Vithanage Primali Anuruddhika Weerasinghe

Rapid urbanization in tropical Asia has fundamentally transformed land use–land cover while intensifying urban thermal stress, yet the relationship between land cover change and thermal conditions is frequently assumed to be spatially uniform. This study challenges that assumption by demonstrating that land cover–thermal relationships in Colombo District, Sri Lanka, are highly spatially and temporally heterogeneous, with statistically significant associations detected in only 17–47% of the study area in any given year, underscoring that context, not land cover type alone, governs thermal outcomes. Using multi-temporal Landsat satellite imagery, LULC maps were derived, and the urban heat island effect (UHIE) and urban thermal field variance index (UTFVI) were calculated for seven time periods (1989, 1996, 2002, 2009, 2014, 2019, 2024). Geographically weighted regression (GWR) was applied to model local relationships between LULC classes, namely wetland vegetation, water bodies, impervious surfaces, and other pervious surfaces, and thermal indices across a 500 m spatial grid, revealing a 74% loss in wetland vegetation and a 326% increase in impervious surfaces over the study period. Water bodies exhibited spatially variable cooling effects relative to wetland vegetation, most pronounced in eastern regions during earlier periods, while impervious surfaces showed consistent, spatially persistent warming effects concentrated in western and southern urban cores. By coupling GWR with a 35-year multi-sensor time series, this study provides a spatially explicit, longitudinal account of how land cover–thermal relationships evolve as tropical urbanization intensifies, offering an evidence base for spatially targeted rather than uniform climate adaptation planning in rapidly urbanizing tropical cities.

Mango (Mangifera indica L.) is a globally important perennial crop, valued for its nutritional, medicinal, economic, and ecological significance. Comprehensive analysis on mango variety characterization, rootstock selection, climate resilience, and germplasm conservation remains underexplored. Therefore, this review systematically analyzed 90 studies published between 2000 and 2025, following the PRISMA protocol, using databases including Scopus, Web of Science, ScienceDirect, Google Scholar, and relevant grey literature. Inclusion criteria focused on studies addressing mango varieties, morphological and physicochemical traits, rootstocks, climate resilience, and conservation mechanisms. The review highlights substantial global diversity in mango traits, with certain cultivars like Tommy Atkins, Kent, and Keitt exhibiting superior fruit quality, export potential, and climate adaptability. Rootstock selection strongly influences growth, yield, and stress tolerance, and several genotypes demonstrate resilience to drought, salinity, and other environmental stresses. Climate changes, especially fluctuations in precipitation and temperature, threaten mango phenology and production, but resilient cultivars offer opportunities for adaptation. Conservation of local and underutilized germplasm can be enhanced through socio-economic incentives such as payments for ecosystem and agrobiodiversity services. These findings emphasize the importance of integrating morphological, physicochemical, and genetic data to guide breeding and climate adaptation strategies. Targeted conservation and cultivar selection based on stress resilience and market potential can support sustainable mango production under changing environmental conditions.

The Rainfall Erosivity Factor (R) is crucial in assessing raindrop impact on soil erosion and improving disaster management in tropical regions. This study investigated changes in mean annual rainfall and raindrop impact on soil erosion in Sri Lanka’s Gampaha District over 40 years, identifying vulnerable areas for soil erosion. Maps showing rainfall and the R factor for four decadal periods (1982-1992, 1992-2002, 2002-2012, 2012-2022) were prepared using ArcGIS 10.8 and CHIRPS v.2 precipitation data (5 km resolution). Analysis across four decades (1982-2022) revealed significant increases in both rainfall and erosivity. The mean R factor grew by 59.2 MJ mm ha⁻¹ h⁻¹ yr⁻¹ (26.92%), while average annual rainfall increased by 572.01 mm (26.93%) in Gampaha District. High-R factor zones (> 285 MJ mm ha⁻¹ h⁻¹ yr⁻¹) and high-rainfall areas (> 2422 mm) expanded notably from the 1982–1992 to 2012–2022 period. Mean annual rainfall ranged between 2124.05–2696.06 mm, and mean rainfall erosivity ranged from 219.91-279.11 MJ mm ha⁻¹ h⁻¹ yr⁻¹ in Gampaha District. These trends suggest climatic shifts potentially linked to climate change, as evidenced by significant increases in mean annual rainfall and R factor between 1992-2002 and 2002-2012. The Dompe, Attanagalla, and Mahara Divisional Secretariat Divisions are particularly vulnerable to fluctuations in rainfall erosivity, primarily driven by the southwest monsoon, necessitating focused erosion mitigation efforts. Overall, the study demonstrates that climatic fluctuations have amplified rainfall-induced soil erosion over the past four decades, highlighting the urgent need for adaptive management strategies.

