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Nitrogen loads to New Zealand aquatic receiving environments: Comparison with regulatory criteria

journal contribution
posted on 2024-06-21, 03:51 authored by Ton Snelder, Amy Whitehead, Caroline Fraser, Scott Larned, Marc Schallenberg
There is concern about the deteriorating nutrient status of aquatic receiving environments in New Zealand. We estimated the amount by which current nitrogen (N) concentrations and loads exceed criteria in rivers, lakes and estuaries nationally. Criteria corresponded to national 'bottom-line' (i.e. minimal) environmental objectives set by government policy. Three metrics were evaluated: (1) degree of compliance describes the current TN loads in receiving environments relative to criteria; (2) catchment N status describes the acceptability of catchment N loads compared to criteria; and (3) excess load indicates the amount by which the N load exceeds the maximum allowable load (kg yr‚àí1). Non-compliance with N criteria was broadly distributed nationally particularly in low-elevation catchments. Catchments with unacceptable N status constituted at least 31% of New Zealand's land area, which corresponds to at least 43% of the country's agricultural land. The national excess load was estimated to be at least 19.1 Gg yr‚àí1. We are 97.5% confident that estimated excess loads exceed zero for nine of 15 regions and for the nation as a whole. The analyses provide a strategic assessment of where reductions in N emissions are required to achieve the minimal national objectives.


Funded by the New Zealand Ministry for Business, Innovation and Employment's Our Land and Water National Science Challenge (Toitū te Whenua, Toiora te Wai) as part of project Land Use Suitability


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  • English

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Journal title

New Zealand Journal of Marine and Freshwater Research

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