Distinguishing between clustered and catastrophic vertebrate declines

Understanding the global state of biodiversity remains an open endeavour. A previous analysis estimated that vertebrate populations showed a mean decline of more than 50% since 1970. Here, Brian Leung and colleagues show that this estimate is highly sensitive to extreme populations: excluding the 2.4% most strongly declining populations switches the global trend to an increase, and excluding the 2.4% most strongly increasing populations strengthens the mean decline to 71%. When extreme clusters are statistically separated, no global trend remains across typical populations. Clusters of extreme decline have occurred throughout the world with no obvious spatial pattern, whereas extreme increases have occurred mostly in temperate regions. The findings emphasize the disparate nature of biodiversity trends within and across regions and taxa.