Human impacts can cause extrinsic limitations to dispersal by creating barriers, increasing heterogeneity or by reducing habitat connectivity (Figure 3). In highly fragmented landscapes, distances that must be traveled in order to grow and reproduce often increase, which may lower the fitness of dispersing organisms (Stamps et al. 2005). Although effects of habitat fragmentation are most often studied in terrestrial environments, they are thought to be more severe in freshwater systems (Fuller et al. 2015). Human-made obstacles such as river-crossings and dams can heavily alter species dispersal patterns, including aquatic invertebrates (Brooks et al. 2013; Sondermann et al. 2015), fish (Barbarossa et al. 2020; Duarte et al. 2021) and plants (Merritt & Wohl 2006). In addition, in comparison with terrestrial habitats, fragmentation in dendritic river networks creates habitat patches that are smaller and more varied in size (Fagan 2002; Fuller et al. 2015). Finally, as river networks influence dispersal between lakes, their fragmentation may also affect lake-dwelling species (Yi et al. 2010).