How Your Food Choices Affect Climate Change

21 September 2014

This post explores the options farmers and consumers have to help reduce global warming. We believe that a positive response to global warming could improve our quality of life and address some of the more intransigent issues we face.

Agriculture is a large contributor to climate change. Worldwide it generated over 16% of greenhouse gas emissions in 2011. [1] Aotearoa-New Zealand is a country heavily dependent on agriculture and as a result, the percentage of emissions is much higher: 47% in 2011. [2]

But could agriculture become a way of mitigating climate change?


What is Greenhouse Gas?

Greenhouse gas emissions from agriculture are almost exclusively generated by the release of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). 


Carbon dioxide (CO2)

Agriculture is responsible for one third of carbon dioxide emissions worldwide. It is generated by clearing forests, turning natural vegetation into cultivated land, the intensification of agriculture, and transporting food.

In New Zealand the situation is different. The agricultural sector accounts for only 2% of carbon dioxide emissions because it is offset by tree-planting by the forestry industry, which acts as a carbon sink. This is one good example of the agricultural sector mitigating climate change.  

Is organic farming a better option?

A 1994 study calculated the carbon dioxide emissions of German organic farms to be .5 tonnes per hectare, whereas in conventional agriculture the amount was 1.3 tonnes, a difference of 60%. [3] In organic agriculture, emissions are mainly caused by fuel consumption, whereas in conventional agriculture the majority of emissions are from nitrogen fertilisers, feedstuffs and fuel.

Buying organic also means favouring local seasonal foods.  Organic farming cuts down on the fossil fuels used to manufacture products compared to mainstream agriculture [i].  Organically managed soils capture and store carbon dioxide at much higher levels than soils from conventional farms.

If the USA grew all of their corn and soybeans organically, they would remove 263 million metric tonnes of carbon dioxide from the atmosphere! [ii]

The Rodale Institute has been running trials comparing organic and conventional farming in the US for the last 23 years. US agriculture currently emits a total of 680.3 million metric tonnes of carbon dioxide into the atmosphere. The Rodale Institute trials show that 'converting all US cropland to organic would not only wipe out agriculture's massive emission problem, (but) by eliminating energy-costly chemical fertilisers, it would actually give a net increase in soil carbon of 332.9 million metric tonnes.' [4]

The regular addition of organic materials to the soil is the only way to maintain and increase soil organic carbon (ie carbon absorbed by the soil) and this is the basis of organic agriculture. Conservation tillage combines minimum tillage with fertilisers and herbicides and has been promoted by conventional agriculture as the way to absorb carbon dioxide. But the gains in soil organic carbon from this method are likely to be negated by the increased nitrous oxide emissions from the fertilisers.

A hidden carbon cost in agriculture is that the emission figures do not take into account the transport of food.  Transport accounted for 33% of New Zealand’s carbon dioxide emissions in 2001, but it is not clear how much of this involved the transport of food. A UK study in 2005 reported that 28% of road freight is food or produce[5]. While there is no inherent difference in organic and conventional produce in this respect, Commonsense Organics stresses the importance of seasonal produce by providing a calendar of fruit and vegetables in season, to help customers develop the habit and skills of eating food in season. We also have a policy of supporting local growers to reduce the need for long haul transport.


Methane (CH4)

The vast majority (97.6%) of methane emissions in New Zealand are caused by ruminating animals (mainly cattle and sheep).[6]  Since methane has 21 times the impact on global warming compared with carbon dioxide, it represents the biggest challenge for New Zealand agriculture and this applies to both organic and conventional systems. Methane accounts for 70% of our total agricultural greenhouse gas emissions and 31% of our total emissions from all sectors.[7]


Nitrous Oxide (N2O)

Nitrous oxide is 310 times as potent as carbon dioxide in terms of global warming and agriculture contributes to 65%-80% of total nitrous oxide emissions. This is mainly due to the use of nitrogenous fertilisers and animal waste. In Aotearoa-New Zealand direct soil emissions are from synthetic fertilisers, animal waste applied to soils, N-fixing crops, crop residues and cultivation of organic soils (histosols). Indirect N2O emissions are caused by the amount of nitrogen from synthetic fertiliser and animal excretion that volatises into the atmosphere as N2O.[8]

Organic methods minimise the emissions of nitrous oxide, because:

  • No synthetic nitrogen fertiliser is used, and this limits the total nitrogen level and reduces emissions caused during the energy demanding process of fertiliser synthesis;
  • Agricultural production in tight nutrient cycles aims to minimise losses;
  • Animal stocking rates are limited, thus excessive production and application of animal manure is avoided;
  • Diets of dairy animals are lower in protein and higher in fibre, resulting in lower emission values. [9]


Ways you can minimise greenhouse gas emissions

Buy local, seasonal food

Buying local food reduces the need for long haul transport. Many areas in New Zealand now have farmers’ markets, but it not uncommon to find stallholders selling produce grown in China. This is particularly the case in cities. Ask where produce comes from. Learn what food is in season. If you are eating fresh tomatoes in winter, it is highly likely they are imported or grown in a greenhouse.

