Australia has increasingly been dependent on the interest and capacity of community organisations across the country in order to accomplish environmental sustainability initiatives (e.g. urban nature protection). A comprehensive understanding of how these organisations thrive can be valuable not only for cities like Perth, where two-thirds of bushlands and wetlands have been lost in the past 150 years, but also for government strategies that seek to support these initiatives. This article draws on a systems perspective and utilises a mixed-methods approach to assess the organisational capacity-viability nexus. Findings suggest that inter-organisational ties facilitate a continuous positive feedback mechanism whereby organisations are able to acquire enough inputs and yield significant environmental outputs so that they can keep functioning until their missions are fulfilled. Based on the evidence the article discusses the potential ways to secure the future of urban environmental sustainability initiatives in Perth and beyond.