Land management options for mitigation fall in the following four categories: a) cropland management; b) grazing land management/pasture improvement; c) management of agricultural lands and d) restoration of degraded lands. This description focuses on the restoration of degraded lands. Within this description, a differentiation is made between a) management of organic and peaty soils and b) restoration of other degraded lands.
According to the IPCC the main factors influencing change in the agricultural sector during the last four decades are population pressure, technological change, public policies, economic growth and the cost/price squeeze (IPCC, 2007).
A variety of factors cause agricultural lands to become degraded: excessive disturbance, erosion, organic matter loss, salinization, acidifcation, drainage or other processes that curtail productivity. Carbon storage within these soils can be partly restored by practices that reclaim productivity such as: a) enabling re-vegetation, for instance in the form of planting vegetation; b) improving fertility through nutrient amendmentsl c) applying organic substrates such as manures, biosolids and composts; d) reducing tillage and retaining crop residues and e) conserving water (IPCC, 2007).
Degradation of lands can result in the emission of greenhouse gases. Through restoration of lands, these emissions can be reduced. As an example, Video 1 illustrates the restoration of a peatland.
A variety of mitigation measures to realize GHG emission reductions in agriculture are available. According to the IPCC, the most prominent options are improved crop and grazing land management, restoration of organic soils that are dained for crop production and restoration of degraded lands (IPCC, 2007). Other measures with lower but still significant emission reductions are improved water and rice management, set-asides, land use change, agro-forestry and improved livestock and manure management. Most of these mitigation opportuinities use currently available technologies and can be implemented immediately. However, the IPCC notes that, technological development will be a key driver ensuring the efficacy of additional mitigation measures in the future (IPCC, 2007). .
This description focuses on the restoration of organic or peaty soils and on restoration of degraded lands. Organic or peaty soils accumulated large quantities of carbon due to anaerobic decomposition of the organic matter. Anaerobic decomposition, or decomposition under absence of oxygen, occurs due to the flooded conditions of peatlands. When converted to agricultural lands the soils are drained, which removes the anaerobic conditions as it introduces oxygen into the soil. This process favours aerobic decomposition (decomposition with oxygen) which results in high CO2 and N20 fluxes (IPCC, 2007). Kasimir-Klemedtsson (1997) note that, although methane emissions are suppressed after draining of the soil this effect is by far counteracted due to the pronounced increase in N20 and CO2 emissions.
Peatlands are considered an especially important aspect of land management. This is due to the notion that although peatlands only cover 3 % of the land surface, they store more carbon than the vegetation of all the world's forests combined (peat portal assessment, 2008). This huge carbon stock of peatland ecosystems is atttributed to the often thick layers of peat, as illustrated in Figure 1. Peat consists largely of organic material and has a carbon content of over 50 % (peat portal assessment, 2008).
Freibaueret al., (2004) state that the most significant mitigation practice related to peaty and organic soils is avoiding the drainage of these soils or to re-flood the soils. The full restoration through increasing the water table is illustrated in Figure 1 and Figure 2. Other practices also contribute to lower emissions such as avoiding row crops and tubers, avoiding deep ploughing and maintaining a shallower water table, but these are less effective (IPCC, 2007).
Land degradation in general occurs due to a variety of factors. The IPCC, based on several papers, lists the following factors: excessive disturbance, erosion, organic matter loss, salinization, acidification or other processes that curtail productivity (IPCC, 2007). Carbon storage can be partly restored through practices that reclaim lost productivity such as: re-vegetation, improving fertility through nutrient amendments, applying organic substrates such as manures, reducing tillage, retaining crop residues and conserving water (IPCC, 2007).
Gorham and Rochefort (2002) outline the major goals of peatland restoration, the conditions that favor or oppose restoration and they assess restoration failures and successes.
