*4.1. Setting*

Understanding how the watershed setting of artificial aquatic systems affects their ecology is important both because understanding will be essential for better policy and management, and because the effects of setting may obscure the ecological effects of other factors such as design, management, and time. The condition of the watershed and landscape around any waterbody influences its condition [93], and artificial aquatic systems should be no different in this respect. Since humans tend to create artificial aquatic systems in and around heavily modified landscapes with substantial chemical inputs like agricultural fields, roads, and parking lots, artificial aquatic systems such as ditches tend to have lower water quality than their natural counterparts [94–96]. The communities of artificial aquatic systems also tend to reflect the local and regional species pools, yielding, for example, more exotic species in a restoration in a developed area [97].

Available evidence suggests that setting does exert a strong and often overwhelming influence on artificial waterbodies, and that these effects are similar to those observed in natural systems. Water quality of artificial aquatic systems such as ditches responds to catchment land use in much the same way as that of waterbodies of natural origin [8,98], and agricultural land cover impacts reservoirs food webs [99]. In the Salt River in Arizona, level of urbanization explained much of the variance in communities of plants, birds, non-avian reptiles, and amphibians, for reference, restored, and accidentally restored river reaches alike [15]. A study in the Florida panhandle found that natural streams, altered streams, and ditches within the same forested region had similar macroinvertebrate and fish assemblages [100]. Agricultural intensification around fishponds has contributed to the rapid decline in breeding populations of black-headed gulls (*Chroicocephalus ridibundus*) in central France [101]. More such comparisons between artificial and natural waterbodies in similar settings are needed to disentangle the effects of watershed setting from other factors that influence the condition of artificial aquatic systems.

The predictable responses of artificial aquatic systems to their watershed setting has implications for how these systems are managed and how that managemen<sup>t</sup> could be improved. The importance of watershed land cover for reservoir water quality shapes economically motivated conservation, like New York City's efforts to prevent development in the watersheds of its reservoirs upstate [102]. More generally, stream restoration is more effective in undeveloped than developed catchments [103]. While more studies are needed, the available evidence suggests that the condition of artificial aquatic systems depends strongly on their setting, and that those conditions, and the ecosystems services that depend on them, could be improved by the same watershed-scale policy and managemen<sup>t</sup> that protects natural waterbodies.
