365 Days of Climate Awareness 199 – Decline of the Great Barrier Reef: Pollution

The area of the Great Barrier Reef receives river runoff from nearly 23% of Queensland, much of which is via larger rivers from inland, which contain fertilizers and other organic runoff which leads to algal blooms in the ocean. Sewage has a similar effect. Toxic pollutants are also carried out, and can be taken up by organisms or be absorbed into the sediment. The toxins degrade the overall environment and repeated algal blooms can lower oxygen levels and have large impacts on the ecosystem, particularly by inhibiting the growth of new coral polyps.

Coastal regions showing effects of eutrophication and hypoxia.

Queensland features major sugarcane and cattle industries. Fertilizers from the sugarcane fields and organic wastes from the livestock contribute to the eutrophication of the coastal region, while pesticides poison most life. Aquaculture farms, increasingly important to the Australian economy, are another source of nutrients which upset the ecological balance. Farmed freshwater fish are an increasingly important industry in Queensland, and waste from those farms, livestock (cattle and swine) and sewage treatment plants.

Deforestation across several recent intervals (increasing redness = increasing deforestation). Note accelerated recent trend in the northeast (Queensland). Data from soe.environment.gov.au/…    

The increasing use of northeastern Australian coastal land has led to deforestation: 400,000 ha/988,000 acres,  roughly 2/3 the rate of Amazon forest loss, in 2015-16. Land conversion like this, in addition to removing the carbon sequestering abilities of the trees, frees soil to erode into the rivers and ocean, bringing more organics and a fresh blanket of sediment which further disrupts the local ecology. Studies have shown that sediment loads in Queensland rivers have increased by 5-9 times in the last 200 years.

Solid pollution such as plastics is another major threat to fish, turtles, dolphins and other larger species. Rivers are a consistent source of these solid wastes, but the effects are difficult to quantify, especially when they occur in combination with other influences.

Tomorrow: the crown of thorns starfish.

Be brave, and be well.