Extinction debt of cities and ways to minimise their realisation: a focus on Melbourne By Amy K. Hahs and Mark J. McDonnell The formation and growth of cities sets in train a slow process of local species extinction, although it can take a long time for that extinction to be realised. Using Melbourne as an example, the authors ask What plant species are potentially at risk and what strategies and actions could minimise the predicted negative outcomes? Key words: conservation, indigenous plants, land management, restoration, urban ecology. Amy K. Hahs is an Ecologist and Mark J. McDonnell is the Director at the Australian Res- earch Centre for Urban Ecology (ARCUE) (Royal Botanic Gardens Melbourne, Birdwood Ave, South Yarra, Vic., Australia). They also hold honorary positions at the School of Botany University of Melbourne (Parkville, Vic., Austra- lia; Tel: +61 3 8344 0146; Email: hahsa@uni melb.edu.au; markmc@unimelb.edu.au). This paper arose from the authors’ interest in under- standing how biodiversity is impacted by urbanisa- tion, and how we can better design cities for people and nature. Introduction A ustralia is a highly urbanised nation. In June 2012, the Australian Bureau of Statistics estimated that two-thirds of Australia’s 22.7 million people were living in Australia’s eight capital cities (ABS 2013). In the pre- ceding 12 months, the population growth in these areas was faster than the growth in the remainder of Austra- lia. Over the next 40 years, the Austra- lian population is expected to increase by 8 to 20 million additional people, with a large portion of this growth anticipated to be in urban centres. Given the increasing pressure on our urban areas, we need to seri- ously consider how we can build cit- ies that will cater for the increased human population, but in ways which can equally deliver an environment where indigenous plants and animals can survive and flourish (Fig. 1). This includes designing cities and towns that will allow organisms the ability Figure 1. Potential impacts from the development of our cities may take centuries to be fully realised: yet much can be carried out to minimise plant extinctions. Pictured here is the skyline for Melbourne’s Central Business District from the remnant bushland at Studley Park. (Photo Nicole Middleton). 102 ECOLOGICAL MANAGEMENT & RESTORATION VOL 15 NO 2 MAY 2014 ª 2014 The Authors Ecological Management & Restoration ª 2014 Ecological Society of Australia and Wiley Publishing Asia Pty Ltd doi: 10.1111/emr.12112 FEATURE Ecological Society of Australia