SignificanceLarge changes can occur when ecosystems cross certain thresholds. Crossing such thresholds poses a challenge to ecosystem management because the positions of the threshold are uncertain and change over time. However, as an ecosystem approaches a threshold its resilience declines, resulting in changes in system dynamics that increase variance and autocorrelation. Calculating these statistics requires frequent and sustained sampling efforts. Our study detected an approaching threshold by computing the statistical indicators from data collected by automated sensors, which are far less labor-intensive than comparable manual methods. Thus it may be feasible to monitor for approaching ecosystem thresholds using automated methods. This finding highlights a powerful use of modern sensor technology.