Urban Areas Create Refugia for Odonates in a Semi-Arid Region

Simple Summary In semi-arid regions like western Texas (USA), there is limited natural habitat available for wetland organisms like odonates (dragonflies and damselflies), due to water scarcity that is compounded by anthropogenic land-use activities (primarily agriculture) that compromise water presence and quality. Other forms of anthropogenic land use, however, create wetland habitat for regional biodiversity through the construction of urban stormwater catchments. We surveyed adult odonates at 133 wetlands (49 in natural grassland settings, 56 in cropland, and 28 in urban areas) in western Texas from 2003-2020. Playas in an urban setting had greater species richness than those surrounded by grassland or cropland. We recorded 33 odonate species, seven of which were found only in urban wetlands, compared to two unique species in cropland wetlands and one unique species in grassland wetlands. The remaining 23 species occurred in multiple wetland types. The odonate community in urban wetlands was distinctly different from those in non-urban wetlands. Urban wetlands were not larger in surface area than the other wetland types, but because they were fed from more consistently available urban runoff, they held water longer, even during severe regional droughts. By concentrating water in an otherwise dry area, human environments can support more odonate species than would otherwise be present. Thus, although anthropogenic activities are often seen as being detrimental to biodiversity, some activities can actually create refugia for wildlife. In western Texas, most wetlands are fed from precipitation runoff, making them sensitive to drought regimes, anthropogenic land-use activities in their surrounding watersheds, and the interactive effect between these two factors. We surveyed adult odonates in 133 wetlands (49 in grassland settings, 56 in cropland, and 28 in urban areas) in western Texas from 2003-2020; 33 species were recorded. Most species were widespread generalists, but urban wetlands had the highest species richness, as well as the most unique species of any of the three wetland types. Non-metric, multidimensional scaling ordination revealed that the odonate community in urban wetlands was distinctly different in composition than the odonates in non-urban wetlands. Urban wetlands were smaller in surface area than the other wetland types, but because they were fed from more consistently available urban runoff rather than seasonal precipitation, they had longer hydroperiods, particularly during a multi-year drought when wetlands in other land-cover contexts were dry. This anthropogenically enhanced water supply was associated with higher odonate richness despite presumably impaired water quality, indicating that consistent and prolonged presence of water in this semi-arid region was more important than the presence of native land cover within which the wetland existed. Compared to wetlands in the regional grassland landscape matrix, wetlands in agricultural and urban areas differed in hydroperiod, and presumably also in water quality; these effects translated to differences in the regional odonate assemblage by surrounding land-use type, with the highest richness at urban playas. Odonates in human environments may thus benefit through the creation of a more reliably available wetland habitat in an otherwise dry region.