Metrics for quantifying how much different threats contribute to red lists of species and ecosystems.

Red Lists are a crucial tool for the management of threatened species and ecosystems. Among the information recorded in Red Lists, the threat factors affecting the species or ecosystems listed, such as pollution or hunting, are of special relevance. In this paper, we compare three metrics that quantify the impacts of specific threat factors and may be used as indicators. The first metric, which is based on the Red List Index (RLI), has been used previously and quantifies the temporal change in the RLI caused by a threat. The second metric measures the deviation of the RLI from its reference value attributable to a threat. The third metric estimates the contribution of a threat to the expected loss of species or ecosystems within 50 years. We evaluate the three metrics using data from Norwegian Red Lists. The two latter metrics, which are novel, are found to be more informative than the first one. The third metric is more intuitive than the others and may be preferred as an indicator when communicating with stakeholders or the general public. This article is protected by copyright. All rights reserved.