A tragedy of the commons
Land is owned, but the sea is shared. And we haven’t been sharing very well.
The memory of my first scuba dive is still vivid. The cool water, the gentle descent, the sound of my breath as I inhaled, the sound of bubbles as I exhaled, a leaky mask.
I reached the sea floor and gathered my senses. It was like arriving on a new planet, bursting with life and colour: beckoning kelp, the shadows of black angel fish, rocks painted with coloured sponges, a mooching snapper.
Demoiselles danced above the weed—charcoal fish the size of my palm, with two white stars on each side. I could see a thick swarm of trevally feeding at the surface, and a starburst of kōheru—small schooling baitfish with electric-blue flanks that catch the light like a camera flash. Life encrusted every surface—blushing coralline algae, fine filamentous algae sprouting like hair, a kina/sea urchin or two grazing like hedgehogs among the Ecklonia kelp.
Ten metres above was the undulating surface, and it struck me that I was looking at the other side of the mirror, the boundary that separates this world from the world of air. It felt like science fiction, but on that first dive beneath the waves, it was the most real thing I’ve ever seen.
I’ve been lucky enough to do hundreds of dives since, but that first one at the Poor Knights became a yardstick that I could measure the underwater world against.
I sought out the most interesting places to dive, and it didn’t matter if they were hot or very cold, shallow or deep, good visibility or murky… it was always interesting.
More recently, I stopped diving for fun and started diving for work, and that changed everything. Work took me to some extraordinary places, but also to ordinary places—places that were once pristine but which had changed. It was an eye-opener.
There was the time that the water was so murky I couldn’t see my hands, or the time that the sediment was so thick my arm went in up to the shoulder before reaching stiff mud. I’ve seen plastic hang in the water column like clouds in the sky, farm run-off that stained the water the colour of black tea, and piles of rubbish tipped into a harbour from the end of a wharf. But even in those environments there was life—octopuses living in bottles, fish sheltering under plastic lids.
The thing that really filled me with despair was the day I saw my first kina barren. I was snorkelling when I came across it—a tennis-court-sized patch of rock framed by scraps of kelp and pocked with black sea urchins as though it had caught a disease. In a sense, it had. The malady wasn’t the prodigious number of kina, but rather the profound lack of those things that kept kina under control—crayfish and big snapper.
On closer inspection, the rock wasn’t bare, but covered in coralline algae, and clumps of jewel anemones arranged in groups like bouquets in a florist’s window. There were sponges here and there, but it was as though someone had driven a grader through a rainforest, leaving only low-lying algae and limp wisps of kelp.
A bare patch isn’t a problem in itself, but it’s the sign of a really big problem.
Crayfish were once one of the dominant species on the coast of north-eastern New Zealand and played an important role in the structure of the ecosystem. As keystone predators they kept kina at bay, which allowed kelp to flourish and created habitat for a host of other species.
Early records by ethnographer Elsdon Best described how crayfish were so numerous that Māori would collect them by shuffling along a near-shore reef until they stood on one, then heave it on to the beach. “In about 20 minutes, they caught about 12-15 crayfish,” he wrote. They were also caught by diving and in baited wicker traps, but only in shallow water.
That changed with the advent of commercial fishing. In the early 1900s, crayfish were commonly scooped up by trawlers further out to sea. By the 1930s, there were some 30 boats dedicated to fishing for crays, harvesting nearly 25 tonnes every week.
To understand the impact of that early 20th-century catch, NIWA scientists Alison MacDiarmid and Matt Pinkerton published a doorstop 376-page study on changes to the Hauraki Gulf ecosystem over the past, oh, 1000 years. Their 2015 paper covered everything from bacteria to whales and was based on a myriad of data points—from historical reconstructions of fishing catches to archaeological evidence recovered from middens.
The results make for sobering reading. Their synthesis discovered that whales had declined by 97 per cent in the Hauraki Gulf since 1000AD. The number of seabirds had plummeted 69 per cent. Sharks had dropped 86 per cent. Jack mackerel, blue mackerel, gurnard, leatherjacket, tarakihi, kahawai, rig, flatfish, trevally, barracouta, skipjack tuna—all declined an average of 57 per cent. It was a thousand years of relentless extraction.
