Great Barrier Reef report

Climate change impacts on the Reef





Observed rises in sea levels since 1990 are tracking at a rate of 1 to 2 mm per year. Higher sea levels compound the impacts of storm surges, posing physical risks for dwellings, infrastructure and industries located in and around the Reef 13 . Since a significant proportion of land adjacent to the Reef is low-lying, changes to sea levels will result in greater erosion and land inundation. 14 This can contribute to issues such as flooding, storm damage, and infrastructure failure. This will also impact on juvenile fish that utilise low lying habitats for protection and food resources, 15 and the breeding and foraging activities of many species. 16 Rising sea levels at turtle and seabird nesting beaches would worsen beach erosion and flood nests. 17 Since sea levels are predicted to increase at a higher rate, there is concern as to whether coral reef growth will be able keep pace. There are also potential impacts to the shape and existence of coastlines, cays and islands. 18

The oceans have absorbed nearly one- third of carbon dioxide released into the atmosphere by human activities over the past 200 years. This has increased the acidity of oceans, with potential for serious consequence for Reef life and related industries. For example, increased acidity: – Reduces the capacity of corals to build skeletons, leading to a negative impact on their capacity to create protective habitat for the Reef’s marine life 9 , and leading to slower growth rates and weakened coral structures 10 – Impedes fish reproduction (since fish eggs are more sensitive to pH changes than fish adults) and the ability of fish larvae to locate suitable habitat 11

There are a number of other current and future stressors that threaten the long term health of the Reef. An environment already under pressure is less resilient to the impacts of climate change, and more susceptible to bleaching and disease. This includes: 23 – Growing development and population along the coast of Queensland, impacting on the filtering effect of flood plains, freshwater wetlands, and riparian 24 zones, in how floodwaters flow and are filtered into the Reef. An increased amount of sediment flowing into the Reef is causing damage to sea grasses and corals, and increasing growth of invasive species like crown- of-thorns starfish. This enhances the growth and survival of starfish larvae, and results in damaged nearshore sea grass beds and coastal coral assemblages. 25 Such negative impacts on seagrass health lead to flow on effects to the health of those animals that rely on good quality habitat such as turtles 26 – Growth of mining, and consequential expansion of ports and shipping in proximity to the Reef. This has included an increased need for dredging, and dumping of dredged spoil within the GBR World Heritage Area

Changes in ocean circulation are likely to change and strengthen some ocean currents, including the East Australian Current. This will change the connectivity and productivity of ocean environments, including shifting the geographical limits of some tropical species. 19 Alterations to ocean currents can potentially affect entire marine food webs because it can affect the transport of eggs and larvae within the Reef. 20 Further, microscopic plants (phytoplankton) rely on nutrients brought up from deeper in the ocean, however the process of nutrients reaching the surface is impeded by warming surface water; a result of currents transporting greater volumes of warmer water to the Reef. 21 This has flow on affects to the food supply of larger animals. This may lead to different species of marine life establishing themselves in different areas, 22 altering the biodiversity of the region.


Intense droughts followed by periods of high intensity rainfall events can cause contaminated freshwater plumes, with polluted run-off from rivers entering the Reef. More severe tropical cyclones may cause physical damage to reefs, for example after Cyclone Yasi in 2011, over 89,000 square kilometres of broken corals were reported. 12

9; threats-to-the-reef/climate-change/ocean-acidification 10 11 12 13 14-18

19 20-22 23 24 A riparian zone refers to land alongside creeks, streams, gullies, rivers and wetlands. 25 26 report-feb12.pdf

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