Understanding the Carbon Sequestration Potential of Urban Gardens and Parks: Implications for Sustainable Urban Planning and Environmental Conservation

The primary objective of this study was to assess the carbon sequestration in the above-ground vegetation of urban gardens and parks within the Kathmandu Valley. To identify potential urban gardens and parks in the Kathmandu Valley, we cross-referenced GIS research with input from local government officials. Subsequently, we randomly selected 30 urban gardens and parks, each covering at least 0.5 hectares, across three districts: Kathmandu (18), Bhaktapur (7), and Lalitpur (5). These selected urban gardens encompassed various types, including government, public, and institutional. We conducted a complete tree enumeration and sampling based on the size and density of the urban parks. Complete tree enumeration was carried out in urban gardens smaller than one hectare or those with scattered trees. In contrast, sampling was employed in larger gardens with substantial forest cover. A non-destructive method was adopted for estimating the biomass of individual trees in the selected sample sites, measuring tree height and Diameter at Breast Height (DBH) at 1.3 m. Trees with a DBH greater than or equal to 5 cm were calculated to estimate tree biomass. Tee biomass was computed using the equation developed by Chave et al. (2005), which considers climate and forest stand types. In a Kathmandu Valley urban garden, the number of stems with a DBH greater than 5 cm was found to be 418.08 per hectare. The government-run urban garden exhibited the highest number of stems per acre (673 stems per acre), followed by the institutional urban garden (433.53 stems per acre). The above-ground tree biomass carbon levels in institutional, government, and public urban gardens were 50.10, 72.64, and 13.70 tons per hectare, respectively. The below-ground tree biomass carbon content in institutional, government, and public urban gardens was 10, 14.53, and 2.70 tons per hectare, respectively. The total carbon content originating from trees in institutional, government, and public urban gardens were 60.10, 87.17, and 16.40 tons per hectare, respectively. The calculated carbon level averaged 54.56 tons per hectare, which is lower than the national carbon level, likely attributed to the lower occurrence of stems per hectare in public parks.