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Climate Hustle

Global food production threatens to overwhelm efforts to combat climate change

Posted on 31 March 2016 by Guest Author

The ConversationEach year our terrestrial biosphere absorbs about a quarter of all the carbon dioxide emissions that humans produce. This a very good thing; it helps to moderate the warming produced by human activities such as burning fossil fuels and cutting down forests.

But in a paper published in Nature today, we show that emissions from other human activities, particularly food production, are overwhelming this cooling effect. This is a worrying trend, at a time when CO₂ emissions from fossil fuels are slowing down, and is clearly not consistent with efforts to stabilise global warming well below 2℃ as agreed at the Paris climate conference.

To explain why, we need to look at two other greenhouse gases: methane and nitrous oxide.

The other greenhouse gases

Each year, people produce about 40 billion tones of CO₂ emissions, largely from burning fossil fuels and deforestation. This has produced about 82% of the growth in warming due to greenhouses gases over the past decade.

The planet, through plant growth, removes about a quarter of this each year (another quarter goes into the oceans and the rest stays in the atmosphere and heats the planet). If it didn’t, the world would warm much faster. If we had to remove this CO₂ ourselves, it would cost hundreds of billions of dollars each year, so we should be very grateful that the Earth does it for free.

Apart from CO₂, there are two other main greenhouse gases that contribute to global warming, methane (CH₄) and nitrous oxide (N₂O). In fact, they are both more potent greenhouse gases than CO₂. The global warming potential of methane and nitrous oxide is 28 and 265 times greater than that of CO₂, respectively.

The human emissions of these gases are largely associated with food production. Methane is produced by ruminants (livestock), rice cultivation, landfills and manure, among others.

Other human-induced emissions of methane come from changes to land use and the effects of climate change on wetlands, which are major producers of global methane.

Nitrous oxide emissions are associated with excessive use of fertilisers and burning plant and animal waste. To understand how much excess nitrogen we are adding to our crops, consider that only 17 of 100 units of nitrogen applied to the crop system ends up in the food we eat.

Sinks and sources

Just as humans pump greenhouse gases into the atmosphere, the land also produces and absorbs them. If the land absorbs more of a gas than it produces, we think of it as a “sink”. If it produces more than it absorbs, we call it a “source”. The ability of the land to absorb and produce greenhouse gases is affected by human activity.

We wanted to know how human activities on the land are affecting these sinks and sources. Globally, the land currently absorbs more CO₂ than it produces (we don’t include fossil fuels in this), so it is considered a carbon sink. But we found that this is overwhelmed by production of methane and nitrous oxide, so overall the land is a source of greenhouse gases.

This study highlights the importance of including all three major greenhouse gases in global and regional climate impact assessments, mitigation options and climate policy development.

Another recent study calculated that the size of this combined greenhouse gas source is about equivalent to the total fossil fuel emissions of CO₂ in the 2000s. Looking at the chart below, if you add up the carbon emissions from the “LUC gross source” (emissions from deforestation) and the emissions from methane and nitrous oxide (in blue and green), then you can see they are roughly equivalent to those from the combustion of fossil fuels.

So it’s a huge part of our contribution to climate change.

Importantly, CO₂ emissions from deforestation together with methane and nitrous oxide emissions are mainly associated with the process of making land available for food production and the growing of food in croplands and rangelands.

Unfortunately, there has been limited discussion about major commitments to decarbonise the food production system, as there has been about decarbonising the energy system.

Countries, particularly emerging and developing economies, have shown little interest in placing the food system at the forefront of climate negotiations. One reason is what’s at stake: feeding their people.

A continuation of the current growth trends in methane and nitrous oxide emissions, at a time when growth of CO₂ fossil fuel emissions is slowing, constitutes a worrying trend. The greenhouse gas footprint of food is growing while the role of the food system in climate mitigation is not receiving the attention that it urgently needs.

Opportunities for mitigation in this sector are plentiful, but they can only be realised with a concerted focus.

Pep Canadell, CSIRO Senior Principal Research Scientist, and Executive Director of the Global Carbon Project, CSIRO and Hanqin Tian, Director, International Center for Climate and Global Change Research, Auburn University

This article was originally published on The Conversation. Read the original article.

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Comments

Comments 1 to 8:

  1. There is just one tiny point I disagree with slightly. You said, "The greenhouse gas footprint of food is growing while the role of the food system in climate mitigation is not receiving the attention that it urgently needs." In my opinion food production has the attention. It even has well vetted solutions that are simply huge due to the very size of agriculture worldwide. BUT the problem is that there is tremendous backlash and opposition to actually making those changes. Almost insanely high levels of backlash.

    This should help a whole lot.

    The System of Rice Intensification (SRI)… … is climate-smart rice production

     

    This also has great promise, although not quite as vetted.

    Pasture Cropping: A Regenerative Solution from Down Under

     

    And of course one thing that keeps popping up in agriculture all over everywhere one looks:

    Holistic management (agriculture)

     

    One reason I believe the resistance is so huge for these changes is the results are so huge and so beneficial it literally is embarrassing to those who implemented their destructive agricultural practices we have now. For example take a look at the results from pasture cropping.

