Nearly 200 million tonnes of soil are being lost in New Zealand every year - an out-of-sight problem that could pose far-reaching consequences for our environment and economy.
A major Government report out this morning also found nearly half of that loss was coming from pastures, at a time when dairy intensification was packing more cows into paddocks.
The quality and quantity of soil is crucial to the overall health of our land and wider environment, storing water, carbon and nutrients, growing food, breaking down contaminants and hosting an abundance of species.
It's also vital for our economy: half of New Zealand's export earnings come from primary industries that use half of our land and depend on productive soils.
The Ministry for the Environment and Stats NZ's latest stocktake, Our Land 2018, found 192 million tonnes of soil was being lost to erosion every year.
Environment Minister David Parker acknowledged more action was needed and he had now asked officials to start work on a National Policy Statement for Versatile Land and High Class Soils.
Across 11 regions, between 2014 and 2017, almost half of tested sites fell short on two of seven indicators of soil health.
Those were phosphorus content, which measures fertility, and macroporosity, which measures how many pore spaces there are in the soil and gives a general picture of its physical status.
Of tested sites, 33 per cent had soil phosphorus levels that were too high.
Excess phosphorus could travel into waterways through erosion and run-off, where it could trigger growth of unwanted plants and hurt water quality.
Forty-four per cent fell below the target range for macroporosity, indicating soil compaction.
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.
Unsurprisingly, land that was used more intensively - whether for dairy, dry stock, cropping or horticulture - rated worse for those two indicators.
Half of tested dairy sites had excess soil phosphorus and a further 65 per cent were below the target range for macroporosity.
Some horticultural and cropping sites also had high phosphorus levels (37 per cent) and low macroporosity levels (39 per cent).
While the rates of erosion are similar between the North and South islands, one region of each island stood out for high rates of soil loss and related sedimentation of waterways.
Compared with national mean rate of soil erosion - 720 tonnes per square kilometre per year - Gisborne's annual rate was 4844 tonnes per sq km, while the South Island's West Coast had an annual rate of 2106 tonnes per sq km.
Too much erosion was a worry because it can reduce farm productivity, increase flooding to towns and cities, and degrade the health of our fresh water, estuarine and marine environments.
In 2015, economic losses associated with soil erosion and landslides were estimated to be at least $250m to $300m each year.
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 were recently warned by government officials that "the fundamental eradication of soil fertility" could be just decades away in some places.
"The report makes it clear that we need to pay attention to what's going on in our soil, which underpins our economy," said Penny Nelson, deputy secretary at the Ministry for the Environment.
"It shows us where we need to focus. This report also reinforces that our land use decisions are putting our environment under pressure."
A landscape transformed
Even in the past two decades, dramatic changes have unfolded in our countryside.
The most recent survey of our land cover shows that just under half of the land area is naturally blanketed by indigenous forest, tussock grassland, scrub, waterways and bare ground.
The rest of it has been changed by us, into exotic forests, pastures, crops and towns and cities – and some 71,000ha of native land cover was lost between 1996 and 2012 alone.
That included 31,000ha of tussock grassland, 24,000ha of shrubland and 16,000ha of forest, which was cleared, converted or developed.
For comparison, a full-size rugby field was just over one hectare in size.
Once-widespread coastal and lowland ecosystems, including wetlands, had declined and two-thirds of New Zealand's rare and naturally uncommon ecosystems were now threatened.
The amount of land used for dairy has meanwhile surged by more than per 40 cent since the early 2000s, while that used for sheep and beef has dropped by 20 per cent, in step with dairy's white gold rush.
New Zealand's dairy country now spanned 2.6m ha, while sheep and beef farms covered 8.5m ha – and the switch from one to the other was the most striking in Canterbury and Southland.
There had been a shift in the past 15 years to higher numbers of animals farmed per hectare.
It wasn't just agriculture eating up our natural landscape – urban sprawl was consuming some of the country's most versatile productive land.
Studies indicated that between 1990 and 2008, a third of new urban areas had spread on to this land.
The greatest expansion of urban areas was in Auckland (up 4211ha), Waikato (up 3900ha) and Canterbury (up 3829ha).
Just outside urban centres, there has been a sharp increase in the number of lifestyle blocks over recent decades.
A 2013 study showed that of the 175,000 lifestyle blocks that occupied 873,000ha of land in 2011, more than 40 per cent had been established since 1998 - an average of 5800 new blocks a year.
The same study found that 35 per cent of Auckland's most versatile land was used as lifestyle blocks
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.
The conservation status of seven bird species, three gecko species, and one species of ground weta was worsening.
Except for some offshore islands and fenced sanctuaries, exotic pests were found almost everywhere, eating native animals and plants and spreading disease.
Since humans arrived here, New Zealand had already suffered one of the highest extinction rates on the planet, losing 59 birds, eight plants, four insects, three frogs and two reptiles.
There still wasn't enough data to assess what was happening to more than a quarter of land species considered by the Department of Conservation's threat classification system – especially invertebrates.
But there were some positives: the report found 20 bird species – among them the North Island brown kiwi, the northern New Zealand dotterel and the mohua, or yellowhead - had improved conservation status.
Our changing climate
The impacts of climate change would heap yet more pressure on our land.
It would bring more intense rainfall events and more droughts, wildfires and pests – worsening erosion and sediment pollution, and making yet more land unsuitable for farming and some orchards.
Since the early 1970s, soils at a quarter of monitoring sites around the country had been getting drier.
Over the same period, the number of days that reached over 25C had also increased at a third of measured sites.
Numbers of invasive wasps, which eat indigenous insects and compete with indigenous birds, bats, insects and lizards for honeydew, had increased in beech forests near Nelson because of increasing spring temperatures.
