Re: Food and Climate Research Network
The food system is estimated to contribute approximately 20-30% of global human-made GHGs although there is huge inherent uncertainty in these estimates.
The major impacts come from farming/agriculture and land-use change (see above), with fertilisers, pesticides, manure, farming and land-use change together contributing as much as around 24% of global GHGs. Livestock alone contribute 14.5% of human-made GHG emissions.
Stages later in the food system such as packaging, retail, transport, processing, food preparation and waste disposal combined contribute around 5-10% of global GHGs although their importance and likely impacts are set to grow.
These stages are discussed in more detail later in this chapter (Sections 3.3 and 3.4).
Within food systems, consumption patterns and production are interrelated, both impacting on one another.
Agriculture contributes to GHG emissions both directly (emissions from agricultural production) and indirectly (land-use change for agricultural purposes).
For the three major greenhouse gases, direct emissions include:
• CO₂ from fossil fuel use (e.g. agricultural machinery, fertiliser production, pesticide production, production of farm structures (e.g. polytunnels)
• Methane from enteric fermentation from ruminant livestock such as cows and sheep, as well as from manure, from rice paddies and from decomposing organic matter (e.g. waste in landfill)
• Nitrous oxide from soil bacteria, from legume production, from livestock manure and urine and from nitrogen fertilisers.
Indirect emissions are primarily CO₂ emissions from land-use change (such as deforestation and conversion of peatlands to create agricultural land).
The GHGs emitted from agriculture and associated land-use change shown here (around 10 gigatonnes of GHGs) account for 24% of human-made GHG emissions.
As shown in the graph, direct methane and nitrous oxide emissions constitute around half of this, and these emissions have increased in recent years.
Emissions from land-use change and forestry (mainly CO₂) approximately make up the other half. Most, although not all land use change and deforestation is driven by agricultural expansion. Agriculture is estimated to be responsible for 80% of worldwide deforestation (Kissinger, G., M. Herold, V. De Sy. Drivers of Deforestation and Forest Degradation: A Synthesis Report for REDD+ Policymakers. Lexeme Consulting, Vancouver Canada, August 2012.). Land degradation (deteriorating forests and other lands, rather than actual clearing of forests) is driven more by timber extraction and logging, rather than agriculture.
The land-use change referred to here relates to actual change of use, such as deforestation for crop production or livestock grazing, rather than land and forest degradation. Although degradation is also an important source of CO₂ emissions, it is not included here as an impact within food systems.
Some of the carbon losses from deforestation have in recent years been offset by afforestation (re-foresting land), but the net contribution from agricultural land-use change is still highly significant. There are large regional differences, with afforestation more prevalent in northern regions, and deforestation more so in southern regions of Asia and South America.
Agricultural production (including direct emissions from agriculture, and fertilizer production, pesticide production and energy use for animal feed) contribute the great majority of food system GHG emissions.
Post-agricultural production stages (processing, refrigeration, storage, packaging, processing, retail, catering and consumers, and waste disposal) contribute much less but can be significant for some food types.
On a global scale, there is a great deal of uncertainty in measurements.