Identifying biodiversity hotspots over time: Stability, sampling bias, and conservation implications

The conservation of biodiversity is a major challenge facing society. In order to design effective conservation strategies, we must be able to identify the areas in which biodiversity is concentrated (i.e., biodiversity hotspots). However, observed patterns of species richness are often heavily biased by sampling effort, undermining the reliability of hotspot detection. Therefore, it is important to understand how the location of identified hotspots varies over time as knowledge about the identity and distribution of species increases. Using what is likely the most comprehensive insect database in the world (the butterflies of Great Britain), we examine the survey effort achieved over time, estimating the degree of congruence in the identification of butterfly biodiversity hotspots at different time intervals. This congruence is low over much of the 215-year period studied, remaining so for hotspots based on a rarity metric even after 1980, when the inventories were already relatively complete. The location of hotspots based on species richness has been more stable in recent decades, reflecting one the more complete sampling coverage in these years. These results highlight the risk of misidentifying biodiversity hotspots based on inadequate data and point to the need for greater sampling effort for insects to improve inventories before identifying and proposing areas for conservation. This study has significant implications for biodiversity conservation, as it provides insights into the usefulness of identifying priority areas based on incomplete inventories, such as those we currently have worldwide.