Improved water management

Improved water management is a fundamental step to support the sustainable management of peatlands. Water is probably the most fundamental component of a peatland, with most peatlands being approximately 90% water. The extent, nature and depth of the peat are frequently a function of water extent and depth. Drainage thus has one of the most important and long-lasting impacts on peatlands. Drainage of temperate and tropical peatlands which lowers the water table by 1m, leads to a CO₂ emission of between 30 and 100 tonnes of CO₂/ha/year respectively (Wosten 2002, 2006). Drainage also increases vulnerability to fire; one of the most significant courses of peat degradation and GHG emissions. Fire does not normally occur continuously, but when burning does take place it may lead to the emission of up to 4000 tonnes of CO₂/ha in the tropics and 2000 tonnes of CO₂/ha in temperate regions. Peatland fires are becoming more frequent in some regions, e.g. Southeast Asia. This is generally a result of accelerated rates of land clearance as well as the large-scale drainage of peatlands. More than 2 million ha of Southeast Asia’s peatlands were burnt in the past 10 years. Fires were persistent, with many burning for between 1-3 months, leading to large CO₂ emissions. Indonesia is now considered to have the 3^rd highest CO₂ emissions globally, primarily as a result of persistent peatland fires (Silvius et al. 2006).

Drainage has greatly improved the ability to farm peatlands, but it leads to loss and subsidence of peat soils. A balance between drainage and conservation is needed in order to protect peatland soils. Drainage has greatly improved the ability to farm peatlands. However, it can lead to significant subsidence of peat soils (depending on the drainage period and depth and temperature), as well as large amounts of CO₂ being lost to the atmosphere. Excessive drainage of peatlands can also cause the shrinkage or loss of wetland area, as well as the reduction of water levels in adjacent wetlands and mineral soils.

As peat subsides, the depth of the fertile topsoil also decreases and risk of flooding increases. This means that further drainage, cultivation and pasture renewal are needed to maintain productivity, therefore increasing the cost to farmers. When managed properly, peat is a valuable and highly productive resource.

To be able to farm on peat soils over the long-term, farmers must find a balance between keeping the water table low enough for production, but high enough to minimise peat losses and CO₂ emissions.

It is possible to use peatlands for agriculture without draining by using species such as sago palm, or yams in the tropics or maintaining natural peatland sedges for hay production in the temperate regions. These plants require little or no drainage.

Appropriate management is critical to maintain water pollution sink, flood control and water supply functions of peatlands. Although it is not ecologically appropriate for peatlands to be deliberately used for water purification in heavily-polluted areas, in some regions they may be found downstream of polluting operations. As a result, they play an important role in the removal of pollutants from streams.

Drainage and gully erosion are major causes of peatland degradation and associated losses of carbon storage, biodiversity and ecosystem services around the world. Gully erosion occurs when vegetation cover is lost, for example due to inappropriate burning or overgrazing. The effects of gullying and drainage are similar, though the problems associated with gullying tend to be more severe. Drainage of lowland peats in much of the western world took place mainly in the 19th century to improve land for agriculture by lowering the water table.

Blocking drains and gullies in peatlands can stem carbon losses, and sequester and store carbon as channels re-vegetate. Blocking drains and gullies in peatlands can reduce subsidence and fires and hence stem carbon losses by sequestering and storing carbon as degraded peat and channels re-vegetate (Worrall et al. 2003). Ditches and gullies are blocked to raise the water table to its former level and to re-wet the peat. If this does not lead to natural re-vegetation, reseeding or the planting of wetland species can be undertaken (Price 1997, Evans et al. 2005).

Modification of agricultural practices

Conversion of natural peatlands for agriculture is one of the main root causes of the loss of peatland biodiversity and functions. In terms of area of peatland affected, the most extensive impacts on natural peatlands have come from the drainage and utilisation of peatlands for agricultural purposes. Agricultural use generally involves the drainage of peat by 30cm-1.5m, and the replacement of the natural vegetation with crops such as potatoes, cabbage, vegetables, oil palm, maize, buckwheat or pineapples. The selection of species depends on the climatic and ecological situation and water levels (degree of drainage) as well as the macro-economic and agriculture commodity situation of the time.

