Ecology traditionally has been fragmented into separate branches that emphasise different localities, ecosystems, habitats, levels of organisation, applications, etc., and that use distinct terminologies and methods. Individual-based ecology (IBE) can unify these branches. By taking into account the variation, behaviours, and interactions of individual organisms, IBE links the responses of organisms to the responses of ecological systems: if we understand enough about individuals, we can predict complex system dynamics, even under novel conditions. But we must also consider the system level to know what characteristics of individuals are important. In IBE, both individual and system levels are considered simultaneously, either by collecting data at both levels or at least by linking data observed at one level to existing patterns or theories at the other level. Through this comprehensive perspective, IBE unifies the many separate branches of ecology. Methodological and conceptual
advances already developed in the 21st century allow us both to make observations
at both individual and system levels and to link them using individual-based models. These advances are transforming IBE from a vision into a feasible and necessary approach that makes ecology fit for addressing the shifts and challenges of the future.