| In the past, the average forester in South Africa did not seem overly grateful if he was blessed with many wetlands on his property, especially if he was responsible for harvesting or silvicultural operations – but times have changed.
A peatland bog in a KZN Midlands plantation.
With the introduction of EIA’s, wetland delineation, audits and assessments, many foresters have discovered and embraced the fascinating world of wetlands. And those that are truly fortunate are the ones that have precious peat on their properties.
Identifying peat on your property
Peat is partly decomposed plant material in a wetland that has accumulated in situ as a result of being waterlogged. Often, the easiest way to assess if peat is present on a timber farm is to question the manager about ground-fires in wetland areas during the dry months. If ground-fires are present in wetland zones then the probability that you have (or had) peat is quite good.
An easy way to determine whether you have peat is to visit the potential peat site, take a handful of the soil/material and squeeze. If the water that oozes from your hand is clear and after dropping the soil/material it leaves your hand fairly clean, it is almost certain to be peat. With clay or organic sand, muddy water will be released from the squeezed material and the clay or soil will cling to your hand. If the peat is too dry to squeeze it is possible that your commercial timber plantation trees are too close to the wetland, which has resulted in the peatland drying out due to the lowering of the water table.
Another test is to ask your companion at the site to jump up and down next to you – if you are standing on peat, your friend’s jumping activities will result in a hollow sound and you will experience the sensation of standing on a large sponge.
Peat and its formation requirements
Peat requires specific conditions to form:
Permanent water (from high rainfall or a raised water table), or both;
low energy systems (fairly flattish topography) with poor drainage;
annual vegetation growth where the growth rate is greater than the decomposition rate of the vegetation.
Peat can be identified as a dark soil that is formed in acidic, anaerobic conditions and consists mainly of partially decomposed, loosely compacted organic matter with a carbon content in excess of 50%.
Local climatic conditions and geology has a great influence on peat formation – high rainfall and nutrient levels result in enhanced vegetation growth and thus improved peat production. Due to timber production in South Africa being restricted to high rainfall areas, it is also expected that a large percentage of the local peatlands are present on commercial timber plantation land.
Peat is formed when plants die and sink into wetlands, these plants are covered by other dead plant matter and animals, trees, pollen or fruit that may fall in or be blown into the peatland. When the plants die, the roots and stems that are below water level, form channels, and these fill with organic matter. Peat forms where this organic matter sinks to the anaerobic or sulphide zones and the decomposition is arrested. In Europe, the dumped bodies of people that lived hundreds of years ago were found to be preserved in peatlands. In South Africa fossils of sable, hippo and blesbok have been found in the Gerhard Minnebron peatland near Potchefstroom.
A valley bottom peatland in the Goukou River Catchment –
Western Cape. Erosion and loss of peat extend hundreds of metres.
Importance of peatlands and mires
Globally, mires and peatlands are the most widespread wetland type in the world, covering an estimated 3% of the terrestrial and freshwater land surface. They store approximately one third of the world’s soil carbon and may contain as much as 10% of the global freshwater resources. However, less that 1% of the world’s peatlands are found in Southern Africa and South America.
In South Africa peatlands are a rare and unique wetland type and occur in inter-river valleys on the Highveld and escarpment, and inter-dune and inter-river valleys along the coast. Approximately 15% of the South African wetlands along the KZN coastal plain contain peat.
Peat accumulates over thousands of years to thicknesses of 0.5 to 10m. Although large amounts of organic matter accumulate in wetlands annually, only a small amount of this becomes peat – the remainder is completely decomposed or used as nutrients by other plants.
The rate of peat accumulation depends on local climatic condition and vegetation growth. In areas with high rainfall and vegetation growth (such as Northern KZN), peat accumulates at about 1,06 mm per year. In the colder Highveld area, where conditions are not as favourable, peat accumulation can be as little as 0,5mm per annum.
In the northern hemisphere, most peatlands consist mainly of sphagnum moss. It is also called peat moss and foresters using bags of imported sphagnum peat for remediation of oil spills will recognise it as one of the locally available ‘spill or eco-sorb’ materials. This peat moss should not be confused with our highly decomposed peat in Southern Africa.
The plants in wetlands are adapted to thrive in anaerobic, acidic conditions and also contribute to the acidification of the water. We do not know of plants endemic to peatlands in South Africa but there are several that are characteristic of this habitat type.
The dominant peat-forming plants in South African peatlands are:
Papyrus/reed swamps – Cyperus papyrus and Phragmites australis.