Rice production constitutes a critical component of food security across numerous Asian nations. However, rapid urbanization has significantly constrained the availability of agricultural land resources. This study evaluated the efficacy of remote sensing (RS) techniques for generating comprehensive paddy land maps across three distinct phenological stages—initial establishment, development, and harvesting—while simultaneously detecting land use land cover (LULC) transformations in Gampaha district, Sri Lanka, during the periods 2008/2009 and 2018/2019. Three remote sensing methodologies were systematically assessed: (1) supervised classification, (2) Tasselled Cap Transformation integrated with Normalized Difference Vegetation Index (NDVI), and (3) Land Surface Water Index (LSWI) combined with NDVI analysis. LULC change detection was conducted utilizing Landsat 5 and Landsat 8 satellite imagery processed through ArcGIS 10.8 software. Classification accuracy assessments revealed overall accuracies of 85.5% and 89.5% for supervised classification, 84.0% and 88.5% for Tasselled Cap-NDVI methodology, and 85.5% and 53.0% for LSWI-NDVI approach across the 2008/2009 and 2018/2019 periods, respectively. Results demonstrated that supervised classification proved most effective for identifying paddy fields during the harvesting stage, while Tasselled Cap-NDVI methodology exhibited superior performance during the development stage, and LSWI-NDVI analysis showed optimal results for initial stage detection. Temporal analysis revealed substantial LULC transformations during the study period, with built-up areas experiencing a 126.4% increase, concurrent with a dramatic 76.5% reduction in paddy cultivation areas. These findings underscore the severe pressure of urban expansion on agricultural land resources in the region.

Disasters are sudden, high-impact events that disrupt ecological systems, displace populations, and damage infrastructure. Effective mitigation and recovery require a systematic application of the disaster management cycle, encompassing pre-disaster, during disaster, and post-disaster phases—namely, mitigation, preparedness, emergency response, and recovery. In Sri Lanka, literature addressing the integration of all stages remains limited, resulting in insufficient empirical evidence on the effectiveness of full-cycle application and a lack of practical resources for disaster management personnel. This study presents a comprehensive evaluation of the disaster management cycle as implemented during the 2014 Meeriyabedda landslide in the Badulla District—one of the most significant landslide events in Sri Lanka. Pre-disaster interventions included land use regulation, hazard mapping, early warning systems, and risk monitoring. Immediate response actions involved evacuations to temporary shelters and coordinated relief provided by governmental bodies, NGOs, and community volunteers. Post-disaster efforts focused on resettlement, rehabilitation of affected families, and support systems for orphaned children. Findings highlight the partial effectiveness of implemented strategies but also reveal gaps, particularly in community participation, sustainable land-use planning, and institutional readiness. The analysis underscores the need for enhanced government leadership, expanded public education, and the integration of scientific research into disaster policies. This case study affirms that comprehensive, phase-by-phase implementation and evaluation of the disaster management cycle is essential for reducing vulnerability and building resilience in hazard-prone areas. The insights drawn from the Meeriyabedda experience offer a replicable model for holistic disaster risk reduction across Sri Lanka and similar contexts.

Plastics cause severe environmental and societal issues when post-consumer plastics are discarded in the environment without proper management. Pyrolysis of plastic waste is a promising method for plastic waste management due to its valuable by-products such as fuel oil. The objective of the present study was to pyrolysis waste polypropylene (PP) and waste low-density polyethylene (LDPE) plastics into fuel oil in a low-cost, lab-scale apparatus at the maximum temperatures of 330°C and 355°C, respectively, and in turn to assess the physical properties, gross calorific value, density, kinematic viscosity, flash point, ash content, and sulfur content, of resultant fuel oil. Commercially available, recycled grades of LDPE and PP pellets, 70.0 g of each, were obtained, and pyrolysis was done in a lab-scale, low-cost batch reactor. The experiment was triplicated, and the resultant fuel oil was analyzed for physical properties by ASTM standard methods. The properties of resultant fuel oil were also compared with diesel grade criteria. Results revealed that the highest yield of fuel oil was obtained from waste PP at 79.57 wt.% while the waste LDPE resulted at 74.06 wt.% of fuel oil. No wax formation was observed in the waste PP pyrolysis process, unlike in the waste LDPE pyrolysis. The gross calorific values of waste PP and waste LDPE were 12 016 kcal/kg and 11 961 kcal/kg, respectively. It was higher than the standard value of commercial diesel. The distillation results indicated that short-chain hydrocarbon content is higher in the waste PP fuel oil sample than in the waste LDPE fuel oil sample. The results indicated that the resultant fuel oil samples were nearly closer to the diesel grade criteria. Therefore, the fuel oil produced from waste plastics is a viable alternative to traditional fossil fuels, with potential applications in power generation and transportation.