Ecohydrological nature-based solution for climate resilience and biodiversity enhancement in water-limited ecosystem: Perspectives and proof of concepts

Following the declaration of the UN Decade on Ecosystem Restoration, nature-based solutions (NbS) are at the forefront of the sustainability discourse. However, this solution needs operational clarity to avoid the commonly mentioned vagueness of the concept. This paper highlighted application of the ecohydrological principles to guide the conception, planning, designing, implementation, and monitoring of nature-based solutions. The paper proposed an ecohydrological nature-based solution that is emanated from the natural sequence of self-regulating patch-interpatch at the hillslope scale to restore highly degraded hillslope in Lake Hawassa sub-basin of Ethiopian Rift Valley Basin. The active restoration site is found to have a landscape organization index value of 0.94 (= 94% of the gradsect is consisting of resources conserving patches) as compared to 0.16 at the passive site. In terms of landscape functionality, the active site showed significant stability (p(x≤T) = 0.01), infiltration (p(x≤T) = 0.001), and nutrient cycling (p(x≤T)=0.005). It also exhibited significant improvement in soil moisture (p(x≤T) = 0.001). Ecologically, the active site is found to be more diverse (richness index 18 (active) vs. 8 (passive); heterogeneous (Shannon diversity index=1.22 (active) vs. 0.44 (passive)); well distributed (Simpson's index= 0.62 (active) vs. 0.28 (passive)); less dominance of few species (Evenness index (0.99 (passive) vs. 0.96 (active)). Limitation of this study is linked with the short span of the restoration period which tends to be not adequate to observe the full ‘dual’ regulation between hydrology and biota. For this, the research can be considered as a prerequisite towards full restoration of the landscape.