A cost effectiveness approach to identify cheap and accurate indicators to assess livestock impact on biodiversity
2008
Tichit, Muriel | Barbottin, Aude | Makowski, David | Cadet, Claire
During the last 20 years, numerous agro-environmental indicators have been developed and combined into models to assess the impact of livestock on biodiversity and to monitor agro-environmental policies. Surprisingly, most studies on indicators do not explicitly mention accuracy and cost as desirable properties. This paper reports the results of a study aimed at (i) measuring the accuracy and cost of a wide range of indicators combined into models for the assessment of livestock impact on biodiversity and (ii) discussing their usefulness on the basis their cost and accuracy. Nine model selection procedures (MS) and two cross validation techniques (CV) were used to combine two types of biodiversity indicators (stocking rate and sward characteristic) measured on 252 grazed plots during two years. Sensitivity, specificity, and probability of correctly ranking plots were estimated for each model. Results showed that MS and CV had low influence on accuracy. Accuracy and cost of models were mainly influenced by the type of indicators. Models based on stocking rate indicators only were less accurate (-8%) than those based on sward characteristics but they had the lowest cost (531 versus 2495 €) with a satisfactory discriminatory ability (c. 75%). This statistical method could support researchers, farm advisers, and decision makers in comparing various indicators.
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