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Restoration of organic soils

Restoration of organic soils
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Description

Soil restoration refers to actions to regenerate natural soil cycles through revegetation with shrub and creeper species, reforestation with native arboreal species and containment work with stakes. The aim is to stabilize the soil and increase the supply of organic matter, which promotes restoration. Geomesh is also used when the soil is highly eroded and degraded and the slope exceeds 25%. Soil is restored in accordance with the particular biological and edaphological conditions, and this also determines which species will be selected. The plants are obtained from local nurseries to ensure their adaptability and safeguard the site’s endemic genetic diversity.

Location

This measure is used to recover poor, degraded or low-permeability soils. It is applied in deforested or eroded areas where there is a risk of landslides, but it is also useful on the boundaries of conserved areas to buffer the impact of the expansion of the agricultural frontier. It may be applied to improve the structure and fertility of compacted soils on livestock farms.

Threats and Impacts it Addresses

Restoring soils raises their infiltration capacity, which recharges aquifers and increases water availability. Increased moisture content helps tree and shrub species take hold, and their roots retain soil and prevent erosion and landslides. The trees generate a microclimate that reduces the effect on crops or ecosystems of frost, abrupt temperature changes, strong winds, extreme heat, hail and intense rainfall. The set of processes that arise from the presence of trees regulate temperature and moisture in the surrounding soil and air, which decreases the potential for drought.

Implementation Steps

  1. Evaluate the soil's condition and devise the restoration programme with technical support
  2. Plant pioneer species to increase the stability and organic matter content of the soil.
  3. Plant live stakes of native arboreal species measuring about 1.2 m on slopes with severe erosion and reinforce with stakes placed perpendicular to the slope of the terrain.
  4. Reforest with native species from local nurseries or transplant seedlings from surrounding forest areas, where feasible. Assume an average density of 1200 trees/ha.
  5. Carry out complementary actions for soil and water retention.
  6. Perform maintenance work.
  7. Assess the programme and take follow-up actions.


Inputs and Costs

The cost of restoring 1 ha of land is given below. The main items are the labour required for the forestry work, the purchase of trees from nurseries, seeds and tools, as well as geomesh, in the event of extreme erosion. Three days of training and five days of annual maintenance are included.

Soil restoration, 1 ha US$
Labour 1440
Materials 1266
Training 180
Total 2886

Economic and Ecosystemic Benefits

Each year, about 75 billion tons of soil are eroded from the world’s terrestrial ecosystems and most of this erosion occurs on agricultural land (Pimentel and Kounang, 1998). Multiple benefits are obtained from protecting the soil with plants: an increase in flora and fauna; improved soil quality, moisture and fertility; erosion control; carbon sequestration; temperature and water regulation; and improved biodiversity and agricultural productivity (Durán and Rodríguez, 2009). A project in Brazil that established nurseries to restore degraded tropical forests, with an approximate cost of US$ 3500/ha, had several of the benefits listed above. The TEEB (2009) projects the net present value of these restored forests, 40 years after restoration, at about US$ 105,000/ha with a discount rate of 1%. In the short term, restored areas provide neighbouring communities with natural resources that support their livelihoods.

Limiting Factors

There is little information on the basis of which to quantitatively value the short-term benefits of restoration, which may create the false impression that it is not important, necessary or cost-effective. Species must be selected on the basis of a prior analysis of the site and they should be adapted to local climate conditions and be of the required genetic quality; otherwise, the investment may be lost or the equilibrium of the ecosystem disturbed.

Learned Lessons

Reforestation must include maintenance and monitoring for at least two years to ensure high survival rates. This is a long-term process with integral benefits for the entire community; hence, it requires the participation and ownership of the beneficiaries. During the restoration process, care must be taken to avoid colonization of the area by opportunistic species from degraded locations so as to ensure the development of local species and those characteristic of healthy forest areas.

Additional Considerations

This technique should be combined with complementary works like infiltration pits, contour trenches, drainage systems and terraces to promote proper water and soil management as well as the survival of the vegetation. Ideally, this measure is applied collectively, because it involves large areas of land and must be applied irrespective of property boundaries. Maintenance of the reforested trees decreases two years after planting, but the steps taken to care for the area should remain in effect until the ecological cycles of a healthy forest have been established.

Units to Monitor Project Progress: Restored soil area (ha).

Unites to Monitor Measure's Impact: Inhabitants who benefited from restoration actions (number).

References

  • Rivera, J. and J. Sinisterra (2005). Restauración Social de Suelos Degradados por Erosión y Remociones Masales en Laderas Andinas del Valle del Cauca Colombia con la utilización de obras de Bioingeniería. V Congreso Nacional de Cuencas Hidrográficas. Cali.
  • Vargas, O. (2007). Guía Metodológica para la Restauración Ecológica del Bosque Altoandino. 2nd ed. Universidad Nacional de Colombia.
  • Durán, V. and C. Rodríguez (2008). “Soil-Erosion and Runoff Prevention by Plant Covers: A Review”. Agronomy for Sustainable Development 28 pp. 65–86.
  • Pimentel D. and N. Kounang (1998). “Ecology of Soil Erosion in Ecosystems”. Ecosystems 1 pp. 416–426.
  • TEEB – The Economics of Ecosystems and Biodiversity for National and International Policy Makers (2009). Chapter 9: Investing in Ecological Infrastructure.