Nature-based climate adaptation through riparian restoration: evidence from the Isiukhu River, Kenya

Riparian degradation can alter river water quality and aquatic biodiversity, yet evidence linking land cover, water quality and biota remains limited in Afrotropical rivers. We assessed land-cover change and variation in water quality and macroinvertebrates along the Isiukhu River, Kenya, and implications for riparian restoration and climate adaptation. Sentinel-2A imagery (2015, 2023) classified a 165.43 km² area; monthly measurements (September-December 2023) covered 16 forest, grassland, agricultural and urban sites. Natural forest declined from 82.55 to 68.15 km² (17.44%) and grassland from 30.79 to 25.66 km² (16.66%), while agricultural land rose from 48.63 to 68.01 km² (39.85%) and urban settlement from 3.46 to 3.61 km² (4.33%). Forest sites had the lowest temperature and turbidity and highest dissolved oxygen; urban sites the opposite. Of 1,350 macroinvertebrates, forest sites had the highest abundance, grassland sites the greatest abundance and proportion of Ephemeroptera, Plecoptera and Trichoptera, and agricultural sites the highest taxon richness. Baetis, Heptagenia, Elmis and Lepidostoma were more abundant in forest and/or grassland, whereas Chironomus and Tubifex predominated in agricultural and urban sites. Restoration was indicatively costed at USD 2,400 per hectare; ecosystem-service benefits were not monetised. Protecting forests and restoring corridors could support climate-resilient management, though longer-term monitoring is needed.