Biodiversity and agri-environmental indicators—general scopes and skills with special reference to the habitat level

Abstract

This synoptic review has the intention to summarise and highlight results in respect to the area “biodiversity and habitat” considering the current “state of the art” with regard the development of biotic indicator approaches that refer to the fauna of agro-ecosystems. Most political statements (e.g. “Convention of Biodiversity Development”: Agenda 21, Convention of Rio 1992) as well as existing approaches regarding the development of biotic agri-environmental indicators focus mainly and almost exclusively on “biodiversity”, the enhancement of which is the overall target for the development of agricultural landscapes towards sustainability. In this regard the understanding of the term “biodiversity” is rather different: it is largely interpreted as species richness, only occasionally as the richness of varieties, cultivars or genetical expressions (e.g. microorganisms). A survey on the understanding of biotic indicators is presented including aspects of nomenclature, categorisation and definitions as well as preconditions and rules for their use. Requirements for different taxa (mostly invertebrates) to act as biotic indicators are summarised and several attempts to use animals on the population and/or community level as biotic indicators for biodiversity or other goals in agro-ecosystems are discussed critically as well as their replacement by surrogate indicators. Regarding the sensitivity of indicators it will be highlighted that it is necessary to evaluate and to compare cultivation intensities, that are rather similar (e.g. gradual differences in conventional managed farms and landscapes) as well as those displaying much larger differences (e.g. organic farming versus conventional farming), because conventional farms currently cover nearly 90% of the agriculturally used area in Europe. Other fundamental problems regarding the development of biotic indicators as baselines, sample size, frequency of surveys, mutual neutralisation of indicators, double assessments, selection of taxa, etc. are addressed. Finally an assessment of the practicality, the power of indication statements and the remaining work required to validate indicators will be provided for discussion, as well as suggestions for a simplification of indicator systems in order to minimise the input needed for data recording.