Ecological quality assessment: A framework to report ecosystems quality and their dynamics from reference conditions

Abstract Worldwide, ecosystems are suffering important taxonomic and functional modifications in response to anthropogenic disturbances, operating at multiple spatial and temporal scales. Awareness on biodiversity losses has led to the adoption of conservation policies and the development of programs devoted to the conservation and the restoration of terrestrial, freshwater, and marine ecosystems. The assessment of the ecological health of ecosystems requires measuring and characterizing restoration or degradation dynamics and their consequences on the ecological quality with respect to reference conditions defined pragmatically as conservation targets. Methodological innovations, in terms of data collection, analysis, and visualization, have an important influence on the ability of ecologists to understand biodiversity changes. The assessment of the quality of ecosystems with respect to reference conditions requires to address, notably, three main challenges: the definition of reference conditions, the assessment of the degree of achievement of conservation objectives, and the qualitative and quantitative characterization of recovering and departing patterns. We propose here the ecological quality assessment (EQA) framework as a data‐driven approach to track ecological quality focusing on the distance of the tested stations with respect to a chosen reference envelope using fuzzy logic and trajectory analysis. We take advantage of those analytical tools to propose a general and flexible multivariate framework by quantifying the achievement of reference conditions, measuring restoration and degradation dynamics when temporal series are available, and representing and synthesizing this information. To take into account the natural spatiotemporal variability of sites considered as reference, we gave two variants to our framework: a state‐based variant when no temporal replications are available and a trajectory‐based variant specially devoted to compare whole trajectories to a trajectory reference envelope defined by a set of reference trajectories. These two complementary approaches were illustrated through two terrestrial and marine ecological applications using the R package “ecotraj” in order to evidence ecological observations that meet conservation objectives from those that do not meet them. EQA constitutes a flexible framework for the assessment and reporting of ecosystem quality, including restoration and degradation dynamics adaptable to multiple questions in the different fields of ecology and conservation.