Sustainability Perspectives of Urban Green Spaces from Their Carbon Stocks and Sequestration Potential in Two Cities of India

The assimilation capacity of the biosphere and the sustainability of the living resources are enhanced by the efficient and continued contribution of the vegetation from all ecoregions of the Earth. The urban greenery fulfills many regulatory ecosystem services (RES) as well. In this regard, the importance of urban green spaces (UGS) in helping to reduce the adverse impacts of overcrowding and changing climate is of pertinence. Lack of quantitative information from urban settings in different climatic regions seriously constrains the recognition of the important role UGS play in carbon storage and sequestration. To assess how the UGS is aiding the retention of carbon, which is photosynthetically assimilated into biomass and/or sequestered, relevant field parameters were collected from 4010 trees belonging to 34 different species, different hedge plants, and groundcover grasses spread in 24,991 m2 area in three parks of Panaji city, India. Standard methods were followed to derive carbon stock and sequestration rates by trees, hedge plants, and groundcover. Notwithstanding wide differences between tree species, the weighted mean of CO2 sequestered per tree averaged 55 kg y−1 (ca. 78.82 tons ha−1) in Panaji city. Accordingly, the CO2 sequestration potential of trees, in the UGS of Panaji (by 76,751 trees) and Tumkur (with an estimated 38,152 trees) cities, respectively, was 4221.31 tons y−1 ha−1 and 2098 tons ha−1 y−1 @ 55 kg tree−1 y−1. It is apparent from this first-time study that calculated tree carbon biomass and species-wise yearly carbon sequestration rates (CSRs) of 78.82 tons ha−1 y−1 and that of carbon production rates of 31.77 tons ha−1 y−1 are far higher than the previously reported CSR estimates variously from 1 to 8 tons ha−1 y−1 and carbon production rates 3.23 to 6.55 tons ha−1 y−1. The hedge row carbon biomass averaged 13.18 tons ha−1 and sequestration of 48.38 tons ha−1 y−1 CO2. Similarly, occupying over 42% of the UGS, the groundcover carbon biomass averaged 14.69 tons ha−1 with sequestration of 53.92 tons CO2 ha−1 y−1. Combined CSP of existing trees, groundcover, and hedge plants in Panaji and Tumkur city UGS apparently neutralize carbon footprint of over 4550 and 2200 Indians at an annual per capita emission of 1.94-ton. It is thus undeniable that in our global fight against climate change, the addition of inputs and data from studies like these can aid in planning mitigation measure as well as in fulfilling local/regional sustainability plans and needs.