Of leeks and land (and units of measure)

(This post primarily focuses on Eline de Backer, Joris Aertsens, Sofie Vergucht, Walter Steurbaut, (2009) "Assessing the ecological soundness of organic and conventional agriculture by means of life cycle assessment (LCA): A case study of leek production", British Food Journal, Vol. 111 Iss: 10, pp.1028 - 1061)

What's in a unit?

In my first read-through of ‘the leek paper’ (as I shall refer to it), I found myself flummoxed by something that seemed like it should be very simple - the ‘functional unit’ definition. This is a core life-cycle analysis concept, and at first it seemed obvious - this was the unit of measure we were going to use. This is science - we always need units of measure. No problem, right? The paper defined two functional units; ‘one kilogram of leeks’ and ‘one square meter of leek production’. These were what we were going to compare the environmental impact of between conventional and organic farming methods.

While I ‘smiled and nodded’ on reading about those two units, my inner pragmatist subconsciously seized on the kilograms right away, and didn't let go for the entire first readthrough. This was the only thing that intuitively made sense to me. After all, if we are growing leeks, what matters is how many bundles of leeks we grow, right? That's what we will sell and, more importantly, eat. The amount of land seemed useful (to my subconscious mind) only as an underscore - as in, kg/m^2 (how many kg of leeks can I grow in a square meter?)

After these units were chosen, the authors covered a lot of other ground - the scope of the analysis, the source of the data, and the farming processes under analysis (planting, fertilization, weeding, harvesting, etc.) They also covered the types of environmental impacts they would measure, which I talked about at some length here.

Massive yields

Before digging into the environmental impact per functional unit, the authors called out a key point, one that had popped back into my head back at the beginning of the paper: kg/m^2. It turns out that the organic leek farms yielded a lot less product per area of land. 27% less, to be precise. For the same amount of land where Clive the conventional farmer produces 10 kg of leeks, Oliver the organic farmer next door gets only 7.3 kg. To make up that extra 2.7kg, Oliver needs to farm 37% more land. (2.7kg is 37% of 7.3; 2.7/7.3 = .369) This ends up making Oliver have to use more diesel to get his tractor around all that extra land, and also use a whole lot of extra manure to cover the additional acreage as well.

This starts making a big difference when you look at your environmental impacts by the kilogram. It several categories (for more about what these categories are and what the units mean, go read this), it ends up with organic leek production actually being environmentally worse -

• abiotic depletion (kg antimony equivalents) 
• ozone depletion (kg CFC-11 equivalents) 
• photochemical oxidation (kg. acetylene equivalents)
• eutrophication (kg phosphate equivalents)

So with Oliver's kilogram of organic leek production, there's slightly more damage to soil and water systems, slightly more ozone damage, more smog-forming compounds in the air, and more nasty algae blooms.

Now, even with the lower yields, the organic leeks win out on several categories, even with a kg unit:

• Human ecotoxicity (kg of 1.4-dichlorobenzene equivalents)
• Terrestrial ecotoxicity (kg of 1.4-dichlorobenzene equivalents)
• Climate change potential (kg of CO2)
• Acidication (kg SO2 equivalents)

The toxicity is pretty much due to all the pesticide Clive puts on his conventional crops, it turns out - which Oliver isn't allowed to use in this case. Climate change potential for the organic leeks is about half of that for conventional ones; even with Oliver's extra tractor use, the nitrous oxide in the mineral fertilizers used by Clive's conventional farm ends up dominating that - the manure fertilizer used by organic farms doesn't have the same kind of impact, though it is responsible for the eutrophication mentioned above. And acidification is marginally lower for Oliver, also due to the differences in fertilizer.

But still - in fully half the categories, the environmental impacts for the organic leeks are actually worse. This doesn't seem great, even if the organics are only a bit worse in most areas.

Happy land

Now if you look at the impacts per square meter of leek production, you see a different story. In every single category, conventional farming has a worse environmental impact than organic farming. Some are closer than others, but there's no question which is less damaging when you are going by area of land.

However, here's where I got stuck - why do I care about the area of land? The authors of the paper spend quite some time discussing how there's not a real consensus on what is the 'right' functional unit to use for this kind of comparison. And they (along with some others they cite) point out that an assessment by area tends to end up looking more like an environmental impact assessment than anything else. Of course it's nice to know that the acre of organic leek farm across the way from my house is less likely to poison me than the acre of conventional leeks down the street by a neighbor I don't like so much. (hypothetically, of course)

Which is fine, but I keep thinking - isn't how much food is grown the real value of agriculture?

Land is more than leeks

The authors allude to this a couple of times, but agriculture can be seen as a producer of more than just food. Any good use of a piece of land can produce other 'ecosystem services'; carbon capture, water and soil retention, habitat for useful creatures such as pollinators, local climate control, and so on. On my second readthrough of the leek paper, that's what started to make the idea of a land-based functional unit make sense to me. 

The issue is, it's easy (relatively) to know and understand the value of a kilogram of leeks. It's a lot harder to wrap my brain around the 'value' of healthy honeybees living in Oliver's fields (Clive's pesticides killed the bees in his), or the fact that Oliver's farming practices might keep the topsoil in his fields around longer and in better health. 

I'm predisposed to be in favor of sustainable farming practices, and without an easy way to talk about these 'added values', even I find myself drifting back to thinking about straight up crop yields. But if we can define a suite of ways to measure environmental impacts, can we come up with a set of methods to quantify environmental services and benefits that are equally measureable?

Without that, I don't know if it will be possible for most people to get past the ultimate measure of agriculture being a bundle of leeks, and not an acre of healthy land.