Nature-based solutions for hydro-meteorological extremes in South Asian countries: Current practices, gaps, and opportunities

South Asian countries are highly susceptible to different forms of hydro-meteorological extremes (HMEs) like cyclones, storm surges, floods, erosion, sea level rise, etc., while changing patterns of climate variability also make the situations worse. Nature-based Solutions (NbS) in different forms, like mangrove forests, coral reefs, salt marshes, beach nourishment, reforestation and afforestation, wetland restoration, etc., can help to reduce the magnitude of impacts. This study was conducted in South Asia countries to understand the existing practices, challenges, and potentiality of NbS regarding HMEs. The findings of sea level rise-induced extreme events are summarized as follows: (a) Significance of coastal ecosystems in mitigating impacts of HMEs, (b) NbS approaches for coastal protection and restoration, (c) Co-benefits of NbS for coastal protection and restoration, (d) Coastal Protection and NbS: South Asia Perspective- (i) Current practices of NbS to protect the coastal region, (ii) Challenges to ensure NbS regarding coastal protection, and (iii) Potentiality of NbS to protect the coastal region. Unusual rainfall patterns and their connection to landslides, along with the environmental and socioeconomic consequences and threats to vulnerable groups, are examined. We also delve into NbS interventions that stabilize slopes and prevent erosion-related events, emphasizing the significance of early warning systems, community-based strategies, and disaster preparedness measures to enhance resistance and resilience. Case studies from Chittagong Hill Tracts and Rohingya Camps in Bangladesh demonstrate the customization of NbS approaches to meet particular needs. An in-depth analysis of diverse NbS approaches, including forest and floodplain restoration, construction of wetlands and green infrastructure, and several other solutions for urban flood prevention, is presented. The extent of their effectiveness and barriers to expanding NbS practices are discussed, encompassing a range of contexts from high-income urban areas to medium and low-income regions. The focus lies on the adaptability and potential impact of NbS in various contexts, providing valuable insights into their applicability. Barriers to large-scale implementation of NbS for urban flood prevention are elucidated, encompassing legislative, financial, and societal challenges that impede the integration of NbS in practice and policies, which hinder employing initiatives for a long-term national plan for NbS. Strategies to surmount these barriers are discussed, offering insights for stakeholders seeking to navigate the complexities of NbS integration. We conclude that although NbS can be considered a cost-effective and sustainable way to protect natural ecosystems and human properties, it needs more concentration to integrate into decision-making aspects from policy to practice perspectives.