Are you going to wash your hands before lunch?”

We are in the dunes of Mason Bay, on the west coast of Stewart Island, and this question is posed to Dr Mike Hilton as he pokes through a palmful of possum droppings. “I’m looking for the smoking gun,” Mike explains, “or the warm poo, so to speak.” He is seeking the vector of the Russell lupin (Lupinus polyphyl­lus), which is spreading throughout the ecosystem, and a tell-tale seed in excrement is a significant clue.

“Aha!” he says triumphantly. “See what the possum had for tea? You see this?” Tiny translucent silver berries have passed through the possum, and he ruminates aloud on this mystery. “Why is this berry on the possum’s menu? Why didn’t he chew them?”

Mike, a world heavyweight in dune ecology, has been studying dune systems for a dec­ade, and he has never seen anything that comes close to the active dune system of Mason Bay. “Without moving sand we wouldn’t have this ecology. There is nothing like this globally,” he states. “This is geomorphically unparalleled.”

By the time I’ve finished scribbling geomorphically unparalleled in my notebook, the scientists have moved over the next dune, their footsteps crisscrossed by stag, possum and kiwi tracks. The “tracks” of beach grass, too: the wind has scratched circles in the sand with the tips of marram. As a child scampering through the dunelands of Cape Cod, in the US, I affectionately called these circular signatures compass roses. But the North­ern-Hemisphere beach grass does not belong in this antipodean habitat, and most New Zealand conservationists do not look upon marram grass, Ammophilia arenaria (which translates as “sand lover”), with any affection. For marram is not a healthy lover, but a clingy, creepy, leg-humping, invasive, boundary-issue lover of the worst kind.

There is no mystery about the vector of Mason Bay’s most widespread and damaging exotic: from the 1930s to 1960s, farmers deliberately planted the grass to tame the dunes. By the mid-1980s, the last farmer had left Mason Bay, and the land became Department of Conservation property. While some fences and an old homestead serve as quaint reminders of the farming era, the marram grass continues to spread unquaintly in a dense swathe throughout Mason Bay. The fore-dunes are a monotone of pale grey-green.

Hectare by hectare the weed is smothering native vegeta­tion such as the sand-binding pingao (or pikao)—golden sand sedge (Desmoschoenus spiralis)—and the many unique micro-ecosystems of the ancient dune system. Projections based on aerial photographs predict that, left unchecked, the marram grass will take over every bit of Mason Bay real estate, sending the endangered native vegetation packing into oblivion.

But that hasn’t happened yet and it isn’t too late to pre­vent it doing so. Unlike many New Zealand dune systems, Mason Bay still features areas that have not been overrun by marram grass, where one can observe coastal turfs, ephem­eral wetlands, rocky outcrops, temporary lakes and a myriad rare plant species.

In 2001, DOC decided to take action. A mere restraining order wasn’t going to do the trick: the creepy sand-lover was served the death sentence. An attempt to eradicate marram grass from Mason Bay with herbicide was launched.

Six years into the programme, Mike is assessing progress, accompanied by Stewart Island-based DOC staffers Eammon Ganley and Brent Beaven. We walk onto a coastal turf, one of many micro-ecosystems in the dune’s ever-shifting landscape. At least a dozen tiny species of plant, including the rare Gunnera hamiltonii, flourish in a patch of earth as small as a hand.

“Pretty lush for a desert,” says Mike, referring to a recent Southland Times article that described Mason Bay as a desert, ruined for visitors.

Even though the eradication project is ground-breaking, and scientists from around the world have been observing it with keen interest, the decision to remove a pernicious weed from a precious ecosystem seemed a no-brainer to many in the business. So why, according to the Southland Times, the “wide debate, with some islanders hotly against it”? Here is where science butts its head against the human heart. What would Starry Night look like if Van Gogh hadn’t had blue pigment on hand? Without its swathe of grey-green grass across the dunes, Mason Bay would look wrong to people who remem­ber it clad thus. Statistics, aerial photographs and facts carry weight with some folk, but they are weak contenders against memory, nostalgia and the heart’s attachment to a place.

If you make a Stewart Islander grumpy, they might have the odd word with you outside the shop (Ship to Shore, the Island’s only store, is a natural meeting place for locals). If an Islander gets really fired up, then pen goes to paper and letters are printed in the Southland Times (assuming the old pub sort-out doesn’t take place; fortunately, the comparative merits of dune-binding sedges don’t usually incite fisticuffs).

The Southland Times printed an article under a headline worthy of a pit-bull attack: ANGER AT KILLING OF GRASS (30/3/07). Long-standing Stewart Islanders were quoted, lamenting the demise of Mason Bay at the hands of DOC. The paper followed this up with an editorial entitled BUT IT’S JUST NOT NATURAL (31/3/07), alluding to a “doctrinaire DOC” whose policy jumped the line between idealism and fanaticism. This sparked a flurry of letters to the editor regarding the marram eradication.

