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Desertification Indicator System for Mediterranean Europe


1. Definition

Name

SOIL EROSION (USLE) - as used in Spanish NAP

Brief definition

Quantity of estimated soil losses at sub-watershed scale caused by water.

Unit of measure

T/ha·year

Spatial scale

Sub-regional

Temporal scale

Annual measures

2. Position within the logical framework DPSIR

Type of Indicator

Impact

3. Target and political pertinence

Objective

Identification and mapping of ESAs. Prioritisation of mitigation actions to combat desertification.

Importance with respect to desertification

Environmental effects of soil erosion:

  • soil productivity decrease,
  • soil infiltration rate decrease,
  • vegetation cover degradation,
  • flood risk increase,
  • water quality decrease,
  • irregularity of rivers flow,
  • increase of sedimentation in dams.

International Conventions and agreements

The UNCCD states that soil erosion is one of the main causes of land degradation. "Land degradation means reduction or loss, in arid, semi-arid and dry sub-humid areas, of the biological or economic productivity and complexity of rainfed cropland, irrigated cropland, or range, pasture, forest and woodlands resulting from land uses or from a process or combination of processes, including processes arising from human activities and habitation patterns".

Secondary objectives of the indicator

To generate the map of soil erosion state at sub-watershed level in Spain estimating soil losses.

4. Methodological description and basic definitions

Definitions and basic concepts

The erosion risk depends on several factors, such as the slope gradient, the vegetation cover, the soil type and the rain and wind erosivity. In Spain the erosion process goes beyond the tolerable limits in almost 42 % of the national area and in almost 12 % of the area the erosion rate is critical.

Benchmarks Indication of the values/ranges of value

Three classes of soil losses have been established:

  • less than 12 T/ha·year
  • from 12 to 25 T/ha·year
  • more than 25 T/ha·year

Methods of measurement

Generally the methods of measurement are based in the USLE Model. For instance, the Map of Erosive Levels of Spain (Mapa de Estados Erosivos de España) establishes a methodology for the application of this Model on large areas and allows the establishment of the confidence limits confronting the estimations with the measures taken from the witness plots, out of which a certain number of data were taken per plot and year.

The methodology is structured in the following phases:

  • Homogenization phase: generation of data bases out from the different factors and definition of the homogeneous stratum though the intersection of such factors.
  • Phase of sampling and photo interpretation: sampling design to characterise the different stratum.
  • Quantifying phase: including field measures and checking, as well as measurement over aerial photographs with a view to defining the values of the USLE equation parameters.
  • Phase of classification and determination of the erosive levels: the numerical values corresponding to each of the stratum definition are transfer to the data bank. The results are two maps: one will represent the mosaic of homogeneous areas, indicating the established stratum; the other will establish the different sorts of erosive levels.

The process of updating and improvement of this Map of Erosive Levels is channelled through the INES, Spanish acronym of the National Soil Erosion Inventory, which maps different types of soil erosion in the whole national territory at scale of 1:50.000. Is based in the RUSLE method and follows a cyclical sequence of surveying to update the values every 10 years. The data comes directly from field work: 1 field plot per 25 km. The current, and first, cycle covers from the year 2002 up to 2012. At the same time, it is possible to perform a measurement of the erosion in experimental field plots, exactly as it is carried out in the RESEL network, Spanish acronym for Network of Experimental Stations for the Assessment and Monitoring of the Erosion and Desertification in Spain. The obtained results are used, inter alia, as a reference to characterise the erosion and desertification landscapes covering areas with similar characteristics.

Limits of the indicator

As the systemic sampling requires a high number of field plots providing field measures, the cost of the method is bound to be high.

Linkages with other indicators

Rainfall erosivity, Infiltration capacity, Slope gradient, Wind speed, Soil loss index, Vegetation cover, Erosion protection, Dam sedimentation, Water quality, Soil erosion control measures.

5. Evaluation of data needs and availability

Data required to calculate the indicator

Systemic methodological approach to evaluate the different erosion factors and subsequent erosion modelling through parametric approach (USLE, RUSLE).The annual soil losses measured in experimental field plots distributed throughout the country, representatives of all the different erosion landscapes.

Data sources

Erosion factors maps and field data gathering.

Availability of data from national and international sources

The Erosion State Map of Spain, the Erosion State Map at Watershed Level and the National Soil Erosion Inventory (INES, published by provinces) are available at the Dirección General para la Biodiversidad (Ministerio de Medio Ambiente, Spain).

6. Institutions that have participated in developing the indicator

Main institutions responsible

Dirección General para la Biodiversidad, (Ministerio de Medio Ambiente, Spain).

Other contributing organizations

7. Additional information

Bibliography

DGCN (2001): Programa de Acción Nacional Contra la Desertificación. Borrador de Trabajo". Dirección General de Conservación de la Naturaleza, Secretaría General de Medio Ambiente, Ministerio de Medio Ambiente, Madrid.

Other references

DGCN (2000): Estrategia Forestal Española". Dirección General de Conservación de la Naturaleza, Secretaría General de Medio Ambiente, Ministerio de Medio Ambiente, Madrid.

DGCN (2002): Inventario Nacional de Erosión de Suelos; INES". Dirección General de Conservación de la Naturaleza, Secretaría General de Medio Ambiente, Ministerio de Medio Ambiente, Madrid.

ENNE, G. and ZUCCA, C. (2000): Desertification Indicators for the European Mediterranean Region". ANPA, Rome.ICONA (1987-1994): Mapa nacional de Estados Erosivos".

ICONA, Ministerio de Agricultura, Pesca y Alimentación.ICONA (1991): Estudio sobre restauración hidrológico-forestal y control de la erosión".

ICONA, Ministerio de Agricultura, Pesca y Alimentación.MMA(1995): Proyecto LUCDEME. Ministerio de Medio Ambiente, Madrid.

Contacts Name and address

Leopoldo Rojo Serrano
Dirección General para la Biodiversidad
Ministerio de Medio Ambiente
Gran Vía de San Francisco 4
28005 Madrid (Spain)

<LRojo@mma.es>