The latest national report on the state of New Zealand’s freshwater delivers a sobering assessment on the worsening quality of the natural resource.
The report, Our Freshwater, by the Ministry of the Environment and Statistics New Zealand, shows that while some of our freshwater bodies are in a reasonably healthy state, many have been degraded by the effects of excess nutrients, pathogens and other contaminants from land.
Between 2011 and 2020, 45% of lake monitoring sites worsened, while 36% improved. It is estimated 45% of NZ’s total river length is not suitable for activities like swimming, according to models of campylobacter infection risk between 2016 and 2020.
For all lakes larger than 1 hectare, 46% had poor or very poor health between 2016-2020 and only 2% were rated as good or very good.
NZ Freshwater Sciences Society and director of Our Land and Water National Science Challenge/ Toitū te Whenua, Toiora te Wai Professor Jenny Webster-Brown said the report has little good news.
“One of the new statistics is that nearly 70% of our indigenous freshwater birds are now threatened with extinction or at risk of becoming so threatened,” she said.
“As with other ecosystem indicators of environmental health and taonga, this signals that we are still failing to reduce the key pressures on these species; poor water quality, reduced habitat and introduced predators and competitors.”
Victoria University of Wellington Institute for Governance and Policy Studies, Te Herenga Waka senior researcher Mike Joy said the report “unflinchingly identifies” the appalling state of lowland freshwaters of NZ, and Dr Tim Chambers of the University of Otago’s Department of Public Health called it a “sobering snapshot” of the state of the country’s freshwater.
“The report outlines the core pressures that have led to substantial degradation of our freshwater, which have serious economic, socio-cultural and health implications,” Chambers said.
“The report also highlights what we do not know and where research investment is required. These areas include better investment in national monitoring and reporting, research into the health impacts of key contaminants and mātauranga Māori.”
The report says that modelling shows that efforts by farmers to reduce fertiliser use and keep stock out of waterways helped to reduce the amount of phosphorus and sediment reaching rivers between 1995 and 2015.
However, because the number of farms grew, it is estimated the total amount of nitrogen reaching rivers increased.
“Models estimate that on-farm mitigations like fertiliser management and protecting waterways from livestock reduced the amount of phosphorus and sediment that reached our rivers between 1995 and 2015, but not nitrogen.
“While the mitigations were estimated to reduce nitrogen losses from individual farms, this was not enough to offset the effects of the expansion of dairy and intensification of pastoral agriculture, which resulted in an increase in the nitrogen that reached our rivers during this period,” it says.
NZ has experienced one of the highest rates in the world of agricultural land intensification over recent decades.
The intensity of agriculture and number of dairy cattle has increased since the 1980s as more sheep and beef farms switched to dairying.
The amount of irrigated land almost doubled between 2002 and 2019, from 384,000ha to 735,000ha – a 91% increase.
Over the same period 73% of increases in irrigated land area were related to farms with dairy farming as their dominant farm type; 18% to grain, fruit and berry and vegetable growing; and 9% to sheep and beef.