In the hundreds of containers lining the fridges, a few have special significance.

One of the many incredible things about New Zealand's native snails is how different they can look, even if they're geographically close.

Within a few kilometres, you can find different species and sub-species which never overlap, each on their own private evolutionary trajectory.

Snails have told us what the world used to look like. The similarity between snails found in both Nelson and Horowhenua, for example, was early evidence of an ancient land bridge between the two areas.

"It always seems to me like they're painted on the landscape," Kath Walker says.

"You can tell where a snail is from by the way it looks. The shells show genetic differences. We've got this patchwork that if we can put it together, like a jigsaw, we can work out what New Zealand was like five, 10 million years ago."

One of the most striking discoveries about P. augusta since its captivity is that there are three different types, separated long ago.

Nearly all of the more than 6000 snails collected were from the northern end, which had yet to be mined. But 24 of the snails were collected from the south, which had already been destroyed. They are likely distinct enough to qualify as a sub-species. A few more were in the middle, a sort of hybrid between south and north.

The northern and southern types lived a few hundred metres apart but rarely seemed to crossover; They were likely separated by a single forested gully, or a sudden event like a fire long ago. For thousands of years they would have evolved as neighbours. The southern types are bit bigger, and usually a lighter colour. Side by side, they could be a different species entirely.

Rodney Phillips and Kath Walker in the Hokitika DOC office. GEORGE HEARD/STUFF Rodney Phillips and Kath Walker in the Hokitika DOC office. GEORGE HEARD/STUFF

Five of the original 24 southern snails are still alive, each well into their 20s. They have successfully reproduced, and now there are around 150 southern P. augusta, most of them babies.

There are roughly the same number of southern P. augusta as there are Kākāpō. When Kākāpō numbers dropped to 50, they had an international advisory group and round the clock minders, hot water bottles in their nests and vets on call. The southern P. augusta are well cared for, too, but remain obscure. As it would be with Kākāpō, releasing them all into the wild at once would be an enormous risk.

DOC was unsure how it would look after the species when it was tasked with starting the captive programme. There was no local precedent.

It has come with occasional bouts of trouble. In 2011, one of the fridges malfunctioned, killing around 800 snails.

It happened due to a series of improbable events - the chiller unit automatically reduced the temperature in response to the malfunctioning temperature gauge, which was recording incorrect warmth. Because it was a long weekend, it was discovered too late.

It was a devastating blow for the DOC staff who had spent years experimenting to make the conditions just right. (The chiller unit is now connected to a text message warning system, and snail numbers have fully recovered).

While DOC has figured out what works, how long the programme should last has been a dilemma for the department, which is obliged to save a species with no viable habitat. The species' recovery plan stresses persistence is the aim - its goal, first and foremost, is to keep the species alive.

Internal debate about the species' future has been fraught, documents obtained under the Official Information Act show, and almost resulted in the programme being axed entirely.

The documents show a proposal to release all of the captive snails into the wild by the end of 2018, "mothballing" the facility in case they needed to be brought back.

That didn't happen after expert advice warned it would be risky, particularly for the southern type.

“Early release of all snails would almost certainly mean extinction/swamping of the southern subspecies and loss of genetic diversity within the species,” part of the advice said.

"Extinction of the southern sub-species would be likely and a reduction in genetic diversity probable."

It was just one of many issues. The tiny area of suitable habitat put the species at risk of "stochastic" events (basically a random disaster, like a fire or a drought); an early release "could pose high reputational risk for the Department".

The species was named a priority on the draft threatened species strategy - chosen by an algorithm used to decide which species were most worth saving - which would have meant the species' population would need to increase, not just persist.

One of the fridges. GEORGE HEARD/STUFF One of the fridges. GEORGE HEARD/STUFF

So what next? The captive programme is safe until 2020, funded by the taxpayer. DOC is exploring ways to cut costs - they could include scaling the programme back, a privately run model, or corporate sponsorship.

What happens after 2020 is still unclear, and depends on a lot of unknowns. By then, it would have been 10 years since they started monitoring the re-released snails in the wild, and nearly 15 years since the species was refrigerated.

In that time, Solid Energy dug up the coal but accumulated $400m of debt from which it couldn't recover. It went into liquidation in March.

Over the life of its wildlife permit, Solid Energy paid around $7m to keep the snails alive in fridges, as well as the original $10m cost to move them.

When the company hit trouble, the Government took on the company's environmental liabilities at a cost of more than $100m, many times the price of keeping the snails alive. The taxpayer continues to subsidise Solid Energy by paying for the snails it was willing to sacrifice. The term for the things an industry abandons before they're used up is a 'stranded asset'. Usually it's a power plant, or a mine. In this case, it's a native species.

Some of the conservationists involved in this saga see it as a horror story; undoubtedly a metaphor for something grim, or a microcosm for the wider forces that govern New Zealand and its environment.

"The New Zealand public and the Department of Conservation are always left holding the baby," Rod Morris says.

"They're left tidying up the mess [after] these flash-Harrys promise wonderful employment. It's just the nature of boom and bust industries, we just somehow don't seem to learn from one experience to the next.

"If ever there had been a case to leave the mountain alone, leave the snails where they were, Mount Augustus was that case. And we mucked it up."

For those who fought against the snails being refrigerated in the first place, the current dilemma is a painful realisation of their worst fears.

"This is exactly what we predicted," says Frances Mountier, of Save Happy Valley.

"A whole species is languishing, it has nowhere to go … by pushing through with the mining of Augustus, Solid Energy effectively locked them into this fate."

The name Augustus means to inspire, to be dignified.

In her description of the species, written after the peak was gone, Walker said the name was a fitting memorial to what had been lost, which would live forever in the name of the species that evolved alongside the mountain.

In a parallel universe, Mount Augustus still exists, and the snails live happily in their odd little habitat. Walker looked carefully at the bag and noticed the subtle differences only she could have spotted. There was more habitat remaining, with more snails, and a population could have been saved.

P. augusta are not snails but stunning birds that soar, not slither, a species New Zealanders proudly claim as their own. Instead, they are snails, entering their second decade in a fridge.

Clarification: This story was updated to clarify that Fred Singer was noted for downplaying the health risks of passive smoking, rather than smoking more generally.