Swamp forests – Ficus trichopoda and Syzigium cordatum.
Sedge/grass swamps – Fimbristylis longiculmis, Leersia hexandra and Schoenoplectus corymbosus.
Numerous other common peatland species are known but can not all be listed here. Most of the South African peat forming plants have a high volume and a low density – this encourages peat formation.
The thickest peatland in South Africa is the Vankersvelvlei Fen near Sedgefield with more than 11.5 m of peat (currently surrounded by commercial plantations). The Mfabeni Swamp Fen at St Lucia in KZN (previously within State owned plantations) is about 10m thick and around 45 000 years old – one of the oldest known active accumulating peat systems in the world. The thickest recorded peatland in the world is in France, the Grande Pile in Haute Saore and it reaches down to 30m.
Peat related definitions
There are several types of peatlands, classified according to vegetation type and source of water – some of these are:
A Peatland – is a landscape area with a layer of peat at the surface, but not necessarily accumulating peat. Peatlands are often defined as having a layer of peat in excess of 30cm thickness.
A Mire – is a peatland, which supports vegetation that actively accumulates peat.
A Bog – is a peatland that is fed from rain water only, these are normally higher than their surroundings (mounds) also known as ombrogeous mires. In these ‘high’ mires the peatland has no contact with groundwater and can be described as perched wetlands – normally nutrient poor.
A Fen – is a peatland that is fed from both rainwater and groundwater, as well as surface runoff, often in landscape depressions and also known as geogenous mires. These ‘low’ mires have a bowed water table that arches up into the peatland adding mineral elements from rocks underground.
Horizontal mires – also known as terrestrialisation, are mires where peat develops in ‘open’ water and can be subdivided into schwingmoor mires (floating mats of Papyrus islands) and immersion mires where peat accumulates underwater at the bottom (Phragmites stands). Water movement is largely vertical, (e.g. fluctuations of water level).
Sloping mires – also known as paludification, are mires where peat accumulates directly over formerly dry, paludifying mineral soil. Water movement is mainly horizontal and vegetation growth and peat accumulation actively cause a rise of the water table in the mire and often also in the catchment area.
Many uses for peat
PEAT is mined in SA mainly for the growing of mushrooms and the nursery industry. Globally it is used for numerous different industries (soil enrichment, mulch, nutrition briquettes, peat pots, growing boards, depolluting agents, support systems for micro agents, etc.)
Peat offers an ideal substrate for horticultural and silvicultural plant production and forms the basis of a business that is worth around $US 300 million annually. In 1999, almost 40 million m3 peat were used in horticulture globally.
Belanger, A., Potvin, D., Cloutier, R., Caron, M. and Theriault, G. 1998. Peat, a resource of the future. CQVB.
Grundling, P.L., and Dada, R. 1999. Peatlands of South Africa. Share-Net.
Grundling, P.L. 1997. Save the peatlands of South Africa. SA Wetlands No. 8.
Schumann, M. and Joosten, H. 2006. A global peatland restoration manual – 1st Draft. Greifswald.
Additional peat related questions or the reporting of peat on your property can be directed to Piet-Louis Grundling at firstname.lastname@example.org or André Marais at email@example.com Readers with a desire to learn more about peatlands can also register with the IMCG (International Mire Conservation Group) on their website www.imcg.net
About the authors
PIET-LOUIS GRUNDLING started off as a geologist at the Council for Geoscience in Pretoria. The country was busy evaluating all energy resources and peat was seen as a potential energy resource. It was during those times (middle 90s) that Piet and colleagues realised that peat deposits were actually active, sensitive ecosystems and in need of conservation management. The Council for Geoscience then embarked on a peatland survey for conservation purposes.
Piet joined the Working for Wetlands Programme in 2000 and was then appointed as Technical Advisor when it became a fully fledged programme under the South African National Biodiversity Institute in 2003. In 2006 he decided to pursue a PhD in peatland hydrology at the University of Waterloo, Canada, and plans to be back in South Africa in time for the 2010 World Cup. Readers can contact Piet with any enquiries concerning wetlands at firstname.lastname@example.org
ANDRÉ MARAIS has many years of experience working first as a forester and later doing research on Marion Island and in the Kalahari. In 1996 he returned to forestry as environmental manager for a large private company and completed a Masters in Environmental Management at the University of the Free State. In 2002 Andre started his own consultancy, Biological Diversity Services (BioDivS for short), focusing on wetlands (delineation, functionality assessments and rehabilitation), faunal surveys and baseline diversity studies.
Issue: Sept/Oct 2006