Pathogens, sediments and nutrients: the nasties making our rivers unsafe

This was first published in the Listener, 31 July 2014.

When I was a kid, in the 1970s, the only “unsafe” water I was aware of was the geothermal hot pools of the Taupo Volcanic Zone. If you put your head under the water, I believed, an amoeba would swim into your ear and eat your brain. Or something like that.

I was happier swimming in cold water. On South Island holidays, we’d swim in freezing glacier-fed lakes and rivers. Sometimes, closer to home, we’d free camp on Wairarapa farmland and swim in the local rivers.

But I don’t think I’d take my children to some of the same swimming spots – especially the ones on farmland. In July 2013, the Ministry for the Environment reported that 61% of the river sites it monitored were unsafe for swimming and should be avoided. Annual reports on recreational water quality have now been dropped, so it’s hard to know if things are getting better or worse.

What makes our fresh water “unsafe for swimming”? In a 2012 report on the science of water quality, the Parliamentary Commissioner for the Environment said the three main water pollutants of greatest concern to our fresh water – rivers, streams, lakes, wetlands and estuaries – were pathogens, sediments and nutrients.

If you’re swimming, the biggest risk to your health comes from pathogens – bacteria or viruses – that can enter your body through your mouth, nose or ears. Pathogens can enter waterways through contamination from human sewage or animal manure; for example, from effluent run-off from farmland, human wastewater discharges, stormwater outfalls and domestic- and wild-animal waste.

Pathogen levels are often highest after rainfall when faecal matter is carried from the land into waterways. According to the environment ministry’s 2013 Suitability for Swimming indicator update, the potential human health effects of these pathogens are numerous, although mostly “minor and short-lived”.

The list includes “gastro-intestinal illnesses with symptoms like diarrhoea or vomiting, and infections of the eye, ear, nose and throat. However, there are other potentially more harmful diseases such as giardiasis, cryptosporidiosis, campylobacteriosis and salmonellosis. Hepatitis A can also be contracted from contaminants in the water and can lead to long-term health problems.”

Nutrients such as nitrogen and phosphorus are useful on land, where they can stimulate plant growth. But in water they can cause excessive growth of weeds, slime and algae and can be toxic – including for humans – at very high levels.

Most nitrogen in waterways comes from urine, through animals urinating in or close to streams, or from dairy-shed effluent. Phosphorus, spread as fertiliser on paddocks cleared of forest, washes into waterways along with soil, so levels of the element are closely linked to sediment load.

Accelerated erosion, mostly from deforestation, has increased the amount of sediment in our rivers. Sediment is not such a problem for humans – although it can obscure underwater hazards such as rocks and logs – but it can upset a waterway’s natural ecosystem by interfering with plant and animal life.

As for the amoeba that scared me in the 1970s, Naegleria fowleri is a single-celled animal that lives in the soil surrounding natural hot pools and is sometimes found in the water. Nancy Swarbrick writes on Te Ara that “diving into such pools or even immersing the head can force water up the nose, allowing the amoeba to invade the brain”.

There were nine fatal cases of amoebic meningitis between 1968 and 2000; commercial hot pools now filter water to keep it safe.

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Particle Fever review

The thing that differentiates scientists,” says physicist Savas Dimopoulos in Particle Fever, “is purely an artistic ability to discern what is a good idea, what is a beautiful idea, what is worth spending time on and, most importantly, what is a problem that is sufficiently interesting, yet sufficiently difficult that it hasn’t yet been solved.”

Theoretical physicist and Particle Fever producer David Kaplan describes the Higgs as “unlike any other particle … it’s the linchpin of the standard model … the crucial piece responsible for holding matter together”. The search for the Higgs boson involves the biggest and most expensive scientific experiment in history, involving more than 100,000 scientists from 100 countries. The Large Hadron Collider, a particle accelerator with a circumference of 27km, is designed to make two beams of protons collide with enough force to disturb the Higgs field – a theoretical field that fills all of space and gives particles mass – and create a Higgs particle.

The “beautiful idea” at the heart of this documentary, screening at the New Zealand International Film Festival, is the standard model of physics, a “theory of everything” developed in the 20th century. But the problem with this model, which was designed to explain the interactions between subatomic particles – all the different sorts of quarks, leptons and bosons – is that it made sense only with the existence of an undiscovered theoretical particle called the Higgs boson.

