Abstract
•Residential properties contribute significantly to urban biodiversity.•Garden accreditation schemes can incentivise gardening for biodiversity.•We developed a method for rating residential properties for their biodiversity.•We account for habitat extent, quality, connectivity & management practices.•Trials on 89 properties indicate the rating tool performs well.
Residential property certification schemes can inform and incentivise householders to enhance native biodiversity in their urban properties, but the certification process requires the development of a robust biodiversity evaluation tool. We used a modified Delphi process and conjoint analysis to identify and rank features associated with biodiversity to produce a tool to evaluate residential property biodiversity. We evaluated its performance in 89 residential properties in South Island, New Zealand. Property sizes assessed ranged from 260 m2 to 7195 m2. Biodiversity scores ranged between 10 and 52 out of a possible 100, indicating the challenge of obtaining a score higher than about 60. The relationship between property size and biodiversity score was positive but variable, however all properties < 500 m2 had scores lower than 30, suggesting a need for a size-specific rating system for smaller properties. Trained assessors evaluated properties in 1–2 h, with an additional hour required for collecting information online and performing calculations. Similar scores derived by a second assessor for seventeen properties (one year later) indicated that the method yields a repeatable score independent of assessor. Property assessment scores could be converted to a star rating system and used in various circumstances. A Residential Property Star rating system could be adopted by local government, housing developers, or community groups and NGOs, for example, to incentivise homeowners to enhance and sustain backyard biodiversity, to track trends in urban biodiversity, and to help meet regional and national biodiversity strategic goals.