Case Study Experiment - reclamation methods to increase land resilience to soil erosion by wind
The researchers in Iceland are testing the effectiveness of various selected land reclamation methods with respect to increased land resilience. Different methods are being applied, including synthetic fertilizer, organic fertilizer, grass seeding, lupine seeding, tree establishment.
|A land reclamation area in the Hekluskógar area. This is an old active sand advancing front that has been stabilized with Lyme grass (Leymus arenarius)|
The figure shows how treatments responded variously from zero to 2 t/ha biomass.
The biomass was highest in Leymus, Lupinus and bone meal treatments (see photos below).
The Gunnarsholt area is located in South Iceland (64°05'N; 19°50'S) and covers 900km2. It is mostly flat, with slopes generally < 5°. Soils are characterized as Leptosols and Arenic Vitrisols, and complexes thereof. This area was used as rangeland (grazing) but is mostly protected today. The average annual temperature is < 3.7°C, and mean temperatures in January and July are < -1.8°C and < 10.9°C, respectively. Annual precipitation is >1000mm.
Main soil threat
Icelandic soils are predominantly of volcanic origin. They are classified as Andosols soils, typically having low bulk density, high water holding capacity and low particle cohesion. These properties make them inherently unstable and fragile if they are exposed to the elements, especially in areas like Iceland where freeze-thaw processes are common throughout the winter. Consequently, wind and water erosion are dominating land degradation processes where the vegetation cover has been impaired or damaged; due to abiotic events (weather, volcanic eruptions) or human-induced activities (land uses such as deforestation and grazing). Severe soil erosion has been estimated to affect at least 50% of the Icelandic drylands whereas severe and extremely severe erosion is present on 25% of the land.
Although both wind and water erosion are very active processes, wind erosion is often responsible for more dramatic degradation events. This was the case in the proposed Case Study area. During the few last decades of the 19th century and the first of the 20th, severe sandstorms ravaged the area. The sand covered fields and buried farms and consequently, many farms were abandoned. This area is still largely covered by sandy deserts, but many areas have been reclaimed successfully, especially in the Gunnarsholt area. The reclamation work began early in the 20th century as people tried to stop the drifting sand by erecting stone walls and seeding Lyme grass (Leymus arenarius) to stabilize the land surface. But it was later, when grass seed, artificial fertilizers and appropriate equipment became available, that real success was achieved. Large areas that were previously black basaltic deserts are now possible to reclaim.
Often they possess diverse plant communities, and more importantly, producing fertile organic soils, thereby increasing the resilience and resistance of local ecosystems. However, this approach to land reclamation, no matter how successful it has been, is expensive and cannot be used on a large scale. Thus reclaiming the entire area that was lost in the erosion ca. 1900 is impossible with this small-scale approach. Today, land reclamation in this area focuses on establishing woody vegetation islands at selected locations in cooperation with local farmers as well as assisting them in reclaiming degraded areas around their homesteads through a programme called "Farmers heal the land". It is hoped that the vegetation islands will expand over time as seed production increases and eventually cover the area. Using woody species in this area is critical as they are able to survive and stabilize another natural hazard evident in the area, i.e. volcanic ash deposition.
Other soil threats
The Gunnarsholt area and Iceland in general, are threatened with land degradation and desertification. As in most cases, wind and water erosion are associated, with the latter being more prominent on hill slopes. Over 40% of the dry land area is considered in a degraded or eroded state (Landmælingar Íslands, 1993). Water erosion is another dominating process where vegetation cover is poor. These effects are consequences of the interaction of soil properties, climate, and the land management regime.
Location and Digital Elevation Model (DEM) of the Gunnarsholt (Source: viewfinderpanoramas.org)
Geology & Soils
The Case Study is an area exposed to frequent volcanic activities due to its proximity to the Hekla volcano, situated near the American – Eurasian fault line that transects Iceland. As a consequence of the volcanic activity, both soils and landscapes are young, hence covered with soil types that are relatively undeveloped and thus highly erodible. The bedrock is of basaltic origin, and soils are predominantly of volcanic origin. They are characterized as Leptosols and Arenic Vitrisols, and complexes thereof (Arnalds & Gretarsson, 2002). They are classified as Andosols soils, typically having low bulk density, high water holding capacity and low particle cohesion (Arnalds, 2004).
