Multi‐Metric Monitoring: Comparing Occupancy and Abundance Based Metric Sensitivity for Detecting Threatened Species Responses to Environmental Change

ABSTRACT Detecting how threatened species populations respond to accelerating environmental change requires monitoring frameworks that are sensitive and precise. Yet it remains poorly understood how the most common population status metrics (occupancy and abundance) respond to the same environmental processes when inferring population status. We compared occupancy and abundance monitoring for their ability to detect koala population responses to environmental drivers, using double‐observer drone surveys across 169 sites spanning 176,000 ha in mid‐northern New South Wales, Australia. We modelled occupancy‐abundance relationships, quantified both metrics' sensitivity to environmental covariates, and simulated koala population responses to three threat scenarios representing key drivers of global change. Occupancy and abundance exhibited a nonlinear relationship, with abundance declining substantially before occupancy changes became detectable. Abundance models identified 40% more significant environmental predictors than occupancy models, with effect sizes generally larger and with less uncertainty. However, under simulated threat scenarios, the relative sensitivity of each metric varied with threat type and intensity. Abundance monitoring provided superior early‐warning capability for gradual environmental degradation, while occupancy proved more sensitive to habitat loss‐related local extinction risk scenarios. Our findings demonstrate that no single population metric captures the full spectrum of koala responses to environmental change. For threatened species facing multiple, interacting threats under global change, we recommend multi‐metric monitoring frameworks that integrate both occupancy and abundance. This approach maximises detection of population responses across threat types while providing the comprehensive population assessment needed for evidence‐based conservation.