Using citizen science data to define and track restoration targets in urban areas.
Habitat fragmentation and land degradation, directly and indirectly caused by urbanization, are drastically altering the world's ecosystems and are therefore driving an imperative for ecological restoration within the world's cities. Current methods for the implementation and monitoring of restoration are limited. Restoration ecology needs cost-effective and repeatable tools for tracking changes at global scales, but with local relevance. We propose the Urban Greenspace Integrity Index-a locally relevant measure of an urban greenspace's response to urbanization, derived from widely accessible citizen science data. Unlike classical measurements of biodiversity (e.g. species richness, species diversity), this index measures species-specific responses to continuous measures of urbanization. Increases in this index are evidence of a successful urban restoration project; that is, restoration results in a community shift that favours urban-sensitive species. Importantly, data for this index are easily and efficiently collected by citizen scientists, providing long-term repeatable data. This urban index, calculated from greenspace surveys, correlates with and complements traditional biodiversity metrics. Synthesis and applications. Policymakers and practitioners can use the index-a measure of the urbanness of the local bird community-to define and track restoration of urban ecosystems, effectively measuring changes in biodiversity in response to urbanization: measuring whether the urbanness of the bird community changes through time. Importantly, this index can be calculated using citizen science data, providing a potentially long-term monitoring effort of restoration projects.