Left: Land use; right: Soil map (Sources: National Snow & Ice Datacenter and diva-gis.org)
The average annual temperature is <3.7°C, and mean temperatures in January and July are <-1.8°C and <10.9°C, respectively. Annual precipitation is >1,000 mm
The entire area has historically been used as grazing land for free-ranging sheep. Over time, due to land degradation and erosion, the suitable grazing land area was reduced. Today, large areas are protected from grazing and consequently partly allocated for revegetation or reforestation. The current extent of land reclamation areas is 14,500 ha and reforested areas cover 1,000 ha (SCSI, unpublished data and Aradóttir et al., 2011, p.71-74). Farming activities are still present in areas which were not affected by the catastrophic land degradation. The Hekluskógar area also provides various other ecosystem services including fishing in the rivers and farming activities. The area is an important water source for nearby town communities and farms and there are large populations of wild birds that depend on this area for nesting during the summer. This area is also a potentially important area for carbon sequestration but available data has yet not been compiled (SCSI, unpublished results). The area is now also popular for hiking and recreation as tourism increases. All these services are at risk if wind erosion escalates to previous levels.
Old land reclamation area in the Hekluskógar area. This is an old active sand advancing front that has been stabilized with Lyme grass (Leymus arenarius).
The old sand dunes can be easily seen. Mt. Hekla in the background
Drivers and pressure
Iceland was settled in the 9th century. Prior to that, no large grazers existed. Individual species were thus neither adapted to grazing (Bryant et al., 1989) nor were the plant communities. It is commonly accepted that large-scale deforestation followed as land was cleared for creating grazing land and land for cultivation. The traditional grazing scheme that was adopted was based on year-long grazing; animals were grazed around the homesteads during winter but allowed to range freely in the summer. This also led to decrease in tree densities as regeneration, either by root sprouts or from seed was inhibited. Over time this resulted in massive shift in vegetation cover as the land went from being covered in forests over to being dominated by graminoids (Thorsson, 2008), although the process occurred at different times in different regions (Sigurmundsson, Gísladóttir, & Óskarsson, 2014). Moreover, the uncontrolled grazing reduced biomass cover gradually, thus affecting both soil producing properties and changing the disturbance regimes. The consequence was a shift to abiotic disturbances regime, such as cryoturbation.
The vegetation cover is the most important barrier against frost heaving. It both provides thermal insulation and physical strength to the soils through root-mass reinforcement (Thorsson, 2008). With this barrier impaired the cryoturbation intensified, eventually leading to formation of areas with bare soils exposed to the elements. Soils with high water content capacity and low particle cohesion are especially vulnerable to frost heaving. This is apparent by the formation of needle-ice as soils freeze and area-frost heaving during the winter. If no management inputs are in place to revert the process, the bare soil areas will expand and eventually coalesce, creating large areas with exposed soils, especially vulnerable for wind erosion.
The Thorsa River carries enormous amounts of sediments every year that accumulate in the riverbed. Once the vegetation had shifted from being woodland dominated to graminoids, the resistance against eolian material had also been decreased as the grasslands have less resilience than the woodlands (Aradottir & Arnalds, 2001; Aradóttir, Petursdottir, Halldorsson, Svavarsdottir, & Arnalds, 2013). Over time the sandy sediment was carried southwards. This was acerbated by frequent volcanic depositions from Hekla; 18 eruptions have been recorded since the beginning of settlement until today (Hjartarson, 1995). The woodlands had high resilience against the natural disturbances caused by volcanism and eolian material as is obvious from the pristine woody patches still remaining. Nevertheless, the removal of the woodlands left the land exposed to the elements until a threshold was reached and large-scale wind erosion started.