Agricultural activities that involve peatland drainage will lead to the loss of peatlands and their associated functions, and cannot be classified as sustainable. Any agricultural practice that involves drainage of peatland will lead to loss of the peat layer through oxidation, compaction and erosion. In addition the natural processes which lead to peat formation stop so that no further growth of the peat layer takes place. As a result, drained peatlands will continually subside and eventually (providing drainage continues) the entire peat layer will be lost, exposing the underlying mineral soil.

Agricultural drainage in peatland areas is frequently badly designed and leads to peat degradation as well as reduced agricultural yields. In many places the agricultural drainage system may be too deep and have inadequate water management systems. This can lead to over-drainage of the peatlands. In Malaysia for example, most of the drains developed in peatland areas were based on the designs of drains in mineral soils. As a result they lowered the water levels too much and led to rapid subsidence.

Agricultural production techniques that maintain or increase peatland carbon stores need to be developed and promoted. Agricultural or agro-forestry activities that do not involve the drainage of peatlands, that maintain natural water levels and that can maintain or increase the natural carbon stores should be developed or promoted, over and above those techniques that drain or lead to the loss of carbon storage. Agriculture or agroforestry systems what can maintain or enhance Peatland carbon storage include sphagnum farming, cultivation of reeds, alder, jelutong (chewing gum tree), and sago as well as hay making.

Modification of livestock management on peatlands

In many parts of the world, grazing-induced erosion is a major cause of peatland degradation. Erosion induced by overgrazing is a major cause of peatland degradation in many parts of the world (Evans et al. 2005), and in some areas this is expanding rapidly. Peatlands generally cannot sustain high stocking densities.

Grazing can have a major impact on peatland vegetation dynamics which can affect carbon storage as well as biodiversity. A number of studies have examined the effect of grazing on peatland vegetation dynamics. Grazing has a profound effect on species composition (favouring grazing-tolerant species such as tussock grasses), and depending on its intensity, can reduce competitive vigour and potentially kill plants.

Reduction and removal of grazing from peatlands can stop degradation and lead to recovery of peatlands, but other measures may be needed to restore peatland functions and vegetation. The effect of reducing and removing grazing from peatland has been investigated in a number of exclosure studies. Rapid recovery only occurs in the total absence of grazing (Marrs and Welch 1991), but for some peatland habitats, a combination of herbivores using the land (including grazers and browsers) at different intensities and times of year, has been found to optimise biodiversity.

Some low intensity management of livestock may locally enhance biodiversity. Grazing and the cutting of hay in shallowly-drained meadows reduce the competition between grasses and other plants and also create possibilities for pioneer species to colonise the area. Lightly grazed areas also may have a mosaic of microhabitats with differential relief and nutrient status. As a result, peatland grazing meadows that have been managed for long periods in a traditional low intensity manner for hay cutting or light grazing may support a higher diversity of plants (including many rare or restricted species).

Modification of forestry practices

Management or rehabilitation of natural forest on peatlands is an important management strategy. Peatlands in many regions of the world (e.g. the Boreal zone, Africa, South-east Asia and North and South America), are naturally forested. They therefore need to be managed.

Clear felling, over extraction and high impact logging techniques in forested peatlands are a major cause of peatland degradation, leading to a loss of biodiversity and reduction in carbon storage. Clear felling and over extraction of trees in forested peatlands may lead to changes in the peatland water balance, as well as degradation and the loss of biodiversity. In tropical peat swamp forests, large-scale harvesting leads to the drying of surface peat layers and increases the chances of fire. In addition, the open conditions are often unsuitable for the growth of most peat swamp forest species, leading to the development of secondary forests dominated by a limited number of pioneer species. High impact log extraction techniques include the use of heavy excavators. These compact peat, and alter the drainage of peatlands prior to logging in order to facilitate access. Logs may also be extracted via drainage canals. Such logging techniques have been shown to significantly reduce the chances of natural regeneration, while the drainage leads to significant subsidence and enhanced fire risk (Danced 2003).

Forest resources from peatlands that are naturally forested can be sustainably harvested using low impact logging/extraction techniques. These techniques help maintain biodiversity and carbon storage. Resources can be sustainably harvested using low impact logging/extraction techniques, while also maintaining biodiversity and carbon storage.

