The loss of soils through human-driven erosion on top of naturally high erosion rates has significant consequences for the productivity and resilience of the food and fibre sector.
There is also growing recognition that existing structural flood protections are inadequately prepared for increased pressures.
These are the key messages in Our Land 2024, a three-yearly update released by the Ministry for the Environment and Stats NZ that reports “our communities and economies are at risk if we do not protect our natural ecosystems and landscapes”.
Our Land 2024 brings together updated Stats NZ indicator data as well as insights from research literature, showing how the ways we use land have wide-ranging effects on diverse ecosystems and biodiversity with impacts on our economies, homes, resilience to disasters, cultural identity and public health.
MfE’s deputy secretary for strategy, stewardship and performance, Natasha Lewis, said ecosystems such as soil, indigenous forests, wetlands, flood plains and dunes are the foundational natural assets and infrastructure that underpin our economy, help to protect us against disasters and support public health.
These services include supporting our food sector, reducing soil erosion, draining catchments and protecting coastal areas against storm surges and sea level rise.
“We appreciate the benefits that built infrastructure provides, but many of us don’t think of, or value, natural ecosystems and landscapes in the same way,” Lewis said.
“Soil is crucially important because it is the foundation for other natural infrastructure. It also plays a vital role in our economy.”
In the year ended June 2023, New Zealand’s food and fibre sector accounted for $55.3 billion in export revenues, which represented more than 75% of the nation’s export goods.
Soil is a strategic asset.
“A lot of our GDP is in the top 15cm of the ground we walk on, but degrading or developing over our natural infrastructure increases the food and fibre sector’s susceptibility to soil erosion, pests, diseases and the effects of climate change and extreme weather.”
The Treasury has estimated that damage to the sector from Cyclone Gabrielle and the 2023 Auckland floods may total between $700m and $1.1bn in recovery costs.
A recently updated Stats NZ indicator in the report shows that 5% of our land is classified as highly erodible land and at risk of mass-movement erosion.
Of this highly erodible land, 60% is in the North Island.
“Topsoil is a finite resource, but 182 million tonnes of eroded soil entered our waterways in 2022.”
Lewis said other threats to the primary food sector include loss of fertile land to urban expansion.
Deloitte estimated in 2018 that fruit and vegetable prices could rise by up to 58% across the country by 2043 if fertile land at Pukekohe is developed.
“This is important contextual information for decision makers who decide where development can occur.”
Other examples of natural infrastructure include urban green spaces that soak up stormwater, improve air quality and provide recreational areas that support our wellbeing.
“The ways we use land are placing our natural infrastructure under pressure.
“Accounting for the full range of benefits that nature provides will help us to develop enduring solutions for the way we manage land.”
The report highlights that many areas across NZ have significantly higher proportions of highly erodible land at risk of mass movement.
Manawatū-Whanganui has the largest area, 17%, of highly erodible land in NZ and of all regions Gisborne has the highest proportion, 15%, of its area classified at risk of mass movement erosion.
The report also highlights that soil quality is not always within target ranges on land that supports NZ’s primary industries.
“The availability of highly productive land has decreased and should present trends persist it is highly likely that the availability of highly productive land will continue to decrease.
“The reduced availability of highly productive land can challenge types of food production.
“Land-based industries will almost certainly experience increased economic risks due to degrading natural infrastructure.
“It is highly likely that the degrading state of our natural infrastructure will reduce the regulating and flood protection services provided to surrounding communities.”
Meanwhile the area of exotic land cover has expanded, mostly with conversion from exotic grassland to exotic forest.
Development on floodplains has exposed communities and built infrastructure to flood and erosion risks and led to the need for engineered flood protection systems.
Urban and agricultural development is also occurring alongside braided rivers, constraining their channel margins.
Extreme rainfall associated with climate change is also likely to place increased pressure on these systems over time.
While measures that restrict the natural movement of river systems such as engineered channels and stopbanks are designed to protect communities, they also alter river systems’ natural capacity to provide flood and erosion benefits.
“Climate change is expected to increase risks to communities in flood-prone areas and there is growing recognition that existing structural flood protections are inadequately prepared for these pressures.”