The documentary follows six physicists – theoreticians and experimentalists – from 2007, during the final construction of the Large Hadron Collider at the European Organization for Nuclear Research (Cern) in Switzerland, to the announcement of results in 2012.

“It’s big, no?” says Kaplan as he tours the magnet-filled underground tunnels. There’s a lot of big stuff in this movie – big instruments, big science, big intellects.

Installing the calorimeter for ATLAS, one of the four main experiments of the large hadron collider. Photo courtesy of CERN.

Installing the calorimeter for ATLAS, one of the four main experiments of the large hadron collider. Photo courtesy of CERN.

To people who question the value of the project, Kaplan says it might only help scientists to better understand the laws of physics. But he also points out that there could be unexpected spin-offs. The world wide web, for example, was invented at Cern as a way for physicists around the world to communicate with each other.

From the stylish opening title sequence, reminiscent of a 1970s paranoid thriller, to the final revelation, this is an intense and visually striking movie. There’s tension as this massive machine – “like a five-storey Swiss watch”, says one of the scientists – faces a lengthy shutdown and repairs, and as physicists wait to see if theories they’ve spent their lives working on are going to stand up in the face of experimental data.

At stake are two competing theories about the nature of the universe. Dimopoulos is one of the proponents of supersymmetry, the idea that the Higgs and the other particles of the standard model are part of a much bigger symmetry and there are many more particles yet to be discovered – hopefully by the Large Hadron Collider.

Younger theoretical physicist Nima Arkani-Hamed has a competing theory: that our universe is a tiny speck in a mostly inhospitable and random multiverse and the information we need to explain things such as dark matter could be hidden in other universes. On one side is “symmetry, beauty and order”, on the other chaos, randomness and “the end of physics”.

A lighter Higgs boson, about 115GeV (giga­electronvolts), would suggest supersymmetry. A heavier Higgs, about 140GeV, would favour the multiverse theory. Which will it be?

At a time when Hollywood is making monster movies about giant robots, this is a small but beautifully realised film about one of the biggest machines humankind has ever built. I look forward to seeing it on the big screen.

Particle Fever, directed by Mark Levinson, plays at the New Zealand International Film Festival:



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Call for papers – The Fukushima Effect: Nuclear histories, representations and debates

At the APSTSN conference in Singapore this July, I had the pleasure of meeting Richard Hindmarsh, associate professor at Griffith University, Australia, and editor of Nuclear Disaster at Fukushima Daiichi: Social, Political and Environmental Issues.

We were each presenting papers in a session entitled “States of Risk II”: Richard’s paper, Nuclear Disaster at Fukushima Daiichi: Social, Political and Environmental Issues – An Overview, introduced the major themes in his recent book. My paper, Nuclear Power: ‘A Malevolent Uncultured Arbiter of our Destiny or ‘A Servant of the Industrial Revolution’?, was about early attitudes to nuclear power in New Zealand. In our session, and in other parts of the conference, there were many other papers about nuclear histories and current attitudes to nuclear technology – many of them referencing the Fukushima disaster.

Richard and I got talking after our session, and kept on talking after the conference, and developed a plan for a follow up volume to Richard’s Nuclear Disaster at Fukushima book. We’re calling the new book The Fukushima Effect: Nuclear Histories, Representations and Debates and are currently seeking submissions.

Here’s some brief information about the aim of the book and the two areas it will cover:

Aim: to produce a high-quality edited book on the effect of the Fukushima disaster three years out from the disaster as another relatively early benchmark on this ‘effect’ and to determine the extent and scope of it, politically and culturally, on either:

Area 1: national histories, debates and policy responses on nuclear power development (in both well established ‘nuclear nations’ and emergent ones (apart from China, South Korea, Taiwan and New Zealand, for which we already have authors).

Area 2: long standing international and national debates in political and cultural context, such as the safety of nuclear energy, radiation risk, nuclear waste management, effect of radiation leaks on marine ecosystems, development of nuclear energy vis-à-vis other energy options, the moral debate, anti- nuclear protest movements, nuclear power representations, and so on.

Abstract submission deadline: 6 December 2013.

Send abstracts to:

Full details are contained in the attached pdf.

Call for papers Fukushima Effect

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The enigmatic and endangered Kermadec storm petrel

A version of this story first appeared in The Listener on 26 September 2013.

