Nearly all of the country's rivers and lakes in populated areas exceed environmental guidelines according to a government report that warns our freshwater is at breaking point.

Human impacts on the country's waterways are not only having dramatic impacts on recreation and the economy, but three quarters of our native freshwater fish species are threatened with or at risk of extinction.

The situation is also forecast to get worse under climate change, unless New Zealanders change their ways, according to the report Our Freshwater 2020, released today by the Ministry for the Environment and Stats NZ using the latest evidence showing how the country's waterways are impacted by urban development, farming and forestry.

Forest & Bird advocate Tom Kay said the report showed New Zealand's freshwater had reached "breaking point".

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The latest report on the country's freshwater spells dire warnings. Photo / File
The latest report on the country's freshwater spells dire warnings. Photo / File

"The path we are on threatens our native species and our own wellbeing."

The report also highlighted the interconnectedness between the various impacts, from overuse to the loss of habitat for our native species, and made clear the link between human arrival in New Zealand and dramatic degradation.

Before humans arrived in New Zealand, forests covered about 80 per cent of the land, but in 800 years only about a third of forest remained, and 10 per cent of wetlands.

Data showed the vast majority of remaining unpolluted waterways were in areas of native vegetation.

In urban settings, 99 per cent of rivers exceeded one or more environmental guideline, although this covered just one per cent of the country's river length.

Meanwhile, in pastoral and plantation forest catchments, which cover about half and 6 per cent of total river length respectively, one or more guideline was exceeded in 95 per cent of waterways.

Over the past 15 years irrigation has doubled - soaking up more than half the country's entire water use, soils at a quarter of monitored sites are drying out - meanwhile the past two decades has seen below average rainfall and severe droughts - expected to worsen under climate change.

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The way freshwater is used and treated has also had a dramatic impact on freshwater species, with 76 per cent of our native freshwater fish (39 of 51 species) either threatened with or at risk of extinction.

"This report makes clear that New Zealand urgently needs a major transition away from old models of business, because they are harming us, and they are harming the environment," Kay said.

"Right now, we have an opportunity to transition away from environmentally destructive farming, forestry and urban development practices."

There needed to be a shift to low-irrigation farming practices, and sustainable and restorative agriculture in New Zealand, he said.

"A future-focused economy would encourage more diversified crops and fewer animals on the land shifting away from volume, and move towards increasing the value and quality of good."

Actions were also needed to respond to the impacts of climate change, he said.

"Restoring our lost wetlands and protecting native forests from development and pests will absorb greenhouse gases, increase water retention, reduce evaporation and minimise flood and erosion damage."

Greenpeace sustainable agriculture campaigner Gen Toop said the Government's Covid-19 infrastructure and stimulus package provided an opportunity to accelerate the clean-up of lakes, rivers and drinking water.

The organisation's Green Covid Response package called for a billion dollar regenerative farming fund to help farmers adopt lower-polluting practices, and major investment in upgrading and modernising the urban stormwater and wastewater network.

They were also calling for the Government to bring in the "long-awaited" regulations to protect freshwater, including a cap on synthetic nitrogen fertiliser.

Fresh water?

New Zealand has 70 major river systems that run for more than 425,000 kilometres.

There are 249,776 hectares of wetland, along with 50,000 lakes – 4000 which are larger than one hectare.

About 440 billion cubic metres of water flow in New Zealand's rivers and streams, with a further 711 billion cubic metres stored in underground aquifers.

The report found pollution affected almost all of New Zealand's rivers, and many lakes and aquifers.

Water quality was found to be worst in urban areas, largely due to waste and stormwater issues, although they contained just 1 per cent of the nation's river length.

Computer models showed for 2013-2017 more than 99 per cent of the total river length exceeded one or more environmental guideline for nutrients and turbidity.

E. coli and nitrates in urban rivers were twice as high as those in catchments in farming, and 36 and 23 times higher respectively than in native forested areas.

