Ecological Restoration in Semi-Arid Landscapes: Comparing Exclosures and Pasture for Vegetation, Soil Nutrients, and Carbon Stocks

Abstract

Land degradation in semi-arid regions poses a major threat to Sustainable Development Goal 15 (SDG 15) by undermining ecosystem services and biodiversity. Although restoration strategies like exclosures are gaining attention, there remains a critical gap in quantifying their long-term ecological and carbon sequestration benefits, particularly in severely degraded landscapes such as Ethiopia's Tigray region. This study addresses that gap by comparing 15-year-old exclosures with adjacent open pasture using a mixed-methods approach. We assessed 62 plots (31 per land use type) for species diversity (Shannon-Wiener and Simpson indices), biomass (via allometric equations), soil properties (at 0–15 cm and 15–30 cm depths), and carbon stocks, employing Principal Component Analysis (PCA) and Pearson correlation. Results showed that exclosures significantly outperformed pasture, supporting 174 plant species versus 69, higher soil organic carbon (18.71 g/100 g vs. 15.91 g/100 g at 0–15 cm, p < 0.001), and greater above-ground biomass (40.72 t/ha vs. 14.24 t/ha, p < 0.001). These findings underscore the potential of exclosures as a scalable and cost-effective strategy for restoring degraded semi-arid ecosystems, offering robust empirical evidence to inform national policy integration, advance SDG 15, and support climate change mitigation across similar regions globally.