The Shag River slips with little fanfare under State Highway 1 to join the Pacific, the sand bar shimmering in the distance. I park my car and walk through the muddy kingdom of rural Otago—pine trees and lucerne paddocks, dry pig skins slung over barbed-wire fences.
The river’s last bend swings in against the gorse-covered hill, forcing me to wade up to my waist. Black swans slip away and gulls scatter overhead, their shadows racing across the sand in the midday sun.
I arrive on the spit of land that feels crowded with ghosts. This was once the site of one of the largest Māori hunting villages in the South Island. A couple of hundred people lived here for half a century, leaving behind the remains of thousands of fur seals, moa and other birds and moving on as the animals vanished. It’s a pattern that repeats itself around New Zealand.
Nine species of moa disappeared from New Zealand in the wake of human arrival. With them went the giant Haast’s eagle and dozens of smaller bird species including adzebills, endemic geese, mergansers, harriers, teal, snipe and rails.
The landscape and ecology of this country have been spectacularly and irrevocably changed in the geological blink of an eye. According to the latest studies, moa were wiped out in less than 200 years by a population of Māori that numbered no more than 2000—not even enough to fill Auckland’s Civic Theatre.
How could this have happened? The clues lie buried at places like the Shag River mouth, and what they tell us allows us to understand not only the processes that have shaped New Zealand, but the impact humans have had on wildlife all around the world.
Around 70,000 years ago, Homo sapiens emerged from Africa and began a creeping expansion around the globe. They crossed into Australia around 50,000 years ago, where they walked amid lumbering diprotodons, three-metre-high kangaroos, massive goannas and marsupial lions.
Within some tens of thousands of years, all these animals had vanished, and the ecology of that continent was changed forever.
At the same time, humans expanded into Central Asia, Europe and the hostile north—an icy tundra teeming with bison and mammoths. Lower sea levels during the last glacial maximum allowed our species to cross the Bering land bridge into North America for the first time around 25,000 years ago. The North and South American continents were at that time populated by the most spectacular suite of big animals since the dinosaurs—mammoths, mastodons, ancestral horses, dire wolves and sabre-toothed tigers in the north, and in South America an equally astonishing fauna, including enormous ground sloths and armadillos so large that early hunters made homes out of their shells.
All of this is now gone. From the cave bears of Europe to the horned turtles of Vanuatu, our planet has, in the period since we left Africa, been subject to the biggest faunal vanishing since the asteroid impact that ended the Mesozoic era.
Scientists have a term for this phenomenon, “megafaunal extinction”, and wherever humans have ventured, it has followed. For many scientists, there is no doubt what causes it. The idea that humans entering a new ecosystem are capable of eradicating, in a short period of time, the large animals that live there is the basis of the “overkill hypothesis” first proposed by American Paul Martin in the 1960s. But ever since Martin laid out his theory, acrimonious debate has raged.
Climate change, it is often argued, played a far more pivotal role in these extinctions than direct hunting pressure. But while the major animal extinctions of Eurasia, the Americas and Australia happened so long ago that evidence for their causes is rare or absent, in New Zealand, the blood has barely dried. All of our big animals have either gone extinct or suffered major range contractions in the 750 years since the first Polynesian explorers set foot on these shores.
According to University of Otago geneticist Nic Rawlence, New Zealand is perhaps the best place in the world to study the mechanisms of megafaunal extinction. “In other areas of the world it’s very difficult to determine whether it was humans or climate change,” he says. “At best, you can say it was a one-two whammy. But when the extinctions occurred in New Zealand, the climate was stable, so we can rule that out as a cause.”
I’m poring over a folder of scientific papers in a windowless office at the University of Otago. This is where the old New Zealand exists now—caged in screeds of jargon, reimagined in genetics labs. The documents paint a picture of beaches heaving with fur seals, sea lions and elephant seals, forests dripping with birds, skies punctured by the silhouettes of giant eagles. There are lagoons packed with waterfowl and entire mountain ranges that jabber with the screeches of millions of burrowing seabirds.
A recent article by Rawlence and his team used ancient DNA analysis to show that, prior to human settlement around 1450 AD, the Chatham Islands were the breeding site of more than 50,000 sea lions.
“You’re looking at an island archipelago that would have been filled with fur seals and sea lions,” he tells me. “You would have had islands dominated by bird life—petrels, shags, flightless rails and species of flightless duck.”
