Tanzania Journal of Forestry and Nature Conservation, 77: 25-34The possibility of global climate change, due to increasing levels of CO 2 concentrations is one of the key environmental concerns today, and the role of terrestrial vegetation management has received attention as a means of mitigating carbon emissions and climate change. In this study tree dimensions and assessment of plant species composition were used to quantify the potential of urban ecosystems in acting as carbon sink and mitigating climate change through carbon assimilation and storage and the potential of the system to enhance biodiversity conservation taking Morogoro Municipality as a case study. Biomass/carbon models for trees were developed and used to predict biomass/carbon storage based on tree diameters. The model was in the form B = 0.5927DBH 1.8316 (r 2 =0.91, P< 0.01). The carbon content was computed as 50% of the tree biomass. The tree carbon for Morogoro municipality ranged from 4.63±3.39 to 21.18±12.41t km -1 length of ground surface along roads and avenues. Newly established areas seemed to have lower carbon storage potential while areas established earlier have highest carbon storage potential. About 36 different tree species growing/planted in the Morogoro municipal were identified, dominated by Senna siamea, Azadirachta indica, Polyalthia longifolia, Leucaena leucocephala, Pithecelobium dulce and Mangifera indica. Apart from being natural amenity the tree species also act as CO 2 sink through photosynthesis and areas of ex-situ conservation of plant diversity. Urban forestry can store large amount of carbon in addition to biodiversity conservation especially where they cover extensive areas like parks, gardens and avenues managed over long periods, as is the case in urban ecosystems. Improved management of urban forests will likely improve the potential for carbon storage by terrestrial vegetation as a means of mitigating CO 2 emissions and climate change as well as biodiversity conservation.