Using Simulations to Evaluate the Utility of Geohistorical Reference Conditions for Assessing Ecological Quality

Incorporating paleontological data into the methods and formats familiar to conservation practitioners may facilitate greater use of paleontological data in conservation practice. Benthic indices (e.g., Multivariate-AZTI Marine Biotic Index; M-AMBI) utilize reference conditions for monitoring ecological conditions. However, reference conditions from monitoring records are limited in temporal scope and often represent degraded conditions, which can cause inaccurate assessments of ecological quality. Paleontological data, such as molluscan death assemblages, have potential to provide long-term, location-specific reference conditions, which are otherwise inaccessible to decision-makers. Here we use simulations of living communities under constant and changing environmental conditions to evaluate the capacity of death assemblage reference conditions to replicate M-AMBI values when used in place of reference conditions from the living communities. Reference conditions from all death assemblage scenarios successfully replicated correct remediation decisions in most simulation runs with environmental change and stability. Variations in M-AMBI values were due to overestimated species richness and Shannon entropy values in the death assemblages and effects of changes to these parameters varied across scenarios. Time averaging was largely beneficial, particularly when environmental change occurred, and short-term observations of the living communities produced incorrect remediation decisions. When the duration of time averaging is known, death assemblages can provide valuable longer-term perspectives with the potential to outperform temporally constrained baseline information from monitoring the living community.