Mānuka-Dominated Riparian Plantings for Recovering the Mauri of Lake Waikare

Maria J Gutierrez Gines (ESR), Tawera Nikau (Matahuru Marae), Olivia Adamson (University of Waikato), Tanya O’Neill (University of Waikato), Matthew Taylor (Waikato Regional Council), David Clarke (EcoQuest Education Foundation), Kristin Bohm (ESR), Richard Dean (ESR), Brett Robinson (University of Canterbury), Alexandra Meister (ESR), Robyn Simcock (MWLR), Kevin I-Kai Wang (University of Auckland), Akshat Bisht (University of Auckland), Glen Tupuhi (Ngaa Muka DevelopmentTrust)

The Lake Waikare, in the lower Waikato, in its hypertrophic state, is one of the most polluted lakes in Aotearoa. For generations, the lake and surrounding wetlands have been important to local iwi as they provided sustenance to the communities living around them. The lake and wetlands were a source for mahinga kai (food gathering), a source of irrigation for food crops, and a site of cultural and spiritual significance. These uses and people’s connection to the lake have been lost due to the current state of degradation. For this reason, there is a significant effort by the local authorities and iwi to restore the mauri (health) of Lake Waikare with a multitude of projects and strategies, riparian and native plantings being one of them.

A 4-ha, 40,000 plant, Experimental Plot was set up in 2017 in Nikau Farm, mostly by volunteers from the local communities and the collaborators in this project, to investigate the role of maanuka-dominated riparian plantings in reducing impacts of farming activities on adjacent freshwater. However, it soon became evident that the benefits of this experiment extended beyond water quality and beyond scientific goals. The “Waikare Learning Community” became an example of working in a transdisciplinary team of scientists, regulators, and iwi, from different worldviews and expectations, but with similar values and visions for the environment.

Run-off collectors, weather station, soil sensors, suction cups, and dip wells were installed to monitor the movement of water through the maanuka-dominated plots. Plant establishment and growth, soil quality, and soil biodiversity were also monitored. Results showed that phosphorus, total nitrogen, total organic carbon, and Escherichia coli were the main pollutants in the run-off samples. Nitrate was the main form of nitrogen leaching through the deeper soil horizons. Water management by maanuka (rain interception and evapotranspiration) was probably the most important factor regulating the losses of nitrate through the riparian planting compared with a grassed (unplanted) riparian band. Most areas of the Experimental Plot (planted at 1.9 plants/m2) reached full canopy cover and up to 3.3 m height within 3.5 years. The improvement of soil health in riparian plantings (soil quality and soil biodiversity) will likely have a positive effect on further mitigation of water pollution in the future, as well as recovering biodiversity and ecosystem functioning.


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07 Nov 2022