Among the losses were two species with an outsized influence on the undersea environment: snapper, which declined 83 per cent, and crayfish, 76 per cent.
It wasn’t a straight line. Fur seals were extirpated by Māori between their arrival and 1500AD, and whales almost vanished with the arrival of European whalers after 1790. Most other species, however, saw their steepest declines only after 1950, when commercial and recreational fishing effort really gauged up.
MacDiarmid and Pinkerton’s data also revealed radical changes in the order of life. Species that had historically played a powerful structuring role in the ecosystem—such as whales, seals and crayfish—played a less important role when there were fewer of them. And other critters, perhaps less desirable as food for humans, played a more important part—crabs and sea snails, for instance, both of which increased in abundance as others declined.
Crayfish went from the sixth-most-important group of seafloor-dwelling organisms to the least important, simply because there are now so few. Today, crayfish are considered “functionally extinct” in the Hauraki Gulf. They are still around, but have little or no structuring role in the ecosystem, including keeping kina in check.
“It’s a sad story,” says MacDiarmid, “but it’s a different story to the changes in ecosystems on land. On land, we’ve lost dozens of species, but in the oceans, almost all the species are still there, albeit in a very depressed state of abundance. So if human behaviour changes, there is hope to rebuild many of those species, and the marine ecosystem will respond.”
Ecosystem changes didn’t happen immediately. By the 1960s, divers were noticing odd patches of bare rock where once there had been lush kelp forests.
In December 1964, diver and University of Auckland botanist Frank Dromgoole wrote a story in Dive magazine in which he described barrens at “a few localities in the Hauraki Gulf”, namely Leigh Cove, Goat Island Beach, Ti Point, Takatu Point, Kawau Island and Little Barrier Island.
Dromgoole described how kina would gnaw away the slender stalk of Ecklonia seaweed, just above the holdfast where it attaches to the rock, either bending the weed over to devour the rest, or compromising it to the extent that waves tore it off the reef to drift away, “literally slaughtered by the ravages of the common sea-urchin”.
He worried for the future of these reefs and the host of species they supported. “The loss of these Ecklonia plants represents a serious damage to animal populations associated with the seaweed forests,” he wrote. “These plants provide favourable shelter for numerous fish, shellfish and small invertebrate animals. These in turn represent a food source for larger fish such as rays, ground-sharks, snapper, hapuka and many other economically important species. If the Ecklonia plants continue to disappear at the present rate then it is almost certain that those animals linked with this particular food chain will also show a marked decline.”
Dromgoole went on to take a stab at the cause: “Perhaps the removal of crayfish in large numbers from certain areas of the New Zealand coastline has allowed the sea-egg [kina] populations to increase. At present we cannot be certain that this is the correct explanation.”
Uncertainty didn’t last long. Dromgoole’s colleagues at the University of Auckland noticed, too, and connected the problem to the diminishing population of crayfish and large snapper that were predators of kina.
The reefs at Goat Island where Dromgoole first noticed the barrens were designated a marine reserve in 1975. In the absence of fishing, life returned. Snapper populations increased until they were eight times as abundant as outside the reserve, with much larger fish. Crayfish boomed to ten times the abundance compared with adjacent reefs that were fished. And the kelp returned.
Marine reserves are a sort of reference text for what a healthy, functioning ecosystem looks like. They demonstrate that when limiting factors are removed, life can return. If we have known for half a century that marine reserves are an effective solution, why haven’t we made greater use of them?
The reason is that we think about land and sea very differently. Some 30 per cent of our land area is protected. In the sea, it’s less than one per cent. Native creatures in the terrestrial environment are afforded a sort of reverence by New Zealanders. We head out with binoculars in the hope of spotting a native bird. We lavish natural habitats with attention and protection, and we wouldn’t dream of stuffing seven kiwi into a backpack on the weekend and bringing them home for a family feed.
