2. Biodiversity

The Reef’s mainland coastline spans approximately 2300 kilometres of the Queensland coast. This assessment considers a range of coastal types including sandy beaches, rocky shores, estuaries, and tidal flats. The Region’s mainland beaches and coastlines have aesthetic value and are readily accessible, providing an array of recreational opportunities that contribute to the local economy. Mainland beaches support seabird and turtle nesting as well as important migratory shorebird habitat.^101,102 They also include many sites of cultural and spiritual significance to the Reef’s Traditional Owners.

The Region’s coastline is monitored to measure shoreline trends, erosion and hazard lines, beach fluctuations, and storm demand (the removal of sand from beaches during storms).¹⁰³ Many factors contribute to the complex equation of whether a particular beach will recede or grow.¹⁰⁴ In general, beaches that are receding have a deficient supply of coarse sediments, such as sand and shingle, while other beaches build seaward where there is abundant supply of these sediments from the adjoining nearshore zones.¹⁰³ Understanding of the movement of mainland beaches and coastlines at scale has advanced considerably since 2019 with the availability of new data sources, improved remote sensing techniques, and increased computing power for analysis.^105,106 Analysis of satellite images shows that mainland coastlines within the Region have been less stable in the past few years (2019 to 2022) than the long-term average (1988 to 2022).⁹⁹ These changes are largely driven by higher recent rates of coastal erosion, possibly linked to the influence of La Niña conditions on wave direction.¹⁰⁷ Compared to the long-term average, the most significant coastal changes have occurred within the mainland Townsville–Whitsunday management area (Figure 2.3).⁹⁹

While most beaches remain resilient at present, sea level rise is slowly intruding on estuaries and low-gradient shores and is expected to begin affecting beaches in the coming decades.¹⁰³ This effect is not expected to occur uniformly across the Region. Local changes are likely to be further complicated by coastal development and associated changes in freshwater and coarse sediment dynamics.¹⁰⁹

Non-rocky coastlines remain dynamic. Observed changes over recent years are likely to predominantly reflect natural variation in climatic and oceanic influences, but sea-level rise is expected to increase rates of erosion, recession and inundation in coming decades.