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Feds back recommendations for Overseer improvements

Fuseworks Media
Fuseworks Media

Federated Farmers backs the call from the Parliamentary Commissioner for the Environment for more work to be done to improve the accuracy and transparency of Overseer.

"The PCE report released today highlights many shortcomings with Overseer - particularly for use as a regulatory tool - pinpointing issues that Federated Farmers has been raising for some time," Feds environment spokesperson Chris Allen says.

"Even for types of farming systems and geography within models that have been calibrated, actual results for nitrogen losses can be 25-30 percent off the mark - in either direction. Outside these calibration ranges, results can be up to 50 percent inaccurate.

"The significant inherent inaccuracies in the Overseer model means that is very unfair when the model is used to regulate farming activity central to farmers’ livelihoods, and even more importantly to mount prosecutions," Chris says.

"How would an ordinary New Zealander feel if he or she was prosecuted for speeding in their car based on the model they are driving and when the radar or speed camera had an accuracy range of plus or minus 50%?"

The PCE has found uncertainty with Overseer data input standards, a series of issues with how to handle Overseer upgrades/version changes where a farmer’s modelled nutrient losses can jump around by up to 80 percent, and the inability of the modelling tool to represent farm systems in particular regions.

"Federated Farmers agrees with the PCE that Overseer needs more government investment, third party peer review, greater transparency and most particularly that Overseer should not be used to assign absolute limits to discharges on farm activities, that can then be traded," Chris says.

"It is more useful for guidance about relative change or ‘direction of travel’ in terms of reducing nutrient losses, or a comparison of changes to farming systems rather than assigning absolute numbers."

Overseer’s other shortcomings also need to be recognised. Overseer simply models, and not that accurately, nutrients lost from the farming system - it does not model what happened to the nutrients after that and certainly does not accurately model the effect on the surrounding environment

"For example, other processes below the root zone (such as attenuation) and catchment processes are critical to successfully addressing water quality challenges. New Zealand needs much more research on that as our knowledge in that area is embryonic," Chris says.

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