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Gisborne Landcare office to close

Landcare Research’s Gisborne office will close this week after 42 years playing a crucial role in studying the region’s world-famous erosion issues. Source: The Gisborne Herald

The office, established in 1975 by the then New Zealand Forest Service, was never meant to be permanent, though. It shifted around several locations, the most recent on Awapuni Road.

Its first job was to facilitate research towards better understanding the erosion processes and geology in Mangatu Forest.

Robin Black, the first technician appointed to the Gisborne region, and Professor Max Gage produced a ‘Terrain Stability Map’ of Mangatu Forest.

Later, other areas were similarly mapped by Chris Phillips and Andy Pearce.

But exactly what caused erosion on such a large scale and how trees reduced the erosion was still poorly understood.

Dr Mike Marden, a member of the ‘Soils and Landscape’ team, took over the office in 1985 as the first appointed scientist, 10 years after its “temporary” opening.

It was a one-man office for 32 years, and now Dr Marden is retiring, Landcare Research has decided to close the office.

During his time here large areas of exotic forest have been established on severely eroded hill country, particularly following Cyclone Bola in 1988.

The devastation caused by Cyclone Bola drew attention from researchers the world over.

“That storm was a real eye-opener, and really showed the vulnerability of land on the East Coast.”

Bola provided scientists with an opportunity to assess the performance of exotic forest, and other vegetation types in slowing erosion during a severe storm.

Dr Marden and colleagues discovered just how effective the different forest types (exotic, indigenous forest and mature reversion) could be in preventing shallow landslides.

They found once the tree canopy had ‘closed’ and the trees had developed a significant root system, the incidence of landsliding reduced by 90 percent when compared with treeless landscapes.

This in turn led to investigations of the tree root systems of different species and their role in stabilising land.

When harvestming began in Mangatu Forest in 1990, Dr Marden’s research focus switched to measuring root decay rates following forest removal, and how this affected the land’s stability.

At around the same time, and in response to the severity of erosion to farmland during Cyclone Bola, the East Coast Forestry Project provided funding towards the reforestation of large areas of badly damaged East Coast farmland.

Dr Marden was able to demonstrate to the then Ministry of Forestry that as gullies were the dominant source of sediment, the most effective means of reducing sediment generation from them was to map all the gullies throughout the region, and use this database to prioritise their treatment.

This knowledge is still being used today to target funding to treat gully erosion.

In the mid-1990s, local and international studies focussed on tracking the rate of sediment movement from the headwaters of the Waipaoa catchment to the ocean, identifying where the sediment was accumulating, and whether it posed a tsunami risk should an earthquake trigger a landslide on the sea floor.

At this time Dr Marden’s research focussed on better understanding the geological and climatic processes that over the course of the last 15,000 years resulted in river downcutting and subsequent abandonment of a well-preserved sequence of alluvial terraces in the Waipaoa and Waimata catchments.

More recently the resurgence in interest in manuka for honey, pharmaceutical products, and to sequester carbon, has reinvigorated research on rates of root reinforcement and canopy development.

Research will provide evidence of the time required for manuka to become an effective erosion control option for marginal land that has a high erosion risk.

During his time here Dr Marden has given numerous politicians, international scientists and students tours of sites of interest, the Tarndale Slip being the highlight.

“Local and international universities have in the past and continue to bring busloads of students to the East Coast to see first-hand our erosion problems and solutions used to treat it.”

While it will be the end of this Crown Research Institute’s permanent presence in the region, research projects will continue, for example, on climate change impacts on land use in the Waiapu catchment.

A team has also recently received funding for a three-year project to investigate alternative and more sustainable land use options than pine forest on severely erosion-prone land, where in recent years it has been linked to adverse environmental impacts.

Dr Marden will also keep links with Landcare Research as a part-time research associate, while retaining an interest in local issues.

“It is by no means the end of Landcare Research’s or my involvement with this region,” Dr Marden said.