Peat moss shouldn’t be used in your organic/ecological garden because peat is not a sustainable resource and harvesting it contributes to climate change.
By Wendy Priesnitz
For many years, bales of peat moss were on my list of Spring gardening supplies. But I have discovered that peat is not a sustainable resource and that, as our knowledge of the dangers of climate change increase, gardeners around the world are moving away from using it. Here’s why.
Peat can be derived from different materials, but the bulk of it sold commercially in North America is from Canadian sphagnum moss. Peat is simply the decomposed product of the moss and more logically could be called “moss peat.” Although peat was dried and burned in some countries as a source of fuel for centuries, only since the 1940s has it been used on any scale for horticulture. It is typically sold screened and dried, in either bags or compressed bales, to be mixed in with your garden soil. It is often sterilized, for starting cuttings or seeds. Most commercial potting soils contain peat. It is useful for growing plants requiring an acidic (lower pH) environment. It also has good water and air holding qualities, although it is virtually devoid of nutrients.
Mining the Resource
Peat moss develops in a peat bog or “peatland,” which is a wetland on which decomposing moss has accumulated to a depth of at least 16 inches. Peat accumulation is around one millimeter (1/25th of an inch) per year. Approximately three percent of the earth’s surface is covered with peat bogs that have been developing for thousands of years. Finland has the largest expanse in the world, followed by Canada, Ireland, and Sweden.
The peat moss is commercially harvested from these bogs. The process involves digging a network of drainage ditches and settling basins so that the water drains away from the wetland and the bog begins to dry out and die. Once that happens, all surface vegetation is removed and the deposit is ready for peat production. The surface peat layer is dried by the sun and wind. The topmost layer is typically harrowed to enhance the drying process. After a few days, the dry peat layer is collected using a large vacuum harvester or other equipment, then transported to a processing facility for screening and packaging.
Peat bogs are seen by some scientists to be as important and fragile as rainforests. And that’s where the concern lies about the use of peat moss by gardeners. Peat companies are destroying these fragile, unique, and valuable bog ecosystems by removing the peat.
Destroying Peat Bogs
Wetland loss due to agriculture and development is a major biodiversity problem worldwide, threatening wildlife habitat. But peat bogs have their own special ecosystem issues and threats. They are home to rare wildlife, including untold numbers of highly specialized native plants, many of which may be endangered and found only in the peat bog.
Peat bogs are also a rich source of social and environmental information. The highly acidic conditions in peat bogs result in very slow decay. That means they provide a unique and irreplaceable record of climate, vegetation and human activity dating back 10,000 years. There have been some remarkable finds in peat bogs, including people buried thousands of years ago and wooden artifacts that have not survived elsewhere.
In addition, peat bogs, like other wetlands, are Nature’s water purifiers. They contribute to healthy watersheds and, in some areas, to safe drinking water for nearby populations, filtering an estimated ten percent of global freshwater resources. They also provide effective flood prevention. Destroying a bog destroys these benefits. Furthermore, the ditches required to extract the peat lower the water table and often negatively impact local waterways.
Perhaps the biggest contribution of peat bogs to a healthy environment is as “global coolers,” helping to fight climate change. As the mosses grow, they absorb carbon dioxide, which is locked up within the plant structure as the plants turn to peat. Scientists think these bogs contain more carbon than all the world’s tropical rainforests. But when the bogs are drained for peat extraction or otherwise disturbed, the peat starts to decompose. That results in the carbon dioxide being released back into the atmosphere, where it acts as a potent greenhouse gas.
In the U.K., the National Trust estimates that country’s bogs store carbon equivalent to about 20 years’ worth of national industrial emissions. Fearful that two centuries of damage is causing the bogs to dry out, releasing the carbon into the atmosphere, the Trust is urging the government to conserve and protect the country’s declining number of peat bogs as a way of curbing climate change.
Peat Moss is Not Renewable
Approximately 99 percent of Canada’s total national production comes from the combined operations of the 20 corporate groups that form the Canadian Sphagnum Peat Moss Association (CSPMA.) Collectively, they mine about .02 percent of the country’s 270 million acres of peat bogs, the majority of which are in southern and southeastern Quebec and eastern and northeastern New Brunswick. In spite of that small footprint, Canada is the leading world peat producer and the market is steadily growing in size, especially in the U.S.
