LAND DEGRADATION SURVEILLANCE

Previous efforts to assess the extent and severity of soil degradation at national, continental and global levels have been based on expert opinion and lack sufficient scientific validity to permit comparisons over space and time. More rigorous quantification is needed for targeting land and water management investments and policy decision-making.

To overcome these limitations we are developing a protocol for surveillance of soil degradation using principles adapted from medical diagnostic studies. Surveillance is the ongoing systematic collection, collation, analysis and interpretation of data; and the dissemination of information to stakeholders for action. Surveillance is fundamental for prevention and control of disease or land degradation problems.

Key Objectives of Soil Surveilance:

+ Estimate the size of a soil degradation problem
+ Early warning of soil degradation ‘outbreaks
+ Monitor soil degradation trends
+ Identify management risk factors
+ Monitor progress toward control objectives
+ Evaluate interventions and preventive programmes
+ Identify research needs

Surveillance starts from a case definition of a specific problem that is measurable and repeatable. Most previous assessments of soil degradation have not achieved this degree of rigour. Once the problem is measurable, then its prevalence (number of cases per unit area) can be assessed. From measurement of degradation prevalence it is possible to identify putative (tentative) risk factors, which are the keys to problem management. These, however, can only be confirmed through measurement of incidence (number of new cases per unit area per unit time) through monitoring programmes (prospective studies).

Surveillance systems also aim to be action-orientated, realistic and timely. Screening tests for rapid and accurate diagnosis of cases is a cornerstone of any surveillance programme. For instance, in modern disease surveillance there is very large investment in standard laboratory methods and laboratory confirmation of priority diseases. Apart from the general lack of case definitions for soil degradation, conventional soil laboratory tests are time consuming and expensive, making it impractical to adequately sample spatial variability. As a result, large area assessments are rarely attempted. A major thrust of our work has been to develop diffuse reflectance spectroscopy as a laboratory-based screening tool for soil condition and test its use in conjunction with satellite imagery to interpolate ground-based measurements over large areas.

Since many soil problems are often strongly inter-related (just as multiple diseases often are) we put emphasis on an integrated approach to assessing soil degradation. We seek a quantitative understanding of how soil functional capacity (a soil's ability to perform production and environmental functions) is affected by natural processes in the landscape and how man's action is affecting soil functional capacity through mediation of those processes.

 

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