Mopping up spilt milk: pollution in the New Zealand dairy sector

It's been slow to dawn on New Zealanders, but for a country that prides itself on a '100% Pure' image our environmental pollution record is fairly appalling - and shows few signs of alleviation. Politicians who point to the large percentage of the nation's electricity generation coming from renewable sources, not to mention the slow but sturdy growth in hybrid vehicles, are completely missing the point: it has been claimed that over half of New Zealand's greenhouse gas emissions emanate from agri business.

Although the quantity of sheep in the country has plummeted from a 1982 peak of around 70 million to less than 30 million last year, cattle numbers continue to rise. There are about 3.6 million livestock on beef farms and circa 6.5 million dairy cattle. The latter sector generates twenty percent of New Zealand's exports and seven percent of its GDP, so it forms a substantial component of the kiwi economy. But with plans to double the country's dairy production by 2025, the term 'sustainable development' appears to be, well, unsustainable.

Since cattle create as much waste product as fourteen humans, it's not difficult to imagine some of the more obvious forms of dairy pollutant, smell and all. As New Zealand dung beetles are primarily forest dwellers there have been trials of introduced dung beetle species to help clean up the waste, with a reduction in nitrous oxide emissions from the soil and a lowering of cattle disease as side benefits. However, pastoral poo is only one element in the catalogue of pollutants caused by dairy farming.

Last summer I was taken to an outdoor swimming hole not far from Wanganui, consisting of a rectangular concrete-lined pool situated on the edge of a forest. I was informed that children had swam there until a decade or so, but no more: several signs warned that the water is contaminated and no longer safe for humans. This story has been repeated throughout New Zealand, with agriculture being by far the most common culprit. It isn't just artificial environments that have this problem; reports suggest that within the past twenty years about two-thirds of monitored swimming areas within rivers have become too polluted. And that's just for people; there's far less concern for the effects on river fauna and flora.

Although environmentalists have been issuing warnings for years, not enough has been done to alleviate this problem. Last month approximately five thousand inhabitants of Havelock North were taken ill due to tap water contaminated by campylobacter. The source was a series of bores which the director of the Infectious Diseases Research Centre at Massey University, Professor Nigel French, put down to pollution from sheep and cattle. Sources of contamination could include carcases of dead livestock, as well as faecal matter getting into waterways that provide the source of unchlorinated - and therefore at risk - tap water.

In fact, the outbreak appears to be the tip of the iceberg. Despite some hundreds of cases of illegal effluent discharge brought against New Zealand farmers each year, many more escape prosecution. It has to be said this seems to be a regular occurrence for the Ministry for Primary Industries, judging by the recent reports of their waiving prosecutions for commercial fishing vessels caught flouting bycatch and dumping laws. Turning a blind eye seems to be the order of the day when it comes to protecting food production - or at least the food producers. This philosophy seems to be driven by those who clearly have little understanding of the complexity - and at times fragility - of food webs. Not so much short-term thinking as profound myopia!

In addition to the organic matter there are chemical pollutants that can find their way into water supplies situated close to farms. Since the 1990s, the New Zealand Ministry for the Environment has been monitoring ground water for nitrates and has found levels substantially above those recommended for drinking water. Although chemical fertiliser has been blamed in addition to livestock effluent, environmental mapping suggests the latter is the primary cause, since the polluted areas heavily coincide with the widest-scale dairy production.

As well as polluting waterways dairy farmers have also been caught stealing billions of litres of water each year from rivers and aquifers, especially in the Canterbury region. Whilst not a form of pollution per se, this is obviously somewhat lacking in the environmentally-friendly stakes. The deforestation of low-lying plains for cattle grazing is also a source of pollution, as the lack of tree roots, besides allowing greater flooding, can generate increased run-off into rivers. This polluted water can lead to algal blooms, lowering oxygen levels and so endangering freshwater fish. That might not sound of any great concern except to diehard anglers, but for any whitebait fans, four of the five Galaxiidae species whose young form this delicacy are now said to be threatened.

The systematic destruction of forests to make way for pastoral land use has been repeatedly raised as a concern not just by environmental organisations but by the New Zealand Ministry of Agriculture and Forestry (MAF) itself. Their 2006 report claimed close to half a million hectares of the nation's forests were at risk of conversion to land for cattle grazing.

