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Sphagnum peatland

sphagnum moss

Sphagnum - not the easiest name to spell or say. It probably doesn't make it any more enticing if I say that it is closely associated with bogs. But Sphagnum provides us with really valuable services.

Background

Sphagnum anatomy

Sphagnum plants are mosses- small plants that have no veins.  Hence mosses are soft to the touch. Mosses have no flowers, and reproduce via spores instead of seeds.

structure of a sphagnum plant
structure of a sphagnum plant

Sphagnum distribution

The sphagnum mosses (a group of about 400 different species) covers more of the world's land surface (3%) than any other single genus, making it an extremely important element in world biota. Sphagnum species are found on every continent except Antarctica.

Peatlands-Global-Distribution
Peatlands-Global-Distribution

Sphagnum ecology

Sphagnum are plants of wetlands -variously called bogs, fens, mires, marshes, swamps etc which occur all over the globe. They grow in carpets of green and red, often dominated by one particular species. They can survive in low nutrient environments, although this varies by species. Because the surrounding water is not moving, conditions below the surface are effectively anaerobic. As the mosses grow, the accumulated amount of dead moss sinks but does not decay as the cell walls of the plants are rich in phenolic compounds. This results in an accumulation of decayed organic matter called peat. Many bogs contain peat metres deep which has accumulated over millenia.

Sphagnum plants are home to a wide variety of microscopic organisms including desmids, diatoms, algae, cyanobacteria, amoebae, rhizopods, flagellates, ciliates, rotifers (wheel organisms), worms, nematodes (round worms), flat worms and heliozoans (sun animals). These in turn, are preyed upon by pond dwellers such as skaters, dragonflies, damselflies, caddis flies, mosquitoes, midges, bloodworms, water boatmen, water beetles, water lice, and frogs.


Services

In some countries, peat has been harvested, cut into squares and allowed to dry out so it can be used for fuel. Peat moss is harvested commercially as a soil conditioner, a terrarium substrate, and as a growing medium for orchids, and other epiphytic plants. Sphagnum has also been used as a raw material e.g. in bandages and and for fibre.

Sphagnum plants can hold more than 20 times their own weight in water due to their cellular structure. As well as photosynthetic cells, they contain specialised water holding cells with thickened walls. This allows sphagnum to store water from rainfall and snowmelt, then release the water slowly thus keeping the bog wet. Without this happening, the wetland area would be much more susceptible to desiccation and erosion.

Sphagnum cells can absorb impurities in water, hence peatlands are natural water purifiers.

Sphagnum mosses provide suitable conditions for a wide variety of other species and they are keystone members of their communities.

Peat areas often contain human artifacts from prehistoric times e.g. an estimated 20,500 archaeological sites are preserved under or within peat in the UK, so they are important in that they preserve human history.


Summary of services provided for us

ecosystem services derived from sphagnum peatland
ecosystem services derived from sphagnum peatland
  • Fibre for horticulture
  • Fuel
  • Soil conditioner
  • Nutrient recycling
  • Erosion protection
  • Water purification
  • Habitat for biodiversity
  • Medicinal products
  • Recreation
  • Education
  • Spiritual inspiration

Threats to the services?

Intact peat wetlands peatlands are the largest natural terrestrial carbon store. Worldwide, the remaining area of near natural peatland (>3 million km2) contains more than 600 gigatonnes of carbon, representing 44% of all soil carbon and exceeds the carbon stored in all other vegetation types, including the world’s forests.1

Wetlands have been cleared for agricultural purposes. When peat isn’t covered by water, it could be exposed to enough oxygen to fuel aerobic microbes. The oxygen allows the newly dominant microbes to grow extremely fast, enjoying the feast of carbon-rich food, and releasing carbon dioxide into the atmosphere. Damaged peatlands contribute about 10% of greenhouse gas emissions from the land use sector. CO2 emissions from drained peatlands are estimated at 1.3 gigatonnes of CO2 annually. This is equivalent to 5.6% of global anthropogenic CO2 emissions.

Peatland restoration would prevent the release of 394 million tonnes of carbon dioxide equivalent per year (MtCO2e/year). That’s comparable to the emissions from 84 million passenger vehicles per year.2

Draining peatlands also decreases biodiversity thus making ecosystems more fragile.1

IUCN threat to species scale
IUCN threat to species scale

Extracting sphagnum peat for horticultural purposes has resulted in a global industry which has not always been well-regulated and sustainably managed. In the UK, where peat harvesting has been practiced for centuries, just 20% of UK peatlands remain in a natural state.

Of 5 Sphagnum spp. recorded in the IUCN Redlist, only 1 species is considered to be surviving successfully (as 2017). 1 species is considered Critically endangered, 2 are considered Endangered and 1 Vulnerable.

What can we do to retain these services?

Peatlands have not been studied thoroughly in the past. It was not until 2017 for example, that the extent of peatlands in the Congo basin under the forests was scientifically explored. It is impossible to protect these areas with insufficient knowledge of their distribution and functioning. A number of major initiatives have been launched to overcome these shortcomings, e.g. The Global Peatland Initiative was started in 2013 at a UN meeting with the mission to promote understanding of peatlands and protect them from exploitation and damage.

Peat harvesting is being legally banned in England after it was found that that a voluntary scheme was not working.3

Dig deeper

 

  1. Peatlands and climate change [] []
  2. https://nature4climate.org/science/n4c-pathways/wetlands/peatland-restoration/ []
  3. https://www.theguardian.com/environment/2022/aug/27/englands-gardeners-to-be-banned-from-using-peat-based-compost []
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