Fired-up folk speak in strong terms, and journalists write in superlatives—both decidedly different from the measured language of science. Point zero zero one per cent equals might. “It might happen,” the scientist ventures, which freaks out the angry local, who has the conviction of a zealot. “Might?” cries Joe Public. “So you’re definitely killing some kiwis out there!” It’s a vicious cycle of cross-communication.

Some fans of Mason Bay who decry the marram eradica­tion programme have claimed that DOC is destroying kiwi habitat and therefore kiwi. In fact, studies with radio trans­mitters have shown that kiwi forage in the bush at the edge of the dune system, and also on the beach, but do not nest, or even rest, in marram grass. If alarmed, a kiwi might seek tem­porary refuge in a patch of marram, but the birds generally avoid the denser areas altogether. Marram grass, a one-trick pony, knows only how to grow densely, and is thus destroying kiwi habitat.

I ask Brent whether he finds all the verbal to-ing and fro­ing frustrating.

“No,” he says, “I just feel like I failed to communicate well, and I have to try and fix that now, and communicate more with the locals about the programme.” He has gone from door to door, visiting the writers of letters opposed to the eradication project and discussing the issue. As he relates the endless civilised chats over cuppas and diplo­macy bickies, the tabloid reporter in my head is yawning, “Booorrr-riiiingg.”

“But doesn’t it all just make you nuts sometimes?” I press on. “I mean, really.”

“No,” says Brent. “I love Stewart Island; this is a beauti­ful place and a great community, and I feel really lucky to live here.”

In a small, tightly knit community, DOC staff have the job of relaying heavy data in layman’s terms and doing so without sounding condescending. Eamonn peeks over my shoulder as I scrawl in my notebook and corrects my spelling: “Uh, not quite like the Beatles.”

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It takes 40 minutes to walk across the peneplain—the “Great Stonefield”—just south of Duck Creek. The vast expanse is dotted with tufts of dead and dying marram grass that has been treated with Gallant, a spray that kills only grass, leaving other plants unharmed. Native grasses are identified and marked so they aren’t sprayed. Sprouts of wiry orange baby pingao abound, along with tiny endemic flowers. This cheers the dune heavies considerably, and we climb up into the dunes and ascend Big Sand Hill, followed by a gaggle of university students who have been staying at the Mason Bay hut under Mike’s tutelage.

“Look at that shape,” says Mike. “That’s the classic, beau­tiful, bicycle-helmet shape of a shadow dune.”

Bicycle helmet? It’s not easy for the uninitiated to get their heads round dune terminology. Hang around with dune guys and you’re certain to hear the word hummocky; this describes the low, pingao-clad shadow dunes, more rounded and subtle than the tall, jaggedly-scarped, marram-mantled fore-dunes. Parabola sparks disquieting memories of maths classes for many of us, but in dune-speak the parabolic dune is the basic dune unit. “The parabolic dunes define the large features of the landscape, and the shadow dunes define the details,” explains Mike.

From atop Big Sand Hill we look east over Freshwater Flats, and Mike’s eye picks out old parabolic curves beneath a growth of manuka and bush. You can see the ancient history of the place, the dune formations of past millennia.

Fingers of sand have blown into the bush, and manuka trees surrounded by sand are part of the weird beauty of the Mason Bay landscape. This sight has worried some Island­ers, who fear that once the marram dies, the wind will blow all the sand into the bush and destroy it. In fact, scientists anticipate that less than 10 ha of bush will succumb to sand over the next decade.

Marram exerts such a grip on the dunes that the roots of even dead plants will still ensnare the sand for decades to come. The root system is a massive snarl that extends to a depth of several metres. Eammon shows me a dune that he treated with Gallant two years ago: the roots of the dying plants cling to the sand despite the westerly wind screaming off the sea. The fear that, as soon as the marram grass has been sprayed and killed, whole dunes will blow away into the bush is unfounded. The wind can’t blast the sand away even when it tries, and if you’ve ever been to Mason Bay you’ll know it gets an A for effort.

The vocabulary of the big marram dunes lends itself to the defence of the plant: stability, security and strength are reassuring words; roots that run deep must be trustworthy. In contrast, erosion, transience and blowouts, descriptive of the low pingao dunes, suggest weakness and instability. But this is the very nature of the active dune. It moves, it flies, it should be unstable. Blowouts are a natural, healthy and nec­essary part of dune ecology at Mason Bay. How do you re­programme someone’s mind to see these aspects as positive? Can you do it over a cuppa? Perhaps a cuppa wine…?

Perhaps never. Some opponents to the marram project hold such staunch views they’ll just have to agree to disagree. In June, Mike Hilton presided over one public meeting in Invercargill and a second on Stewart Island, at which “lines were drawn in the sand” and the term “differing philoso­phies” was diplomatically adopted.

