. So it is easy to see why the same characteristics that give Sphagnum their competitive edge in a bog also make them irresistible to gardeners.
But what happens to the delicate balance in a bog when peat is harvested? One of the first things to go is the water buffer; water that would normally be stored in the bog runs much more quickly to waterways, sometimes flooding areas. Paleo-archives would be lost forever unless peat cores were taken prior to harvesting. And once taken away, the same volume of peat can’t be grown back in a human lifetime; decomposition and compaction processes in a bog ensure that peat only accumulates at a rate up to one millimetre per year.
Golden tamaracks and birch trees as seen in the fall in Mer Bleue, a protected bog located about 10 kilometres east of Ottawa.
Even though Ramsar has classified peatlands as important, this doesn't automatically protect them. In Canada, the provinces regulate peatland use but there is no uniform national policy on whether and how they should be harvested. Two groups on the opposite ends of the peatland debate spectrum — the International Peat Society, of which peat harvesters are members, and the International Mire Conservation Group — have worked together for the past eight years to change that, and have developed guidelines for a wise-use approach. Gerry Hood, the president of the Canadian Sphagnum Peat Moss Association — a group comprised of peat moss producers and marketers — says the peat community has been trying to get it adopted as policy in Ramsar countries. “We're hoping that in November when the next Ramsar convention is held, this will be part of their implementation plan,” he says.
Under the recommendations of the approach, most harvested peatlands are between 10 and 20 feet deep. The top two-thirds may be harvested but about a metre or more of peat is left to provide a surface for restoration. “Then we go to a virgin bog and chop up about 10 centimetres of live peat and spread it across the harvested bog,” says Hood. “For every acre of peat we remove from a natural bog, we can cover 10 acres of a harvested bog.” Once the Sphagnum spores are in place, the land is covered in straw. Then the ditches made during harvest are blocked to raise the water table. “In a year or two, we start to see the natural bog plants, and in three years, a great carpet of Sphagnum, and that bog will probably never be harvested again,” says Hood.
Agricultural development has been the single greatest cause of wetland loss in Canada since settlement, claiming about 15 per cent, and peat harvesting has had the smallest impact of about 0.02 per cent, according to a 2001 issues paper published by the North American Wetlands Conservation Council in partnership with Environment Canada’s Canadian Wildlife Service and the Canadian Sphagnum Peat Moss Association. “If you put all of Canada's peatlands into the United States, they would cover the size of Washington, Nevada, Oregon and California,” says Hood. “And the size of what we’re harvesting is smaller than the city of Portland, Oregon.”
At present, there doesn't seem to be an alternative accepted by peat producers and horticulturalists; a composted bark and peat blend is nearest they have come to accepting a replacement. Hood cites drainage, amount of airspace for roots, expense, and quality control as the main problems with alternatives such as compost and coir. And volume. ”There is more than 40 million cubic metres of peat used annually by the horticulture industry worldwide; no other product can supply even a small percentage of that,“ he says.
”The problem with compost is that it compacts, and you can't get consistent quality control because municipal site compost may have chemicals from other people's pesticide use, or hormones from farmers' cows.“
Coir, or coconut fibre husk, is a product imported via ocean vessels from Sri Lanka, India, the Philippines and Mexico, and it has many of the same characteristics as peat. ”But is expensive to buy and the supply is only about 10 per cent of what is required for the horticultural industry,“ says Hood. ”It is also cleaned with brackish water and so may have a high salt content. It would be the closest alternative to peat, but there are problems — shipping, quality control and cost.“
Tamaracks atop the bog mat, a sea of saturated peat, at Mer Bleue.
A team of Canadian ecologists is experimenting with live Sphagnum and their preliminary results promise to take some of the pressure off peat bogs. “Peat may not be a renewable resource but it can be sustainable,” says Stéphanie Boudreau of the Peatland Ecology Research Group in Quebec. “Sphagnum mosses can be grown as a fibre to add to peat substrate and so may be considered renewable.”
The group, led by Dr. Line Rochefort of Laval University, is currently working with members of the peat industry — including the Sphagnum Peat Moss Association — and the Canadian government to develop methods for peatland restoration using Sphagnum cultivation. They hope the cultivated Sphagnum could improve lower-quality peat and be reintroduced into harvested peatlands for restoration purposes. “If it works well, we are expecting that 30 centimetres of Sphagnum mosses could be grown in 10 to 15 years,” says Boudreau. “It’s not a viable alternative to harvesting bogs, but it could avoid the opening of other peatlands.”
