Human activities that impact on water quality
As individuals, we all undertake everyday activities that may impact on the quality of water in local waterways and downstream marine environments. Whether you live in a major city, small town or in the country, what you do on the land and at home, work or school may affect the quality of water entering the Great Barrier Reef. Many of your daily activities may increase the levels of nutrients, sediments and other pollutants being discharged via local waterways to the Great Barrier Reef.
Many human activities can contribute to declining water quality in the Great Barrier Reef. Some of these activities include:
Increasing population combined with the popularity of living near the coast has resulted in the expansion of towns, cities and other developments along the Queensland coast. In fact, over the last 200 years this expansion has seen the loss of significant areas of wetlands and important vegetation areas within the Great Barrier Reef Catchment. Today the coast adjacent to the Great Barrier Reef Marine Park contains marine tourism infrastructure, ports and harbours, urban and resort development and industrial development. These developments may result in sediment, nutrients, chemicals and other pollutants being discharged to local waterways and the Great Barrier Reef. With more people living in the Great Barrier Reef Catchment and using the Reef for recreational and commercial activities like boating, fishing, tourism and shipping, there is potential for more human impact on the Great Barrier Reef into the future.
Agricultural industries, including grazing and cropping, are the largest users of land in the Great Barrier Reef Catchment. Today 80% of the land adjacent to the Great Barrier Reef Marine Park supports agricultural production, primarily beef cattle grazing and intensive cropping.
Extensive clearing of vegetation in the Great Barrier Reef Catchment has occurred to allow for cattle grazing. This, combined with over-stocking on farms, can result in widespread soil degradation, particularly during drought conditions. This degradation results in soil erosion and the transport of eroded material to the Great Barrier Reef during times of heavy rainfall.
Sugarcane cropping covers the largest area in the Great Barrier Reef Catchment. Other major crops grown in the catchment include a variety of grains, cotton, bananas and other fruit and vegetables. Cropping involves the application of fertilisers (such as nitrogen and phosphorous) and pesticides. Use of these has increased significantly since the 1950s. Some of the fertilisers and pesticides are taken up by the crop but a significant portion applied to the land may end up in coastal waters. Poor agricultural practices may result in soil erosion and the discharge of sediments, nutrients and pesticides into rivers, estuaries and eventually the Great Barrier Reef.
Aquaculture facilities located within and next to the Great Barrier Reef Marine Park produce a range of marine and freshwater species including pearl and edible oysters, prawns and barramundi. Aquaculture in Queensland is a growth industry with most facilities utilising pond-based operations to produce prawns.
Traditionally, aquaculture farms have often discharged high concentrations of suspended solids and nutrients to nearby waterways. However, this situation is improving with the implementation of new techniques such as settlement and bio-filtration ponds that contain algae, bivalves or fish in new and some existing aquaculture farms. Today, discharges from aquaculture farms are regulated to ensure they protect the water quality of local waterways and the Great Barrier Reef.
The majority of heavy industry in the Great Barrier Reef Catchment is in the Gladstone/Calliope and Townsville/Thuringowa areas. Some of the existing industry operations include refineries, smelters and power generation stations. Coal production is the major mining operation carried out in the Great Barrier Reef Catchment, with mines in the region producing approximately 96% of Queensland's 95 million tonnes of annual black coal production. Other mining operations close to the coast include shale oil, silica and magnesium.
Ships regularly transit the inner shipping route of the Great Barrier Reef Marine Park carrying a wide range of cargoes including bauxite and alumina, manganese, iron ore, coal, sugar, silica sand, general container freight and petroleum products. These ships transport these and other products to and from ports and communities along the Queensland coast.
Oil or chemical spills released from ships following an incident have the potential to cause serious environmental damage to the marine environment. However, waste products and garbage from the day-to-day operation of a ship can also pollute the waters of the Great Barrier Reef. These wastes include oils, chemicals, sewage, garbage, toxic compounds released from anti-fouling paints and ballast water.