Status of soil threat
Already from the 1600s, one third of the area appears to have suffered from severe wind erosion (Árnason, 1958). Only 200 years later, in the late 1800s, the advancing sand and wind erosion fronts had reached the southernmost part of the Hekluskógar area (Jónsson, 1958). The extent of wind erosion has recently been manifested by (Arnalds, 2010; Arnalds, Thorarinsdottir, Thorsson, Dagsson-Waldhauserova, & Agustsdottir, 2013; Dagsson-Waldhauserova, Arnalds, & Olafsson, 2014). Iceland is one of the largest dust sources in Northern Europe, thus the scale of wind erosion here is immense. Wind erosion is still active in the Hekluskogar area (Thorarinsdottir & Arnalds, 2012; Arnalds, Gisladottir, & Orradottir, 2012; Thorarinsdottir & Arnalds, 2012) and can be expected to increase temporarily if an volcanic eruption occurs (Arnalds et al., 2013). Nevertheless, the scale is considerably smaller than before as large areas have now lost their Ando surface soils. The risk for wind erosion goes in hands with proportional vegetation cover, so as long as large areas are unvegetated, risk of wind erosion must be considered being present.
Maps on the current state of land use, soil degradation and soil conservation in the case study area have been produced using the WOCAT (World Overview of Conservation Approaches and Technologies) methodology
The steps of this process are as follows:
1) The area to be mapped is divided into distinctive land use systems (LUS).
2) The team gathers the necessary data on soil degradation and conservation for each LUS using a standardised questionnaire, in close consultation with local land users, and supported where possible by remote sensing or field data.
3) For each LUS, the soil degradation type, extent, degree, impact on ecosystem services, direct and indirect causes of degradation, as well as all soil conservation practices, are determined.
4) Once collected, the data is entered in the on-line WOCAT-QM Mapping Database from which various maps can be generated.
Following the principles of all WOCAT questionnaires, the collected data are largely qualitative, based on expert opinion and consultation of land users. This allows a rapid and broad spatial assessment of soil degradation and conservation/SLM, including information on the causes and impacts of degradation and soil conservation on ecosystem services.
More details about the methodology used to produce these maps and their interpretation can be found here.
Land Use (click on maps to expand)
The "effectiveness" of conservation is defined in terms of how much it reduces the degree of degradation, or how well it is preventing degradation. The Effectiveness trend indicates whether over time a technology has increased in effectiveness.
Administrative and socio-economic setting
Both the national and local governments recognise the importance of reverting land degradation and soil erosion. By law, land reclamation activities are under the responsibility of the Soil Conservation Service of Iceland (SCSI) and reforestation is under the responsibility of the Icelandic Forestry Service (IFS). NGOs activities and participatory approaches, initiated by the SCSI have increased over the last decades. District afforestation programs have also been initiated by the national government and are overseen by the IFS. Both are supported by the local governments.
Land reclamation and land afforestation are both placed high on the national agenda, both for the purpose of land reclamation but also to meet the requirements of the Kyoto protocol (Umhverfisráðuneytið, 2010).
Population in Gunnarsholt (left) and GDP per capita trends for Iceland and the Euro Area (right)
The Soil Conservation Service of Iceland started land reclamation activities in the area early in the 20th century and they have been ongoing until this day (Crofts, 2011). Considerable success has been attained as sandstorms do not occur any more. Aradóttir et al. (2013) analysed 100 restoration projects, representing 75-85% of all land restoration activities in Iceland. Their outcomes showed that, despite good, results catastrophic erosion is still ranked as an important threat in the 2000s, thus underlining the scale of this problem in Iceland. Other drivers were also strong motivators, including socioeconomic (farming, food provisioning, wool production), although their internal emphasis changed over the 20th century. At the end of the 20th century a change was observed as the emphasis on aesthetics increased as well as “repaying the debt to the land” emerged. United Nations Climate Change Convention became a driver for restoration in the end of the 1990s, and importance of nature conservation and recreation increased. Policy has not been found to be an influential driver in the Case Study, and neither technology nor financial incentives have been identified as drivers.
Relevant end-users and local stakeholder groups include;
- Local farmers
There is already strong cooperation between the Soil Conservation Service of Iceland (SCSI) and the farmers in the area as they participate in the "Farmers heal the land" programme. They have been actively participating and donating land for this project. The Icelandic Forestry Service will also be involved as they have been active in establishing woodland vegetation islands in some of the area.
Left: Land reclamation sites are shown in green (NIR, SPOT 5); Right: Land reclamation activities in the Hekluskógar area (front). An erosion escarpment can be seen on the right, indicating the amount of soils lost due to wind erosion. This is an example of the “Farmers heal the land” co-operation between SCSI and local stakeholders
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