Areas with highly productive land like Pukekohe have become increasingly fragmented with decades of development. Photo / Jason Oxenham
Areas with highly productive land like Pukekohe have become increasingly fragmented with decades of development. Photo / Jason Oxenham
The toll of decades of intensive dairying and urban sprawl across some of New Zealand's best land has been laid bare in a just-released stocktake.
The Ministry for the Environment and Stats NZ's latest joint report, Our Land 2021, 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.
"Land is central to our identity as people of Aotearoa New Zealand," Secretary for the Environment Vicky Robertson said.
"It is our tūrangawaewae, our place to stand. The choices we make for where we build, what we grow for ourselves, and what we export are creating tensions for the best use of available land.
"Climate change and a growing population are only going to make future choices more difficult."
Our area of land covered with native ecosystems continued to shrink, mainly through conversion to agriculture or forestry.
Development had made our most productive land - often found on the fringes of swelling cities - more fragmented over the past two decades.
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.
The total area of land used for agriculture and horticulture has been shrinking since 2002, easing back 14 per cent by some 1.8 million hectares, and there were also nearly 20,000 fewer farms than there were 20 years ago.
At the same time, however, 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, the figure was still twice what it was in the 1980s.
Dairy cattle numbers are now twice what they were in the 1980s. Photo / Alan Gibson
Use of irrigation had similarly nearly doubled since 2002. By 2019, dairying accounted for nearly 60 per cent of irrigated agricultural land – which itself accounted for about 5 per cent of all agricultural land.
Amid dairying's "white gold rush", the sale of grass-boosting phosphorus fertiliser peaked in 2005 at 219,000 tonnes per year, before falling back to about 154,000 tonnes, while nitrogen fertiliser sales soared from 62,000 tonnes in 1991 to 452,000 tonnes nearly three decades later.
Nationwide, 80 per cent of monitoring sites now failed to meet the targets for at least one soil quality indicator, although data showed no declining or improving trend since around 1994.
Between 2014 and 2018, macroporosity - a key measure of pore spaces in soil and a potential indicator of soil compaction - was below the target range in 65 per cent of sampled dairy farming sites, 48 per cent of drystock farming sites and 46 per cent of orchards and vineyards.
That made soil less productive, hampered plant growth and drainage, increased greenhouse gas emissions from urine-soaked soils and led to more phosphorus and eroded soil reaching waterways.
Levels of Olsen phosphorus, an indication of soil fertility, were above the recommended target range for 61 per cent of the dairy farming and cropping sites, and 46 per cent of orchard and vineyard sites sampled between 2014 and 2018.
Importantly, high levels of Olsen phosphorus in the soil indicate that too much fertiliser has been applied.
Along with damaged soils, this also came with a cost to our waterways and climate.
In groundwater dated using tracers, a sharp increase in nitrogen and other agrochemicals was observed after 1955 - corresponding to the start of intensified agriculture.
Nitrogen and phosphorus could drive algal blooms in rivers and lakes, hurt fish and plants – and posed threats to our own health.
In areas with high cattle density, particularly, a recent preliminary study of nitrate contamination of drinking water in New Zealand found concentrations were sitting above potentially harmful levels.
More than two thirds of dairy farms have compacted soils - and nearly the same proportion have too much phosphorus from years of fertiliser use. Photo / Duncan Brown
The amount of sediment gushing into our streams, rivers, lakes and beaches was already globally disproportionate.
New Zealand accounted for just 0.2 per cent of the planet's total land area but contributed 1.7 per cent to global sediment loss.
Soil productivity, specifically, could be affected with the loss of topsoil - something which could cause landslides, make pastures unproductive, force farmers to add more nutrients through fertiliser, and sometimes take generations to regain.
Overseas, the problem has been especially prominent in the UK, where farmers have been warned by government officials that "the fundamental eradication of soil fertility" could be just decades away in some places.
Meanwhile, just over half of New Zealand's greenhouse gas emissions came from methane and nitrous oxide – and most of that came from agriculture.
But farming wasn't the only driver putting the squeeze on our landscapes.
While urban areas make up just one per cent of our total land, 87 per cent of Kiwis live within them.
The main centres will see the bulk of New Zealand's population growth over the next two decades - or some 80 per cent of it.
That pressure would only further intensify as the number of people in this country ballooned to a projected 6.8 million by 2073 – bringing even more demand for land to supply food and housing.
While about 15 per cent of land in the country was currently considered highly productive, requiring less irrigation and fertiliser, and ideal for growing potatoes, onions, and leafy green vegetables, much of it surrounded these fast-expanding centres.
The report showed that, over the past 20 years, residential development like 5ha lifestyle blocks was gradually eating away at it.
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 of Auckland – areas like Kumeu, Pukekohe and Franklin – which were once sites for market-gardening, but now largely fragmented after rezoning.
Rising populations in urban areas will heap more pressure on the productive land surrounding them. Photo / Jason Oxenham
In 2019, around a third of the two highest classes of land either already had been, or was soon to be, developed.
The picture was dire for New Zealand's native biodiversity and ecosystems, which continued to be under threat.
Many of the habitats that remained for our surviving species were scattered around the countryside in smaller and more isolated fragments.
Aside from habitat loss, of assessed species, nearly 83 per cent of native birds, bats, reptiles and frogs were either threatened or were at risk of extinction.
In the South Island's postcard Mackenzie Basin, tenure review and agri-development has led to less than 10 per cent of the valley floor retaining protection - despite this being the home of many threatened plants and animals.
Government Statistician Mark Sowden said the report came with new and updated indicators – but there were still data gaps.
"We have an incomplete picture of the impact on the environment and our wellbeing of what we do on the land," he said.
"We need better and more targeted data to understand the impact of intensive land use, particularly on native ecosystems."
Forest and Bird spokesperson Annabeth Cohen argued it was now "physically impossible" to continue growing food as it is currently done in New Zealand.
"This report makes clear that there is simply not enough water, soil, or fertiliser capacity to continue on this dead-end path," she said.
"Our farming leaders and policy makers have a straight-forward decision to make - either help farmers transition to food production systems that protect biodiversity, the climate, and fresh water, or continue to allow the fertiliser and irrigation industries to destroy rivers, soil, and the climate."
