In her opinion piece If veganism is the answer, what was the question?, Dr Jacqueline Rowarth wrote that forgoing animal products entirely from your diet is not going to save the planet.
Today on The Country, Rowarth, who has a PhD in soil science (nutrient cycling) and has been a vegetarian since 1975, spoke to Jamie Mackay about what we should actually be doing to mitigate climate change.
Mackay: Jacqueline ... if you don't mind me saying so ... you get bit of a free shot here because you're a vegetarian and you can have a crack at veganism.
Rowarth: What I'm really trying to do is point out the logic that might be behind any choices we make and thinking that veganism will save the planet is not logical, because people haven't done the calculations.
There's lots of talk about how veganism is taking off, but I have to say that having been vegetarian since 1975 I was told then than vegetarianism was taking off and it's still less than 10 per cent of the world.
Remembering that quite often it's linked to belief and religion and there have been more people born into the world with particular religious belief that eschew animal factors than non-religious beliefs.
Mackay: Jacqueline, on a personal scale how much more difficult is it to be a vegan than a vegetarian, because obviously veganism rules out other food groups that vegetarians can enjoy.
Rowarth: Yes it's the eggs and dairy things in particular and that I think is why people are saying they're flexitarian - which I would've said is omnivore, but it allows them some sort of virtue signalling - they're cutting down on the meat.
It is much easier to be vegetarian and healthy than it is vegan and healthy and partly the problem with veganism is that you miss out on some crucial co-factors that are found in animal products.
There's quite a lot of research that explains how the size of the human brain ... was developed once people had access to animal foods and indeed the whole social structure of humans has been enabled because of the access to animal foods which give high-quality protein.
It is possible to be healthy on a vegan diet. It takes a lot of knowledge and work, and that's why Italy's still debating whether they make veganism illegal for anybody under four, because the parents don't always have the knowledge to bring up the child as a vegan healthily and there have been incidents, terrible incidences of babies dying.
Mackay: Talking about diets, we're constantly fed a diet of ... "dairy farming is bad, pastoral farming is bad, horticulture is good" - not quite the case when it comes to greenhouse gas emissions.
Rowarth: Not necessarily. It depends which type of crops you're thinking about. Animals are the ones - ruminants - that produce methane and it's been methane that has really been the target of the Interim Climate Change Committee and indeed the Parliamentary Commissioner for the Environment saying "how do we reduce methane"?
It is a significant factor for New Zealand because of the number of ruminant animals and because it's relatively short-lived in the atmosphere. If we make a difference if we pull it down, that will have quite an impact rather quicker than trying to control carbon dioxide.
Listen to the full interview below:
But it's actually fuel-based carbon dioxide that are increasing most rapidly in New Zealand - and the whole energy factor.
So there's all of these components that need consideration. If we just look at some of our horticultural crops, yes the greenhouse gases are as much or sometimes more than intensive dairy production, but we also need to think when we're into market gardening, about sediment and nitrate.
This morning we had all over the news the animals in mud campaign, well check any bare paddock, whether it's come out of potatoes or onions or maize grain or it's been a fodder crop for cows, it is susceptible in our climate, this heavy rain that we have, and our relatively unconsolidated soils, there will be losses.
Mackay: Living car-free ... might save about two tonnes of greenhouse gas per person per year, not flying to Los Angeles and back would save four tonnes.
Rowarth: And that's economy.
Mackay: Yeah that's economy! Let's double that for premium economy. Let's triple that for business. What about that well-known Wairarapa farmer Jimmy Cameron on his private jet - what the hell's he using?
Rowarth: Now I can't calculate that, it's so beyond the normal calculations one can do. It depends on the size of the aeroplane, how many people are travelling, what they actually have to go to - which is of course my point - what can we actually do that is sensible to assist the planet?
This whole vegan component "get rid of animals in New Zealand" and there are quite a lot of people who think well ruminants weren't here therefore they should go.
We feed, remembering agriculture is 0.1 per cent of the greenhouse gases for the globe, that's produced in New Zealand, we feed 0.5 per cent of the population their animal proteins.
And if we're not doing it - what happens? Remembering Ireland is trying to cut down, the UK is trying to cut down. So we leave it to the developing countries and that's where we're losing some of our indigenous tropical forests that's going into soybean to produce beef or fed directly to humans - this is insane.
Mackay: A final question for you. If you were to do one thing - this is us collectively as a nation - if we were all to do one thing to save the planet, serious question here - what would be our best option? Would it be to go and buy an electric car?
Rowarth: It would be check public transport, live car-free, and not go to Europe of course, but live car free on a daily basis and have much better infrastructure for public transport and it should be electricity-driven, because in New Zealand most of our electricity is created by renewable resources, wind, thermal and of course, water.
So that would be the biggest thing. And stay out of aeroplanes. Driving yesterday, just feeding animals, the screeds of traffic that were coming back from Taupo and Turangi and the ski slopes - this is part of our issue - urban tractors - you know, the SUVs in Auckland where we have 1.5 million people, deciding to get out of Auckland and enjoy some of the countryside - and who could blame them? - in great big gas guzzling things so that they can have a weekend on the slopes.
Where oh! There are snow makers guzzling fuel!
We haven't even got into that.