Editing Great Barrier Reef (section)

===Pollution===
Another key threat faced by the Great Barrier Reef is [[Marine pollution|pollution]] and declining [[Water pollution|water quality]]. The rivers of north-eastern Australia pollute the Reef during tropical flood events. Over 90% of this pollution comes from farm [[Surface runoff|runoff]].<ref>{{cite web |year=2003 |url=http://www.epa.qld.gov.au/register/p01258bs.pdf |title=Coastal water quality |work=The State of the Environment Report Queensland 2003 |publisher=Environment Protection Agency Queensland |access-date=7 June 2007 |url-status=dead |archive-url=https://web.archive.org/web/20070614223713/http://www.epa.qld.gov.au/register/p01258bs.pdf |archive-date=14 June 2007 }}</ref> 80% of the land adjacent to the Great Barrier Reef is used for farming including intensive cropping of sugar cane, and major beef cattle grazing. Farming practices damage the reef due to [[overgrazing]], increased run-off of agricultural sediments, nutrients and chemicals including [[fertiliser]]s, [[herbicide]]s and [[pesticide]]s representing a major health risk for the coral and biodiversity of the reefs.<ref name="Human Impact on the Great Barrier Reef">{{cite web |title=Human Impact on the Great Barrier Reef - Pollution |url=http://sitemaker.umich.edu/gc2sec7labgroup3/pollution |publisher=University of Michigan |access-date=12 February 2014 |url-status=dead |archive-url=https://web.archive.org/web/20130429151658/http://sitemaker.umich.edu/gc2sec7labgroup3/pollution |archive-date=29 April 2013 }}</ref>

According to a 2016 report, while higher regulation contributes to less overall pollution from "other land uses, such as industrial, mining, port development, dredging and urban development", these can still be locally significant.<ref>{{cite web |url=https://www.qld.gov.au/__data/assets/pdf_file/0027/109539/gbrwst-finalreport-2016.pdf |title=Final Report – Great Barrier Reef Water Science Taskforce |date=May 2016 |publisher=Queensland Government |page=16 |archive-date=21 November 2021 |archive-url=https://web.archive.org/web/20211121054043/https://www.qld.gov.au/__data/assets/pdf_file/0027/109539/gbrwst-finalreport-2016.pdf |url-status=live }}</ref> Sediments containing high levels of copper and other heavy metals sourced from the [[Ok Tedi Mine]] in Papua New Guinea are a potential pollution risk for the far northern Great Barrier Reef and [[Torres Strait]] regions.<ref>Harris, P.T., 2001. "Environmental Management of Torres Strait: a Marine Geologist's Perspective", in: Gostin, V.A. (Ed.), ''Gondwana to Greenhouse: environmental geoscience – an Australian perspective''. Geological Society of Australia Special Publication, Adelaide, pp. 317–328</ref> Some 67% of corals died in the reef's worst-hit northern section, the ARC Centre of Excellence for Coral Reef Studies report said.<ref>{{Cite news |url=https://www.bbc.com/news/world-australia-38127320 |title=Great Barrier Reef suffered worst bleaching on record in 2016, report finds |last=Griffith |first=Hywel |date=28 November 2016 |work=BBC News |access-date=28 November 2016 |url-status=live |archive-url=https://web.archive.org/web/20161128131749/http://www.bbc.com/news/world-australia-38127320 |archive-date=28 November 2016 }}</ref>

