In addition to hindering speciation, human impacts may also promote speciation in terrestrial and freshwater habitats in at least two ways. First, it has been hypothesized that anthropogenic warming could cause once connected populations to move up in elevation to separate uplifted areas such as within a mountain range, isolating populations and potentially leading to allopatric speciation (Hua & Wiens 2013). However, there is no evidence that this process also occurs in freshwaters, as upward shifts in these habitats are also associated with strong changes in environmental conditions (e.g., water velocity) that cannot be easily adapted to (Timoner et al. 2020). Second, disturbances caused by habitat homogenization and human-mediated dispersal can bring new species into contact and thus promote hybrid speciation. For example, hybrid speciation at ecological time scales in response to human-mediated dispersal has been demonstrated in land plants (Abbott 1992) and freshwater fish (Marques et al. 2019). Once hybrids have formed, altered ecosystems created by humans may further facilitate their survival and spread (e.g., Hoban et al.2012), but whether this process adds new species or removes them will depend on whether it is associated with the gain or loss of habitat and ecological opportunity. Overall, humans have and will continue to impact the diversity and dynamics of communities by reducing speciation potential, but may also in some cases promote speciation.