Selecting appropriate plant indicator species for Result-Based Agri-Environment Payments schemes

Agri-Environment Schemes (AES) have long been implemented across Europe to incentivise farmers to alter their management practices to improve biodiversity and water, air and soil quality. However, the cost-effectiveness of traditional action-based schemes has been questioned, and Result-Based Payment (RBP) schemes have been recommended as an alternative. To evaluate the effectiveness of management actions, RBP approaches often rely on indicator species to monitor changes in environmental conditions. The selection of appropriate indicator species for RBP follows several steps and criteria. One of the mentioned criteria is that the species should react to the farmer?s management choices. Thus, the main objective of this study is to understand how existing lists of indicator plant species (aimed at assessing ecological integrity of grasslands and hedgerows in Ireland) are suitable for RBP schemes, by assessing how different environmental and management variables are related to the presence of the plant species selected. Extensive field surveys were conducted to assess the presence and cover of indicator species in grasslands and hedgerows in two study regions in Ireland. The indicator plant species occurrence and diversity (species richness and Simpson?s Diversity Index) were correlated with variables within farmers? control and variables outside farmers? control. Results showed that grassland indicator species occurrence and diversity was mainly related to grassland semi-naturalness and to the diversity of habitats existing on the farm ? both variables within farmers? control ? and thus were appropriate indicators for assessing the effectiveness of management and suitable for use in RBP schemes. Conversely, the occurrence and diversity of hedgerow indicator species was not strongly related to any of the explanatory variables, making them unsuitable for use in a RBP scheme. For a RBP scheme targeted at hedgerows, clear objectives will need to be established and the farmers? management choices need to be better linked to the selected indicator species. The selection of indicator species needs to undergo scientific scrutiny to develop fair results assessments as shown by the results of this study. The analyses conducted highlight the importance of testing if the species react to the farmers? management choices and should be a key methodological step before final indicator species lists are implemented in RBP schemes. Recommendations for results assessments in RBP approaches are discussed based on the results of this study.