Spatial, temporal and taxonomic patterns of insect extinction in Germany

Abstract

Red lists represent an important instrument for evaluating the decline of species in space and time, for improving decisionmaking and for guiding conservation planning. However, globally, only a fraction of species has been categorized according to a red list, even in countries where insects are relatively well-studied. Such large knowledge gaps hinder conservation planning and ultimately jeopardize the maintenance of ecosystem functions. Given the recent reports on severe insect decline, it is now more than ever of great importance to obtain a reliable complete picture of the state of insects. We here derive an estimate of extinction rates and of the proportion of threatened species for the total insect community in Germany, and asses spatial and temporal of extinction patterns. We found a regional extinction rate of 4.5% (1773-1937 species) for the area of Germany. Among extant insect species, 6% are classified as critically endangered (1856-2024 species), while among remaining species, a staggering 36.1% (10758-11086 species) is classified as threatened. Higher trophic levels of zoophagous insects are often more sensitive to negative environmental changes due to their position in the food web, and at the same time are underrepresented in Red Lists. They are therefore disproportionately affected by these knowledge gaps. This concerns particularly parasitoids which are taxa of regulatory importance and often higher extinction risk levels due to their trophic position. Exemplary examination of the spatial scaling of red list categories indicate a far higher rate and risk and exemplary over ten times higher regional extinction rate when the reference area is gradually scaled down. This illustrates the actual situation regarding the magnitude of regional species extinction events and extirpation risks that we have to assume for certain parts of the reference areas. For a given region, the loss of the gene pool of populations specially adapted to a given region usually represents an irreversible biodiversity loss. In order to avoid further irreparable damage, the species threatened with extinction must be preserved with top priority. There is thus a considerable need for research in order to assess the conservation status of more than 56% of the insect species diversity in Germany and to immediately achieve a more balanced trait group representation in red lists.