Testing the Experts

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In absence ofreliable models and prevailing data paucity expert judgments constitute a valuable alternative for land degradation assessments. Yet, these qualitative expert opinions are branded as subjective and non-reproducible as tests for consistency are missing and qualitative classes remain difficult to interpret. This communication summarizes formal procedures to test expert judgment for consistency, reproducibility while correlation with quantitative data makes qualitative judgments interpretable.

Devastating effectsof land degradation on natural resource quality, landscape heritages and ecology have far reaching consequences for current and future human well-being. The cry for action to curb the catastrophic effects of land degradation at national scale, the level where most decisions on land use take place, seem, therefore, justified. Yet, assessing degradation processes at larger scale is not an easy task. Despite vast resources spent on development of degradation models there are hitherto no reliable quantitative assessment methods available to prioritize interventions at regional or national scale. The main reason is the chaotic and highly unpredictable nature of the degradation process that is influenced by many factors, some of which are poorly understood. Indeed absence of dense and long term monitoring networks impede explanation of the year-to-year variation of land degradation in its geographical dependence of natural resources and land use. Instead land degradation assessments increasingly resort on qualitative expert opinions that express the state of land degradation in ordered qualitative classes information that is easy to collect and inexpensive. Yet, principal criticism on uniformity, reproducibility and interpretability permeate these assessments and this communication aims to address these concerns and by introducing tests for consistency, formalizing the relationship between expert judgments and explanatory variables and quantifying boundaries of the qualitative assessments.