How good is GLASOD?

The Global Assessment of Soil Degradation (GLASOD) has been the most influential global appraisal of land quality in terms of environmental policy. However, its expert judgments were never tested for their consistency and could not be reproduced at unvisited sites, while the relationship between the GLASOD assessments of land degradation and the social and economic impact of that degradation remains unclear. Yet, other methodologies that could respond to urgent calls for an updated assessment of the global environmental quality are not operational or, at best, in progress. Therefore, we evaluate the reliability and social relevance of the GLASOD approach and assess its candidacy for new global environmental assessments. The study concentrates on the African continent, capitalizing on new GIS data to delineate and define the characteristics of GLASOD map units. Consistency is tested by comparing expert judgments on soil degradation hazard for similar combinations of biophysical conditions and land use. Reproducibility is evaluated by estimating an ordered logit model that relates the qualitative land degradation classes to easily available information on explanatory variables, the results of which can be used to assess the land degradation at unvisited sites. Finally, a cross-sectional analysis investigates the relation between GLASOD assessments and crop production data at sub-national scale and its association with the prevalence of malnutrition. The GLASOD assessments prove to be only moderately consistent and hardly reproducible, while the counter-intuitive trend with crop production reveals the complexity of the production-degradation relationship. It appears that increasing prevalence of malnutrition coincides with poor agro-productive conditions and highly degraded land. The GLASOD approach can be improved by resolving the differences in conceptualization among experts and by defining the boundaries of the ordered classes in the same units as independent, quantitative land degradation data.

[1]  B. Sonneveld,et al.  The geographical distribution of underweight children in Africa. , 2005, Bulletin of the World Health Organization.

[2]  Jonathan D. Phillips.  Deterministic Chaos in Surface Runoff , 1992 .

[3]  David Dent,et al.  ISRIC - World Soil Information , 2006 .

[4]  Bert Kramer,et al.  An ordered logit model for the evaluation of Dutch non-life insurance companies , 1996 .

[5]  W. H. Wischmeier.  Use and misuse of the universal soil loss equation. , 1976 .

[6]  J. Bongaarts,et al.  Global Environment Outlook , 1998 .

[7]  R. Lal,et al.  The global impact of soil erosion on productivity. II. Effects on crop yields and production over time , 2003 .

[8]  Rattan Lal,et al.  The Global Impact Of Soil Erosion On Productivity: I: Absolute and Relative Erosion-induced Yield Losses☆ , 2003 .

[9]  Ben Sonneveld,et al.  Formalizing expert judgements in land degradation assessment: a case study for Ethiopia , 2003 .

[10]  Ben Sonneveld,et al.  Formalizing the use of expert judgements for land degradation assessment: a case study for Ethiopia , 2002 .

[11]  I. Scoones,et al.  Sustaining the soil: Indigenous soil and water conservation in Africa , 1998 .

[12]  M. Hill,et al.  Multi-Criteria Assessment of Tensions in Resource Use at Continental Scale: A Proof of Concept with Australian Rangelands , 2006, Environmental management.

[13]  O. Tietje,et al.  Explorative data analysis of heavy metal contaminated soil using multidimensional spatial regression , 2003 .

[14]  B. Minasny,et al.  Digital Soil Map of the World , 2009, Science.

[15]  Michael E. Schaepman,et al.  Quantitative global assessment of land degradation and improvement: Pilot study in North China , 2005 .

[16]  P. J. Albersen,et al.  Water erosion assessment based on expert knowledge and limited information using an ordered logit model , 1999 .

[17]  Guenther Fischer,et al.  Agro-ecological land resources assessment for agricultural development planning. A case study of Kenya. Resources data base and land productivity. Technical Annex 6. Fuelwood productivity. , 1993 .

[18]  Greg Hancock,et al.  Evaluation of proposed waste rock dump designs using the SIBERIA erosion model , 2006 .

[19]  D. Pimentel,et al.  Environmental and Economic Costs of Soil Erosion and Conservation Benefits , 1995, Science.

[20]  D. P. Shrestha,et al.  Analysis and classification of hyperspectral data for mapping land degradation: An application in southern Spain , 2005 .

[21]  R. Joseph Monsen.  Living beyond our means , 1981 .

