Moth trends and traits in Flanders (northern Belgium).

This code is related to the investigation of species traits as a guidance for moth conservation in the highly anthropogenic European region of Flanders (northern part of Belgium) based on Multi-Species Change Indices (MSCIs). Abstract Insects appear to decline rapidly in recent decades. This so-called sixth mass extinction garnered significant media attention, raising public awareness. Macro-moths—a species-rich and ecologically diverse insect group—face severe declines, particularly in urbanised and intensively farmed areas. Flanders is a highly anthropogenic region, serving as a case study where the impact on macro-moths of stressors like intensive agriculture, industrialization and urbanization has been quantified through a recently compiled Red List. Here, for 717 macro-moth species, we calculated relative changes in distribution area between a reference period (1980-2012) and the subsequent period (2013-2022). By correlating these species-specific trends with ten key ecological and life-history traits, we calculated more general Multi-Species Change Indices (MSCIs). These MSCIs showed that species associated with wet biotopes and heathlands declined on average by 20-25%, while (sub)urban species increased by more than 60%. Species feeding on lichens or mosses increased by 31%, while grass-feeding species decreased by 20%. Both very small (+34%) and very large species (+15%) increased, whereas medium-sized species decreased by 5%. Monophagous (+17%), migrant (+88%), and colour-invariable species (+5%) increased, while colour-variable species decreased (-8%). Finally, Holarctic (-21%) and Palearctic species (-5%) decreased, while Mediterranean (+27%) and Western-Palearctic species (+9%) increased. Our trait-based approach identifies key threats and mitigation strategies for moths in anthropogenic regions, offering evidence-based insights for crafting efficient management recommendations and informed conservation policies to safeguard moth communities.