Improving biodiversity in Central and Eastern European gardens needs regionally scaled strategies

Amid ongoing urbanisation, gardens are expected to play an increasing role in enhancing urban biodiversity by supplementing green areas and improving landscape connectivity. Biodiversity-friendly gardens also improve human well-being and foster connections between nature and people. To study these benefits, we distributed a questionnaire (n=5255), and used a scoring system to evaluate gardens’ ecological value (GAR index), gardeners' attitudes (RES index), and pesticide use habits (PES index). We used machine learning to explore how these indices interact and what sociodemographic factors drive them across Central and Eastern Europe (CEE). Our aim was to explore the ecological values of gardens and gardening practices, identifying characteristics that might contribute to building high biodiversity. We found significant variability within and between countries, with Romania scoring low and Czechia high in all indices. Domestic pesticide use was ubiquitous across CEE and largely unaffected by sociodemographic factors. Increased time spent gardening was associated with the highest pesticide use and a greater potential for fostering high biodiversity. Gardeners aged over 55 tended to uphold longstanding conventional practices and thus lowered both PES and GAR index scores. The local differences highlight the need for regionally tailored biodiversity-friendly gardening guidelines instead of standardised regulations across Europe. Effective environmental education and community programs can be developed based on local biodiversity and the three indices we used. These programs should inform gardeners about the environmental and health impacts of pesticides and provide comprehensive biodiversity-related knowledge. This is especially important in CEE, where such initiatives are currently underrepresented. • Questionnaire study was conducted across nine Central and Eastern European countries • Significant variability both between and within countries in gardening practices • Improving biodiversity in gardens needs regionally scaled strategies • Reducing pesticide use and increasing public awareness are key • Our indicators can support local strategies to increase urban biodiversity