346. Soil carbon is a highly flawed climate policy, Part 1
The idea of paying farmers to sequester carbon in agricultural soils has once again become politically prominent. It is still an idea with little potential benefit for farmers.
Soil carbon features in the Australian Government’s “Technology Investment Roadmap” and has been widely spruiked this year by the Minister for Agriculture, David Littleproud. The Government hopes that it can make a major contribution to achieving a target of net zero emissions by 2050, which the Prime Minister has flagged will become the national target. To that end, we are promised a new “National Soils Strategy”.
Prominent economist Ross Garnaut is also enthusiastic about the prospects for soil carbon. In his 2019 book Superpower: Australia’s Low Carbon Opportunity, he says “Australia can make an exceptional contribution to climate action by creating natural systems to store more carbon in soils”.
Thirteen years ago, in PD127, I wrote that “Unfortunately, in my judgment, payments for extra carbon sequestration in soils from changes in land management will result in little, if any, benefit to Australian farmers.” This matters because farmers won’t participate unless they see a benefit for themselves.
I gave four reasons for this pessimism:
1. It is difficult to increase the amount of carbon stored in most cropped soils in Australia. Here is a recent quote from Michael Crawford, CEO of the CRC for High Performance Soils. “Australian soils and our climate and our farming systems don’t lend themselves to storing great amounts of carbon.” … “Australian crop growers have been practising methods advocated for improving soil carbon for decades and soil carbon levels haven’t changed all that much”.
2. Soil sequestration is a once-off process. People seem to imagine that new carbon can continue to be sequestered indefinitely, but once farmers change their management to increase soil carbon, it increases up to a new equilibrium level after about 20-30 years and then stops. Farmers need to stick with the new management regime to avoid releasing the carbon they have sequestered, so costs continue to be incurred, but not new benefits that would justify further payments.
3. It is costly to measure the amount of carbon stored in soils. Regular soil testing is needed to confirm that carbon has been sequestered (indicating that a payment is justified) but the current cost of testing probably outweighs any benefit of the program.
4. The process of storing carbon in the soil also ties up other nutrients (nitrogen, phosphorus and sulphur) that would otherwise be available to plants. The cost of replacing these with fertilizers (or the loss of yield if they are not replaced) further reduces the benefits of the whole approach.
To these, I would now add two more problems.
5. One of the main methods being suggested for increasing soil carbon is converting land from crop production to perennial pastures. (It is the one practice that is highlighted on the Government’s Soil Carbon web page.) Not only would switching to perennial pastures be substantially less profitable for many crop farmers – a far greater drop in profit than can be offset by any plausible carbon payment – but it will actually increase emissions overall, at least with current technologies. What farmers do with pastures is use them to run livestock, and methane emissions from livestock are a bigger concern than emissions from cropping. Sooner or later, governments will realise this and they will rule out making any payments unless livestock are excluded from the pastures, which will make the approach a non-starter for farmers. Scientists have been working on ways to reduce emissions from livestock for at least 20 years, but there doesn’t yet seem to be a practical solution.
6. Australia has regular droughts. When there is a drought, carbon is released from the soil. In principle, farmers would need to pay back an amount to cover the losses. Politically, that will never happen, but we will still need to account for those losses when we report internationally. That will surely put a dampener on the Government’s enthusiasm for continuing the policy at that point.
The Technology Investment Roadmap that I mentioned has an objective of reducing the cost of testing soil carbon from $30/ha to $3/ha. This is described in the document as a “stretch goal”, which I suspect means it is just a number out of the air, without any particular basis for thinking that it can be achieved. But even if it can be achieved, it only addresses one of the six problems I’ve summarised above.
I worry that a lot of farmers are being misled into thinking that there are great financial opportunities here. I think there is only one way that farmers could benefit, and that is if the government designs its policy extremely badly such that farmers get paid more than is justified by the amount of new carbon that is being sequestered. That could happen, but then it would not be a climate policy but a farmer subsidy policy.
24 thoughts on “346. Soil carbon is a highly flawed climate policy, Part 1”
I’m in the U.S. Midwest and most farmers and soil scientists think of increasing the organic matter in the soil as a win-win. It is better for agricultural production as well as for the environment and farmers regularly get soil tests that they pay for in order to optimize nutrient management, etc. Given your climate it might be harder to increase organic matter but it seems that that might be exactly why farmers would benefit from some increases. I think that it might be that after some point, there are no further benefits to farmers of increased carbon sequestration and costs would thus increase but I think some of the problems could be mitigated by careful policy design.
