Ecological restoration often aims to recreate so-called pre-settlement conditions, but this can be problematic in urban areas where human activities have erased most traces of pre-settlement conditions. NRS researchers Paul Gobster and Lynne Westphal and a German colleague, Matthias Gross, analyzed urban restoration projects and developed several alternative models that articulate the various possible types of restoration projects. The classical model restores sizeable patches of indigenous plants, through traditional practices like invasives control and replanting. The sensitive species model focuses on protecting and enhancing sensitive individual species, often a specific bird or butterfly. The habitat model aims more broadly to provide appropriate conditions for a range of desired species such as wetland-dependent birds, as well as appropriate non-native species to provide food and cover. The cultural landscape restoration model recognizes the importance of human endeavors and their history as reflected on the land in addition to plant and animal assemblages present. In the rehabilitation model, restorationists work from almost nothing to bring back natural systems in severely degraded sites. Together, these models can help project managers determine what kind of restoration is desirable and if it is possible.