But the sea is different. You can catch native species every single day and your Facebook likes will soar—especially if they’re big ones. In fact, current regulations allow each fisher to legally take up to 68 fish from 22 regulated species, and an unlimited number of fish from other species, every day of the year. Plus three crayfish, 20 scallops, 10 pāua, 50 mussels, 150 pipi, 150 cockles… it’s a staggering allowance, especially considering some of them are near extinction.
Consider the crested weedfish, an animal that makes a living out of looking like a plant. It is luminous yellow, the colour of a canary, with a blush in the cheek and a dark line that runs down from the eye like a stream of tears. Above its eye is a stalk, which gives the fish an attitude of permanent surprise, and along its back from the brow to the tip of its tail is a golden mohawk—a crest as tall as the body is high.
The weedfish lives its life in seaweed, predominantly the lush golden fronds of Ecklonia that fringe most of the north-eastern coast of New Zealand—a sort of canary in the coalmine for our kelp forests.
Unlike New Zealand’s reptiles or birds, which are often dull critters, the weedfish has a singularly bodacious colour scheme. But it’s not to make it stand out in its environment—every feature of the weedfish makes it blend in.
“Crested weedfish are not particularly rare, they’re just really hard to find,” says ecologist and NIWA commercial diver Crispin Middleton. “You can spend ages looking, find one right in front of your face, lift your camera to take a picture, and be unable to see it again. It’s like it just disappeared.”
Crispin and his wife, marine ecologist Irene Middleton, have made it their mission to find and photograph crested weedfish—see a short documentary below. But the once-pristine landscape is transforming before their eyes.
“I’ve been diving on the Tutukaka coast for 15-odd years and noticed huge changes,” says Crispin. “Certainly in Tutukaka Harbour, that’s completely changed. It used to be really kelpy, but it’s pretty much all kina barren now.”
Same goes for Rocky Bay out on the coast, previously heaving with kelp, now dominated by bare rock down to a depth of eight metres or so.
“I’ve got a lot of friends who are spearos, cray hunters and fishos,” says Irene. “They can’t get anything on that coast any more. There’s nothing there. You go for a free-dive or a snorkel and see nothing. It’s desolate.”
Recently, the couple ventured out to the Mokohinau Islands for the first time in ten years—a remote group in the outer gulf some 50 kilometres off the coast. Where they had previously seen lush kelp forests, there was only bare rock.
“Even the kina looked sick; they were losing their spines,” recalls Irene. “I’m not normally one to get emotional, I’m normally quite analytical, but it does make you upset.”
Crispin noted that the Mokohinau group was otherwise similar to the Poor Knights—a small, remote, offshore island group with complex, rocky topography and, previously, a high abundance of marine life. The key difference is that you can fish at one and not the other.
“The difference between the two, marine reserve versus non-marine reserve, is incredible,” says Crispin. “The sad thing is that we dive all along the coast of Northland and unfortunately we’re subject to that sliding baseline effect ourselves. We kind of expect kina barrens now. Finding an area on the coast that is not kina barrens is unusual. It’s a sad situation.”
Marine ecologist and New Zealand Geographic science lead Arie Spyksma spent eight years diving on the Karikari Peninsula in the Far North. A doctoral candidate studying kina at the time, he noticed increasing kina numbers, and the creeping barrens.
“It wasn’t really until I started postgrad research that it clicked for me,” says Spyksma. “I realised then that this is a real phenomenon. It’s not localised, it’s everywhere. From that point on, every time you went in the water, you were seeing barrens.
“North-eastern New Zealand seems to have the perfect combination of conditions to allow barrens to form and perpetuate… low sedimentation, high fishing pressure and the presence of kelp as the primary structure on the reefs.
“We know for sure that the lack of predators due to overfishing is the major driving force for the formation of barrens. The predators have a direct effect by eating the urchins, but also an indirect effect whereby the presence of predators actually alters the behaviour of sea urchins. They will graze for a shorter period of time before retreating back to a crack or crevice, and if one does get eaten, the others move location. The presence of predators reduces the grazing pressure sea urchins can exert on a reef.”