Major goals of peatland restoration
The primary goal is to repair the eco-system itself. This includes the re-establishment of peatland hydrology, biogeochemical cycling and energy capture that will allow renewal of peat accumulation. An important operational necessity for peatland restoration is to act as soon as possible after the exploitation of the land has ceased. This minimizes degradation of the surface peat, which occurs through decomposition and compaction. Rewetting of the soil should be performed in a careful fashion as well as otherwise the water may cause erosion and frost-heaving. As such, Gorham and Rochefort (2003) note that it is essential to precede the restoration process with an accurate and detailed spatial evaluation of current hydrology of the soil, which should involve a study of peat structure, hydrologic conductivity and vertical seepage.
Another goal of restoration of peatland is stabilization of the peat surface. Stabilization can be done naturally by the use of plant species known to be effective, or artificially through the introduction of coarsely woven and biodegradable matting (Gorham & Rochefort, 2003). In the case that drainage has converted the open peatland into forest, which is the case in many drained peatlands, it is necessary to remove the trees.
Figure 4 illustrates the hydrological methods that are available to restore peatland areas.
The Global Peat Restoration Manual (2008) summarizes the major goals of peatland restoration into three points: a) The restoration of peatland diversity; b) the restoration of peatland hydrological functions and; c) the reduction of greenhouse gas emissions from peatlands.
Standard management approaches to peatland restoration
As the Global Peat Restoration Manual (2008) notes, peatlands are complex systems due to three main characteristics. First, they consist of sophisticated interrelations of vegetation, water and peat. Second, they provide a wide variety of products and services. Finally, they can be damaged via a large variety of different actions.
According to the Global Peat Restoration Manual (2008), previous restoration practices of peatlands and wetlands have shown that restoration projects that depart from too simplistic an approach often fail to achieve their objectives. Basically, the manual notes that to realize succesful restoration it is important to realize that all relations of eco-systems can be brought down to two aspects:
a) input-relations, which applies when the system itself acts as a sink for another source.
b) output-relations, which applies when the system itself acts as a source
These two aspects are essentially ruled by two limits of tolerance: the limit of minimally required and the limit of maximally tolerable.
As such, the degradation to wetlands and peatlands can be categorized into four fundamentally different forms of degradation.
1) Underfeeding : The system has too little input of something.
2) Overfeeding: the system has too much input of something.
3) Stoppage: The system has too little output of something.
4) Loss: The system has too much output of something.
The Global Peat Restoration Manual (2008) notes that there subsequently four management approaches to peatland restoration.
1) Supply: Measures against underfeeding
2) Disposal: measures against stoppage (“getting out”).
3) Resistance: : measures against overfeeding (“keeping out”).
4) Retention: measures against loss (“keeping in”).
From this, several standard management practices can be identified. The Global Peat Restoration Manual (2008) notes that to achieve the reduction of greenhouse gas emissions from peatland the following management practices are recommended.
The key to reducing greenhouse gas emissions from peatlands is to minimize oxidation. Therefore, optimizing water management in peatlands is the single highest priority to mitigate greenhouse gas emissions from peatlands (Parish et al., 2007). The main categories of actions the manual uses are:
a) Re-activate peat formation. This can be done through the reduction of aerobic decomposition. The reduction of aerobic decomposition is performed through effective water management, i.e. raising water levels, reducing evapo-transpiration and raising the catchment water level. In addition, re-activiation of peat formation can be achieved through improvement of habitat conditions to support current peat forming activities and through the re-introduction of peat forming plant species.
b) The reduction of erosion. To realize this category it is important to reduce the damage and disturbances to the vegetation and the peat surface. Therefore, human impact and herbivore impact need to be minimized. In addition, it is important to stabilize bare peat to prevent it from washing away. This can be done through re-vegetation of bare areas or through covering loose and bare areas with stabilizing material (for instance geo-jute sheets or nets.) Moreover, erosion can be reduced through the improvement of catchment hydrology. For instance, realizing a stable flow of water with a minimum of floods and draughts reduces erosion. Additionally, in case of the presence of permafrost, preserving the permafrost through the re-establishment of insulating species also prevents erosion of the peatland.
c) The reduction of noxious substances. This can be done through the harvesting and removal of biomass, the stimulation of chemical precipitation and the removal of degraded land surfaces.
d) Finally, fire-management is also an essential aspect of peat restoration. Preventing fires results in a more stable peat land and prevents greenhouse gas emissions. This can be achieved through a variety of methods. First, access to the peatland can be restricted in fire-sensitive periods and to fire-sensitive areas. Second, a fire monitoring system can be put in place. This can be done through watchtowers, regular patrols and aerial monitoring. Third, providing fire breaks (passages which the fire can't cross) and providing water supplies for fire-fighting purposes prevents the expansion of fires. The development of fire risk models, re-wetting the peat surface in fire-sensitivie periods, and providing fire safety maps are several other options to effective fire management.
