Testing native plants to improve lake quality

Testing native plants to improve lake quality

A new field trial is underway in Wairarapa using native plants to clean up farm runoff going into Lake Wairarapa.

Scientists from ESR, (Institute of Environmental Science and Research), are looking at the potential of mānuka and of other native trees to reduce the leaching of nitrate and other pathogens from farm run-off.

Dr Maria Gutierrez-Gines, a scientist at ESR, says laboratory work has already demonstrated that mānuka and kānuka enhance the die off of E.coli in the soil and reduce nitrate leaching more effectively than pasture or pine trees. Recent research also suggests that other plants such as rata and horopito may have similar properties.

Dr Gutierrez-Gines says the trial is an opportunity to test those findings in a real farm setting.

“Our part in the project is to study the contribution of each plants species into nutrient and pathogen fluxes in the soil and in the plants and to see which one offers the best potential to remediate the impact of farming activities into the lake.”

The trial is a collaboration between ESR, local iwi and Greater Wellington Regional Council who have been planting out native trees on land donated by iwi and local farmers.

GWRC land management advisor Kolja Schaller says he is getting a lot of support from those farming around the lake to participate in the trial.

“The land owners want better water quality that is why they’ve put their hands up and given their land for this trial.”

Schaller says the plantings have been set a range of widths to see what density of plants is required to get the same or similar environment outcomes. He also says they will also be looking to get data on the impact of the buffers to help inform farm nutrient budgets.

Local farmer Julie Wrigley says the reasons for joining in the project is about protecting the environment for future generations. “We farm on the edge of this beautiful lake, so if there is anything we can do to minimise future damage – we are lucky to be part of it.”

Phase two of the planting project got underway on the western side of the lake late last week. ESR scientists will start monitoring the impacts of the plantings next year.

Mr Schaller says longer term he sees big potential for native plant dominated riparian zones.

“If we can plant a species like mānuka that provides an ecosystem service, reducing the nitrates and at the same time there’s an economic benefit because of the oil and the honey it’s a win win win.”

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