A case for soil preservation

As a geoscientist with a strong interest in soil science, I have long despaired over the poor regard for, and limited understanding of, this country’s soils (“Down to earth”, September 11). Along with water, soils are the paramount resource and should be treated accordingly, especially those of high class (high versatility).

Drs Allan Hewitt and Megan Balks and I recently published The Soils of Aotearoa New Zealand. At the time of its launch, the irreversible loss of high-class soils (only 5% of the country) to urban development, despite regulations to the contrary, attracted attention. The regulatory authorities have allowed substantial losses of 40,000ha annually of soils, many high-class, to urban expansion, industry and lifestyle blocks.

To put that figure in perspective, horticulture extends more than 70,000ha in total. High-class soils are ancient and reflect many thousands of years of development, so are precious taonga because they are non-renewable.

This latter aspect seems to elude most councils and politicians making decisions. They lack the imagination or incentive to develop housing other than on high-class soils, and irrationally blame a “shortage of land” for high property prices, despite large areas of land being better suited for housing or industry than the 5% of high-class land optimal for food production.

Professor David Lowe

University of Waikato, Hamilton

Earthworms are essential for the health of soils that are not cultivated. On farms with cattle-grazed pasture, earthworms counter the weight of cattle, especially