A generally unrecognized side effect of this globalization is the introduction of alien species, at least some of which may be invasive. Global mobility has undermined the sense of place that previously provided a psychological anchor to most societies. The speed at which many modern people live, including great mobility, seriously compromises their ability to develop a sense of place, a clear vision of the future, or a sense of origin. This makes it much more difficult for people to distinguish between native and alien species, or to be concerned about the difference. Linked to the global marketplace, the world is becoming increasingly urban, with half the world's population living in cities at the turn of the century.
Cities tend to be the focal points of the global economy and the entry points for many invasives.
Many invasive species are most prolific in urban and urban-fringe environments where long histories of human disturbance have created abundant bare ground and many opportunities for invasion. Many urban dwellers seek ornamentals from a wide range of sources, and these may become invasive. Urbanization involves large and mobile populations that can easily escape the environmental penalties from mis-using resources. Settlement patterns also involve transportation links, and the distribution of many invasives seem to follow transportation corridors. They might also be worried that they would be expected to compensate those who are negatively affected.