In farming catchments, which contain about half the country's river length, computer models for nutrients and turbidity estimated 95 per cent exceeded one or more guideline for 2013–17.

The models also estimated E. coli levels for nearly a quarter of these rivers exceeded expected concentrations for natural conditions.

The report found the shift from sheep and beef farming to dairy farming was linked to an increased leaching of nitrogen from soils.

From 1994 to 2017, the number of dairy cattle in New Zealand increased by 70 per cent (from 3.8 million to 6.5 million).

The area of land used for dairy farming has also increased 42 per cent between 2002 and 2016.

Nitrogen applied in fertiliser had increased nearly six-fold since 1990, and the use of agricultural pesticides had increased at about the same rate.

Areas with worsening trends for E. coli included Manawatū-Whanganui, Hawke's Bay, Taranaki, Wellington, Marlborough, Canterbury and Southland.

Areas with worsening trends for nitrate-nitrogen levels included the central North Island - including parts of Waikato, Gisborne, Taranaki - and in the south-eastern South Island, including parts of Canterbury, Otago, and Southland.

About 6 per cent of the country's rivers were in catchments with plantation forest, and 95 per cent of these were found to exceed at least one guideline, mostly for sedimentation issues linked to clear felling and soil disturbance.

Lakes are also doing poorly, with 77, 70 and 67 per cent of lakes with upstream catchments dominated by urban, pastoral, and exotic forest land cover respectively polluted with nutrients.

Computer models estimated 46 per cent of lakes larger than one hectare were in poor or very poor ecological health.

Groundwater was also being impacted, with a national survey of 29 different emerging contaminants finding the plasticiser bisphenol-A - active ingredients of sunscreen, and sucralose (an artificial sweetener) detected most often. All were at low concentrations.

Changing water flows

The area of irrigated agricultural land almost doubled between 2002 and 2017, from 384,000ha to 747,000ha, rising the most in Canterbury from 241,000 to 478,000ha.

Meanwhile, annual precipitation was below average in nine of the years between 2000 and 2014.

About 10 per cent of New Zealand's land is estimated to be artificially drained to make it more suitable for agriculture.

The high use of water also reduced the habitat for freshwater fish and other species.

The journeys that native fish need to make up and downstream to complete their life cycles are more difficult or impossible when there are low flows and barriers like weirs and dams in rivers and streams.

Reduced or less variable flows can increase the temperature and the concentration of nutrients and pathogens in a waterway, and increase the chances of harmful algal blooms

Climate change

All of the challenges posed to freshwater are expected to be exacerbated by climate change with impacts on when, where, and how much rainfall, snowfall and drought occur.

This may change the amount of water in our soil and in glaciers, lakes, rivers and groundwater, meanwhile the frequency of extreme weather events is expected to increase.

Droughts could cause communities that depend on rain for drinking water to run out, the cost of treating water during a drought may increase, and droughts are also likely to cause food shortages.

Since 1972/73, soils at a quarter of monitoring sites around New Zealand have become drier.

From 1977 to 2016, glaciers are estimated to have lost almost 25 per cent of their ice.

By the numbers

• 76 per cent of native freshwater fish were classified as threatened with or at risk of extinction in 2017.

• 90 per cent of freshwater wetlands, particularly swamps, have been drained since pre-human settlement.

• 95 to 99 per cent of river length in urban, pastoral, and exotic forest areas exceeds water quality guidelines.

• 67 to 72 per cent of lakes in urban, pastoral, and forestry areas are in poor ecological health.

• 58 per cent of water allocated for consumption (excluding hydroelectricity) was for irrigation — our highest allocated use.

• About 100 large dams are used to generate electricity. Others are used for irrigation, flood control, water supply, or a combination.

• A quarter of monitoring sites around New Zealand have soils that are drier since 1972/73.

• A quarter of the ice in our glaciers is estimated to have been lost from 1977 to 2016.