Kermadec storm petrel. Photo by Gareth Rapley.

Kermadec storm petrel. Photo by Gareth Rapley.

One night on Macauley Island, in the Kermadec Islands group, in 1988, ornithologists Alan Tennyson, Graeme Taylor and Paul Scofield noticed something flitting around the Tilley lamp inside their tent. A close inspection of the tiny grey and white bird revealed a Kermadec storm petrel, a species known from only a handful of specimens shot at sea in the 1920s. The bird wasn’t nesting on Macauley, whose seabird population had been devastated by rats, cats and goats, but over subsequent years the birds were occasionally spotted at sea. In 2006, a Navy helicopter dropped Karen Baird and Mike Imber on Haszard Island – a rocky islet next to Macauley – to search for signs of the bird.

Haszard Islet. Photo by Terry Green, Department of Conservation

Haszard Islet. Photo by Terry Green, Department of Conservation

“The area on top of the island is quite small and the ground is soft,” says Baird. “Mike stuck his hand down a burrow and out came a Kermadec storm petrel on an egg. We looked at the amount of habitat available and estimated there were 100 burrows at most, so maybe 100 breeding pairs.”

Haszard Island is a grass-topped lump of volcanic rock sticking sharply out of New Zealand’s northern ocean. The many species of seabirds that live in the Kermadec Islands can survive patrolling sharks, erupting volcanoes and tropical storms, but the rats, mice and cats introduced in the 19th century decimated many species. Haszard Island, though, has remained pest-free, providing a haven for this vulnerable seabird who spends months each year raising a single chick in an earthy burrow.

The Kermadec storm petrel (Pelagodroma albiclunis) is one of the entrants in Forest & Bird’s annual Bird of the Year competition. Bronwen Golder, of the Pew Environment Group’s Kermadec Initiative, is campaign manager for this enigmatic little bird. “The Kermadec storm petrel is one of New Zealand’s endemic species – they’re found nowhere else in the world – but they are critically endangered,” she says. “But it’s a bird we know hardly anything about. How can one of our endemic birds be a total enigma? We want people to know about it, we want people to champion it; ultimately, we want to support scientists to study them and find out more about where they go, and when we find out that, we find out more about our ocean and how it’s working.”

The tiny storm petrel is facing tough competition. About 35 birds are competing for this year’s prize, with celebrity campaign managers backing the weka (Weta Workshop), fairy tern (Hayley Holt), bittern (Te Radar), pukeko (Seven Sharp), kereru (Barnaby Weir), New Zealand dotterel (Sam Judd), shining cuckoo (Wallace Chapman) and black petrel (Jacinda Ardern).

I’m backing the underdog, the enigmatic, critically endangered storm petrel. Thanks to the island eradication expertise of the Department of Conservation, the cats and rats are gone from the Kermadecs now, so perhaps there’s a chance for the storm petrel to spread its wings and find new breeding spots.

You can vote now at

The first Kermadec storm petrel found breeding on Haszard Island in 2006. It's so little and cute! Photo by Karen Baird

The first Kermadec storm petrel found breeding on Haszard Island in 2006. It’s so little and cute!
Photo by Karen Baird

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New Zealand scientists and the atomic bomb

How proud New Zealand must be that the foundations of the amazing discovery
concerning latent atomic energy were laid by her own great scientist Rutherford.
– Viscount Bledisloe in telegram to New Zealand, 9 August 1945[1]

After atomic bombs were dropped on Hiroshima and Nagasaki, Viscount Bledisloe, New Zealand’s former Governor-General, congratulated the country on her role in the victory: Rutherford’s work on the atomic nucleus was acknowledged as laying the scientific foundations for the development of what was then known as the ‘atomic bomb’.

