Trend analysis

Abstract: ABSTRACT Aim Many insect species are facing existential crises, primarily due to diverse human activities. Most insect assessments, however, are based on relatively short time series or some iconic species. Here, we assess how the occupancy of ground beetles has changed in Germany over the last 36 years. Location Germany. Methods In close collaboration with taxonomic experts from natural history societies, we compiled the best available occurrence data for ground beetles in Germany, estimated the changes in species occupancy over time, and related these changes to species traits and characteristics. Results We obtained trends for 383 species and found that 52% of species significantly declined, and 22% significantly increased in site occupancy over the last 36 years. The remainder of the species (26%) all showed a mean negative trend, albeit nonsignificant. Species classified as non‐threatened in the German red list declined at a similar rate as threatened species, with 64% of the Near Threatened species experiencing significant declines (highest among all red list categories). Across all traits, we found that large (compared to medium‐sized) and omnivore (compared to predator) species declined less. Conclusions Since ground beetles are key predators in many natural and agricultural ecosystems that play an important role in pest control and the food chain, their decline should raise concerns. Thus, we urgently plead for more harmonised and systematic monitoring of this insect group.

TL;DR: In this article, a model is described in an lmer call by a formula, in this case including both fixed-and random-effects terms, and the formula and data together determine a numerical representation of the model from which the profiled deviance or the profeatured REML criterion can be evaluated as a function of some of model parameters.