The problem is, once the kelp has been felled by a “feeding front” of urchins, and a barren has formed, it takes very few kina to actually maintain that barren, as any skerrick of kelp is quickly consumed.
This is a process called “trophic cascade”, where an ecosystem falls so far out of balance that one level collapses down upon the next, like storeys of skyscraper crashing down. Once it has collapsed, it is no longer useful as habitat, nor can it easily rebuild.
“It’s a tipping-point scenario,” Spyksma says. “There’s a crucial number of urchins that will cause a kelp forest to flip to a barren, but it will take a very significant reduction in numbers for that barren to transition back to a kelp forest. And not everywhere will recover at the same rate. Some places might never recover, some will recover much more quickly. There’s still a lot we don’t know.”
In 2018, New Zealand Geographic became determined to understand the problem better. At the time, research methods required scientists to painstakingly count all the species in a one-metre-square quadrat in order to understand a problem hectares in extent.
Borrowing tools from aerial surveying, software from virtual reality production and gaming, and hardware from underwater photography, Spyksma started working on a new way of capturing data underwater and visualising it using 3D technology. Soon, he was 3D-mapping 200 square metres of reef in just six minutes, accurate down to the millimetre.
It allowed researchers a landscape-scale view of a reef for the first time, as well as the ability to examine and measure the smallest details without watching the needle on their air pressure gauge.
“You’re not hamstrung by having to conduct research solely underwater,” says Spyksma. “You can cover ten times the area you could capture using traditional methods, and have unlimited time on land to process that data.”
We didn’t like what we saw. In each 100-metre transect in the outer Gulf, we counted around 800 individual urchins, and 1000 at The Noises island group, closer to Auckland, which has been devoid of crayfish and large snapper for a longer period. At some sites there were patches of dense kelp at depth, giving way to a broad band of kina barrens in the shallows. At other sites there wasn’t a shred of kelp to be seen.
In time, New Zealand Geographic’s project morphed into a research fellowship with the University of Auckland, where Spyksma has been working alongside Nick Shears and Kelsey Miller. They chose five research sites around the gulf that were dominated by barrens, modelled them, then systematically removed all the kina.
In one bay at The Noises, barely 100 metres from point to point, divers spent hundreds of hours removing some 120,000 kina. It was laborious, and if nothing else, proved that manual extraction was not a practical mitigation technique. But it did show something else critical to our understanding—how barrens recover.
A year after the removal of kina from the reefs, the shreds of remnant kelp had tripled in extent. In some places they increased 10-fold. The results underscored the nature of the problem, and presented the best solution too—millions of kina-eating machines, preferably crayfish and large snapper, which happen to work for free.
In 1986, the abundance of snapper between North Cape and East Cape was estimated at just 14 per cent of its original, pre-human biomass. That was the year Sanford’s Head of Fishing, Colin Williams, started out in Hawke’s Bay, introducing what was billed as the world-leading Quota Management System (QMS).
“I’ve got a strong belief in the QMS, how it’s turned out and what it delivers,” says Williams. “I acknowledge that it could have a few tweaks, but certainly the state of the Snapper-1 fishery was in dire straits in 1986.”
The QMS helped, but it took 27 years to increase the abundance of snapper just five percentage points to 19 per cent in 2013 (see ‘Natural numbers’, below). A new snapper survey will be published in 2022 and Williams is predicting a huge increase.
“I’ve definitely seen it come back in strength and biomass,” he says. “I’m an avid recreational fisher. I spend a lot of time out of the gulf and have come across numerous significant marks on the sounder; schools nine metres tall… just absolute abundance. We estimated one little mark had about 30 to 40 tonnes of fish in it. I keep finding fish wherever I go.
“So when I hear about kina barrens, and I’m not saying they don’t exist, but I’m actually quite surprised, given the size and the frequency of snapper that I keep coming across.”
