A new study on biodiversity shows that species richness is not a reliable measure for monitoring ecosystems. According to the study, seemingly healthy ecosystems with a constant or even increasing number of species may already be on the path to decline and loss of species. Even in long-term datasets, such negative trends may only become apparent with a delay, according to scientists from the University of Oldenburg (Germany) and the University of Girona (Spain), which has recently been published in the journal Nature Ecology & Evolution.