Long-term impacts of urban floodplain management and habitat restoration on lizard communities in a Sonoran Desert city

Abstract

Riparian zones are critical for biodiversity but have suffered widespread degradation and therefore are key targets for ecological restoration. In urban contexts, restoring riparian ecosystems can have widespread benefits but these efforts are often limited by needs to mitigate flood risks and by a lack of long-term monitoring to evaluate efficacy, presenting important challenges for managers. To evaluate restoration potential in urban riparian systems, we studied responses of a diverse Sonoran Desert lizard community to combined flood control and habitat restoration efforts along a major river course and tributary drainage over 15 years in urban Tucson, Arizona. We used a before/after-control/impact design and linear mixed-effect models to estimate species responses to treatments that included bank stabilization and detention basin construction for flood and erosion control combined with passive water harvesting, native vegetation planting and seeding, and targeted creation of microhabitats. Despite marked declines of relative abundances and richness at treated sites immediately following construction, overall impacts were mostly positive or neutral, and negative for just one of six focal species. Most species recovered to pre-treatment levels of abundance within 2–3 years, but recovery dynamics varied with differences in life history traits and habitat use among species. In general, widely-moving, faster-maturing terrestrial species recovered more quickly and responded most positively to restoration, whereas more arboreal species with longer generation times and smaller home ranges took longer to benefit from restoration treatments. Few studies assess impacts of paired urban flood control and habitat restoration on wildlife, and our findings suggest management of urban riparian systems can provide simultaneous benefits to humans and wildlife. Future efforts may be improved by preserving and fostering more heterogeneous cover including key resources such as mature trees, as well as potentially translocating animals into restored but disconnected patches of habitat in urbanized landscapes.