A renewed focus on what lies beneath our feet is providing more good reasons to tread lightly, writes Tom McKinlay.
The soil in Dennis Enright's hands looks just about good enough to eat.
The Taieri vegetable grower and soil scientist has forked up a good two handfuls of the stuff from a line of carrots, which have clearly benefited from their time in it.
But we are concentrating on the dirt around the orange veg. The stuff without which there is no carrot.
It's a rich chocolate brown, crumbly like a Flake, which is to say, friable, in soil-speak.
Mr Enright is pretty happy with it.
''To me, this is what I think is good soil,'' he says.
As well as being friable, it's full of roots and there's likely to be plenty of biota less easily detectable by the human eye.
We're on the fringe of Mosgiel, on Hagart Alexander Dr, just beyond the point of creeping urbanisation.
Soil here is some of the best in the world, Mr Enright says.
A precious resource worth some consideration.
''Soil is fundamental, it's fundamental to pretty much everything you do.''
Mr Enright has spent a good part of his adult life considering the soil.
He spent 20 years, until the mid-'90s, as a researcher at AgResearch Invermay, and the past 20 growing organic vegetables on his 1.2 hectares of Taieri dirt.
As a result, soil appears to have taken up semi-permanent residence in his hands, occupying any lines and cracks.
He's close to it physically as well as philosophically.
And he has some concerns about it.
Among them is that conventional agriculture is asking too much of our soils.
Economic pressures means growers apply fertiliser and push land into providing a further cash crop rather allowing soil to recover.
''The big problem in the world today is that [soils] are not able to handle what we throw at them,'' he says.
Part of the reason is that many people don't realise what a precious resource soil is, he thinks.
There are fairly limited areas, even in a country as green as New Zealand, where we can grow good/high-quality food.
''It is hard for people to say, `don't use this for any other purpose but growing food' because people say `what about over there or over there','' he says.
That's unlikely to be comparing like with like.
The ability of the soil he holds in his hands to grow nutritious food is superior to the soil on the side of nearby Saddle Hill, for example, he says.
It is not an issue for New Zealand alone.
In fact, the UN General Assembly has declared 2015 the International Year of Soils.
As part of that, the UN Food and Agriculture Organisation (FAO) hopes to raise awareness about the ''profound importance of soil for human life'', and its crucial role in food security, climate-change adaptation and mitigation, essential ecosystem services, poverty alleviation and sustainable development.
The spotlight on soil comes with concerns about the world's ability to feed itself.
Back in the 1960s, 0.4ha of arable land was available for food production per person, but today it has dropped to half of that area and by 2050, it is expected to be just 0.1ha per person.
At the same time, the world needs to increase food production by about 50% to 70% by 2050 to feed a growing population.
• Associate Professor Marta Camps, of Massey University, is a member of the Intergovernmental Panel on Soils and just back from Europe working with the panel on the FAO's Global Soil Partnership.
Part of the panel's work has been to update the World Soil Charter, a document first put together in the 1970s but soon filed on a dusty shelf.
It opens with the statement: ''Soils are fundamental to life on Earth but human pressures on soil resources are reaching critical limits.''
Prof Camps says that was true in 1970 and remains true, if more urgent, today.
Many of the world's soils are degraded, she says.
Among the familiar bogeys are erosion, nutrient depletion, contamination, salination and sealing soil under the concrete and asphalt of urbanisation.
''Because the original villages and cities were based in fertile areas, when these started to grow they started to cover very fertile soils, this is happening as well in New Zealand.
"So we need to make sure that we design the cities or the growing areas in the cities in such a way that we do not cover these fertile soils,'' Prof Camps says.
''We have to stop that degradation process, to make sure that we keep that surface available for cropping.''
But not just cropping. Soil performs all sorts of ''ecosystem services'', Prof Camps says, that are also vitally important.
Soil filters water, recycles nutrients, and stores biodiversity and carbon.
Some of this thinking is quite recent, she says, even soil scientists having paid little attention to the biodiversity value of soil in the past.
''It's the same, for example, with the human body,'' she says.
''We have been taking so many antibiotics the biota in the gut has suffered, because we have been destroying it. It is the same for the biodiversity pool of soils.
"We have been applying pesticides and we have been cultivating the soil, decreasing the organic matter of the soil and that all affects the biodiversity.''
Similarly, the importance of soil as a carbon pool, capturing and storing carbon that might otherwise be in the atmosphere, is attracting new attention.
''People are not that well aware that the soil is the largest carbon pool of the terrestrial ecosystems,'' Prof Camps says.
Poor soil management is depleting soil carbon, with the result that it is lost to the atmosphere, potentially adding to climate change.
''In my view it is all about awareness, so if people are aware of the importance of soils, that will provide the trigger for policy makers to take action.''
Celebrate soil
• As part of 2015 International Year of Soils and Food Revolution Day, Organic NZ and the Northeast Valley Project hosts a potluck feast at Dunedin North Intermediate School hall on Friday, May 15 at 5pm, also featuring Delgirl, Catgut and Steel, Kat Anna Fiddle and pecha kucha.
Digging the dirt
• According to Landcare Research .5% of New Zealand's high-class land has been urbanised in the past 20 years. 10% of high-class land is now occupied by lifestyle blocks.
• The FAO says 95% of the world's food is directly or indirectly produced on soils.
• It can take up to 1000 years to form 1cm of soil.33% of soil globally is moderately to highly degraded due to erosion, nutrient depletion, acidification, salinisation, compaction and pollution.
• It is estimated that sustainable soil management could produce up to 58% more food.
• Nowhere in nature are species so densely packed. More than 1000 species of invertebrates may be found in a single square metre of forest soils.
• A typical healthy soil might contain several species of earthworms, 20-30 species of mites, 50-100 species of insects, tens of species of nematodes, hundreds of species of fungi and perhaps thousands of species of bacteria and actinomycetes.
