Urban ecology emerged as a sub-discipline of ecology in the early 1970s due, in part, to the fact that human impacts on the planet were becoming well documented and the growing size of human settlements was resulting in serious environmental problems that threatened the health and wellbeing of both urban and non-urban dwellers around the world. Influenced by these events, coupled with the demise of the ‘balance of nature’ paradigm, ecologists have acknowledged that human settlements are legitimate subjects of ecological study. The creation of the UNESCO Man and the Biosphere Program (MAB) in 1974 and the establishment of two urban LTER programs by the US National Science Foundation in the late 1990s were instrumental in encouraging the study of the ecological and social components of urban ecosystems around the Globe. Urban ecology has evolved as a unique field of study through the integration of several disciplines that investigate the ecological and human dimensions of urban ecosystems. Urban ecologists can be engaged in basic (i.e., fundamental) research focused on understanding the structure and function of urban environments, or they can be engaged in applied (i.e., practical) research that is focused on solving important environmental problems. The interdisciplinary field of urban ecology is at the forefront of creating the knowledge base, conceptual frameworks and tools that are crucial for building and maintaining sustainable and resilient cities and towns in the future.