Those endemic Chatham Island species have since vanished, along with the Chatham Island sea lions, themselves a genetically unique lineage.
Rawlence’s paper found that the sea lions became extinct in less than 200 years, and pins the blame squarely on human hunting, claiming it would have taken a harvest rate of just one sea lion per person per year to cause the collapse.
It seems unimaginable that a small group of people (no more than 2000 at its peak) could exterminate so many animals. Chatham Island historian Bill Carter has also studied the extinctions and his background in the wool industry gives him an interesting perspective. He sends me a spreadsheet, of the kind used by farmers to analyse and manage a sheep flock. His model replaces breeding ewes with female sea lions and lambs with pups, factoring in birth rate, natural attrition and recruitment of young animals into the following year’s breeding stock. By plugging figures into the boxes, I can kill off as many sea lions as I like and instantly see the results.
The first revelation is that you can kill a high percentage of each year’s pups without having a big impact on overall numbers. These results are reflected on Campbell Island today, where up to half the sea-lion pups die of natural causes without adverse effect on the population as a whole. Similarly, I can get rid of a good percentage of breeding-age males. But, kill as little as five or 10 per cent breeding-age females and the population immediately starts to slump because you’re effectively killing a dependent pup, and potentially an unborn pup as well. Maintain that harvest over three, four, five years and you’re on your way to a complete population collapse.
What Carter’s model reveals is the key to the overkill hypothesis: You don’t need to eat every animal; you don’t even need to eat a quarter of them—just the critical breeders. Mathematics takes care of the remaining 50,000 individuals. Once the population is below a sustainable level, extinction is all but inevitable.
In any animal population, there is a ratio between what biologists call “effective breeders”—the animals that will pass their genes on in any given year—and the overall population. For most mammals, this ratio is surprisingly low—as little as 10 per cent of the total population are producing offspring in any one season.
Because of sea lions’ polygynous harem-based breeding strategy, where only a small fraction of breeding-age males get the chance to mate, most of the effective breeders are females. During the breeding season, these would also have been the easiest to hunt, conveniently clustered together in harems close to the hunting camps.
“Sea lions are very slow-breeding,” says Rawlence. “They can’t handle large amounts of hunting pressure. We know that the whole age range, from newborn pups to the largest adults, are in the midden sites [piles of shell and bones that were the remnants of hunting activity]. So they’re hunting the whole lot, they’re not being picky. If you take out a female, you’re suddenly stopping the population being replaced.”
Beaches must have swarmed with sea lions in the early days. The hunters probably thought it would be impossible to make even a dent in the colony, but within a few generations, the whole population was gone, down to the last animal.
Rawlence’s Chatham Islands research presents us with a micro-model for what happened on the New Zealand mainland some 200 years earlier. From 1280 AD onwards, Māori and the rats (kiore) and dogs (kurī) they brought with them swept across the country and deep into the heart of moa country—Canterbury and Otago. The scale of the hunt became industrial, with large processing bases established on the coast for the cooking and preservation of moa flesh, perhaps for trade with other groups further north.
It’s believed that male moa incubated the eggs and therefore would have been easy prey for hunters. Eggs were also harvested in great quantities.
For reasons that are not entirely understood, Māori burned much of the land, destroying breeding habitat and changing the ecosystem drastically. At the same time, hunters were targeting sea lions, fur seals, elephant seals, penguins and shags along the coast.
“Fur seals were breeding right up to the top of the North Island,” says Ian Smith, a University of Otago archaeologist who has extensively studied fur-seal remains from midden sites around New Zealand. “They were providing more meat for early Māori than moa, from one end of the country to the other.”
While Smith sees no evidence of massive, large-scale harvesting of seals, he believes sustenance-level human hunting intensified an already-high natural mortality rate, quickly leading to their widespread disappearance.
“What you see in the archaeological sites is that it’s predominately juvenile animals and young adults—the ones that aren’t being culled out by nature—that are being culled by people.”
Smith also points to the strong tendency of seals to return to the site they were born at as a factor in their demise. Even low levels of hunting pressure would soon cause accessible colonies to be stripped of seals.
The archaeological record stored in middens charts the disappearance of pinnipeds around our coast. Sea lions were extirpated from the mainland by around 500 years ago. Elephant seals, once a common sight on our beaches, also vanished. Fur seals retreated to remote offshore islands and inaccessible rock stacks.