Rising sea levels and storm surges would mean more and worse coastal flooding and erosion, threatening habitats and low-lying infrastructure.
The new report followed other recent government stocktakes that have focused on the state of our atmosphere, freshwater estate and marine environment.
Government Statistician Liz MacPherson said important parts of the land story were missing.
"There are significant gaps in our knowledge and the available data, especially integrated data at a national scale.
"Without more up-to-date information on land cover, land use, erosion, soil and ecosystem health, we cannot fully understand the extent of pressures, the rate of change, or what impacts changes in soil and biodiversity are having on our social, cultural, economic and environmental wellbeing.
"That's an issue we and the Ministry for the Environment, along with others, will actively address."
'Insightful and frankly worrying'
David Parker said he was particularly troubled by how much of our urban growth is occurring in our irreplaceable highly productive land.
"Even in a country as lucky as New Zealand we only have limited quantities of these high-class soils," he said.
"We have to ensure we have enough land to build the houses people need, but we must protect our most productive areas too."
Parker said he was taking steps to address issues such as the loss of prime-market gardening land around Pukekohe, as Auckland expands, as well as the impact of lifestyle blocks on our most productive land.
The Government's billion trees planting programme would help address erosion issues, he said.
"The report also confirms the continued loss of our limited wetlands, which contain some of our most precious biodiversity, and filter contaminants from land. We must do more to protect these," the minister said.
"I had already asked officials to begin working on a more comprehensive freshwater national policy statement to address concerns about sediment, wetlands and estuaries."
Forest and Bird chief executive Kevin Hague said the trends were a result of directing the economy toward commodity markets like milk powder, raw logs and bulk tourism.
"Our land, soils, water and native species are taking the hit," he said.
"Intensive farming has major consequences for the environment, but it also has impacts on our ability to farm in the future.
"Compacted soils, with high phosphorous content, are bad for water quality but they're also not productive.
"This approach to land use is a lose-lose for both the economy and the environment."
Hague said the report should act as "a call to action" for the new Government.
"Our land-based nature in New Zealand urgently needs investment, stronger rules to reverse the tide of loss we are seeing in our lowlands and forgotten places, and an economic approach that works with our natural environment rather than against it."
Fish and Game chief executive Martin Taylor called the report "sobering" - and highlighted the damage caused by intensive agriculture.
"The current practice of overwintering stock also needs tighter control," he said.
"Packing animals into small paddocks to eat crops to the bare ground is producing expanses of mud which wash into streams and rivers, smothering aquatic life with sediment.
"We have to do better, for the sake of our environmental and economic well-being.
"After a decade of neglect, we need proper protection of our resources, forest and rivers."
Dairy NZ chief executive Tim Mackle said the sector was working hard to address soil loss and water quality.
"We are seeing more and more farmers using mitigations like standoff pads and removing stock from the paddock at times when the soil is most vulnerable to compaction, and management of areas highly susceptible to erosion and sediment loss," he said.
"We also know that good winter management, and targeted planting at specific times of the year, can all improve soil condition and therefore positively impact the levels of contaminants in our water."
Mackle said New Zealand was an agricultural nation whose success depends on balancing productivity and profit with sustainability.
"This report highlights where more work is required."
Horticulture New Zealand chief executive Mike Chapman was also well aware of the issues.
"We believe the valuable growing soils – which are often termed elite soils – should be protected by central Government policy," he said.
"We can't afford to keep losing these soils if we want to continue feeding New Zealand their favourite fruits and vegetables.
"The group had been talking to Government about this issue in Pukekohe, near Auckland, as well as other prime growing areas for fruit and vegetables.
"Some of this soil is unique, particularly the volcanic soils around Pukekohe where vegetables can be grown all year in a frost-free environment. This area feeds a lot of New Zealand."
Chapman said many growers were spending large sums of money on long-term riparian planting plans to protect waterways on their properties and enhance the environment.
"There is also a Sustainable Farming Fund project underway called Don't Muddy the Water, focused on keeping soil on the land where it belongs and out of the waterways.
"Started three years ago, this project quantifies the relative effectiveness of the best management practices for reducing sediment and phosphorus loss.
"Results so far have shown the effectiveness of silt traps that capture sediment so it cannot run off the land.
"Preliminary results also show the cumulative discharge of sediment is lower on cultivated production land protected with silt traps compared to construction sites.
"The project is ongoing but it will continue to inform best practices."
Environmental Defence Society chief executive Gary Taylor said the report had some serious data gaps but was otherwise "a useful, insightful and frankly worrying analysis that shows mostly declining trends".
Taylor called on Parliamentary Commissioner for the Environment Simon Upton to review the report and recommend responses.
The EDS itself recommended a major overhaul of the Resource Management Act, a new national policy statement on native biodiversity and a stronger one on freshwater management, lower stocking rates, better urban planning, more oversight from regional councils, a forestry planting review and more funding for the Department of Conservation's core core functions, along with pest and weed management.
Federated Farmers environment spokesperson Chris Allen echoed Taylor's concerns around gaps in the report's data.
"If we are serious about monitoring land use and its quality, we need to get our act together and fund the science appropriately," Allen said.
"Most of the data in this report is six years out of date. That's not acceptable or helpful."
The five big figures
• 192m tonnes: the amount of New Zealand soil being lost every year from erosion, nearly half of it from erosion.
• 42 per cent: the increase in the area of land used for dairy between 2002 and 2016, in which time the area used for sheep and beef fell by 20 per cent
• 83 per cent: the proportion of our native birds, bats, reptiles and frogs classified as threatened or at risk of extinction.
• 71,000ha: the area of native land cover lost between 1996 and 2012.
• 10 per cent: the increase in the total size of our towns and cities between 1996 and 2012.