A group of opponents to marram eradication attended the meeting, including former Mason Bay farmer Tim Te Aika. Tim had prepared a speech and a DVD presentation, illustrating his concerns about the removal of marram grass, some of which he had planted himself. While he conceded some marram had been planted for agricultural purposes, the rest had been planted to preserve wildlife, bush and relics of Maori settlements by protecting them from wind-borne sand. He described a marram-free Mason Bay as a “weeping sore”, and blowing sand as “relentlessly destructive”.

“I believe marram to be one of nature’s healers,” Tim stated. According to him, this healer had saved much of the coastal forest, which he maintained sand had been swamp­ing at a rate of 20 metres per year; it provided a nursery for other native plants; and since its planting, pingao had made a strong recovery. He said that marram had been used to rescue a shag rookery in peril of inundation by sand, and had been instrumental in extending kiwi habitat. Some of those with Tim echoed the sentiment that marram was a beneficial plant that had been Mason Bay’s saviour, and that removal of the grass would be ruinous. One man asked how on earth Mason Bay had ever managed without marram grass.

Yes, differing (sometimes fisticuffing) philosophies; dif­ferent views of the same place. If you asked Mike about the shag rookery rescued by marram, he would explain that it was in fact a temporary lake, not meant to last for eons and that such impermanent bodies of water are one of the many fascinating features of active dunelands.

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Needless to say, people are passionate about Mason Bay, and they have a picture in their minds’ eye of how it should be. If DOC succeeds in removing marram from the dunes, the Mason Bay palette will be significantly altered. The dichromatic colour scheme of green and beige will give way to a multiplicity of hues: the spring-green of sand tussock; the fiery orange of pingao; the rich copper of red tussock. The Mason Bay dune ecology existed for thousands of years before humans showed up and planted marram grass in the 1930s. If there are people alive today who harbour fond memories of frolicking at a marram-free Mason Bay, bless their hearts, they’re pushing 90.

Mike’s university students, born in the post-farming at-Mason-Bay era, have been taking dirt cores, trekking through the dunes on educational outings, and weeding out lupins and baby marram plants on command. They are costumed in goggles, bright-orange vests, and shorts over striped leggings; their unlined faces glow with future, and they are filled with exuberance, angst and youthful prattle. They make the rest of us feel eight million years old.

The scientists ask them what they would like to study next year.

“The kakapo!” chorus a few.

The kakapo? What about the southern New Zealand dotterel?”

Eager young faces cloud with uninterest. You can almost hear their internal voices: Dotterel? Whatever!

The kakapo is an endangered avian celebrity—big, green, personable and fun. The southern New Zealand dotterel? Not so much. And pingao is even further from the popular heart. Ditto sand tussock, Pimelea and the Pimelea moth.

Native dune-binders and the critters that thrive among them lack sponsorship and a catchy phrase. Many of them still go by nerdy Latin names because they are so rarely observed that no one’s made them cool with a nickname. “Save Euphorbia glauca” doesn’t fit on a bumper sticker; “Bind it like Beckham” sounds good but doesn’t make any sense.

Dune botanists will tell you that pingao relies on the sand, as do a myriad other life forms, but we generally perceive sand as a nuisance, blowing all over us, scouring our eyeballs and half burying our picnics.

“Sand is foundation and fertiliser,” says Mike, explaining that it carries nutrients. The native flora and fauna of Mason Bay are wired to expect an ever-shifting landscape. The shags will rebuild their nests at a new temporary lake.

After catching our breath atop Big Sand Hill, we return to the old homestead at Mason Bay, where the students are called upon to demonstrate their dirt-coring skills. A young fellow sets up a hand drill bigger than himself to the teasing banter of onlookers (“Got a license to drive that thing, son?”).

They proceed to bring up soil samples and arrange them on a tarp. One young woman gets on her knees in the piles of dirt and sifts through them, noting varying degrees of grittiness.

“You wouldn’t even touch that a week ago,” says Eammon with a grin. “Now you can sew on your dirty-hand badge!”

At Mason Bay, you don’t have to be a student of science to get dirty. Anyone who has tramped through the mud-wrestling pit of Freshwater Flats, or smushed scores of sandflies against their skin, or handled dozens of random stinky, gooey objects in a fruitless search for ambergris, knows that to experience Mason Bay is to “get amongst it”. Nevertheless, visitors leave Mason Bay feeling refreshed. Purified. Spiritually exfoliated.

Heading back to the (relative) bustle of Half-Moon Bay, I mull the scientific jargon I’ve learned, and run through the dumb, writerly adjectives that won’t ever aptly describe the awesome expanse of bush, beach and undulating hummocky dunes. My mind’s eye conjures a last image before we turn east and homeward—the dune heavies in silhouette, standing in the surf, performing a familiar Mason Bay ritual. It’s a cleansing process, a simple wee dance: walk to the water’s edge, do a shuffle in the tide with your boots, then hunker down and, palms flat and fingers splayed, rub your hands joyfully in the sand.