This is the irony of trophic collapse—fishers will keep seeing and catching fish, right up until the moment that the resource collapses completely. Improvements in technology—fishfinders, better bait, more capable vessels, even social media—mean that catch rates remain high, masking the problem. It’s not the number of fish that matters most, but the health of the whole ecosystem—and it’s hard to see through that mirror.
Even as the QMS maintains commercially valuable fish stocks at sustainable levels, the barrens march on, metre by metre, a desert consuming a forest.
Sanford has fished the Hauraki Gulf for 157 years. It has a long history around our coast, and a big stake in the future of the fishery as well.
“We’ve only got one ocean,” says Williams. “And if we bugger it up, or are party to buggering it up, we’ve got no business tomorrow. It’s that binary for us, it really is.”
As the kina barrens extend outward and downward, the weedfish and its brethren will be forced into an increasingly narrow band of kelp, at greater depth, at greater distance from human interference.
“But there will come a point where it can’t go deeper, the habitat just won’t be suitable for it any longer,” says Crispin Middleton. “That will be it for the crested weedfish, and I don’t think many people will notice, to be honest.
“The loss of the kelp, the loss of the crested weedfish, is a sign of a collapsing ecosystem.”
If the fish we eat are not abundant enough to perform their roles in an ecosystem—maintain balance, sustain reefs—what sort of future are we building for our marine environment? If we maintain commercially and recreationally valuable fish species, but ignore the damage that selective fishing does to the wider ecosystem, will we not all lose out?
In 1776, Scottish economist Adam Smith wrote that nations become wealthy when individuals act out of rational self-interest. Sixty years later, English economist William Forster Lloyd identified a difficulty with Smith’s theory. He coined the phrase the “tragedy of the commons” to describe a situation where users deplete a shared resource—such as public grazing lands—by acting in their own self-interest. It would be profitable for an individual herder to graze more cattle than his neighbours do on the common, but if all herders made the same economically rational decision, the common would be overgrazed. The effect creates a race condition between economic interests that ends in the destruction of the resource.
There couldn’t be a better description for our unbridled exploitation of the seas around New Zealand over the past millennia.
Have we been aware of the impact, and cynically fishing all the while, just because other people are? Or have we been sleep-walking towards the oblivion of a shared resource we all value?
Our choices today are quite plain—we consider the health of the environment, or we watch it collapse.
“It’s a question of whether we can fish in a way that doesn’t destroy the habitats that sustain other species,” says Alison MacDiarmid.
“We need to be more thoughtful in how we harvest, and we need to be fishing at such a rate and in such a way that we are enabling and sustaining the ecological processes that are necessary to keep a whole ecosystem sufficiently healthy for those fisheries to be sustained, too. Lots of fish may be available now—but do we need to take all of them now?”
So, what’s the answer? Barrens are a sign of imbalance, and correcting that balance involves drastically reducing or eliminating the take of key species, or introducing marine reserves.
Goat Island Marine Reserve has demonstrated that strict no-take regulations can restore natural order. But so far, partial protections that stop short of full no-take have failed. (Mimiwhangata Marine Park in Northland, for example, allowed limited recreational fishing, but that attracted more fishers, increased the take, and resulted in fewer fish in the reserve than outside of it.) We need marine reserves, we need better regulation outside the reserves, and we need a radical change in how we consider our seas.
“Our experience with marine reserves shows that if you remove the major effects of fishing then things will rebound. So with proper management, species will recover,” says MacDiarmid. “Fur seals are a good example. I grew up in the Bay of Islands, sailing up and down that coast with my family when I was a youngster. Back then, we never, ever, saw any seals whatsoever. They just weren’t there. But now they are. And that’s not surprising, given that they were hunted to local extinction early on in human occupation, and then almost killed off entirely by the European sealers. But since they became a protected species and no longer culled, their numbers have rebounded, and that’s a success story.
“It does show that there is resilience there in the ocean still. And we’re not in the situation that we are on land where we’ve lost the moa and close to 100 other species. So that gives me hope. But it will need a change in how we relate to marine ecosystems.”