Afforestation of naturally unforested peatlands can have important negative effects. The afforestation and associated drainage of naturally un-forested peatlands can cause significant changes in hydrology and ecology, leading to a reduction in water quantity and quality, loss of biodiversity and reduced carbon storage. Although forest managers now attempt to maintain or increase biodiversity through careful planting design (Anderson 2001), there is a still an increasing area of peatland that is being commercially afforested in some countries.

Afforestation of peatlands is often associated with drainage and fertiliser application which together lead to major ecological changes. Drainage ditches lower the water table, while the trees, whose roots reach far deeper into the soil profile than the natural vegetation, can cause the water table to lower even further. Compression and shrinkage can lead to subsidence and cracking of the peat surface (Shotbolt et al. 1998, Anderson et al. 2000). This alters conditions for ground layer plants, and reduces the availability of the fresh-water habitats that characterize many peatlands (e.g. blanket bogs). Fertiliser application can change the species composition of ground layer plants by altering the nutrient availability and pH. Also, as the trees grow, they can change the microclimate for the ground layer plants. This in turn can lead to further changes in species composition. Combined with changes in the soil, these alterations can cause an increased prevalence of earthworms, slugs, moths and beetles (Makulec 1991), while spiders and wasps may become less abundant (Coulson 1990). Birds that favour open ground are gradually replaced by forest birds. These impacts can be felt far beyond the forested area, as bird communities may be affected up to a kilometre from the edge of the plantation (Moss et al. 1996). Although tree felling can cause the water table to rise again, the soil structure (and consequently the drainage) may have been irreversibly altered by the forest. Given the unique biodiversity value of many peatland habitats, these types of environmental changes may be associated with the loss of rare and endangered species, and are therefore cause for concern.

Although trees sequester and store carbon in their biomass, the changes that take place in the soil after peatlands are afforested lead to significant carbon loss. Peatlands are significant carbon stores – for example, peatlands are the UK’s largest carbon store, holding more than all the forests of the UK, France and Germany combined (Worrall et al. 2003). Although trees sequester and store carbon in their biomass, the changes that take place in the soil after peatlands are afforested lead to significant carbon loss (Cannell et al. 1993). Research has indicated that peatland afforestation can result in a net release of carbon dioxide into the atmosphere (Holden 2005). Fertilisation of peat soil also leads to significant emissions of N₂O which has a global warming potential 310 times higher than that of CO₂.

Improvement of management measures for forest plantations on peatlands can reduce losses of biodiversity) and GHG emissions while at the same time reducing risks for production. In Indonesia large-scale tree plantations have been developed in peatlands to supply pulp and paper mills. These plantations are currently in Sumatra and cover an area of about 800,000 ha. The main tree planted is Acacia crassicarpa which is not an indigenous peat swamp forest species. The peatlands are thus drained to a depth of 0.8-1.5 metres to enable the trees to grow and minimize the chance of roting of the root mass. Although the trees are relatively fast growing and achieve canopy closure in one year, they are harvested on a 4-5 year cycle which leads to regular clearance and opening up of the land. High levels of peat subsidence linked to the drainage have led to significant management problems which are now being assessed.

Modification of Peat extraction

Peat extraction operations can affect biodiversity and impact GHG emissions, both directly and in adjacent areas. The extraction of peat for use in energy generation or horticulture is one of the significant uses of peatlands worldwide, although the area used is much less than for forestry and agriculture purposes. Extraction of the peat normally involves the clearance of surface vegetation, drainage of the peat and extraction using machinery. The extracted peat is then stockpiled before transportation and utilisation. The clearance of the vegetation directly impacts the biodiversity while the drainage and extraction of the peat often leads to changes in the hydrology of adjacent areas which can affect GHG flux.

Use of peat as a substrate for horticulture is a significant source of peatland degradation and carbon emissions. This problem can be reduced through the careful selection of extraction sites and development of appropriate alternative growing media. The extraction of peat for horticulture has led to significant impacts on conservation sites in some countries and has led to long-term conflicts. This has, in turn, stimulated consumer boycotts of horticultural peat in some countries. In response the peat industry has developed codes of practice which ensure that mining is focused on those sites with little conservation value, including abandoned agricultural land. In addition, in some countries the peat industry has actively developed post-mining restoration techniques and has introduced sphagnum farming methods. Development of alternatives to peat for use in horticulture, such as compost or coco-peat (from processed coconut husk fibres), is also underway.