Contents lists available at ScienceDirect Applied Geography journal homepage: www.elsevier.com/locate/apgeog Using remote sensing and traditional ecological knowledge (TEK) to understand mangrove change on the Maroochy River, Queensland, Australia Matthew I. Brown a , Tristan Pearce b,c,* , Javier Leon a , Roy Sidle b , Rachele Wilson a a Sustainability Research Centre & School of Science and Engineering, University of the Sunshine Coast, 90 Sippy Downs Drive, Sippy Downs, Queensland, 4558, Australia b Sustainability Research Centre, University of the Sunshine Coast, 90 Sippy Downs Drive, Sippy Downs, Queensland, 4558, Australia c Department of Geography, University of Guelph, 50 Stone Road East, Guelph, Ontario, N1G 2W1, Canada ARTICLE INFO Keywords: Ecosystem services Traditional owners Indigenous knowledge Kabi Kabi Gubbi Gubbi Participatory mapping Knowledge system ABSTRACT Mangrove forests support a variety of ecosystem functions and services imperative for ecosystem health. Despite the importance of mangroves, however, mangrove forests worldwide are under threat from human development and climate change. To date, most research on mangrove change in Australia has drawn on approximately 40 years of remotely sensed imagery, a fraction of the time period required to assess spatial change. To improve our understanding of mangrove change, data were collected using historic and current remotely sensed satellite imagery and participatory mapping with Kabi Kabi Traditional Owners to assess mangrove change on the Maroochy River, Queensland, Australia. The results indicate that mangrove extent in the lower Maroochy River has changed significantly since European colonisation in the mid to late 1800s, and declined in recent decades by approximately 30%, a rate similar to global estimates of mangrove loss. Past drivers of change included land clearing for cattle grazing and sugar cane production, and present drivers include agricultural activities, po- pulation growth, rapid urbanisation and discharge of pollutants and sewage. These changes have consequences for coastal protection, water purification, biodiversity and cultural services. This research demonstrates how using traditional ecological knowledge (TEK) and remote sensing for understanding ecosystem change, parti- cularly where scientific data are limited, can increase the time period during which change is assessed and enhance the detail and scope of the assessment. 1. Introduction Mangroves grow exclusively within the intertidal zone of tropical and sub-tropical coastal regions, while saltmarsh ecosystems typically occupy the upper tidal zone but below the highest astronomical tide- mark (Aslan, Rahman, Warren, & Robeson, 2016). These transitional ecotones are uniquely placed where ocean, land and fresh water con- verge, and perform a number of ecological functions that are vital to the health of near-shore marine environments and surrounding terrestrial systems (Kathiresan & Bingham, 2001). Research on mangroves in the Caribbean Sea (Sedberry & Carter, 1993), Indian Ocean (Pinto & Punchihewa, 1996) and Coral Sea (Morton, 1990) show that ecological functions are highly productive within large mangrove forests (Nagelkerken et al., 2000). The benefits provided by mangroves, how- ever, stretch far beyond ecological boundaries. The estimated financial capital provided by these ecosystems approximates to US$1.6 billion (1997-dollar value) globally each year in ecosystems services (ES), which benefit many coastal communities (Aburto-Oropeza et al., 2008; Costanza et al., 1997). The Millennium Ecosystem Assessment (2005) categorised ES into four key factors: supporting, provisioning, reg- ulating and cultural services. These services include water purification, nutrient cycling, carbon sequestration, biological control, food pro- duction, pollution control, shoreline defence, and sense of place and spirituality (Kathiresan & Bingham, 2001; Zedler & Kercher, 2005). Mangrove and saltmarsh ecotones are sensitive to the onset of both natural and anthropogenic drivers of change (Lovelock et al., 2015). For example, human population growth and changes in desired spatial oc- cupancy has seen more than 50% of the global population relocate to coastal areas prompting rapid development in these regions (Marine, 2006). Consequently, large expanses of coastal ecosystems including wetlands, mangroves and saltmarsh have been removed, reclaimed or heavily degraded, reducing water quality, habitat availability and vital ES (Polidoro et al., 2010). Conditions that are considered to have the greatest impact globally on mangroves include, sea-level rise (SLR), extreme high-water events, storms, and changes in precipitation, tem- perature and ocean circulation patterns (Gilman, Ellison, Duke, & Field, https://doi.org/10.1016/j.apgeog.2018.03.006 Received 29 May 2017; Received in revised form 11 March 2018; Accepted 13 March 2018 * Corresponding author. Sustainability Research Centre, University of the Sunshine Coast, 90 Sippy Downs Drive, Sippy Downs, Queensland, 4558, Australia. E-mail addresses: matthew.jm.brown@gmail.com (M.I. Brown), tpearce@usc.edu.au (T. Pearce), jleon@usc.edu.au (J. Leon), rsidle@usc.edu.au (R. Sidle), rwilson2@usc.edu.au (R. Wilson). Applied Geography 94 (2018) 71–83 0143-6228/ © 2018 Elsevier Ltd. All rights reserved. T