====Loss of coastal wetland====
The runoff problem is exacerbated by the loss of coastal [[wetland]]s which act as a natural filter for toxins and help deposit sediment.<ref name=wetlands>{{cite web |author=Great Barrier Reef Marine Park Authority |title=Wetlands |url=http://www.gbrmpa.gov.au/corp_site/key_issues/water_quality/wetlands |access-date=13 March 2007 |url-status=dead |archive-url=https://web.archive.org/web/20061002034022/http://www.gbrmpa.gov.au/corp_site/key_issues/water_quality/wetlands |archive-date=2 October 2006 }}</ref><ref name="Brodie07">{{cite web |year=2007 |author=Brodie, J. |url=https://research.jcu.edu.au/tropwater/resources/06%2007%20Nutrient%20mgmt%20zones%20in%20the%20GBR%20catchment.pdf |title=Nutrient management zones in the Great Barrier Reef Catchment: A decision system for zone selection |publisher=Australian Centre for Tropical Freshwater Research |access-date=14 March 2009 |url-status=dead |archive-url=https://web.archive.org/web/20170325202543/https://research.jcu.edu.au/tropwater/resources/06%2007%20Nutrient%20mgmt%20zones%20in%20the%20GBR%20catchment.pdf |archive-date=25 March 2017 }}</ref><ref>{{cite web |author=Australian Government Productivity Commission |year=2003 |title=Industries, Land Use and Water Quality in the Great Barrier Reef Catchment – Key Points |url=http://www.pc.gov.au/projects/study/gbr/docs/finalreport/keypoints |archive-url=https://web.archive.org/web/20080816135937/http://www.pc.gov.au/projects/study/gbr/docs/finalreport/keypoints |archive-date=16 August 2008 |access-date=14 March 2009 }}</ref> It is thought that the poor water quality is due to increased light and oxygen [[Competition (biology)|competition]] from [[algae]].<ref name=waterquality>{{cite web |author=Great Barrier Reef Marine Park Authority |year=2006 |title=Principal water quality influences on Great Barrier Reef ecosystems |url=http://www.gbrmpa.gov.au/corp_site/key_issues/water_quality/principal_influences.html |access-date=22 October 2006 |archive-url=https://web.archive.org/web/20061016155955/http://www.gbrmpa.gov.au/corp_site/key_issues/water_quality/principal_influences.html |archive-date=16 October 2006 |url-status=dead }}</ref>

====Eutrophication====
Farming fertiliser runoff release [[nitrogen]], [[phosphorus]], and [[potassium]] into the oceanic ecosystem, and these [[limiting nutrient]]s cause massive algal growth which eventually leads to a reduction in oxygen available for other creatures in a process called [[eutrophication]]. This decreases the biodiversity in the affected areas, altering the [[species composition]]. A study by Katharina Fabricius and Glen Death of [[Australian Institute of Marine Science]] found that hard corals numbers were almost double on reefs that were far from agricultural areas.<ref name="Human Impact on the Great Barrier Reef"/>

Fertilizers also increase the amount of phytoplankton available for the crown-of-thorns starfish larvae to consume. A study showed that a doubling of the chlorophyll in the water leads to a tenfold increase in the crown-of-thorns starfish larvae's survival rate.<ref name="Human Impact on the Great Barrier Reef"/>

====Sediment runoff====
Sediment runoff from farming carries chemicals into the reef environment also reduces the amount of light available to the corals decreasing their ability to extract energy from their environment.<ref name="Human Impact on the Great Barrier Reef"/>

====Pesticides====
Pesticides used in farming are made up of heavy metals such as lead, mercury, arsenic and other toxins are released into the wider environment due to erosion of farm soil, which has a detrimental effect on the coral.<ref name="Human Impact on the Great Barrier Reef"/>

====Pollution from mining====
Mining company Queensland Nickel discharged nitrate-laden water into the Great Barrier Reef in 2009 and 2011 – on the later occasion releasing {{convert|516|t}} of waste water. The [[Great Barrier Reef Marine Park Authority]] (GBRMPA) stated "We have strongly encouraged the company to investigate options that do not entail releasing the material to the environment and to develop a management plan to eliminate this potential hazard; however, GBRMPA does not have legislative control over how the Yabulu tailings dam is managed".<ref name="Clive Palmer's nickel refinery pumped toxic waste into Great Barrier Reef park">{{cite news |last=Milman |first=Oliver |title=Clive Palmer's nickel refinery pumped toxic waste into Great Barrier Reef park |url=https://www.theguardian.com/environment/2014/feb/12/cliver-palmers-nickel-refinery-pumped-nitrogen-great-barrier-reef-park |access-date=12 February 2014 |newspaper=The Guardian |date=12 February 2014 |url-status=live |archive-url=https://web.archive.org/web/20140223012657/http://www.theguardian.com/environment/2014/feb/12/cliver-palmers-nickel-refinery-pumped-nitrogen-great-barrier-reef-park |archive-date=23 February 2014 }}</ref>