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Ask Natural Life:
Does Peat Moss Have a Place in the Ecological Garden?
by Wendy Priesnitz
Q:
For many years, bales of peat moss have been on my list of garden
supplies each spring and I’ve never given a thought to where peat
moss came from. But earlier, this year, a friend suggested to me
that peat is not a sustainable resource and that gardeners around
the world are moving away from using it. So now I’m beginning to
wonder: Does peat moss have a place in the ecological garden? And if
not, what are the concerns?
A: For many years, there has been a debate
between peat producers and conservationists as to the long term
effects of the use of peat moss as a gardening material. That
argument is getting louder as our knowledge of the dangers of global
warming increase. And it now looks like peat moss has no place
in your garden.
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 special type of 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 (or “mined”
– depending on which side of the debate you’re on) 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.
Important Ecosystems
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.
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.
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. In addition, 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 and
the carbon dioxide is 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.
Hardly 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.
Restoration
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 Ecological 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 has 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 ecolonization 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
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.
Wendy Priesnitz is the
co-founder and Editor of Natural Life Magazine and a journalist with
over 40 years of experience. She has also authored
13
books.
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