Nigel Yoccoz (UiT The Arctic University of Norway) delves into the question: How much do we actually know—or perhaps, how much do we not know—about changes in biodiversity data? As monitoring programs become more widespread to assess spatial and temporal trends in biological diversity, one example here is the study of fish diversity in the Barents Sea. While we are aware of the ongoing biodiversity crisis, the challenge remains: how can we accurately quantify it?