This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordThe challenge: Understanding how biotic interactions affect species’ geographic ranges, biodiversity patterns, and ecological responses to environmental change is one of the most pressing challenges in macroecology. Extensive efforts are underway to detect signals of biotic interactions in macroecological data. However, efforts are limited by bias in the taxa and spatial scale for which occurrence data are available, and by difficulty in ascribing causality to co-occurrence patterns. Moreover, we are not necessarily looking in the right places: analyses are largely ad hoc, depending on data availability, rather than focusing on regions, taxa, ecosystems, or interaction types where biotic interactions might affect species’ geographic ranges most strongly. Unpicking biotic interactions: We suggest that macroecology would benefit from recognising that abiotic conditions alter two key components of biotic interaction strength: frequency and intensity. We outline how and why variation in biotic interaction strength occurs, explore the implications for species’ geographic ranges, and discuss the challenges inherent in quantifying these effects. In addition, we explore the role of behavioural flexibility in mediating biotic interactions to potentially mitigate impacts of environmental change. New data: We argue that macroecology should take advantage of “independent” data on the strength of biotic interactions measured by other disciplines, in order to capture a far wider array of taxa, locations and interaction types than are typically studied in macroecology. Data on biotic interactions are readily available from community, disease, microbial, and parasite ecology, evolution, palaeontology, invasion biology, and agriculture, but most are yet to be exploited within macroecology.