The 21st century is already known for unprecedented and fundamental changes and new trajectories think climate change, global economics, migration and population growth. The world is now predominantly urban and will become increasingly so until mid-century when global population is expected to stabilize at around 70% urban. The world has entered a new geological era, the Anthropocene, in which the impacts and artifacts of humans are recognized as a geologic force. In this Century of the City, for the world to be sustainable and resilient, cities must be an essential part of the solution and novel urban ecosystems will play a fundamental role. A new conception, definition, and typology of 21st century novel urban nature is proposed here as the basis for a novel urban ecosystem strategy to provide essential ecosystem services to support urban sustainability and resilience. This proposed novel nature strategy is informed by landscape and urban ecology and collaborates systematically in designed experiments with urban landscape architecture practice. Designed experiments on novel urban ecosystem are necessary to: 1) monitor the performance of innovative designs to provide essential ecosystem services; 2) to mitigate the inescapable ecosystem disservices; and 3) to build public understanding and support for new types and new models of novel urban ecosystems.