Using remote sensing and traditional ecological knowledge (TEK) to understand mangrove change on the Maroochy River, Queensland, Australia

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, population 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, particularly where scientific data are limited, can increase the time period during which change is assessed and enhance the detail and scope of the assessment.