[22]  Robert J. A. Jones,et al.  Pan-European Soil Erosion Risk Assessment for Europe: the PESERA Map , 2004 .

[23]  D. Karlen,et al.  Identification of Regional Soil Quality Factors and Indicators II. Northern Mississippi Loess Hills and Palouse Prairie , 2000 .

[24]  Phillip Stalley.  Environmental Scarcity and International Conflict , 2003 .

[25]  H. Velthuizen,et al.  Agro-ecological land resources assessment for agricultural development planning. A case study of Kenya: resources data base and land productivity. Main report. , 1991 .

[26]  Michiel A. Keyzer,et al.  Using the mollifier method to characterise data sets and models. The case of the universal soil loss equation , 1997 .

[27]  A. J. Thomasson.  World map of the status of human-induced soil degradation: L.R. Oldeman, R.T.A. Hakkeling and W.G. Sombroek, Published by the International Soil Reference and Information Centre (ISRIC) and funded by the United Nations Environment Programme (UNEP). 1990. Price US$25.- (unfolded US$20.-) , 1992 .

[28]  Anthony J. Parsons,et al.  Overland Flow: Hydraulics and Erosion Mechanics , 2007 .

[29]  D. Dent,et al.  Global Assessment of Land Degradation and Improvement: pilot study in Kenya , 2006 .

[30]  D. Thomas.  Sandstorm in a teacup? Understanding desertification , 1993 .

[31]  W. Greene,et al.  计量经济分析 = Econometric analysis , 2009 .

[32]  Descriptors Adult,et al.  of Agriculture, Washington, DC.; , 2000 .

[33]  John H. Aldrich,et al.  Linear probability, logit and probit models , 1984 .

[34]  M. Keyzer,et al.  The effect of soil degradation on agricultural productivity in Ethiopia: a non-parametric regression analysis , 2001 .

[35]  Ckk Gachene,et al.  Evaluation and mapping of soil erosion susceptibility: an example from Kenya , 1995 .

[36]  John Doe,et al.  Soil Map of the World , 1962 .

[37]  Jaroslav Hofierka,et al.  Modelling Topographic Potential for Erosion and Deposition Using GIS , 1996, Int. J. Geogr. Inf. Sci..

[38]  Jay Gao,et al.  A Holistic Approach Towards Assessment of Severity of Land Degradation Along the Great Wall in Northern Shaanxi Province, China , 2003, Environmental monitoring and assessment.

[39]  R. J. Rickson,et al.  Conserving soil resources: European perspectives. , 1994 .

[40]  Guiping Feng,et al.  Preliminary study on assessment of nutrient transport in the Taihu Basin based on SWAT modeling , 2006 .

[41]  P. Crosson.  Will EROSION Threaten AGRICULTURAL PRODUCTIVITY , 1997 .

[42]  P. Crosson.  Soil erosion estimates and costs. , 1995, Science.

[43]  K. Wiebe,et al.  Linking Land Quality, Agricultural Productivity, and Food Security , 2003 .

[44]  Steven M. de Jong,et al.  Imaging Spectrometry For Surveying and Modelling Land Degradation , 2002 .

[45]  A. Dougill.  Sustaining the Soil: Indigenous soil and water conservation in Africa , 1997 .

[46]  John A. Dixon,et al.  Farming Systems and Poverty IMPROVING FARMERS' LIVELIHOODS IN A CHANGING WORLD , 2001 .

[47]  D. Niemeijer,et al.  Commentary: Discrepancies about Soil Degradation , 2002 .

[48]  P. Botterweg,et al.  The user's influence on model calibration results: an example of the model SOIL, independently calibrated by two users , 1995 .

[49]  N. Islam,et al.  Population and food in the early twenty-first century: meeting future food demands of an increasing population. , 1995 .

[50]  P. Krechetov,et al.  The system of assessment of soil degradation , 1996 .

[51]  Jaroslav Hofierka,et al.  Reply to Comment by Desmet and Govers , 1997, Int. J. Geogr. Inf. Sci..

[52]  J. Dumanski,et al.  Criteria and indicators for land quality and sustainable land management , 1997 .

[53]  R. J. Rickson,et al.  Modelling regional soil erosion susceptibility using the Universal Soil Loss Equation and GIS. , 1994 .