The question of the week
” Good morning. I heard on the radio during a report on agriculture that it was one of the main causes of climate change, particularly because of agricultural machinery. (…) Is it true ? What role does agriculture play in global warming? » (Question asked by Maria at chaud [email protected].)
My answer : Yes, agriculture plays an important role in climate change. In France, the share of agriculture is significant, around 20% of our emissions. Globally, agriculture also accounts for around 20% – but this varies greatly depending on the country. It thus accounts for 10% of emissions in the United States and 50% in New Zealand, for example.
1) Why does agriculture emit so much?
The High Council for Climate delivered at the end of 2023 a very comprehensive report on the subject which I highly recommend. It explains well how the climate impact of agriculture in France – the second highest emitting sector after transport – breaks down. Nearly 60% of emissions come from livestock farming, particularly cattle. This is mainly the gas emitted by ruminants during their digestion: methane, whose warming power is much greater than that of CO2. (To find out why meat emits so much, you can listen to this episode of “Human Heat” on the subject.)
Then, it is the crops themselves which are responsible for 27% of emissions from the agricultural sector. Here it is the fertilizers which are at fault: they emit nitrous oxide, a gas even more powerful than methane (itself more powerful than CO2, if you followed). And since they are made using natural gas, their contribution to climate change is significant.
Finally, agricultural machinery accounts for 13% of the sector’s emissions, since tractors and trucks use oil to operate. (We talked about all this in this episode of the “Human Heat” podcast with researcher Nicolas Bricas)
2) But be careful… it’s more complicated than that!
It would be too easy to simply point the finger at the agricultural sector: it is not only an emitting sector, it is also one of the most realistic solutions for massively storing carbon. We talked about it in an episode on soils with professor at the Natural History Museum Marc-André Sélosse. How ? Well by nourishing the soil with organic matter, agricultural waste, for example, so that the carbon is found in the soil rather than in the atmosphere. But this supposes that we make use of the soil a little differently from that of current conventional agriculture. Marc-André Sélosse has since clarified his vision in a column in World.
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