In addition, overseas forests are also affected: since 2008 the amount of palm kernels imported into New Zealand as a dairy cattle feed supplement has doubled to over 2 million tons per annum. This accounts for about twenty-five percent of global production and comes at the expense of destruction of rainforests in nations including Indonesia and Malaysia. Although the state-owned farm company Landcorp Farming Ltd is in the process of moving to a different supplement over the next year or so, the dairy giant Fonterra has not announced similar intentions. What's wrong with those guys: a surfeit of Milton Friedman in their formative years?

Having covered solids and liquids, it's time to move on to gas. As I've mentioned on various occasions, methane is a primary greenhouse gas. It was therefore shocking to discover that per capita, New Zealand has the greatest annual methane emission rate worldwide, accounting for over forty percent of the country's greenhouse gas emanations. The methane emission from dairy cattle alone has continually increased over the past quarter century, although the amount reported varies from ten percent to a whopping fifty percent or so. Perhaps that's not surprising, considering cattle can each generate up to 500 litres of methane per day!

There is some recent cause for hope, with various trials under way to reduce bovine emissions. These range from vaccination to selective breeding to diets bases on forage rape, with the latter showing that the change in feed affects fermentation - and therefore reduces methane production - in sheep. However, it wouldn't hurt to see the Government funding more research in this matter: one widely-reported paper last year was Massey University's The New Zealand Dairy Farming: Milking Our Environment for All its Worth, which received much criticism from the dairy sector when it was revealed to consist primarily of a student thesis.

It's very easy to become depressed with such deleterious effects coming from just one sector. Of course no nation can afford to rest on its laurels: we cannot turn the clock back. The halcyon image of bucolic ruralism is a myth perpetrated by those who have never worked on the land and farmers deserve the benefits of modern technology in their work as much as anyone. The development of sophisticated tools and software can aid the dairy sector in preserving the environment. as long as there is enough public money to support this eco-friendly research. But Government funding for this type of sustainable development appears to be sadly lacking. Doesn't it make sense that those who run God's Own Country should try a little harder to prove that the 100% Pure tagline isn't just marketing spin?

Predators vs poisons: the ups and downs of biological control

Ever since Darwin, islands and island groups have been known as prominent natural laboratories of evolution. Their isolation leads to radiation of species from a single common ancestor, the finches and giant tortoises of the Galapagos Islands providing a classic example. But a small population restricted in range also means that many island species are extremely susceptible to external factors, rapid extinction being the ultimate result - as can be seen from the dodo onwards. Living as I do on an island (New Zealand counts within the terms of this discussion, as I will explain) has led me to explore what a foreign invasion can do to a local population.

Either through direct hunting or the actions of imported Polynesian dogs and rats, almost half the native vertebrate fauna was wiped out within a few centuries of humans arriving in New Zealand; so much for the myth of pre-technological tribes living in ecological harmony! But the deliberate introduction of a new species to pray on another is now a much-practised and scientifically-supported technique. One of the late Stephen Jay Gould's most moving essays concerned the plight of the Partula genus of snails on the Society Islands of Polynesia. The story starts with the introduction of edible Achatina snails to the islands as food, only for some to escape and become an agricultural pest. In 1977 the Euglandina cannibal wolfsnail was brought in as a method of biological control, the idea being that they would eat the crop munchers. Unfortunately, the latest wave of immigrant gastropods ignored the Achatina and went after the local species instead. The results were devastating: in little more than a decade, many species of Partula had become extinct in their native habitat.

(As an interesting aside, the hero of Gould's Partula vs. Euglandina story is gastropod biologist Henry Crampton, whose half century of research into the genus is presumably no longer relevant in light of the decimation of many species. Yet Crampton, born in 1875, worked in typical Victorian quantitative fashion and during a single field trip managed to collect 116,000 specimens from just a single island, Moorea. I have no idea how many individual snails existed at the time, but to me this enormous number removed from breeding population in the name of scientific research was unlikely to do anything for the genus. I wonder whether comparable numbers of organisms are still being collected by researchers today: somehow I doubt it!)

