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By Daniel Collins

Un-muddying the Waters : Waiology : Oct-Dec 2013On 21 November the Parliamentary Commissioner for the Environment, Jan Wright, released her second report on water quality. It warned that business-as-usual dairy expansion by 2020 would leave our lakes and rivers more degraded than they are now, even with improved mitigation. I’d now like to re-cap what the report concluded, how it got there, and how it was received.

The report

The purpose of the report was to illustrate how land use change could affect future nutrient runoff – nitrogen and phosphorus – based on a simple, business-as-usual scenario for 2020.

Motu used a combined economics-land use model called LURNZ to project what land use changes are likely by 2020, driven by commodity process and knowledge of land use practices and landscape characteristics. Sheep and beef farming were expected to give way to dairying, forestry, and even reversion to shrubland.

A team from AgResearch, Motu and Horizons Regional Council then assessed what mitigation measures would likely be adopted by 2020, such as wintering barns or artificial wetlands. In the end, they assumed that nutrient losses for a given area would remain about the same even as productivity increased – more intense production for the same environmental cost, what DairyNZ promotes as ‘holding the line’.

Large-scale land use change to dairy farming leads to an increase in the amount of nitrogen that gets into freshwater. (From the PCE report)

Large-scale land use change to dairy farming leads to an increase in the amount of nitrogen that gets into freshwater. (From the PCE report)

The land use changes and increased agricultural efficiencies then fed into NIWA’s water quality model, CLUES. This produced projections of nitrogen and phosphorus yields based on land use and landscape characteristics.

In general, based on the single scenario considered, phosphorus loads were expected to change little while nitrogen loads were expected to climb. There was a roughly linear relationship between change in dairying area and change in annual nitrogen load. The report’s conclusion was simple: Anticipated expansion of dairying area would lead to increased nitrogen levels in our rivers and lakes, even with anticipated improved management.

Mixed reactions

News of the report understandably precipitated a range of responses from the agricultural and freshwater communities.

Fish and Game NZ’s CE Bryce Johnson welcomed the report, saying

“…it serves as a stark warning that the nation is at a crossroads: we can either continue with the Government’s and primary production sector’s agenda of doubling agricultural output by 2025 – completely wrecking the environment, our waterways, our estuaries and beaches, our tourism sector, our international brand, and the kiwi way of life in the process – or we can look at smarter ways to grow the economy.”

IrrigationNZ’s CEO Andrew Curtis dismissed the report as an unfair representation of recent land use management innovations.

“IrrigationNZ believes win-wins are possible for agriculture and the environment… . It’s disappointing the report disagrees with this. However that’s what happens when you get carried away with gross assumptions that are then modelled.”

Canterbury and Lincoln University’s Professor Jenny Webster-Brown called the report a wake-up call, based on valid modelling and defensible assumptions.

“However, it would be wrong to treat this outcome as inevitable. … We can use this combined land use-nutrient leaching model to see how the outcome changes for alternative economic and land use scenarios. Identifying alternative agricultural and horticultural uses for our land, ones that can provide a similar economic benefit but have significantly less impact on water quality, would surely be a major step forward in future proofing NZ’s water quality.”

AgResearch’s Rich McDowell, on the other hand, calls the assumptions about mitigation simplistic, going on to say:

“…the PCE report does not give due consideration to current policy (which tend to focus on obvious bad practice) and the recently announced freshwater reforms which could require a step change in N and P management on-farm.”

And these are but a fraction of the responses to the report, public and private.

So what now?

The report is a reminder that unless we significantly improve nutrient management in relation to dairy farming, and/or put limits to the extent of dairy farming, then water quality will degrade across New Zealand. The report was not a simulation of what will come to pass, but one of many possible scenarios. Management is of course improving (e.g., Horizon’s One Plan, Environment Canterbury’s proposed Land and Water Regional Plan, National Objectives Framework), and in time we’ll see their effects. But we cannot be sure how far technical and policy innovations will take us until it happens.

Scenario-based modelling studies, like the PCE’s, are an insightful way of presenting alternative visions for New Zealand’s future, adding to the national conversation of where we wish to be heading. Another part of that conversation was put forward by Shaun Hendy and Paul Callaghan in their recent book, ‘Get Off the Grass’. Nations never get rich through agriculture, they say, so we should diversify our portfolio of economic earners. And setting water quality limits at the national and local scale is yet another part of the conversation being held to answer how much dairying, and intensive land use in general, is too much.


Dr Daniel Collins is a hydrologist and water resources scientist at NIWA.