Urban sprawl: NZ now at a 'crossroads' over housing and best land

Rich growing areas like Pukekohe have become increasingly fragmented by urban sprawl over past decades. Photo / Jason Oxenham

Urban sprawl is swallowing up New Zealand's best vege-growing land at a dramatic rate, threatening our ability to feed ourselves.

A major Government stocktake out today found that the country's most productive land - ideal for growing food like potatoes, onions and leafy green vegetables - had become increasingly fragmented by development over the past two decades.

The Our Land 2021 report, released by the Ministry for the Environment and StatsNZ, checked the health of an often overlooked yet vitally important part of our natural estate: soil.

The quality and quantity of soil is crucial for storing water, carbon and nutrients, growing food, breaking down contaminants and hosting an abundance of species.

And it's also critical for our economy: half of New Zealand's export earnings come from primary industries that use half of our land and depend on good soils.

While about 15 per cent of land in the country was currently considered highly productive, requiring less irrigation and fertiliser, much of it surrounded fast-expanding urban centres.

Over the past 20 years, residential development like 5ha lifestyle blocks was gradually eating away at it.

1996-2018: Productive land turned into housing

The area of this land unavailable for agriculture – because it had a house on it – grew by more than 50 per cent over the period, and accounted for more than 100,000ha by 2019.

A striking example was the countryside around Auckland – areas like Kumeu, Pukekohe and Franklin – which were once havens for market-gardening in the 1950s, but had since been transformed by rezoning.

In 2019, around a third of the two highest classes of land across New Zealand either already had been, or was soon to be, developed.

While urban areas make up just one per cent of our total land, 87 per cent of Kiwis live within them - and these centres would see the bulk of population growth projected to hit nearly 7 million by 2073.

Lincoln University's Associate Professor Amanda Black, who provided expert advice on the report, said New Zealand was at a "crossroads" of carrying on as it had, or taking a more informed approach to managing land.

The area of top land unavailable for agriculture - because it had a house on it - swelled by more than 50 per cent over the last two decades. Photo / Jason Oxenham

"Fragmentation and unimpeded urban sprawl that covers our best productive soils threatens to undermine our ability to feed ourselves and pay our bills," Black said.

"Once land is in housing it is gone for good. The loss of good productive soil is bad enough, but the additional spillover impacts of creating urban areas means that we would be limited in how we manage weeds and pests, potentially creating weed and disease havens."

"We need to protect our best land and to do that we need strong policy."

Dr Anne-Gaelle Ausseil, of Manaaki Whenua Landcare Research, agreed.

"Ongoing and uncoordinated expansion on New Zealand's best land might restrict future opportunities for our agricultural sector, which also faces a growing need to not only limit its impacts on the environment but also to adapt to climate change."

In the wake of the report, Federated Farmers called for a halt to further encroachment of housing onto productive farmland, arguing it also had knock-on effects for farmers still on the land.

"They face higher land values and consequently higher rates, along with increased council rules and restrictions that fall upon them due to increased amenity expectations of those new urban residents," the group's environment spokesperson, Chris Allen, said.

But elsewhere, the report found farming itself had wrought a heavy toll on our landscapes.

In the countryside, more than two-thirds of dairy farms had compacted soils – and nearly the same proportion had too much phosphorus from years of fertiliser use.

As at 2019, around a third of the two highest classes of land across New Zealand either already had been, or was soon to be, developed. Photo / Martin Sykes

The total area of land used for agriculture and horticulture has shrunk by 14 per cent since 2002, and there were now also nearly 20,000 fewer farms.

But at the same time, export income from farming products has risen - nearly doubling from $23b in 2010 to $44b in 2019.

And while the six million dairy cattle on our pastures numbered a million fewer than 2015's peak count amid the height of the "white goldrush", the figure was still twice what it was in the 1980s.

Nationwide, about 80 per cent of monitoring sites now failed to meet the targets for at least one soil quality indicator - and environmentalists pointed to wider problems like waterway degradation and greenhouse gas emissions.

The use of irrigation, too, had surged over recent times - but Allen pointed out that just 5 per cent of agricultural land was irrigated, most of it in Canterbury.

He also noted that the Government wanted the sector's earnings to double in the next decade to support the country's recovery from Covid-19.

"That's a hairy and audacious goal when you consider today's report also shows that since 2002 nearly 1.9 million hectares has gone out of agriculture and horticulture production."

"New Zealand's farmers have again and again proven adept at driving up production from less land and from management and genetic improvements but there comes a time when you run up against limits of nature and efficiency.

"The sector is being hammered with all sorts of new regulations and costs, and some farmers are at the end of their financial and mental wellbeing tethers."

But Forest and Bird's Annabeth Cohen argued it was now "physically impossible" to continue growing food as it was currently done.

She said there was an urgent need to redesign cities to make them more compact, and transition farming to more sustainable food production systems.

"This report makes clear that there is simply not enough water, soil, or fertiliser capacity to continue on this dead-end path."