Hydrologically mediated multi-taxa indicator responses to early-stage rangeland restoration using semi-circular bunds in a semi-arid African conservancy

In semi-arid rangelands, land degradation is closely linked to changes in surface water movement-runoff happens quickly, water soaks in slowly, and soil moisture stays low. Nature-based solutions (NbS) like semi-circular bunds (SCBs) are being used more often to disrupt these negative cycles by slowing down surface water, increasing infiltration, and helping soils retain moisture. Despite their growing popularity, the broader ecological effects of SCBs are rarely measured beyond plant responses, especially during early stages of restoration.

This study offers a comprehensive look at how various groups of organisms respond to SCB restoration in Naibunga Conservancy, northern Kenya, focusing on hydrologically driven changes. Using a paired intervention-control design at three degraded sites, we tracked key indicators among plants, macrofungi, invertebrates, herpetofauna, and birds within two to three years of installing SCBs. Fieldwork combined systematic surveys with community science, emphasizing functional groups and indicator species tied to soil health, moisture, and ecosystem roles instead of just counting species.

Restored plots showed strong early signals of ecohydrological recovery. We observed greater numbers of soil engineers such as termites, dung beetles, and ants, along with decomposer fungi, reflecting better soil structure and increased organic matter breakdown due to improved moisture. Early-stage and mid-successional plants flourished in areas around the bunds, indicating more infiltration and less erosion. More ground-dwelling reptiles appeared in restored areas, likely benefiting from the cooler, moister habitats created by SCBs. Bird communities were also richer and more abundant in intervention sites, especially insect- and seed-eating species responding to improved vegetation and food availability.

These results reveal that SCBs set off a chain of ecohydrological recovery, where changes in water patterns drive biological responses across different levels of the food web. Tracking indicator species and functional groups provided early, sensitive measures of restoration success, outperforming overall species counts during early succession. This research highlights the importance of linking hydrological monitoring with multi-species ecological assessments for evaluating NbS in water-limited rangelands.