Tuesday, December 25, 2018

Counting apples and oranges

We are exposed to a virtual torrent of contradictory data and statements about the contribution of food and agriculture to global warming. Depending on what you count and how you count, tree-huggers, vegans, biofuelers, proponents of organic, locavores, industrial agriculture, free-traders, the fertilizer industry, regenerative ranching and others can present figures defending their case.

There are several reasons for why figures differ. Sometimes it is simply because uncertainties are big when we discuss biological system and depending on methodology and assumptions results will differ. This is particularly the case for methane and nitrous oxide emissions, where figures used mostly are guesstimates built on crude models. In addition, in the climate debate, only anthropogenic emissions “count”, despite the fact that all emissions have the same effect and that the classification is much less straight forward than mostly understood.  The methane emissions from a wetland which is converted to rice production will suddenly become anthropogenic even if the methane emissions might have been even higher earlier.

Local and global figures are often mixed up. While in absolute numbers, emissions from the food chain is considerably higher in rich industrial countries, their share of emissions is much lower than in poor countries, where food emissions can be more than half of all emissions. Another example is when global figures for emissions of livestock enters domestic debates and livestock emissions suddenly equals emissions from “meat”. But livestock provide people with many other goods, services and values than meat (milk, leather, skin, horn, savings account, draught power, building materials, wool, fuel, cultural meaning etc.).

Media likes graphs where emissions from food are compared with emissions from transport. But the figure for “food” might include every step and aspect of food production up to final consumption, or even include the waste, while the figure for “transport” only include emissions from the exhaust pipe and not the emissions to build roads, cars, garages nor emissions included in maintenance and repair, tires, lubricants, car washes etc. Mostly it doesn’t even include the massive emissions involved in extracting and processing petroleum oil into diesel or gasoline.

Sometimes emissions for agriculture include changes in land use caused by deforestation and loss of carbon from soils. While this has some merit it is inconsistently done and it is not at all clear for how long period the emissions should be counted for. When it is translated into statements of emissions per kg of a certain product, be it palm oil, soybeans, cocoa or cattle meat it makes all difference if the emissions are distributed over one year, twenty, hundred or more years. This application recently reached a new high when a group of researchers developed a “carbon benefit index” which relates all land based production to a global average potential carbon storage in forests. The index gives land use such a prominence that it basically overpowers any other greenhouse gas emission factor. Using their index, land use of the average European’s food cause much more emissions than all their other emissions counted together. The net result of this is that further intensification of land use with more inputs is the way ahead, and that we don’t have to bother much about fossil fuels if we just produce more per land unit and plant forests on what ever land that is spared.  

Mostly, calculations for agriculture are used to discuss food. In average, farm production has the heaviest footprint of all steps in the food chain, but the total emissions post farm are substantial, possibly as big as the totals on farms. But emissions differ depending on whether a product is cooled or frozen, airfreighted, heavily processed or just a dried stuff like nuts or flour. Then again, when it comes to preparation you mostly eat nuts as they are or just lightly crushed, but flour is mostly made into bread, and baking is very energy consuming.

The figures for agriculture are calculated in many different ways. In the IPCC methodology most of the emission sources from agriculture operations are not included in the agriculture sector emissions (and IPCC has no “food” category). Recent research, Chinese cropping systems are a net source of greenhouse gases despite soil carbon sequestration, by Gao et al 2018 published in Global Change Biology came to the conclusion that the 16 most prominent production systems, comprising some 85 % of Chinese cropping cause a total of half a billion tons of greenhouse gas emissions annually. The major sources were nitrogen fertilizers (30%) methane emissions from cropland, mainly paddy rice (26%) and irrigation (20%). Other sources of emissions were irrigation, fuel for tractors and other machinery, pesticides, and plastic films in horticulture (see graph). Of the total emissions, only methane emissions from paddy rice and nitrous oxide emission from land and manure are part of IPCC’s “agriculture” emissions. Two thirds of the emissions from Chinese cropping are thus not counted under “agriculture” in the IPCC methodology. They all fall under “industry”, “power generation” or any other category. The transportation involved in farming for inputs and outputs (not included in the Chinese figures either) are also not included but booked under “transport”. Essentially this means that no CO2 emissions at all are attributed to farming in the IPCC classification, but only methane and nitrous oxide. This also means that livestock’s share of agriculture emissions is grossly exaggerated and that the opportunities to reduce agriculture emissions through de-carbonization is neglected.


With these conditions in mind it is apparent that almost any interest group can use the climate argument to promote their vision of the future food and agriculture system, just by selecting the right parameters. Media and climate activists should be much more critical to new research and claims that one method or one food is superior (or inferior).

We need to adopt a much broader and systems-oriented perspective on our food systems. They are a part of a number of human socio-ecological systems with multiple functions. We should be wary of simplistic global solutions for reducing the food systems climate impact. There are hotspots and levers to consider, such as ruminants’ methane emissions, land use, global trade, synthetic nitrogen fertilizers, cool chains, fossil fuels in all its functions in the food system and food waste. To focus only on one of them is mostly mistaken.
Being a grower and farmer since forty years, I am inclined to look to the soil, the microbes, the plants and the animals for guidance, and build a sustainable food system from the bottom up. I believe we already know, by and large, how such a farming system will look like. Recognizing the immense challenge of global warming, there is certainly a need for a top-down approach as well. For me, reducing the use of fossil fuels and nitrogen fertilizers are the primary candidates for policy driven reductions of greenhouse gas emissions from the food system. That will have cascading effects and influence the global trading system, nutrient cycles and diets, and make the transition to local food systems easier. Will it suffice? Will it happen? I have no idea.