Regulating agricultural land use to manage water quality: The challenges for science and policy in enforcing limits on non-point source pollution in New Zealand

Abstract

Abstract:The management of non-point source pollution from agricultural land use is a complex issue for the management of freshwater worldwide. This paper presents a case study from New Zealand to examine how predictive modelling and land use rules are being used to regulate diffuse pollution to manage water quality. Drawing on a science studies conceptual framework, the research evaluates the deployment of a numeric regime to enforce compliance with resource limits. It shows that in contrast to claims that a quantitative modelled 'outputsbased' approach would provide certainty and clarity and remove ambiguity in the implementation of resource limits at the farm scale, the opposite is unfolding. It is argued from the case study that in the development of land use policy greater recognition and understanding is needed of the social and political dimensions of numbers and predictive models. This research highlights epistemological, institutional and practical challenges for the workability and enforceability of policy regimes seeking to regulate diffuse pollution that tightly link numbers derived from predictive models to compliance and enforcement mechanisms.Keywords: New Zealand, non-point source pollution, resource limits, water quality, predictive modelling, science policy, knowledge governance Highlights  In contrast to assertions that numbers and models would provide clarity and remove ambiguity, the opposite is unfolding  Seeking to resolve 'upstream' effects presents a range of challenges that centre on credibility and accountability  While the need for credibility is shared, criteria to achieve it differ across the science policy interface  Regulating diffuse pollution is not just a scientific and technical endeavour -it is also a social-political one 2  Relying on numbers presents epistemological, institutional and practical challenges for implementing resource limits IntroductionWorldwide, non-point source pollution from agricultural production is contributing to the nutrient enrichment of freshwater and the diminishment of water quality. Management efforts are exacerbated by lag effects. In New Zealand, the erosion and nutrient leaching legacies of past and current land use change from sheep and beef to dairy farming are merging with challenging implications for science and policy (PCE, 2013). Even with extensive improvements in land use practices and expensive mitigation, authorities have to explain to communities that water quality is likely to get worse before it gets better. This is due to nutrient losses from past land practices still moving through the system into waterways and contributing to the growth of nuisance algae and eutrophication (Goolsby et al., 2001;Howden et al., 2013; PCE, 2012 PCE, , 2013Sanford and Pope, 2013;Sims and Volk, 2013;Skelton and Caygill, 2013 The starting point for this research are assertions that certainty and clarity and the removal of ambiguity would be achieved under a water quality management regime that creates enforceable quantitative limits and a regula...

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