Rutherford was not the only New Zealand scientist involved in the victory. After the bomb was dropped, the Government revealed the formerly secret role of a group of New Zealand scientists who had worked on the bomb programme, and told New Zealanders they should be ‘proud to know that some of her scientists of this generation were at the forefront of this latest development’.[2]

Ernest Marsden, [ca 1940s-1950s]. Alexander Turnbull Library, Wellington, NZ: 1/4-018564-F, sourced from

Ernest Marsden, [ca 1940s-1950s]. Alexander Turnbull Library, Wellington, NZ: 1/4-018564-F, sourced from

The fact that some New Zealand scientists had been involved at all was due, in good part, to New Zealand’s Rutherford connection, and the efforts of Ernest Rutherford’s former student Ernest Marsden, now head of New Zealand’s Department of Scientific and Industrial Research (DSIR). Many of the Commonwealth scientists working on the British nuclear research programme were, like Marsden, past students or colleagues of Rutherford, and Marsden was able to trade successfully on his reputation of being involved in the birth of nuclear physics, which, as Harrie Massey later said, had earned Marsden ‘a place among the immortals’.[3] In December 1943, when Marsden was in Washington DC, he had chanced upon James Chadwick, scientific director of the British nuclear research project, with Australian physicist Mark Oliphant and Danish physicist Niels Bohr, who had been smuggled out of Denmark and was travelling under an assumed name. Following the signing of the Québec Agreement, Chadwick and Oliphant were in Washington with the top-secret task of arranging details of scientific co-operation between the United Kingdom’s and United States’ nuclear research programmes. Oliphant later recalled that they were in their hotel lobby waiting for the elevator when they felt taps on their shoulders and turned to find Marsden in full military uniform. They were taken aback to hear Marsden say, ‘I can guess why two nuclear physicists are here!’[4] During the elevator journey Marsden put in a good word for New Zealand’s participation in the bomb project. He followed this up in London with Sir John Anderson, Chancellor of the Exchequer and the British minister in charge of atomic energy matters.

Robin Williams, a young physicist with the DSIR’s Radio Development Laboratory, recalled reporting to Wellington in July 1944 to find Marsden ‘cock-a-hoop about the fact that he had managed to get a number of New Zealanders in on the atom bomb project’.[5] Their terms of employment seconded them to the United Kingdom DSIR for one year, or for the duration of the war, whichever was longer. Marsden was very keen for New Zealand to launch an atomic research programme when the war finished, and following the secondment the men were required to return to New Zealand for at least one year.

New Zealand scientists on the Manhattan Project
Robin Williams and George Page joined a team of British scientists working on the electromagnetic separation of uranium at the University of California at Berkeley in July 1944. There were two other New Zealand-born scientists on the team who had arrived from the United Kingdom with the British group, one being Maurice Wilkins. (A larger group of New Zealand scientists had travelled to Canada to work with John Cockcroft on the nuclear energy project.)

The electromagnetic separation process involved first accelerating ionised uranium using an electric field, then passing the beam of accelerated ions through a magnetic field which deflected the uranium-235 ions slightly more than it deflected the uranium-238 ions (because of their lower mass), and allowed for separate collection of the two isotopes. The challenge was to design and build the most efficient plant possible, and theoretical and experimental physicists were needed to help solve problems arising from the design challenge and the operation of the plant. Williams mostly worked under Massey with a group of theoretical physicists who contributed to the project by improving the team’s understanding of the fundamental processes involved in uranium separation. Page, along with the engineers on the project, made significant contributions to improving and simplifying the design of the electromagnetic separation plant.

As a scientist-turned-administrator, Marsden was tremendously excited about these new applications of nuclear physics and felt stymied and frustrated in his administrative and managerial role in New Zealand, so far away from the action. He wrote regularly to the American-based scientists, asking, sometimes inappropriately, for details of their research. As he was unable to be involved in the North American research programme, Marsden directed his enthusiasm to plans for a nuclear research team in New Zealand after the war and a search for uranium in the South Island. In an April 1945 letter to one of the New Zealand scientists in Canada, Marsden wrote ‘we shall have a self-contained team on TA [Tube Alloys, the British code name for the nuclear project] in New Zealand in due course’ and ‘we are having quite a lot of fun chasing radioactive minerals (don’t repeat this!). They are fairly widespread in small concentrations and the problem is in care and methods of concentration.’[6] In July 1945 he gained Cabinet approval to place all the men working on the nuclear project in America, together with some remaining in New Zealand, in a special team and on the permanent staff of the DSIR.

New Zealand reaction to the atomic bombs
A year after the New Zealand scientists arrived in the United States, the first weapons were assembled. The first, Trinity, was tested in the Nevada desert in July 1945. Then, on 6 August, an American B-29 bomber exploded a 3-metre-long bomb containing 60 kilograms of uranium-235 above the city of Hiroshima. The press release issued by the White House later that day described the bomb as ‘the greatest achievement of organized science in history’.[7] Three days later, an even more powerful plutonium-based fission bomb was exploded over Nagasaki. Burn injuries and radiation affected many of the initial survivors, and by the end of 1945 an estimated 140,000 people had died from the Hiroshima bomb and 70,000 from the Nagasaki bomb.

