The stock adequacy method to quantify soil natural
capital follows five key steps:
1. Define the land use type (LUT) of interest (e.g. extensively grazed pastoral sheep farming);
2. Identify the key soil services needed for the specified LUT
(e.g. soil water storage capacity to maintain water supply
to grassroots to maintain grass production, Olsen P level,
and soil pH as indicators of nutrient availability, capacity
of soil to hold and prevent nitrate leaching to groundwater, capacity of soil to deliver water to groundwater to
maintain summer stream flows, and so on);
3. For each soil service that is identified determine the soil
functions that drive the service (e.g. the soil profile data
(soil stocks) needed to calculate soil water storage
include potential root depth, soil texture, and stoniness,
or total, readily available, and field capacity soil moisture
retention data, for each soil horizon in the plant root
zone);
4. Estimate the adequacy of each stock (e.g. for a given
rainfall and crop evapotranspiration, evaluate the proportion of the soil water requirements able to be met by
the available soil moisture storage);
5. Collate the adequacy calculations for all the different
required soil stocks to give an overall estimate of the soil
stock adequacy for the given soil and land use.
It is evident that such calculations, if they are to have any
relevance, will quickly become quite complex and depend
on a range of assumptions about crop growth, root depths,
water and nutrient requirements, and the weather conditions,
among other parameters.
18.4.11 Assessment of Soils of High Value
for (Potential) Food Production
Prior to introduction of the Resource Management Act 1991
(RMA), the Town and Country Planning Act 1953 controlled urban development and specifically demanded that
soils of high value for food production (actual or potential)
be protected from urban development. A system of determining what constituted soils of high value for food production was developed. Subdivision of such areas (for
instance, much of the mainly flat-lying, tephra-mantled
alluvial land, supporting a patchwork of Allophanic Soils,
between Hamilton and Cambridge) was limited to a minimum lot size of 10 acres (*4 ha), which was deemed to be
large enough for an economic horticultural production unit.
Under the RMA, there is no specific protection of soils
for food production as the act is permissive, rather than
prescriptive. The purpose (Section 5) of the RMA includes,
among other things, sustainable management of physical
resources to enable social, economic, and cultural well-being
while safeguarding the life-supporting capacity of air, water,
soil, and ecosystems for the reasonably foreseeable needs of
future generations. The soil is thus considered as one of
many ‘environmental’ variables. See http://www.legislation.
govt.nz/act/public/1991/0069/latest/DLM231905.html for
the full statement. Hence, under the RMA, any land use is
acceptable, in theory, so long as it does not reduce the land’s
potential to meet the needs of future generations, reduce its
life-supporting capacity, or damage the environment (within
an agreed framework). A key point is that the activity itself
is not assessed but rather the effects of the activity on the
environment. Provided environmental effects can be mitigated, land use changes are normally permitted.
Between 1991 and 2019, under the RMA, there has been
rapid urban expansion onto land that had previously been
protected under the Town and Country Planning Act. The
lack of protection of the most versatile soils (Sect. 18.4.6)
was the result of the enabling and balancing requirements of
the RMA where economic and social considerations have
held sway. In 2019, the government started the process to
introduce a National Policy Statement (NPS) for Highly
Productive Land to protect some of the soils that are of
high-value for food production, sometimes referred to as
‘versatile’ or ‘high class’ soils. Most regional and district
councils use the additional terms ‘elite’ for LUC class 1 soils
and ‘prime’ for LUC class 2 soils. Thus, the definitions of
what constitutes our most valuable land for food production
are again up for debate.
One widely accepted measure, given that the data are
readily available, is to consider that all land of land use
capability (LUC) classes 1 and 2 represent our most productive land that deserves protection from urban development. Classes 1 and 2 comprise flat or gently undulating
(<7°) land that can be repeatedly cultivated without danger
of excessive water erosion, which is versatile, and suitable
for a large range of crops. LUC 1 and 2 soils are most
common among the Recent Soils and Allophanic Soils but
also occur in some areas of other soil orders. In some
regions, such as the Pukekohe area, a specific combination
of climate and soils has successfully supported intensive
vegetable growing on some rolling (8–15°) land (LUC 3)
and, thus, there is a strong case for some areas of LUC 3
land to also be protected from urban development.
