River water quality threat critical - report
Most of New Zealand’s native freshwater species are at risk of extinction as water quality faces ‘‘serious pressures’’, a Government report says.
Threats to native species were one particularly concerning aspect amid an overall decline in freshwater quality, determined in a joint report by the Ministry for the Environment and Statistics New Zealand.
The report, titled Our fresh water environment 2017, found nearly three-quarters of native freshwater fish species are threatened by or at risk of extinction, as well as a third of native freshwater invertebrates and a third of native freshwater plants.
The report, part of the State of the Environment reporting series, measured water quality, quantity, biodiversity and cultural health. It found problems in all categories.
It found nitrogen levels were worsening at more than half of the measured sites. Nitrogen levels were worst at urban sites but were declining significantly in pastoral areas.
The decline in pastoral areas coincided with an increase in intensive agriculture. Nitrogen leaching from agriculture had increased by 29 per cent since 1990, mainly from livestock urine.
Urban waterways had the worst overall water quality, degraded by stormwater and wastewater. About a quarter of wastewater assets are more than 50 years old.
‘‘Urban water is the most polluted but the trends are worse in pastoral areas,’’ said Secretary for the Environment Vicky Robertson.
‘‘Very high levels of nitrogen can be a problem as they can make water toxic for species and unsafe for drinking.
‘‘We aren’t seeing this playing out yet but as nitrogen levels are trending the wrong way, this is something we need to address.’’
While urban areas had the worst water quality, they covered less than 1 per cent of land but were home to 87 per cent of the population. Pastoral areas covered 40 per cent of land use.
While it was difficult to make an overall assessment due to variation between areas, it was clear there were fairly widespread freshwater issues.
Like other recent freshwater reports, it concluded changes would need to be made if freshwater was to improve.
‘‘New Zealand’s population and agriculture-based economy are growing, and it is expected that high-intensity agriculture and urbanisation will continue to expand to new areas, potentially affecting water quality in more water bodies,’’ the report said.
It found between 65 and 70 per cent of rivers would be deemed swimmable under proposed Government standards.
While much of the water quality debate had been around swimmability, the report highlighted serious issues around the health of native species.
They faced serious threats, largely due to humans. They included degraded habitat through contaminated water, altered flows, and introduced predators.
‘‘Recently there has been a strong focus on how swimmable our waterways are, but that is just part of the story.
‘‘The implications for our freshwater species are really critical,’’ Robertson said.
‘‘Many of our species are found nowhere else in the world so it is even more crucial we don’t lose any under our watch.
‘‘We need to consider the resilience of all species in any decisions we make that affect the environment,’’ he said.
The report said 72 per cent of native freshwater fish were threatened by or at risk of extinction, including four whitebait species, lamprey, and longfin eels.
Based on consented water takes, the report said irrigation had ‘‘the highest potential to cause widespread reductions in downstream river flows, compared with other water uses’’.
It was particularly true in Canterbury and Hawke’s Bay, where many takes were from groundwater.
‘‘Our reliance on irrigation, especially in drier regions, to support our economy, has the greatest potential of all uses to cause altered flows downstream,’’ the report said.
Climate change would exacerbate water quantity problems, with lower rainfall expected in already dry parts of the country.