The Global Peat Restoration Manual (2008) summarizes the greenhouse gas emission reduction measures in peatland restoration in the following Figure.
As the peat portal assessment report notes: "the protection of remaining peatlands is one of the most important and cost-effective management strategies for minimizing CO2 emissions in the land use, land use change and forestry sector" (peat portal assessment, 2008). As such, the potential of protection of peatlands from a mitigation perspective is very high.
The technical mitigation potential per region for all management practices (i.e. restoration of degraded lands; cropland management; grazing land management/pasture management; management of agricultural lands) and all affected GHGs is shown in Figure 4.
While the above Figure 6 aggregates the technical mitigation potential of all management techniques, the Figure 7 below outlines the mitigation potential differentiated between management techniques. It can be seen that restoration of degraded lands is an important mitigation measure in the land use, land use change and forestry sector.
Peatland restoration and restoration of degraded lands contribute to socio-economic development and environmental protection. However, the exact magnitude of the effect depends on the scale and intensity of the mitigation measure taken as well as the sector and policy arena in which they are undertaken (IPCC, 2007). As a preliminary indication, Figure 6 shows the sustainable development benefits from all land management techniques differentiated over the social, economic and environmental factors.
While Figure 8 is relatively rudimentary, several possible benefits can be noted from the restoration of degraded lands and peatlands. First, restoring degraded lands and peatlands improves biodiversity. Second, peatlands purify water and can therefore be regarded as an important water supply source. Third, restored (peat) lands can be more effectively used as flood mitigation areas. Fourth, restored peatlands have been shown to significantly reduce fire risk (peat portal assesment report, 2008). Finally, due to aestetic quality of fully restored peatlands and other degraded lands, sustainable development can be supported through eco-tourism activities.
Restoration of organic soils therefore has a variety of biodiversity and environmental co-benefits. However, the economic impact depends upon whether farmers receive payment for the GHG emission avoidance and reductions achieved. Market based mechanisms might be able to support restoration of peatlands and degraded lands as they add carbon valuation. Restoration of degraded lands will provide higher yields and economic returns, less new cropland and provide societal benefits via production stability.
The role of alternative strategies changes across the range of prices for carbon. At low prices, dominant strategies are those consistent with existing production such as changes in tillage, fertilizer application, livestock diet formulation, and manure management. Higher prices elicit land-use changes that displace existing production, such as biofuels, and allow for use of costly animal feed-based mitigation options. A practice effective in reducing emissions at one site may be less effective or even counterproductive elsewhere. Consequently, there is no universally applicable list of mitigation practices; practices need to be evaluated for individual agricultural systems based on climate, edaphic, social setting, and historical patterns of land use and management.
Currently, degraded land restoration and peat land restoration do not fall under the Clean Development Mechanism. For more information on the CDM baseline establishment and latest news see: http://cdm.unfccc.int/
Global Peat Restoration Manual, 2008. Peat restoration manual provided by the Peat-Portal Restoration website. Document can be found online at: http://www.peat-portal.net/index.cfm?&menuid=112
Parish, F., Sirin, A., Charman, D., Joosten, H., Minaeva, T. & Silvius, M. (eds) (2007):Assessment on peatlands, biodiversity and climate change, Global Environment Centre, Kuala Lumpur and Wetlands International Wageningen.
Peat-Portal Assessment, 2008. Assessment on Peatlands, Biodiversity and Climate Change. Document can be found online at: http://www.peat-portal.net/index.cfm?&menuid=123&parentid=113
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