The Society Islands is not the only place where the deliberate introduction of Euglandina has led to the unintended devastation of indigenous snail species: Hawaii and its native Achatinella and Bermuda's Poecilozonites have suffered a similar fate to Partula. Gould used the example of the Partula as a passionate plea (invoking 'genocide' and 'wholesale slaughter') to prevent further inept biological control programmes, but do these examples justify banning the method in totality?

The impetus for this post came from a recent visit to my local wetlands reserve, when my daughters played junior field biologists and netted small fish in order to examine them in a portable environment container (alright, a jam jar) - before of course returning them to the stream alive. The main fish species they caught was Gambusia, which originates from the Gulf of Mexico but was introduced to New Zealand in the 1930s as a predator of mosquito larvae. However, akin to Euglandina it has had a severe impact on many other fish species and is now rightly considered a pest. In fact, it's even illegal to keep them in a home aquarium, presumably just in case you accidentally aid their dispersion. Australia has also tried introducing Gambusia to control the mosquito population, but there is little data to show it works there either. The latter nation also provides a good illustration of environmental degradation via second- and third-hand problems originating from deliberate introduction. For example, the cane toad was imported to control several previously introduced beetle species but instead rapidly decimated native fauna, including amphibians and reptiles further up the food chain, via toad-vectored diseases.

Gambusia affinis: a big problem in a small fish

This isn't to say that there haven't been major successes with the technique. An early example concerns a small insect called the cottony cushion scale, which began to have a major impact on citrus farming in late Nineteenth Century California. It was brought under control by the introduction of several Australian fly and beetle species and without any obvious collateral damage, as the military might phrase it. But considering the extinction history of New Zealand since humans arrived, I've been amazed to discover just how many organisms have been deliberately introduced as part of biological control schemes, many in the past quarter century. For instance, twenty-one insect and mite species have been brought over to stem the unrestrained growth of weeds such as ragwort and gorse, although the rates of success have been extremely mixed (Old man's beard proving a complete failure, for example). As for controlling unwelcome fauna in New Zealand, a recent promising research programme involves the modification of parasites that could inhibit possum fertility. This is something of a necessity considering possums (first imported from Australia in the 1830s and now numbering around sixty million) are prominent bovine tuberculosis vectors.

Stephen Jay Gould was a well-known promoter of the importance of contingency within evolution, and how a re-run of any specific branch of life would only lead to a different outcome. So the question has to be asked, how do biologists test the effect of outsider species on an ecosystem (i.e. within laboratory conditions) when only time will show whether the outcome is as intended? No amount of research will show whether an unknown factor might, at an unspecified time during or after the eradication programme, have a negative impact. It could have been argued in the past that the relative cheapness of biological control compared to alternatives such as poison or chemicals made it the preferable option. However, I imagine the initial costs, involving lengthy testing cycles, mean that it is no longer a cut price alternative.

Considering the recent developments in genetic modification (GM), I wonder whether researchers have been looking into ways of minimising unforeseen dangers? For example, what about the possibility of tailoring the lifespan of the control organism? In other words, once the original invasive species has been eliminated, the predator would also rapidly die out (perhaps by something as simple as being unable to switch to an alternative food source, of which there are already many examples in nature). Or does that sound too much like the replicant-designing Dr Eldon Tyrell in Blade Runner?

One promising recent use of GM organisms as a biological control method has been part of the fight to eradicate disease-carrying (female) mosquitos. Any female offspring of the genetically altered male mosquitos are incapable of flight and thus are unable to infect humans or indeed reproduce. However, following extremely positive cage-based testing in Mexico, researchers appear to have got carried away with their achievements and before you could say 'peer review' they conducted assessments directly in the wild in Malaysia, where I assume there is little GM regulation or public consultation. Therefore test results from one location were extrapolated to another with a very different biota, without regard for knock-on effects such as what unwelcome species might come out of the woodwork to fill the gap in the ecosystem. When stakes are so high, the sheer audacity of the scientists involved appears breathtaking. Like Dr Tyrell, we play god at our peril; let us hope we don't come to an equally sticky end at the hands of our creation...