Thursday, May 19, 2022

Book highlights soils’ value to NZ

For the first time in a generation, anyone with a connection to soils and their management has a new text to reach for – one that is likely to set a reference benchmark not only in New Zealand, but internationally.

Professor David Lowe hopes the Soils of Aotearoa will become a reference for farmers and academics alike.

For the first time in a generation, anyone with a connection to soils and their management has a new text to reach for – one that is likely to set a reference benchmark not only in New Zealand, but internationally.

University of Waikato professor of earth sciences David Lowe and his colleague Dr Megan Balks, along with Dr Allan Hewitt of Manaaki Whenua-Landcare Research, spent over three years compiling The Soils of Aotearoa New Zealand. 

The 18-chapter text offers a technically detailed, but highly accessible insight to NZ’s complex soil types and their properties.

“It is partly a reflection of how good the previous work by Dr Les Molloy was when it came out in 1988 that we have not had much since then,” Lowe said.

However, a change in how NZ soils were classified after that release prompted Hewitt to consider the potential for a new technical guide. 

He oversaw a new system of classification in 1992 that was based on 15 large groups of “soil orders”, classifying soils that had similar properties, origins and management needs. The new book is based on chapters that deal with the soils in each order. Earlier books had focused upon soils on a regional basis and used older classification systems.

Described as a labour of love, Hewitt started the work around 10 years ago with Balks; Lowe joined the team in 2018 and much of the work was completed in the authors’ own time.

The book provides essential information on each of the 15 soil orders, including the likes of Allophanic soils (soils with properties dominated by a special clay type), Brown soils, Semiarid soils, Recent soils, Gley soils and Pumice soils. Their main physical, mineralogical and chemical features, origins, relationships with landscapes, and management aspects are all covered. 

The book also places considerable context around soil’s value to NZ’s environmental and economic soundness. The authors have also been at pains to highlight the fact NZ’s most valuable, productive soils only comprise 5% of the total available.

Of that, a mere 0.7% of NZ’s land is classified as falling into the highest-quality Land Use Capability (LUC) 1, and 4.5% into LUC 2.

Despite this, over 10% of these most highly productive soils have already been lost to lifestyle blocks and housing, with a shocking one-third of the best land in Auckland and Waikato lost for good to urban expansion under an accelerating process.

The case for protecting these soils from further losses to housing and roading is raised as a compelling one by the authors. 

Lowe says the extremely high-value soils of the South Auckland area (Pukekohe-Bombays) have been facing “death by a thousand cuts” over the past several decades under housing pressure.

“With the introduction of the Resource Management Act, we saw the rapid urban expansion onto land previously protected under the Town and Country Planning Act, something only now being recognised through the 2019 National Policy Statement for Highly Productive Land,” he said.

He said Minister for Environment David Parker has been the first minister to recognise the value of these soils and the urgent need to protect their future loss.

“And we have seen Hawke’s Bay as one area where this has been recognised through the Save Our Plains campaign, helping councils recognise the value of these soils and the need to control expansion,” he said.

Lowe said the authors have tried to keep the book’s language accessible and as useful for undergraduates as it is for farmers, council staff and advisors.

“We have always found most NZ farmers are very well-educated and have a good appreciation and understanding of how their soils differ from place to place on the farm, often requiring different management depending upon their use. The book documents the relationships between soils and landforms, which is how most farmers see their soils,” he said.

The book is the 31st volume in a global initiative under the Springer World Soils Book Series to update publications on countries’ soil types, coming out after countries including Egypt, Bangladesh and Serbia. 

Unlike many, all its chapters are written by the one team, and Lowe said this has ensured greater continuity of style and detail compared to edited volumes with multiple contributors. 

Independent Aotearoa book review website Kete noted Soils of Aotearoa NZ was not necessarily a straightforward read, but one that contained a wealth of fascinating information of value to anyone with any connection to the land and soil.

“A lot of NZ’s wealth has come from our soils and farmers are part of the solution to preserving those soils. I have always found they are very open and happy to help look after them. Our hope is as many farmers as possible will want to have a copy to improve on the knowledge so many already have,” he said.

Soils of Aotearoa New Zealand is available as both a hard copy and digital download.

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