Nature-Based Solutions for Integrated Climate Adaptation in Arid and Semi-Arid Regions: A Systematic Review

Arid and semi-arid regions are among the most vulnerable to climate change, facing the combined pressures of chronic water scarcity, rising temperatures, and an increasing frequency of extreme rainfall events. Climate change is intensifying hydrological variability in these regions, amplifying prolonged droughts while also increasing the occurrence of short, high-intensity storms that generate flash floods, particularly in urban areas. Addressing these compound risks requires integrated adaptation strategies capable of simultaneously managing water scarcity, flood risk, and heat stress. In this context, Nature-Based Solutions (NbS) are increasingly recognized as a promising approach, offering multifunctional benefits that extend beyond the single-purpose performance of conventional grey infrastructure.

This contribution presents a systematic review of NbS applications  based on the analysis of 89 peer-reviewed case studies. The review assesses geographical distribution, typologies, targeted societal challenges, structural and vegetation characteristics, and water management strategies. The focus is placed on the capacity of NbS to generate synergies for climate change adaptation by jointly addressing drought mitigation, flood risk reduction, and microclimate regulation, while enhancing ecosystem services and long-term urban and territorial resilience.

Quantitative evidence from the review highlights the dominance of water-related adaptation objectives. Across all cases, 39% of NbS primarily target drought mitigation, increasing to 61% when combined objectives such as flood mitigation and water security are considered. Green roofs represent the most frequently implemented NbS, accounting for 33% of interventions in arid regions and 24% in semi-arid regions. Rain gardens follow (12% in arid and 16% in semi-arid contexts), while detention and urban parks each account for approximately 10% of cases in arid regions. In semi-arid regions, detention tanks are particularly relevant, representing 21% of applications, reflecting a stronger emphasis on flood management. Importantly, NbS addressing both drought and flood risks are common: green roofs appear in 40% of these multi-hazard cases, while rain gardens and detention tanks each account for approximately 20%, underlining their synergistic role in regulating hydrological extremes.

From an ecosystem services perspective, regulation and maintenance services dominate, particularly runoff attenuation, evapotranspiration-driven cooling, and soil moisture enhancement. Vegetation selection is explicitly discussed in 46 out of 70 vegetated NbS cases, with drought-resistant and native species prevailing, especially in arid climates. Regarding water supply, 88 studies include irrigation systems; when specified, 56 rely on rainwater, 11 on greywater, and only 2 on desalinated water, highlighting both the centrality of water reuse and the limitations of conventional sources in dry regions.

The findings confirm that NbS deliver their highest adaptive value when implemented as integrated systems rather than isolated measures. By combining storage, infiltration, evapotranspiration, and reuse functions, NbS can buffer hydrological variability while providing co-benefits for urban cooling, biodiversity, and livability. However, their effectiveness depends on climate-adapted design, appropriate vegetation choice, and institutional frameworks that recognize NbS as legitimate components of climate adaptation strategies.

Overall, this review demonstrates that NbS offer measurable and scalable synergies for climate change adaptation in arid and semi-arid regions. The quantitative evidence provided supports their integration into planning and policy frameworks as cost-effective, multifunctional solutions capable of addressing multiple climate risks simultaneously.