This thesis set out to investigate the processes that determine the richness and composition of plant communities of spontaneously colonized derelict land in Metro Halifax, Nova Scotia. As urbanization rates continue to rise urban spontaneous vegetation (USV) communities are becoming more common. While typically considered to have no or negative economic value, USV contributes to a variety of ecosystem services not captured in current urban ecosystem models. Vascular plant composition and aboitic conditions of three urban communities (USV, forest and lawn) are described in Chapter 2. USV is diverse and unique, but the abiotic variables measured were not strong predictors of plant diversity. In Chapter 3, ecosystem services provided by the three urban habitats were quantified and compared, showing USV provides several ecosystem services that complement other urban habitats. Studies of urban biodiversity aid in the understanding of the effects of urbanization on biota and serve as a foundation for encouraging diverse communities of organisms within cities. Factors influencing the distribution and composition of USV communities could be vital for preserving native species by incorporating such knowledge into planning and urban development systems. USV should be considered an asset to urban greening initiatives, providing a low-cost, low maintenance approach to landscape planning, while providing a number of ecosystem benefits not provided by traditional elements of landscape design.