The group is also doing greenhouse trials to reduce the amount of peat needed in a growing mix. The research is still underway, but “if they can reduce the amount of peat needed by 30 per cent by using composted bark, and again by 20 per cent by using recyclable Sphagnum mosses, taken from a donor bog and regrown in a two year period, then we could potentially reduce the use of peat by 50 per cent,” says Hood.
The Alfred Bog
Although Hood says that most peatland functions come back after restoration — the flood buffer, wildlife habitat, and carbon and water storage — one cannot ever restore the natural history archive of a local bog. “That’s one reason why you would not harvest the last bog in an area,” he says.
Boudreau agrees, saying the nation’s peat ecosystems “are regionally under pressure,” especially in the southeast of Canada where only a few natural peatlands remain. “It’s important that these ecosystems be allowed to exist from a local biodiversity perspective,” she says. And in southern Ontario, there’s no better example of this type of peatland than the Alfred Bog.
Located about 75 kilometres east of Ottawa, the Alfred Bog is the biggest and rarest of its kind south of the Canadian Shield. “It's a little piece of boreal habitat hundreds of miles south from anything like it,” says Frank Pope,chair of the Ottawa Field Naturalists Club’s Alfred Bog Committee, one of the groups that helped save the bog from peat extraction.
Each year the Alfred Bog moderates flooding in the South Nation River and releases water during the summer, which keeps the local water table high. It also binds toxins such as heavy metals from nearby industries and cleans the water before it enters the wells of local homeowners.
Native orchids, such as this grass-pink in Alfred Bog, thrive in acidic soils that are rich in peat.
The Alfred Bog is also home to many provincially and regionally rare species, some of which only survive in boglike settings. It's habitat for rhodora, a Canadian species of pinkish-purple rhododendron found nowhere else in Ontario, the white-fringed orchid, the rare spotted turtle, and many uncommon butterflies, including the extremely rare bog elfin, which has been found in very few places in eastern Canada. There is also a disjunct moose population in the bog, the most southern herd in North America. In the winter these moose feed in the deciduous forest and bog areas with tall shrubs; in the summer they branch out to feed in woodlots and ditches.
This domed peat bog has been evolving for 10,000 years and is now about 10,000 acres large. But that's only a third of its original size; over the past two centuries, much of it has been drained and burned for agriculture. More recently, it has been mined for peat on privately owned sections. In 1999, about half of the bog was in private hands.
The nature of the bog and its perilous future attracted the attention of the Nature Conservancy of Canada, a charity that preserves ecologically significant areas through outright purchase. For about two decades the NCC had been buying parcels of the bog here and there, but the conservation group hit a big break when it successfully negotiated ownership of the largest remaining private landholding — the centre of the bog and the most pristine part. The governments of Canada and Ontario each donated one-third of the money, and the NCC raised the remaining money through public donations. It now owns about eighty percent of the bog after purchasing it for a total of roughly $3 million.
But while peat remains the gold standard for greenhouses growing en masse, individual gardeners still have choices if they wish to leave peatlands in peace. You can maintain a personal compost heap and control its quality yourself, amend your soil with coir to facilitate more airspace and better drainage, or choose plants that thrive in the soil conditions you already have. A little extra effort is a small price to pay for the small-scale gardener with an environmental conscience.
Since bog soil tends to be more nitrogen-poor, carnivorous plants like this pitcher plant in Alfred Bog get their nitrogen from insects. The plant lures them into its tubular leaves and devours them with the help of digestive enzymes.
Wild About Gardening visitor Anne Sharp suggests using ground up, composted leaves as an alternative additive for container plantings, garden beds and compost piles.
Do this by gathering leaves and shredding them with a lawn mower, chipper/shredder or even a string trimmer (such as a whipper snipper) if the leaves are in a garbage bin. Bag them and store over the winter in a dry location for use in the spring. Avoid leaves from trees that are subject to leaf diseases.
Another alternative, coconut husk fibre, is quickly growing in popularity and availability. Ask your nursery or visit Planters’ Pride at www.planterspride.ca.