The detrimental effects of human-induced environmental change on people and other species are acutely manifested in urban environments. While urban greenspaces are known to mitigate these effects and support functionally diverse ecological communities, evidence of the ecological outcomes of urban greening remains scarce. We use a longitudinal observational design to provide empirical evidence of the ecological benefits of greening actions. We show how a small greening action quickly led to large positive changes in the richness, demographic dynamics, and network structure of a depauperate insect community. We demonstrate how large ecological benefits may be derived from investing in small greening actions and how these contribute to bring indigenous species back to greenspaces where they have become rare or locally extinct. Our findings provide crucial evidence that support best practice in greenspace design and contribute to re-invigorate policies aimed at mitigating the negative impacts of urbanisation on people and other species.

We present evidence of the recent introduction and quick spread of the European firebug Pyrrhocoris apterus in Australia, as documented on the citizen science platform iNaturalist. The first public record of the species was reported in December 2018 in the City of Brimbank (Melbourne, Victoria). Since then, the species distribution has quickly expanded into 15 local government areas surrounding this first observation, including areas in both Metropolitan Melbourne and regional Victoria. The number of records of the European firebug in Victoria has also seen a substantial increase, with a current tally of almost 100 observations in iNaturalist as of July 31st, 2021. The case of the European firebug in Australia adds to the list of examples of citizen scientists playing a key role in not only early detection of newly introduced species but in documenting their expansion across their non-native range. Citizen science presents an exciting opportunity to complement biosecurity efforts carried out by government agencies, which often lack resources to sufficiently fund detection and monitoring programs given the overwhelming number of current and potential invasive species. Recognising and supporting the invaluable contribution of citizen scientists to science and society can help reduce this gap by: (1) increasing the number of introduced species that are quickly detected; (2) gathering evidence of the species’ early expansion stage; and (3) prompting adequate monitoring and rapid management plans for potentially harmful species.Given the range expansion patterns of the European firebug worldwide, their adaptation ability, and future climate scenarios, we suspect this species will continue expanding beyond Victoria, including other parts of Australia, New Zealand, and the South Pacific. We firmly believe that most of the knowledge about how this expansion process continues to happen will be provided by citizen scientists.

Citizen‐science projects focused on ecology and conservation have been growing in popularity in recent years, offering many opportunities for researchers and volunteers alike. Two principal approaches to citizen‐science projects in ecology can be characterized as the data‐first approach and the question‐first approach. Here, we highlight the value of question‐first citizen‐science projects for providing insights into the ecology and management of urban wildlife, using case studies on (1) beneficial insects (pollinators, predators and parasitoids) and (2) possums and gliders in Australian cities and towns. The question‐first approach has many benefits, offering a platform to engage volunteers with the scientific process and the broader context of an ecological or conservation problem, while also connecting them with their local environment. Identifying the questions to be addressed in a citizen‐science project ahead of data collection allows for co‐design and stronger collaboration with volunteers, community groups, local experts, and landscape managers. Question‐first citizen science can also provide valuable ecological data that extend substantially beyond presence‐only records, including presence‐absence data collected via timed surveys and information on animal behavior and interspecific interactions. However, establishing and maintaining question‐first citizen‐science projects can be challenging, requiring the building and maintenance of many relationships and a multidisciplinary approach that goes well beyond the usual activities of an academic researcher. Well‐designed, question‐first citizen science has the capacity to achieve both scientific rigor and meaningful engagement with volunteer participants.

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