Sustaining ex-mining lake-converted constructed wetlands as nature-based solutions: A comprehensive assessment of the carbon-water nexus in Paya Indah Wetlands, Malaysia

Water and carbon, essential for Earth's well-being, face imminent threats from human activities that fuel climate change. This study investigates nature-based solutions, focusing on the carbon-water nexus of ex-mining lakeconverted constructed wetlands, specifically in Malaysia's Paya Indah Wetlands (PIW). Addressing research gaps, it assesses the ecosystem services of these wetlands, emphasising integrated evaluations for informed land management and employing a top-down conservation approach. Methodologically, spatial assessments, soil and water sampling, carbon quantification, water quality index calculations, land cover classification and stakeholder surveys were conducted. Results underscore the significant carbon sequestration and water quality improvement potential of constructed wetlands, with soil and sediment carbon accumulation reaching 1553.11 Mg C ha- 1 (equivalent to 5700 Mg CO2 ha- 1), translating to an annual sequestration capacity of 67.5 Mg C ha- 1 year- 1. Water quality index values ranged from 58 to 81 (Classes II to III). PIW's establishment led to a reduction of over 90% in barren land, with increases in water bodies (36%) and vegetation-covered land (38%), boosting wildlife populations by 30%. Spatial variations in organic carbon density and water quality underscore the complexity of the carbon-water nexus and its impacts on ecosystem health and water security. Despite land use changes, PIW demonstrates resilience, contributing to climate change mitigation. Stakeholder perceptions vary, emphasising the need for adaptive strategies. The study proposes transdisciplinary conservation initiatives and adaptive plans, stressing the pivotal role of ex-mining lake-converted constructed wetlands in enhancing climate resilience.