    "Jones calculates that 171 tons of CO2 per hectare has been sequestered to a depth of half a meter on Winona."

    Any climate scientist that starts plugging in numbers like that into worldwide agricultural acreage and they get numbers so huge they proclaim it just is too good to be true.

    171tons CO2 per hectare X 224.2 million hectares = over 38,000 million tons CO2 sequestered just in changing one crop, wheat, to regenerative agriculture. Start applying similar practices to all agriculture and the numbers get ridiculously huge. People just can't accept numbers so huge. They refuse to believe it really is that simple as simply restoring our soils to fertility.

     

    "I am an organic farmer. I am not afraid of change, I am the change."

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  2. Unexplained on the figure is the huge CO2 sink (ca -5pGC/y) called "Atmospheric Growth". What is it??? I don't recall seeing such sink on any carbon cycle picture of any scientific publication. Is it some mistake/ misnomer? A sink (whatever mysterious its origin is) should not be called "Growth"...

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  3. chriskoz @2, it may be better to think of it as a partition.  The total value of fossil fuels plus net LUC should equal the total value of atmospheric growth, land sink and ocean sink, with the relative ratios showing how the increased CO2 in the total reservoir is partitioned.  Atmospheric growth is then just the growth in atmospheric CO2 concentration.

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  4. Chriskoz,

    I think you have misunderstood the figure.  It accounts for all the emitted CO2.  As you know, the atmospheric CO2 is increasing (3ppm last year), that is a sink.  Since about half the emitted CO2 stays in the atmosphere, it is the largest sink.

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  5. RedBaron, Awsome. I am not familiar with your figures, but sense this is true from my house vegetable gardening, and from my studies for other solutionis. We can do it, we must be a positive contributor to a  healthy ecosystem, and we will be one with nature soon.

    Imagine walking through San Diego Zoo, and that this is the way the whole world is, but instead of enclosures to keep nature in, we live in exclosures, to keep civilization in designed balance with nature. Yes we can!

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  6. 1. Fossil fuel CO2 is additive, unlike the CO2 in soil being at most 100 years old. 1+2 is the amount actually added but the landsink in the figure is taking in just about the same amount of CO2-eq from LUC. Meaning that current areal of (food-crop) land is in perfect balance. If their would be no slash and burn and primaire forest conserved, all is fine. Of course not as the current areal is depleted and has released CO2 over the years now adding artificial fertilizers releasing even more potent greenhouse gasses.

    2. CH4 from animals, manure is from very recent stored carbon and can not influence the balance. Though CH4 is 7 times more potent over 100 years than CO2, capturing CH4 from dairy farms, waste water treatment, landfills (should be phased out) is already done and could be extended. CH4 from permafrost is far more older and does give a problem as it is 1000th of years 'old' carbon.

    3. from https://en.wikipedia.org/wiki/Nitrous_oxide the total amount of N2O is 5.7 Terragrams where a 3.5 terragrams is by natural activities. Being 285 to 310 times more potent than CO2 that would result in 1.76 Petta grams CO2-eq. yr-1, Not 4 as the drawing suggest.

    4.Furthermore the Nitrogen cycle in soil is quite complex and hardly any N2O gets away. More problematic is the escape of N20 by production of nylons and the use of N2O as inhibiting gas/driver gas. My guess is that N20 production from industry is quite an amount higher, not a 20% as suggested but more in the range of 50%.

    5. Nitrogen loss in soil can be controlled by using correct type of fertilizers. Although only 17.1% of the nitrogen ends up in the food (part), the food part represents only 20% of the plant. As for some fertilizers type 40% ends up in the air (as ammoniak), this can be reduced to a mere 5% by applying N fertiliser in the soil and not on top only.    

    "Importantly, CO₂ emissions from deforestation together with methane and nitrous oxide emissions are mainly associated with the process of making land available for food production and the growing of food in croplands and rangelands." 

    CO2 emissions and N20 emissions are mainly due to preparing exisiting, intensive used and depleted -therefore provided with high amounts of artificial N fertilisers- crop lands. Deforsted land is not capturing any CO2 anymore, but it is not releasing vast amounts of CO2. De-watering, and other mechanical does break down soil-life and will release CO2 (and equivalent GHG)  

      

    2. 

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  7. Tom & michael, thanks.

    Now I undesratand the red bars are CO2 "balance sheet" and they all add up to 0.

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  8. Ger,

    Don't confuse the active fraction with the stable fraction of soil carbon. Your claim that soil CO2 is at most 100years old and that it is in almost perfect balance is a bit simplistic and factually incorrect. Those stats you are addressing refer to the active fraction, not the stable fraction of soil carbon.

    The rest of your post is true  in so much as it does apply to the majority of agricultural systems today, but not necessarily so, because there are alternative agricultural systems that function with respect to the carbon and nitrogen cycles quite differently.

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