Māori became increasingly dependent on fish and shellfish as the bigger animals disappeared. Where the people of earlier times had enjoyed peace and plenty, Australian science writer Tim Flannery in his seminal book The Future Eaters, scarcity and conflict now came to define Māori life in Aotearoa.
Although they probably had no way of knowing it, Māori were experiencing a pattern repeated time and time again throughout human history—the end of the golden weather, and the gathering of the storm.
I stand on a river terrace in the upper reaches of the Waitaki Valley, the nor-west wind chasing blotchy cloud shadows across the sere, denuded hills that cradle the valley. I spent a good part of my childhood here, fishing for trout along these riverbanks and, as a farmer’s son, working long days in the constant warm winds of summer and bitter cold of winter.
For the past two weeks, I’ve scanned Google Earth, trying to deduce the movements of the moa hunters in this area, matching my own knowledge of this landscape with what little is known about their ways. (Moa ovens and other tools have been found in the area, suggesting that the valley was very likely a camping site for travelling people in prehistoric times.)
My amateur detective work has led me to this rarely visited river terrace. I wander over ground scarred and depleted by introduced weeds and overgrazing, looking for… I’m not really sure what.
It’s a dead, beaten landscape. Except for the odd rabbit and a lone hawk circling overhead, nothing moves here, just the big river, endlessly destroying and rebuilding its stony banks.
In the excavation of a rabbit hole, I find a blade of unusual rock, a stone obviously alien to the area’s predominant greywacke and schist. It’s almost certainly silcrete, commonly used for tools by early Maori—a direct connection to the ghost-time when people pushed into these hills in pursuit of the great ratites that lived here. It completes a circle that began 25,000 years ago, when the ancestors of these people and mine diverged somewhere in ancient Eurasia.
Without the hindsight of science to guide them, and with equal human helpings of enterprise, hunger and greed, these early explorers broke the fragile fabric that wove an ancient ecosystem together, and ultimately paid the price—their landscape stripped of life, their world shattered.
Just these elusive fragments of their lives now remain, buried from view were it not for the industry of rabbits.
The disappearance of moa and large coastal fauna was just the beginning of New Zealand’s millennium of death, by then entering its second chapter.
The first Europeans to arrive on these shores came for what was left of the New Zealand megafauna, pursuing fur seals and sea lions to their remote offshore colonies and decimating their populations.
At the same time, whaling stations along the coast quickly wiped out the southern right whales that bred there. By killing breeding females, whalers fell into the same ecological trap as early Māori. Collapse, as always, was close behind.
Just 120 years ago, the explorer Charlie Douglas was able to round up enough kākāpō from his Westland campsite to make a fine stew. Around the same time, ornithologists were collecting the last pairs of huia for museums around the world, and the laughing owl could still be heard in New Zealand forests. At least 20 bird species have become extinct in the period since colonisation.
Today, we live in the shadow of the blast, with all of the big species gone or reduced to vestigial populations. Many smaller species cling to existence, some surviving only through constant human intervention. But there is cause for hope, too.
“There’s an inevitability about the impact, but people can learn from that,” says Smith. “By the time Europeans got to New Zealand, Māori had developed ways of managing their resources, like rāhui and so on, and I think that was because they’d figured out they’d cocked it up.”
After almost a century’s respite from hunting, southern right whales and sea lions are starting to breed around the mainland once more. Fur seals are also returning to their old mainland haunts in good numbers.
Penguins in the subantarctic that were reduced to the brink of extinction have made strong recoveries, most notably the king penguins on Macquarie Island, which have regained genetic diversity equivalent to pre-hunting levels just 80 years after nearly being wiped out by industrial harvesting.
Modern science gives us unprecedented tools of hindsight, and what happened in New Zealand is instructive on a global scale. While it’s not possible to make definitive statements about what happened in other parts of the world based solely on the New Zealand example, the case for the human-mediated megafauna extinction in this country is clear, and shows it could easily have happened elsewhere, too.
When the first European settlers arrived in New Zealand, Māori oral tradition carried almost no recollection of the moa. The silence that fell with their passing had seeped deep into cultural memory. Likewise, today, the sites of the old moa-hunting settlements are now camping grounds, towns or farms. A new civilisation has embraced the land, altering it and swallowing the past.
These are the two big lessons of the New Zealand extinction—how easy it is to wipe out a species, and how easy to forget.