Few New Zealanders would have connected the work of New Zealand scientists with the dropping of the first nuclear bombs, but an official New Zealand press release, issued on 13 August 1945, linked the bombs to Rutherford’s early work, provided information about Marsden’s uranium survey, and outlined the role of the New Zealand scientists working in North America, saying how New Zealanders should be proud that her scientists were at the forefront of this latest development.

Japan agreed to surrender the day after Nagasaki was bombed. The general reaction in New Zealand, and in other Allied countries, was one of jubilation and relief. The war that had taken more than 11,000 New Zealand lives and had an impact on every aspect of society was finally over. While it was marvelled at that a single bomb dropped from a great height could cause such devastation, there was initially no awareness of how fundamentally different these bombs were: the conventional bombings of cities like Tokyo, Hamburg and Dresden had produced more casualties than in Hiroshima or Nagasaki, and the longer-term effects of radiation from the bombs were not yet known.

Even people who recognised the horrific aspect of the new type of bomb were able to put a positive spin on it: the New Zealand Listener editorial of 17 August described the use of the atomic bomb as having ‘sickened many people and given others a faint gleam of hope’, but took the stance that it was ‘justifiable to hope as well as to shudder’ — there was hope that the atomic bomb could mean the end of war.[8] There were a few letters to the editor about the bomb — mostly expressing the hope that it could mean an end to war forever — but most New Zealanders were focused on relatives still overseas and on the practical necessities of coping with wartime shortages like how to re-waterproof an old raincoat, or how to make a fowl-house from old sacks and a wooden frame. Some people, however, realised the enormity of this new scientific and military development. A few days after the bombings, philosophy lecturer Karl Popper addressed a packed lecture hall at the University of Canterbury with the words ‘when the first atomic bomb exploded, the world as we have come to know it came, I believe, to an end’.[9]

Robin Williams was holidaying in California with his wife when they saw the news headline announcing the Hiroshima bombing, and he realised that it was the result of the project he had been working on. Williams remembers no discussion of moral issues among the British scientists in his team, and soon after he returned to Berkeley the assembled team began to disperse.

Jim McCahon, who had been employed on Marsden’s South Island uranium search, was in the laboratory in Wellington, analysing samples taken in the search, when he heard a radio bulletin announcing the Hiroshima bombing. He later described himself and his colleagues as having been astounded. When the uranium survey was first announced, they had found the German paper detailing the initial discovery of uranium fission in which ‘they had surmised that this could be used as a source of enormous amounts of energy but … not as an explosion. So we were thinking of nuclear power supplies … but not bombs.’[10]

A Labour Government, under Prime Minister Peter Fraser, was in power in New Zealand when Japan was bombed. There was no big discussion about the atomic bomb in Parliament, but various politicians referred to it, amid debate about other issues, in a mostly positive light. Robert Macfarlane, Labour MP for Christchurch South, accused people who wrote letters to the newspaper expressing indignation about the use of the bomb of being ‘Pacifists’ — a derogatory term during wartime — and saying that apart from its use as a destructive weapon, the atomic bomb ‘might have opened a new era of development for the people of the world, and so some good may arise from its invention’.[11] Major Clarence Skinner, a minister in the Labour Government, spoke proudly of the work of the British and American scientists, who didn’t take long ‘to show the Japanese scientists who could do the best’. He continued by saying, ‘A couple of doses of atomic bomb worked the oracle, and now we see these Japanese taking orders from mere mortal men. I join with other members in offering my gratitude for what has happened during the last few weeks — the ending of the war.’[12] Another Labour MP, Edward Cullen, had a less positive view and expressed his opinion that the atomic bomb was ‘a frightful instrument against humanity’.[13]