At pains to defend the sustainability of the resource, the CSPMA quotes an issue paper entitled Canadian Peat Harvesting and the Environment published by the North American Wetlands Conservation Council that claimed peat in Canada is growing more than 70 times as fast as it is being harvested.
Canadian government regulations require that bogs be returned to functioning wetlands once extraction is complete. Before beginning, a producer must take all necessary steps to reduce impact on the environment, record the flora and fauna present on the bog for restoration purposes, and cooperate with local environmental groups. During harvest, the producer must minimize the acreage being harvested, leave a buffer zone around the bog, leave a layer of peat when harvesting stops and design drainage ditches so the water table can be restored.
Whether peat bog restoration is, in fact, possible, is a matter of some debate. Some wetland experts say that since a peat bog takes thousands of years to evolve, once destroyed it can never be fully reclaimed. It is also noted that when the peat is removed, the underlying soil is often too rich in nutrients for habitat restoration.
However, the CSPMA has been experimenting with restoring harvested bogs. By 2001, ten peat producers had initiated large scale restoration projects using technology developed by Laval University’s Peat Ecology Research Group and published in the CSPMA’s Peatland Restoration Guide. At the same time, the Wetlands Conservation Council published a paper on the Canadian peat industry, which described the choices for reclamation of harvested bogs as returning it to a functioning peat bog or, where that is “impractical or impossible,” farming the land, planting trees or returning it to a functioning wetland or wildlife habitat.
In the U.K., in 2013, the Yorkshire Peat Partnership announced that it had restored more than a quarter of Yorkshire’s peatlands in a multi-million pound project that aims to preserve vital habitats and help cut global warming.
The North American Wetlands Conservation Council estimates that harvested peatlands can be restored to “ecologically balanced systems” – if not peat bogs – within five to twenty years after peat harvesting.
Environmental researchers rightly note that even reclaiming the land into a wetland alters the ecology of an area, puts some species at risk and can never bring back the historic features of the bog. Not only is recolonization by the native flora and fauna probably not going to happen, the complex water tables in adjacent undrained areas are also put under threat.
Some wetlands scientists point out that a managed bog bears little resemblance to a natural one. Like tree farms, these peatlands tend toward monoculture, lacking the biodiversity of an un-harvested bog.
Alternatives to Peat Moss
There are many alternatives to peat moss, some of which are cheaper (often free) and may work better. In fact, the use of peat in horticulture is almost completely unnecessary.
Peat is often used as a soil improver but other materials perform better, since peat has little or no nutrient value. Wood-waste, spent mushroom compost, composted garden or green kitchen waste, leaf mold or well-rotted farmyard manure are more effective and less expensive soil enrichers.
Peat is a poor mulch, tending to dry out and blow away. There are many other more suitable materials available. You could try chipped bark, shredded tree prunings, straw, cocoa shells (a byproduct of the chocolate industry,) spent mushroom compost, composted garden waste or leaf mold.
As a growing medium, commercial nurseries are finding that alternatives like leaf mold compost or coir work well and are even better than peat in some circumstances.
Coir (pronounced “koi’er”) is the fibrous outer husk of a coconut that is used to make rope and mats. During the fiber stripping process, the pulp surrounding the coir fibers is removed as a waste material. And it is now being satisfactorily used as a replacement for peat moss. Unfortunately, coir must be transported from places like Sri Lanka and the Philippines where it is produced, so it’s better to look for things that are more local.
A company in Washington State has developed another peat substitute originating in the dairy industry. It takes dairy fiber from an anaerobic digester at a dairy biogas plant and converts it into a high value peat moss substitute designed for the horticulture industry.
The jury is still out on the question of whether or not sphagnum peat moss can be considered a renewable resource at the level at which it is harvested in Canada. However, with the wide range of alternatives available, I don’t see the need to damage fragile ecosystems that provide natural water filtration, house rare plants and wildlife, and help mitigate global warming.