What if... everyone bought locally?

I'm continuing the food theme for this latest post. Maybe it's my love of eating; or maybe it's because the more I read into it, the more fascinating the carbon economics of food seem to be. This time round it's the local food movement. We should all buy locally, right? Well, what would happen if we did?

You're probably familiar with the concept of food miles - the distance our food travels before it reaches our supermarket shelves. Transporting goods causes greenhouse gas emissions. Reduce your food miles, the theory goes, and reduce emissions from your food. And when 14% of global emissions come from agriculture, there's big savings to be made!

If you've read any of my previous posts, you'll know that things in the world of emissions are never as simple as they first appear. Take the case of Young's, who got in trouble a few years back when it was revealed their locally sourced Scottish prawns where flown to Thailand for shelling before returning to the UK to be sold in our supermarkets. Customers thinking they were buying local produce were unsuspectingly buying a product with 12,000 embedded food miles!

Luckily studies have shown that it's not food miles that count - the methods used to grow your food are much more important. It's helpful here to have a look at a few case studies. Consider the tomato. A 2008 DEFRA study found that tomatoes grown in the UK were responsible for three to four times more emissions than those imported from Spain, even when the additional food miles were taken into account. This is because UK tomatoes tend to be grown in gas heated greenhouses. A similar study by New Zealand researchers found British lamb was four times more energy intensive than New Zealand lamb, even allowing for transport to the UK - due mainly to the use of larger quantities of fertilisers by UK farmers.

He may look tasty. But if he's from the UK, his carbon emissions may be bigger than you think

All the evidence seems to say that, if you're looking to reduce emissions from food, you need to look at the entire lifecycle of the foods you eat. If you do that, as these American researchers did, you'll find that food miles account for only about 11% of emissions from our food. Even more scarily, a study by the University of California looked at what would happen if everyone in their local area of Santa Barbara County bought locally. Amazingly they found it would reduce emissions from food by less than 1%!

So there you have it. If we all ate locally, the impact on food emissions might be as low as one percent!

Tesco now put carbon footprints on products to help consumers make informed choices

So what should you buy? Well in his excellent book How bad are bananas? author Mike Berners-Lee says you can't go wrong with a banana. Good advice if you ask me. Imagine the detrimental impacts to countries like Ecuador - where 61% of the agriculturalGDP comes from banana exports - if we all stopped eating bananas. When you start looking at situations like this, you can see the issue of buying locally extends far beyond just carbon emissions.

If you want more about food miles, the ever brilliant Freakonomics team have produced this excellent podcast. In it they speak to the authors of the Santa Barbara county study.

What if... we all ate organic?

If you've spent five minutes in the aisles at M&S, you'll know that organic food is big business. 'It's better for the environment' claim the marketers, 'It's healthier' and 'think of all those poor animals'. But is it worth splashing extra cash on organic? What would happen if everyone decided it was?

It's worth giving a little thought to the huge benefits industrial agriculture has brought to the world. At the turn of the 20th century, an agricultural apocalypse was looming. ‘unless the chemistry world manages to turn the nitrogen of the air into fertilizer' German chemist Karle Engler told the British Association for the Advancement of Science in 1898 'the western world will starve’.

A few years later Fritz Haber and Carl Bosch came up with a method for the industrial scale production of ammonia, the basis of modern fertilisers. It's difficult to overstate the impact of the Haber-Bosch process. Since 1950 the relative abundance of cheap food has allowed global populations to expand from 2.5 billion to today's seven. Without it, you probably wouldn't be here reading this article.

But intensive agriculture has many side effects. Fertilisers and pesticides can contaminate hydrological and ecosystems in unexpected ways. It is here that organic agriculture, with its reduced reliance on chemicals has clear advantages. You might have also seen claims that organic food is healthier. But extensive studies have found that organic food offers no additional nutritional value. And whilst it might expose you to less pesticides, the levels of pesticides permissible in our food in the UK are so tightly controlled, they pose no measurable risk to health.

Now remember - this blog is about climate change! So does organic food produce fewer greenhouse gases? The evidence is often conflicting but overall the balance seems to point to yes. Nitrate fertilisers used in industrial farming are broken down by bacteria in the soil, which release nitrous oxides into the atmosphere. And the techniques used in organic farming mean that carbon is held, or sequestered, in the soil for longer, keeping it out of the atmosphere.

Comparing emissions across types of agriculture is tricky. Different values are arrived at depending on whether you're calculating emissions per kg of produce or per hectare of land. And figures vary wildly depending on whether you've accounted for the sequestration effects of organic farming or not.

An eight year study by scientists at Michigan State University to measure gas fluxes from agriculture found that, once sequestration effects were taken into account, emissions from organic were 64% lower. Modelling studies show similar reductions. So, if we take the most optimistic predictions, emissions from agriculture could reduce by 64% if we all ate organic (or about 9% of total emissions). But this is likely to be a long way off the actual figure. Far more research is needed to establish the true impact of going organic. 

Comparison of soil carbon gains and losses in different farming systems in long term field experiments
Source: Low Greenhouse Gas Agriculture, FAO (2009)

What is clear is that the social implications would be huge. The reduced yields of organic compared to industrial farming mean it's unclear whether it's even possible to feed the global population entirely on organic. And food prices would undoubtedly rise. In a world where nearly a billion people go hungry, I think we're best sticking to industrial practices for the foreseeable future.