Manuka and Kanuka dominated ecosystems to improve water quality in New Zealand

Freshwater quality is a critical environmental issue in New Zealand. Unacceptable inputs of nitrogen, phosphorous, sediments and pathogens from both agricultural and urban sources are contaminating New Zealand’s waterways. Degraded water quality endangers public health and has a negative impact on tourist income and export earnings.

New Zealand native species are commonly used to intercept effluents before they enter waterways. Our research has demonstrated that there is a large inter-species variation in their ability in reducing the burden of nitrogen, phosphorus, sediments and pathogens entering waterways. We have found that two species in the myrtaceae family, mānuka (Leptospermum scoparium) and kānuka (Kunzea robusta), significantly reduce nitrate leaching and attenuate pathogens in soil (please see our publications below) The development of mānuka-dominated ecosystems in ‘critical source areas’ (areas with a high water pollution potential), could intercept contaminants before they enter waterways. The costs of the retired land could be offset through the production of native honey and essential oils.

The mechanisms by which mānuka and kānuka reduce nitrate leaching and attenuate pathogens are not understood. Unravelling these mechanisms could greatly enhance the efficacy of the mānuka and kānuka designed ecosystems through enabling species selection and soil conditioners that are optimised for individual sites. It will also enable us to design systems that can withstand the recently arrived myrtle rust by allowing the selection of species and ecoytpes that are resistant to this disease.

We seek to develop practical and low-cost systems to improve water quality. Our hope is that landowners and stakeholders will adopt such systems voluntarily.


Manukit Decision Support Tool


Manukit Decision Support Tool documentation

Publications related to this work:

Gutierrez-Gines MJ, Robinson BH, Esperschuetz J, Madejon E, Horswell J, McLenaghen R (2017). Potential use of biosolids to reforest degraded areas with New Zealand native vegetation. Journal of Environmental Quality doi:10.2134/jeq2017.04.0139

Esperschuetz J, Balaine N, Clough T, Bulman S, Dickinson NM, Horswell J, Robinson BH (2017). The potential of L. scoparium, K. robusta and P. radiata to mitigate N-losses in silvopastural systems. Environmental Pollution 225, 12-19.

Esperschuetz J, Anderson C, Bulman S, Katamian O, Horswell J, Dickinson NM, Robinson BH (2017). Response of Leptospermum scoparium, Kunzea robusta and Pinus radiata to contrasting biowastes. Science of the Total Environment 587-588, 258-265.

Franklin HM, Woods RR, Robinson BH, Dickinson NM (2017). Nitrous oxide emissions following dairy shed effluent application beneath Kunzea robusta (Myrtaceae) trees. Ecological Engineering 99,473-478.

Reis F, Gutierrez-Gines MJ, Smith CMS, Lehto NJ, Robinson BH (2017). Manuka (Leptospermum scoparium) roots forage biosolids in low fertility soil. Environmental and Experimental Botany 133, 151-158.

Prosser JA, Woods RR, Horswell J, Robinson BH (2016). The potential in-situ antimicrobial activity of Myrtaceae plant species on pathogens in soil. Soil Biology and Biochemistry 96, 1-3.

Franklin H, Dickinson N, Esnault C, Robinson BH (2015). Native plants and nitrogen in agricultural landscapes of New Zealand. Plant and Soil 394(1), 407 - 420.

Hahner JL, Robinson BH, Zhong HT, Dickinson NM (2014). The phytoremediation potential of native plants on New Zealand dairy farms. International Journal of Phytoremediation 16(7-8), 719-734.