Stability metrics are predictable across data qualities but sensitive to community size

Abstract

Modern biodiversity monitoring is generating increasingly multidimensional representations of wildlife populations and ecosystems. It is therefore appealing for conservation and environmental governance to combine that information into single measure of ecosystem or population health. The Jacobian matrix is a common characteristic used to identify the sensitivity of simulated/mathematical systems to perturbation (a.k.a. its resilience) and predict its near future dynamics. Jacobians have therefore been suggested as a theoretically grounded measure of ecosystem resilience. Whilst historically it has been challenging to estimate the Jacobian from empirical data, recent work has proposed a suite of metrics capable of reconstructing it for real-world community using multi-species time series data. Here we assess the robustness of five resilience metrics influenced by varying time series lengths and data qualities based on that seen in real-world wildlife time series. We generate data using multispecies Lotka-Volterra equations and simulate stressed and unstressed communities of varying species number. These data were then corrupted through the introduction of sampling error (to mimic varying search efforts) and truncating time series (to match the typical time series lengths reported in global biodiversity datasets such as the Living Planet Index and BIOTIME). The robustness of all resilience metrics improved with time series length, whilst the amount of sampling error had little effect on their performance. However, community size (number of species) dramatically altered metric capability, with larger communities decreasing the reliability of resilience metric trends. Overall, resilience metrics behave predictably across realistic data corruptions. Generic resilience estimation is therefore possible from abundance time series alone, and we suggest that, given the increasing availability of multivariate community data, focussing on Jacobian estimates for resilience is a promising avenue of research. However, we also show it is prudent to apply ecological knowledge when selecting which species to contribute.