A major threat to the Great Barrier Reef (GBR) could be new or expanded ports and increased shipping from Queensland. Such concerns have been expressed by Greenpeace. With coal exports set to triple and more LNG coming on line shipping movements will increase significantly. However, such statements by Greenpeace do not account for the scaling of impacts. Whereas climate induced effects impact directly on coral, shipping movements are largely indirect and impact locally if an accident were to occur. Risk analysis would show that although an event is unlikely its consequence in a defined area would be high. ALARP measures put in place should adequately manage risk into the future.
The Great Barrier Reef (GBR) has lost half its coral cover over the last 27 years. The loss is due to 48% storm damage, 42% Crown of Thorns (COT) Starfish and 10% coral bleaching from sea temperature spikes. Coral cover could halve again by 2022, with northern regions fairly stable but southern regions showing dramatic loss. Tropical cyclones in the central and southern parts and COT’s outbreaks over the entire length, plus two severe bleaching events in northern and central regions has stalled recovery. Recovery takes 10 to 20 years but intervals between current disturbances are to short for full recovery. Without COT’s there would be 0.89% recovery per year. Changes to water quality appears to contribute to COT’s population explosions.
As the Queensland and National Government are launching a major review of risks facing the reef, they are more likely to focus on agricultural, urban and port development and the impact of downstream effects from sedimentation and runoff. Sedimentation impacts on biodiversity over 1 to 10 year cycles along the continental shelf – it (urbanisation) along with eutrophication is likely to ultimately be the ‘reef killer’, exacerbating the effect of climate induced impacts.
Disturbances that characterise shelf sediments are caused by mobilisation and transport of sediment in part due to extreme storm events. Biodiversity is controlled by the frequency of disturbance and spatial extent over differing periods of time. Ecological succession in shelf environments appears to range between 1 to 10 years. Storms, eddies, intruding ocean currents and extreme storm events have similar return frequencies. Bed stresses that result include erosion, and increases in bed thicknesses of up to 1m from sedimentation, causing destruction of coral reefs and seagrass beds.
Overlaying disturbance increases in Greenhouse Gas emissions into the atmosphere impact on carbon dioxide (CO2) absorption by the ocean. Increases in the amount of CO2 absorbed by the ocean exceed its buffering capacity, changing the saturation horizon depth and acidifying the ocean. Increased seawater temperature exacerbates this process.
Carbon capture and storage (CSS) may limit the future impact of greenhouse gas emissions on CO2 absorption and acidification of the ocean on corals. However, the public appears ambivalent about this and its use. CSS is expensive and high risk and may increase emissions. Energy hierarchies can highlight the range of options available for meeting climate change and energy security. Energy conservation and efficiency is a more likely solution to reducing greenhouse gas emissions. Combined with better coastal management of infrastructure development, coastal adaptation to climate induced change, and better agricultural practices this may provide a long term solution to stopping and reversing GBR coral loss into the future.
- The decay of the Great Barrier Reef calls for a reckoning (theconversation.edu.au)
- Half of Great Barrier Reef Gone (ecology.com)
- Why the Great Barrier Reef could lose almost all its coral in the next decade (thestar.com)
- Storms to starfish: Great Barrier Reef faces rapid coral loss: study (worldbulletin.net)
- Thoughtful Thursdays: Climate Change is Killing our Coral Reefs (nationalaquarium.wordpress.com)
- Australia’s Great Barrier Reef on Brink of Collapse (ipsnews.net)
- Reef Alarmists Jump The Shark (wattsupwiththat.com)