Scientists were quick to realise the dangers of this new weapon. In September 1945, Williams and Page were among thirteen British Berkeley scientists, including Wilkins, Oliphant and Massey, who, acting on their belief that ‘the advent of this new weapon of destruction ought to be the signal for renewed efforts to achieve lasting world peace’ signed a letter to British Prime Minister Clement Attlee calling for international control of the use of atomic energy and urging co-operation with Russian and other scientists.[14] This desire for international scientific co-operation with regard to nuclear weapons was widespread. ‘Any attempt at secrecy in this epoch-making field of research is fraught with the gravest possible danger to our civilisation,’ Marsden said.[15]

In January 1946, less than six months after the dropping of the first atomic bombs, New Zealand was one of 51 nations represented at the first General Assembly of the United Nations. The first resolution adopted concerned the establishment of an Atomic Energy Commission, comprising the members of the Security Council, plus Canada, to deal with issues related to the peaceful uses of atomic energy and the elimination of atomic and other weapons of mass destruction. In the general debate in the plenary meeting, the New Zealand representative suggested that control of the Commission should not be left exclusively to the Security Council, as had been suggested, but should rather be the responsibility of the entire General Assembly — this way small countries like New Zealand could continue to be able to have a say on such issues — but this was not heeded.

The atomic age begins – with Atomic Red lipstick
In New Zealand, once the excitement of the end of the war was over, there was a growing awareness that a new age, the ‘atomic age’, had begun. In New Zealand, as in the rest of the Western world, the atomic age was seen as a modern and sophisticated new era. In a 1946 issue of the New Zealand Listener, alongside the advertisements for pointy bras, laxatives and cork-tipped cigarettes, were advertisements for Atomic Red lipstick. It seems in appalling bad taste now to link sexuality with weapons that had killed tens of thousands of people, but the Atomic Red lipstick ads promised women they’d be ‘charged with excitement … devastating … all conquering’, saying women who wore the lipstick were chic and daring.

The atomic age was seen as an exciting and sophisticated new era, as evidenced by Monterey’s advertisements for Atomic Red lipstick. New Zealand Listener, 15 Feb. 1946 and 8 Mar. 1946.

The atomic age was seen as an exciting and sophisticated new era, as evidenced by Monterey’s advertisements for Atomic Red lipstick. New Zealand Listener, 15 Feb. 1946 and 8 Mar. 1946.

 This blog post is adapted from my recent book Mad on Radium: New Zealand in the Atomic Age, available here from Auckland University Press.

[1] Viscount Bledisloe to Minister of External Affairs, 9 Aug. 1945, EA1, W2619, 121/1/1, part 1, ANZ.

[2]‘New Zealand Participation in Atomic Bomb Development’, issued to the press on 13 Aug. 1945, EA1, W2619, 121/1/1, part 1, ANZ.

[3]H. H. Massey, in Marsden Editorial Committee, Sir Ernest Marsden 80th Birthday Book, A. H. & A. W. Reed, Wellington, 1969, p. 47.

[4]M. G. Oliphant, in ibid, p. 102.

[5]Robin Williams, ‘Reflections on My Involvement in the Manhattan Project’, seminar at Victoria University of Wellington, 10 Aug. 2001.

[6]Marsden to George, 5 Apr. 1945, SIR1, W1414, 74/10, ANZ.

[7]Richard Rhodes, The Making of the Atomic Bomb, Touchstone, New York, 1986, p. 735.

[8]Editorial, ‘Horror with Some Hope’, New Zealand Listener, 17 Aug. 1945, p. 5.

[9]Dewes and Green, op cit., p. 9; Strange, op cit.

[10]Personal recollections by Jim McCahon, op cit..

[11]New Zealand Parliamentary Debates 269, 1945, p. 266.

[12]New Zealand Parliamentary Debates 269, 1945, p. 752.

[13]New Zealand Parliamentary Debates 269, 1945, p. 486.

[14]Letter to Attlee, signed by Williams and others, 19 Sep. 1945, Robin Williams’s personal archives.

[15]Marsden to Minister of Scientific and Industrial Research, 12 Sep. 1945, EA1, W2619, 121/1/1, part 1, ANZ.
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The dawning of the age of Anthopocene

This article first appeared in The Listener, issue 3716, 30 July 2011

As a geology student in the late 1980s, I learnt a mnemonic to remember the various geological periods, epochs and ages that make up Earth’s history. It started with Cambridge (for Cambrian) and ended with horses (for Holocene), with some Jolly Catholics (Jurassic, Cretaceous) somewhere in the middle. Now some scientists are suggesting we add a new geological epoch, the Anthropocene, defined by the impact of human beings on the planet.

