Is it (socially) contagious? Capturing spatial-temporal trends of pro-environmental gardening using hazard models

Planting native gardens on verges, a form of underutilised public land, can provide biodiversity-enhancing and water-saving benefits that help achieve urban environmental goals. As a result, many governments in Australia offer support programs to encourage the adoption of native vegetation gardens on verges, yet there is limited data on actual adoption rates. By conducting a physical audit of two case study sites within the Perth capital region of Western Australia, we identify verge garden adoption rates of 11% in the Town of Claremont and 18% in the suburb of Daglish. We estimate a hazard model to examine relationships between neighbours' verge garden adoption decisions. Duration analysis shows that a household's adoption of a verge garden may positively impact their neighbours' future decisions, suggesting contagion and social mimicry effects. Between having no other verge garden conversions and the maximum level of Influence, we find a 4- to 44-fold increase in the probability of adopting a verge garden in Daglish and Claremont, respectively. We also conduct a survey of verge garden adopters to better understand the drivers of adoption, which reinforces the importance of neighbourhood norms in motivating adoption decisions. Large proportions (87% in Claremont and 39% in Daglish) of verge conversions were undertaken without participation in any government support programs. Our results suggest that local governments may achieve higher rates of behaviour change under constrained budgets by working with residents in strategic locations to form influential garden demonstration sites that target social norms, rather than solely relying on financial mechanisms to influence behaviour.