Buy organic food

As shown above, organic agriculture reduces carbon dioxide emissions. The challenge now is to turn this reduction into a net increase in carbon in the soil.


Eat less meat and when you do, eat organic

The most effective action that individuals can take is to eat less meat. If you eat meat every day, consider introducing a vegetarian meal once a week and try to increase that as you get used to different menus.  Organic meat will often be more expensive than conventionally grown meat: this is because the meat is less intensively farmed.  Eating less meat but of a higher quality (such as organic) represents good value for money as an environmental and moral choice as organic and free range farming support a healthier ecosystem and a kinder life for the animals.

Lobby for a tax on methane

The government did try to introduce a tax on methane and this attempt was subverted by opposition parties (with the exception of the Greens) ridiculing the idea as a "fart tax". But there was little attempt by the government to educate the population on why such a tax was needed:

"The largest source of emissions within agriculture is 'enteric fermentation' – methane produced by livestock during digestion and released via belches. In 2011, this accounted for 39% of the sector's total greenhouse gas outputs"


Think local

Flowing from a need to tackle climate change, local economies are becoming much more important.  As local economies develop to support each other, here are some positive changes we may see:

  • Local farming will become more diversified as it addresses increased domestic needs. Currently a huge amount of fruit and vegetables available in New Zealand are imported.
  • Small growers will become more viable and supported as the local economy blossoms. 
  • Organic farming methods will gradually restore New Zealand’s soil and waterways.
  • The concept of kaitiakitanga will become central to a revitalised local economy.  In order to survive we will all learn that our earth is sacred and a practical spirituality will become integrated into our lives.
  • Local economies will grow.  We will live and work in our local areas and this will result in a revitalising of local communities – people will know their neighbours.
  • Family life will be strengthened.  We will celebrate 'homemade' – families will cook their own meals together, sew and refashion their own clothes together, repair their own tools and machines with their neighbours, grow their own food.
  • We will get fitter.  Because our lives will be much more local, we will walk instead of hopping in the car, we will live more physical lives and do more within our communities.
  • The need to plant more trees to offset carbon emissions will increase bio-diversity and replace lost species.
  • The 'unskilled' will become skilled.  We will need a much wider variety of skills, particularly manual skills.  Young people who are currently alienated and un-needed in our global economy will become an integral part of the locally-based economy.
  • Reciprocity will once more be central to New Zealand communities.  We will rely on each other to supplement skills and goods we once bought in the global market place.

These are just a few possibilities but many are already starting to happen – what are we waiting for!?

What you can do:

  • Increase your self-sufficiency skills.  Learn to grow your own food organically, so you are recycling everything possible and avoiding organophosphates ('baddies' in the soil).
  • Learn to eat seasonal food – grab one of Commonsense Organics charts showing fruit and vegetables in season.
  • Upskill yourself in useful ways – e.g. take lessons in carpentry, sewing, cooking, gardening.
  • Start living within your ecological footprint – start measuring what it is now ( and plan how to reduce it - walk, re-use, cycle and re-cycle, save energy etc.
  • Ask the businesses you support what their ecological footprint is and what are they doing to reduce it – your power as a consumer is mighty!


This post looks at the issue of food choices and climate change. If the focus is broadened to wider issues of sustainability – the problems of soil degradation, water quality, biodiversity, and nutritional value, then organic agriculture is clearly the most sustainable and nutritious option.

At Commonsense Organics we are future-oriented and take a wide view of sustainability, and this is why we do what we do.  


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[3] Haas and Kopke, 1994, quoted in Organic Agriculture, Environment and Food Security, ed. N. El-Hage Scialabba and C. Hattam, FAO, 2002

[5] J. Pretty & T. Lang, Buy local produce and save the world, Food Policy Journal, UK, February 2005

[6] New Zealand Climate Change Office, Ministry for Environment, (2003) New Zealand national inventory report (NZNIR), Greenhouse gas inventory 1990 - 2001

[8] Inventory of New Zealand Greenhouse Gas Emissions - 2001, NIWA

[9] Kotschi J & Muller-Samann K (2004):  The Role of Organic Agriculture in Mitigating Climate Change, International Federation of Organic Agriculture Movements (IFOAM)

[i]               BBC, (2006),

[ii]               Gore, A. (2006),