The case for protection of LUC 1 and 2 land is a compelling one. In New Zealand, only 0.7% of the land is LUC 1
with a further 4.5% in LUC 2. Thus, only 5.2% of New
Zealand comprises our most versatile and productive land
(Figs. 18.7 and 18.8). Soils on LUC 1 and 2 land have high
versatility (hence have the capability to produce a wide
range of crops), high energy-use efficiency, high yields, high
pollution absorption capacity, and moderate or better soil
resilience. Thus, the further loss of versatile soils from
306
18 Conclusion: Global Context, Formation Pathways …
capital follows five key steps:
1. Define the land use type (LUT) of interest (e.g. extensively grazed pastoral sheep farming);
2. Identify the key soil services needed for the specified LUT
(e.g. soil water storage capacity to maintain water supply
to grassroots to maintain grass production, Olsen P level,
and soil pH as indicators of nutrient availability, capacity
of soil to hold and prevent nitrate leaching to groundwater, capacity of soil to deliver water to groundwater to
maintain summer stream flows, and so on);
3. For each soil service that is identified determine the soil
functions that drive the service (e.g. the soil profile data
(soil stocks) needed to calculate soil water storage
include potential root depth, soil texture, and stoniness,
or total, readily available, and field capacity soil moisture
retention data, for each soil horizon in the plant root
zone);
4. Estimate the adequacy of each stock (e.g. for a given
rainfall and crop evapotranspiration, evaluate the proportion of the soil water requirements able to be met by
the available soil moisture storage);
5. Collate the adequacy calculations for all the different
required soil stocks to give an overall estimate of the soil
stock adequacy for the given soil and land use.
It is evident that such calculations, if they are to have any
relevance, will quickly become quite complex and depend
on a range of assumptions about crop growth, root depths,
water and nutrient requirements, and the weather conditions,
among other parameters.
18.4.11 Assessment of Soils of High Value
for (Potential) Food Production
Prior to introduction of the Resource Management Act 1991
(RMA), the Town and Country Planning Act 1953 controlled urban development and specifically demanded that
soils of high value for food production (actual or potential)
be protected from urban development. A system of determining what constituted soils of high value for food production was developed. Subdivision of such areas (for
instance, much of the mainly flat-lying, tephra-mantled
alluvial land, supporting a patchwork of Allophanic Soils,
between Hamilton and Cambridge) was limited to a minimum lot size of 10 acres (*4 ha), which was deemed to be
large enough for an economic horticultural production unit.
Under the RMA, there is no specific protection of soils
for food production as the act is permissive, rather than
prescriptive. The purpose (Section 5) of the RMA includes,
among other things, sustainable management of physical
resources to enable social, economic, and cultural well-being
while safeguarding the life-supporting capacity of air, water,
soil, and ecosystems for the reasonably foreseeable needs of
future generations. The soil is thus considered as one of
many ‘environmental’ variables. See http://www.legislation.
govt.nz/act/public/1991/0069/latest/DLM231905.html for
the full statement. Hence, under the RMA, any land use is
acceptable, in theory, so long as it does not reduce the land’s
potential to meet the needs of future generations, reduce its
life-supporting capacity, or damage the environment (within
an agreed framework). A key point is that the activity itself
is not assessed but rather the effects of the activity on the
environment. Provided environmental effects can be mitigated, land use changes are normally permitted.
Between 1991 and 2019, under the RMA, there has been
rapid urban expansion onto land that had previously been
protected under the Town and Country Planning Act. The
lack of protection of the most versatile soils (Sect. 18.4.6)
was the result of the enabling and balancing requirements of
the RMA where economic and social considerations have
held sway. In 2019, the government started the process to
introduce a National Policy Statement (NPS) for Highly
Productive Land to protect some of the soils that are of
high-value for food production, sometimes referred to as
‘versatile’ or ‘high class’ soils. Most regional and district
councils use the additional terms ‘elite’ for LUC class 1 soils
and ‘prime’ for LUC class 2 soils. Thus, the definitions of
what constitutes our most valuable land for food production
are again up for debate.
One widely accepted measure, given that the data are
readily available, is to consider that all land of land use
capability (LUC) classes 1 and 2 represent our most productive land that deserves protection from urban development. Classes 1 and 2 comprise flat or gently undulating
(<7°) land that can be repeatedly cultivated without danger
of excessive water erosion, which is versatile, and suitable
for a large range of crops. LUC 1 and 2 soils are most
common among the Recent Soils and Allophanic Soils but
also occur in some areas of other soil orders. In some
regions, such as the Pukekohe area, a specific combination
of climate and soils has successfully supported intensive
vegetable growing on some rolling (8–15°) land (LUC 3)
and, thus, there is a strong case for some areas of LUC 3
land to also be protected from urban development.
The case for protection of LUC 1 and 2 land is a compelling one. In New Zealand, only 0.7% of the land is LUC 1
with a further 4.5% in LUC 2. Thus, only 5.2% of New
Zealand comprises our most versatile and productive land
(Figs. 18.7 and 18.8). Soils on LUC 1 and 2 land have high
versatility (hence have the capability to produce a wide
range of crops), high energy-use efficiency, high yields, high
pollution absorption capacity, and moderate or better soil
resilience. Thus, the further loss of versatile soils from
306
18 Conclusion: Global Context, Formation Pathways …