The trees are doing the mahi and now the science proves it

Published: 11 April 2025

New scientific findings show that trees and native plants, when planted strategically, are helping reduce erosion across our Hawke’s Bay’s most at-risk hill country.

 The findings were presented at the Hawke’s Bay Regional Council’s Environment & Integrated Catchments Committee meeting this week. (Editors: Wednesday, 9 April).

 Committee Chair Sophie Siers says the data is encouraging and shows that years of investment in erosion control are starting to pay off.

 “This is what we all want to know, right? That our rates are going to something real. Something that’s working. And this shows they are,” says Cr Siers.

 “The science is telling us that planting in the right places really can stop slips, keep sediment out of rivers, and protect the whenua. It’s not just theory, it’s happening out there, on farms and hillsides across Hawke’s Bay.”

 Key findings presented to the committee included:

• During Cyclone Gabrielle, around 20 million tonnes of sediment entered Hawke Bay. This is six times more than a normal year.

• When that sediment reaches the sea just 3mm of it can cause damage to marine ecosystems and after the cyclone, deposits of up to 125mm were recorded near river mouths.

• Analysis from 50 farm sites showed that tree-covered land experienced 1,895 fewer landslides — a seven percent reduction, with nine percent less sediment flowing into rivers.

• Over time, planting can reduce erosion by up to 70 percent with poplars and willows, and up to 90 percent with closed canopy forest.

• More than 250,000 hectares of hill country in Hawke’s Bay is considered high risk for erosion.

 Cr Siers says this gives the Council and community a clear direction, use the science, plant smarter and keep the momentum going.

 “We’ve still got a way to go, but this is real progress. We now know where to focus our efforts and how to get the most bang for buck. This is about protecting our environment, building resilience, and doing right by future generations.”

 “So yes, your rates are making a difference. And you can see it in the whenua.”

 The full agenda and reports are available at –https://hawkesbay.infocouncil.biz/Open/2025/04/EICC_09042025_AGN_AT.PDF

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