Destruction is easy, but can we undo degradation and improve riverscapes?

Authors: Skyler Hedden, Julie Carter, George Cathey

Year: 2024

Abstract

Desert aquatic habitats have been negatively impacted for centuries by human induced changes, and it is likely that these impacts will continue into the future. Given that habitat loss and alteration are among the leading causes of imperilment of aquatic species, conservationists should focus on improving habitats whenever possible. However, destruction is easy, but how successful are we at improving previously altered habitats? We assessed if habitat improvement projects could enhance aquatic habitat conditions across three different projects in the upper Little Colorado River basin, Arizona. Habitat renovations varied in spatial extent (0.15 km to 1.75 km) and objectives varied among projects, attempting to either create novel habitats, decrease bank erosion, improve riparian conditions, or to increase water availability for fish. For the smallest project, a disconnected side channel was reestablished, creating novel pool and riffle habitats that were 67% and 43% deeper than control sites. For the next project cut banks were stabilized and floodplain swales and back waters were created to reduce river stress and sediment loading. Based on pre and post construction data, the proportion of silt in the river was reduced by 37% immediately downstream of the project area. For the largest project, we attempted to reduce head cutting, while simultaneously attempting to increase water availability by raising the stream channel. In control reaches, the number of perennial pools were consistent through time, however in the improved reach, perennial pools increased by three-fold, allowing for native fish translocations to occur. We show that all three habitat improvement projects have met their desired results and have improved habitat conditions for fish, likely contributing to species persistence and recovery. Therefore, when clear objectives are set and the proper personnel are involved, habitat improvement projects can contribute to successful conservation management.