A comprehensible short list of ecological network analysis indices to boost real ecosystem-based management and policy making

Abstract

Some basic choices are discussed based on two recently proposed short lists of Ecological Network Analysis (ENA) related indices to assess food webs and ecosystems. The discussion is on the use of either internal carbon flow matrices or extended carbon flow matrices, weighted or unweighted indices and the use of ENA or not ENA related indices. The preference here is the use of weighted indices based on double hand-balanced extended carbon flow matrices. The indices that best seem to be able to serve policy makers and meet most of the requirements of different European Directives (WFD, MSFD) are Relative Overhead (Φ/DC) indicating the systems' resilience, Relative Ascendency (A/DC) indicating the efficiency of the systems’ carbon flow organisation, the Detritivory/Herbivory (D/H) indicating the importance of the detritus flow compared to primary production products, the Connectance Index (CI) indicating the number of connections among all the species (or compartments), The Finn Cycling Index (FCI) expressed as the cycled portion of the Total System Throughflow (TSTc) divided by the Total System Throughput (TSTp) indicating the carbon turnover within the system and the Mean/Average Trophic Level (written as MTL or ATL). In comparison with the medical world, the (Φ/DC) and the FCI can be considered as the thermometer and the stethoscope of the ecosystem, while the CI represents an internal system structure scan comparable to a MRI scan. The D/H ratio and the MTL can be considered as the Diet Quality and the Body Mass indices. These “medical” check-ups (indicators) indicate whether a system operates well and whether it can be considered as being “healthy”.