Index of landscape conservation for urban nature-based solutions. A methodological shift and proof-of-concept

Urbanisation disrupts ecosystem functions and alters landscape conservation. The literature stresses the role of Nature-based Solutions (NbS) in cities in preserving and restoring these functions. However, the relationship between NbS and urban landscape conservation remains underexplored, and dedicated metrics to assess the effectiveness of NbS within the urban landscape mosaic require further research. In response to this gap, this study introduces a methodological shift through a novel spatially explicit framework that recalibrates the Index of Landscape Conservation (ILC). The framework enables scenario-based projection of NbS interventions, tailored to the hybrid nature of urban ecosystems. This approach was tested in a developed urban district (Lyde Green, South Gloucestershire, UK), where the ILC was applied at the scale of a minimum Homogeneous Urban Unit (HUU). Findings show the effectiveness of the ILC framework to capture the conservation status of the urban landscape; the analysed HUU achieved an ILC value of 0.49, corresponding to a medium level of conservation. Scenario modelling revealed that paving private gardens could lower the ILC to 0.39 (i.e., low-level), whereas installing green roofs on 50% of built-up areas could raise it to 0.53 (i.e., high-level). These findings show that the ILC framework can be a robust and adaptable tool for planners and decision-makers, supporting early-stage scenario discussions and spatial prioritisation of NbS tailored to land-cover characteristics. The research concludes by outlining limitations and future studies on the methodological and operational developments of the ILC framework.