The idea that the Earth’s rocks were deposited in a sequence of layers, each representing a different time period and containing distinctive fossils, emerged in the late 18th century. The first full geological timescale, published in 1913, is similar to the timescale used today, from the Precambrian rocks that are host to the first primitive life forms, to the Jurassic rocks in which dinosaur fossils are found, and Quaternary rocks, in which we find the fossils of the first humans along with now-extinct large mammals like woolly mammoths and sabre-toothed cats.

So, why do we need an “Anthropocene”? The word was popularised in 2000 by Nobel Prize-winning atmospheric chemist Paul Crutzen, who suggested the entire Holocene, the epoch that started about 12,000 years ago and is marked by a warm interglacial period and the proliferation of new species, be redefined as the Anthropocene. Crutzen is now on a working group that will report to the International Commission on Stratigraphy (ICS) – which determines changes to the geological timescale – arguing for formal adoption of the Anthropocene as a new geological epoch. There is debate over when the Anthropocene should be defined as starting – at the onset of the agricultural revolution or at the onset of the Industrial Revolution – but there is no doubt that human beings have made their mark on the planet, with some of the biggest impacts being in terms of species extinction, changes to the carbon, nitrogen and phosphorus cycles, and the creation of an “urban stratum” of built, mined, drilled and engineered structures.

But what about New Zealand? I asked GNS Science palaeontologist Hamish Campbell, if another civilisation were to come to New Zealand in 10,000 years’ time, what signs of the Anthropocene would they find preserved in our sedimentary rocks?

“The easiest way to recognise the onset of Anthropocene time in New Zealand, as being the first humans arriving here, would be from changes in pollen abundance,” says Campbell. In many parts of New Zealand, pollen grains – which are much more readily preserved than plant matter – would reflect the change from native forests to grasslands. In terms of animal fossils, we’d see a change from New Zealand’s native avifauna to introduced mammals, with “a preponderance of remains of domesticated animals … an awful lot of hens, pigs, cows, and sheep”. And, of course, humans.

Fossils aren’t the only signs of change. “With the Industrial Revolution we get a very clear metal signal,” says Campbell. Roofing materials brought into New Zealand from the mid-19th century – first copper, lead, zinc and iron, and later aluminium – have leached into our waterways, leaving traces in harbour, lake and estuarine sediments.

In terms of the “urban stratum”, what would remain? “Concrete, bricks, asphalt, metal – they are going to survive,” says Campbell. And pipes. With large areas of east Christchurch about to be abandoned, for example, it’s likely the houses will be demolished and removed, but not the pipes underneath. “The hallmarks of human occupation will be the sewer pipes, water mains and gas pipes,” says Campbell. “They’ve been excavating sewers associated with Pompeii and are finding all the trappings of life at the time, in the form of jewellery and oil lamps that people dropped down the loo at night … nowadays the most common item found in the sewer is the cellphone.” An urban stratum of sewers and cellphones? Let’s hope that a few time capsules are preserved to present a less prosaic remnant of our civilisation.

Fossils are, however, notoriously difficult to make. The natural forces of decay – oxidation, bacterial action and UV radiation – work against the preservation of plant and animal fossils and human artefacts. The best way to preserve something is in a cold, dark, still, muddy environment or beneath deposits from a catastrophic event like a major flood, a mudslide or a volcanic eruption. “Supervolcanoes in the central North Island have the propensity to generate superheated sheets of pyroclastic debris. With the collapse of the eruption column, they just race out across the landscape at up to 800km an hour, almost frictionless. They would just bury everything; you would get instantaneous preservation of cities and towns underneath all this ignimbrite.”

Which is a reminder that no matter how much of an impact we’re having on the natural environment, we’re still at the mercy of physical processes. “We’re powerless when it comes to fighting seismicity and mountain building and volcanism.

Our biggest impact is not so much in physically rearranging the landscape, putting roads and things in; our biggest impact is biological.”

So, does Campbell think the ICS will accept the proposal to declare our current epoch the Anthropocene? “Absolutely. And philosophically, I think it’s quite important. There’s no escaping the fact that we’ve having a massive impact on the planet, and we’re all in this together. The way forward is for societies to plan for, to mitigate against, possible changes. Will recognition of something called the Anthropocene help? I think it might.”

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