Comment: Adopting vegan principles has been promoted as 'saving the planet', but ideology must not be allowed to trump science, writes Dr Jacqueline Rowarth.

Veganism means life without things of animal origin. No woolly jumpers, merino suits, or leather anything. And certainly no meat, fish, eggs or dairy products.

Choose wine, beer and juice carefully in case it was 'fined' with egg or fish skins.

Avoid gelatine – soufflés, panna cotta, some yoghurts, Gummy Bears, marshmallows and many unexpected products, such as cosmetics (check for the term 'hydrolysed collagen').

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Agar agar, of seaweed origin, replaces gelatine in vegetarian and vegan recipes but is considerably more expensive and somewhat more unpredictable to use.

Being vegan is not easy, and obtaining adequate nutrition is difficult. This is particularly the case for young children – to the extent that Italy has proposed making it illegal to raise children younger than four as vegan.

Proponents of veganism point out that malnutrition can occur on any diet, and the deaths that have occurred were related to lack of knowledge – but the fact remains that veganism is not easy.

This doesn't mean it shouldn't be attempted, but the reasons should be clear.

Adopting vegan principles has been promoted as 'saving the planet', but analysis indicates that what appears to be a simple solution is unlikely to achieve this goal.

Greenpeace report

Last year Greenpeace International urged a reduction in the consumption of meat and dairy products for better health outcomes of people and the planet. 'Less is More' presented the Greenpeace vision for 2050.

Contrary to interpretation in New Zealand, it didn't suggest giving up animals in favour of a plant-based diet.

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The report concluded that what was required was a transition to a food production system "where a reasonable number of animal products are produced with the land and resources not required for food or nature needs".

New Zealand has already done this. Crops are grown on land suitable for arable cropping, market gardening, orchards and vineyards. Horticulture and arable covers about 500,000 ha.

Photo / File
Photo / File

Although it has been calculated that there could be another million hectares of land suitable for horticulture, there are reservations about markets and infrastructure as well as labour remain. Fruit and berries are only 14,100 ha, but every year labour shortages feature in the news.

Markets will change as the population grows and wealth increases. Infrastructure can be solved with investment, but what will take considerable research are the environmental issues.

Greenhouse gases

On a per-hectare basis, greenhouse gases (GHG) associated with the production of some horticultural crops are greater than those associated with dairying (which occupy 1.76 million hectares).

Cultivation and sprays are associated with tractor time and fossil fuel consumption.

Cultivation also has the potential to erode soil organic matter. If heavy rain occurs, topsoil and nutrient loss will follow. Topsoil creates sediment in rivers; excess nutrients create algal blooms.

Contrary to popular belief, becoming organic doesn't reduce the problems and on a per-unit-of-crop basis can be less efficient – that is, more GHG and nutrient losses per kg of yield.

Last year Greenpeace International urged a reduction in the consumption of meat. Photo / File
Last year Greenpeace International urged a reduction in the consumption of meat. Photo / File

GHG calculations

GHG calculations for different diets are available.

Shrink That Footprint suggests that, based on northern hemisphere production systems, becoming vegetarian would save approximately 0.8 tonnes of carbon dioxide equivalents a year in comparison with an average omnivorous diet. (Carbon dioxide equivalents incorporate not just carbon dioxide but also methane and nitrous oxides.)

Becoming vegan saves another 0.2 tonnes in comparison with being vegetarian.

These calculations don't take into account the supplements that are often recommended in a vegan diet.

Nor do they take into account all the things provided by animals that have to be replaced by other production systems if animals aren't available.

Clothing, shoes and accessories such as bags and belts are only the start; many substitutes for wool and leather come from crops (cotton and linen) or fossil fuels (polyester).

Food production trade-offs

All food production involves trade-offs that depend on production system and geographical context.

The climate in New Zealand does not yet enable protein crops such as soybeans, lentils and beans to be harvested at yields that can compete with those overseas.

New Zealand vegans import the bulk of their protein.

Similarly, people overseas wanting meat and dairy protein that has been produced at best practice for animals and the environment import from New Zealand.

The primary sector as a whole contributes approximately $45.7 billion to the export economy. Over 60 per cent of the total is from dairy, meat and wool. That money supports the lifestyles of all New Zealanders, which include cars and airplane travel.

Living car-free might save over two tonnes of GHG per person per year. Not flying to Los Angeles and back would save four tonnes.

There are no easy answers, but jumping to a solution means that the question has not been examined.

Veganism might help with weight loss and heart health – but whether that is good or not depends on the starting point.

Veganism won't have as big an impact on decreasing GHG production as reducing road and air travel; again, depending on starting point.

Ideology must not be allowed to trump science – New Zealand and the planet deserve better.

- Dr Jacqueline Rowarth has a PhD in soil science (nutrient cycling) and has been analysing agri-environment interaction for several decades. She has been a vegetarian since before leaving the UK in 1975.