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Canterbury’s Water Pollution – a “One Health” Perspective


“One Health” is a multidisciplinary approach to managing human, animal, and environmental health that recognizes the interdependence of people, animals, and the environment.

One Health looks for the drivers of globally emerging infectious diseases such as SARS, MERS, and corona virus (COID-19) – trade, density of people, movement of people and animals, changing agricultural practices and climate change.

The drivers for Canterbury’s polluted water are agriculture, politics and profit.

Canterbury’s water pollution is the result of changed agricultural practices and the failure of local and central government to acknowledge and respond to a growing environmental and public health crisis preferring to play down pollution for the sake of the short term profits of influential agribusiness lobby groups.


Land use

Statistics NZ data shows that from 1990 to 2017, the number of dairy cows in Canterbury increased from 112,999 to 1,308,058. The number of sheep fell from 10.4 million to 4.4 million. The amount of irrigated land increased from 240,778 ha in 2002 to 478,143 ha in 2017.


Farmers used to rely on bacterial colonies located in nodules within the roots of white clover to fix atmospheric nitrogen. Since the development of the Maui gas field in the 1980’s the Government has taken over the ammonia urea plant and agreed to take the gas (against the advice of leading scientists). The Government presently subsidises 90% of the plant’s CO2 emissions. Pasture production on Canterbury dairy farms has now become dependent on synthetic nitrogen where on average 230 kg of nitrogen is applied annually per hectare

Vulnerable aquifers

The ten-fold increase in dairy cows made possible by synthetic nitrogen fertilizer and irrigation is located on top of New Zealand’s most vulnerable soils – the coarse porous outwash soils of the Canterbury Plains.

Excess synthetic urea and urea from cow urine patches exceed plant uptake allowing nitrate to leech directly into underlying soils. These soils do not retain nitrogen. Canterbury’s groundwater has become so polluted that an increasing number of rural wells contain water that exceeds New Zealand’s maximum allowable value for drinking water. Canterbury’s naturally intermittent lowland rivers and streams fed by groundwater from the polluted aquifer(s) have nitrate levels that are both directly toxic to fish and contribute to nutrient enrichment which results in indirect fish kills from excessive aquatic plant and algae growth. Toxic algae in Canterbury’s waterways have become a summer “norm”. ECan signs warning of risks to dogs and humans are placed at many popular swimming sites.

Pathogens percolate through the soils in a similar manner to nitrate leaving the Selwyn and Hinds catchments with New Zealand’s highest rates of (human) gastroenteritis.

Both human and environmental health is now seriously affected by Canterbury’s polluted water and is getting worse.

Politics and Profit

Catherine Knight’s book Beyond Manapouri (2018) is recommended reading for anyone interested in how we allow situations like Canterbury’s water pollution to occur – “short termism” by cynical politicians responding to three year election cycles, a view that environmental exploitation can occur without consequences, and laws that put individual property rights above the common good that results from protecting the environment are a few examples of her insights.

The greatest damage to Canterbury’s water stems from the Environment Canterbury (Temporary Commissioners and Improved Management) Act 2010, (ECan Act), repeated watering down of the RMA, and by allowing the fate of Canterbury’s water to be determined by water users and lawyers under the oversight of the Government controlled Environment Canterbury Regional Council all for the sake of a short term increase in GDP.

In the Selwyn Water Zone the primary indicator of success of the Central Plains Water irrigation scheme made possible by the Ecan Act was a $300 million increase in GDP.

The primary reason for Ecan not addressing the resultant pollution pouring into Lake Ellesmere/Te Waihora is the estimated $300 million cost of restoration.


A “One Health” solution would be to assemble an interdisciplinary team and simply address the drivers of Canterbury’s water pollution.

Tragically for the sake of short term profits &/or political expediency the solution to date has been to deny that the water pollution exists.

ECan farm environment plans (GMP) will not cut it.

DOC has been “purchased” by Fonterra for $20 million to protect Fonterra’s future profits for 10 years.

The NPS for FM standards for freshwater appear to have been put on hold by a Government scrambling to get re-elected.

Perhaps a multidisciplinary “One Health” team is required to first sort out central and local Government?