Alpine wetlands, key carbon sinks and biodiversity hubs, remain understudied, especially under climate change pressures. Hence, the present study was conducted to assess the variability in soil enzyme activity (SEA) and the carbon management index (CMI) and to utilize principal component analysis (PCA) to explore the variation and correlation between SEA and CMI as influenced by altitudinal gradients in alpine wetlands. This information is essential for exploring the impacts of soil degradation and guiding restoration efforts. The study was designed in blocks (catchments) with six altitudinal variations (from 2500 to 3155 m a.s.l), equivalent to alpine wetlands from three catchments (Senqunyane, Khubelu and Sani) as follows: Khorong and Tenesolo in Senqunyane; Khamoqana and Khalong-la-Lichelete in Sani; and Lets’eng-la-Likhama and Koting-Sa-ha Ramosetsana in Khubelu. The soil samples were collected in February 2025 (autumn season, i.e., wet season) at depths of 0–15 and 15–30 cm and analyzed for bulk density, texture, pH, electrical conductivity (EC), soil organic carbon (SOC), SEA, and carbon pools, and the CMI was computed following standard procedures. The results demonstrated that the soil was loam to sandy loam and was slightly acidic and non-saline in nature in the 0–15 cm layer across the wetlands. The significant decreases in SEA were 45.33%, 32.20% and 15.11% (p < 0.05) for dehydrogenase, fluorescein di-acetate and β-Galactosidase activities, respectively, in KSHM compared with those in Khorong (lower elevated site). The passive carbon pool (C_PSV) was dominant over the active carbon pool (C_ACT) and contributed 76–79% of the SOC to the total organic carbon, with a higher C_PSV (79%) observed at KSHM. The CMI was also greater (91.05 and 75.88) under KSHM at the 0–15 cm and 15–30 cm soil depths, respectively, than in all the other alpine wetlands, suggesting better carbon management at higher altitudinal gradients and less enzymatic activity. These trends shape climate change outcomes by affecting soil carbon storage, with high-altitude regions serving as significant, though relatively less active, carbon reservoirs. The PCA-Biplot graph revealed a negative correlation between the CMI and SEA, and these variables drove more variation across sites, highlighting a complex interaction influenced by higher altitude with its multiple ecological drivers, such as temperature variation, nutrient dynamics, and shifts in microbial communities. Further studies on metagenomics in alpine soils are needed to uncover altitude-driven microbial adaptations and their role in carbon dynamics.

The catchments that contain ecologically critical wetlands supplying the Mohale and Polihali dams under the Lesotho Highlands Water Project (LHWP) are increasingly threatened by expanding agriculture, mining activities, and uncontrolled livestock grazing. Hence, the present study was conducted to assess heavy metal contamination and wetland health across the three higher-altitude sub-catchments in Lesotho: Senqunyane, Khubelu, and Sani. A total of 24 water samples were collected from six wetlands in March 2025 to determine concentrations of copper, iron, manganese, lead, and zinc in accordance with APHA standards. Pollution Load Index (PLI) and Heavy Metal Pollution Index (HPI) were calculated to evaluate water quality. All sites exceeded the HPI safety threshold of 100, with Sani Top showing the highest PLI (5.54), indicating severe contamination primarily driven by manganese and lead. Lead emerged as the dominant pollutant due to its low permissible limits, exacerbating HPI scores across wetlands. Heavy metal concentrations generally declined with increasing altitude, with lead and copper displaying the steepest decreases, while manganese peaked at mid-altitudes (2750 m), potentially linked to local geochemical processes and organic matter decomposition. Principal Component Analysis (PCA) explained 40.6% of total data variance, revealing tight clustering at higher altitudes (3000 m), reflecting uniform, geogenically controlled water quality, whereas lower elevations displayed more variable and anthropogenically influenced patterns. Despite high-altitude sites appearing chemically stable, they carry higher dissolved ions, suggesting treatment needs for water hardness. In contrast, low-to-mid elevation wetlands showed more variable and hazardous metal loads, necessitating targeted management strategies including buffer zones, liming, and pollution source tracing. Findings highlight land use and hydrology in wetland water quality. Continuous monitoring of Lesotho’s alpine wetlands is vital to address heavy metal pollution, guide evidence-based policy, and support prioritized monitoring, mitigation, and restoration for sustainable downstream water management.