Final answer:
Urban ecosystems are characterized by a linear material flow, which refers to the one-way transfer of energy and materials consuming external resources and generating waste without regenerating those inputs within the system itself.
Step-by-step explanation:
Urban ecosystems tend to have a linear material flow. This means that there is often a one-way transfer of energy and resources. In an urban setting, large amounts of energy and materials are imported into the system for consumption, and then waste is generated and exported out of the system. Because urban systems do not typically regenerate the inputs within the system themselves, unlike a more circular or cyclical flow that you might find in natural ecosystems, they rely heavily on external sources.
In contrast to circular or cyclical flows, where materials are reused within the system, urban ecosystems are characterized by a more linear consumption pattern. This pattern has significant implications for sustainability and ecological planning, as the continual need for external resources and the management of waste outputs can lead to environmental strain.