Thanks Laura. Unfortunately I don’t believe the problems can be sufficiently mitigated. In next week’s post I make a case that it is all but impossible to solve the problem by careful policy design.
In the example you mention, if it really is a win-win, then there is no additionality and the optimal payment to encourage it is zero, because farmers will take steps to increase their soil carbon even without a payment to encourage them.
Nice piece Dave. It aligns well with my own less-informed view.
On trivia please fix spelling of phosphorus. Best & Cheers, Jock
Thanks Jock. Spelling fixed. Having done an agricultural science degree, including soil science and plant nutrition, I should have known how to spell phosphorus!
Readers are referred to any of the videos by soil scientist Walter Jehne on Youtube concerning the ‘soil carbon sponge’ for the other side of this discussion. Briefly, soil needs organic matter to encourage growth of fungal mycorrhiza (microscopic whispy filaments) that wrap around the soil particles and release the nutrients bound to them, thereby making them available to plants. This relationship between fungus and photosynthesizing plants has been enabling plants since they moved from the sea to the land in evolutionary terms – the fungus release the nutrients for the plants, the plants gather the energy used by the fungus. That’s why we add manure to soil to improve growth. The economic and “carbon credit” aspects of soil carbon are just an administrative diversion from one of the basic processes of terrestrial ecosystems. Plant growth cools (by transpiration) and preserves soils (by shading, re-nourishing, and improving permeability to rain). It would be a shame if present day economics and policy discourages these essential long-term processes.
As for the climate: – on a hot sunny day, compare with your hand the temperature of a forest path with that of an exposed, hardened paddock or beach, sometimes too hot to walk on barefoot!
Hi John. I’m not saying there are not agricultural benefits from having carbon in soils. I’m very specifically talking about payments to encourage farmers to increase soil carbon as a means of mitigating climate change. The point is that, if those payments accurately reflect the reduction in CO2 in the atmosphere THAT RESULTS FROM THE PAYMENTS, the payments will be very small.
In some situations, the benefits in terms of increased agricultural production as a result of increasing soil carbon might be so large that the actions that deliver higher soil carbon are worth farmers undertaking them even without a payment. In Australia, that is true of no-till. But that means that farmers will adopt them anyway. In that case, any payment makes no difference to adoption, it just becomes a pure subsidy. Assuming that the government is actually trying to address climate change, rather than just subsidise farmers, then that payment would be halted.
I wholeheartedly agree. This policy is only a crowd pleaser for some Ill-informed. Paying to save tropical forests, as foresaw under Howard Government policy rates well in comparison. Systems thinking makes it clear that the theory of limiting factors are at play. When moisture deficit leads to a productivity trap what is the source of extra carbon? The policy completely ignores the additionality principle that should drive these policies. However, when the opportunity cost of funds is zero for those who allocate funds – as it is borne by the future tax payers- the policy will please those who receive the transfers and those who provide the services to implement the policy. Not to mention rural votes.
Very timely post. It reinforces my cynical judgement formed after many years of watching the COALition Government avoid/evade/shun a carbon tax, namely if it is a climate policy advocated by the present Government the presumption has to be that it just political spin paid for by the carbon lobby and rubbish.
Fortunately the states are doing more as is business. But watch the COALition spin and claim credit for whatever emissions reductions the actions of others achieve.
Hi David. Thank you for revisiting this and providing a sound summary. While acknowledging that economics is strong driver for land use change, I am glad that you also acknowledge the co-benefits to soil health / soil condition when aiming to capture and store carbon in our agricultural soils (noted in a response to another commentator). In my opinion improvements in the condition of our soils from increased biomass cover and organic carbon content will be the overall winner, protecting our soils from the challenges of seasonal land / soil degradation, etc. A further comment to add re this carbon story in Australia is the goal to get the permanent (or recalcitrant) carbon fraction deeper into the soil profile – a major challenge for many Australian landscapes and biota. Cheers, Tim O
Hello David. Nice piece with which I agree. One problem is that, a one-time return to regular tillage, will release most of the carbon stored. Another is this: We did a meta-analysis on soil carbon in agriculture (Climatic Change 68(2005): 41-65. We found that conventional tillage actually could sequester more soil carbon than conservation tillage depending on how deep one measured the carbon. It would do justice to redo the meta-analysis. Following Jock, you need to correct “mislead” to “misled”. Kees
Many thanks Kees. In Australia, almost all crop farmers use no-till already, so that’s not the focus of policy here. There is a lot of interest in regenerative agriculture, which seems to be about livestock farmers changing their grazing management (and other things) to increase biodiversity and soil carbon. If the farmers who adopt regenerative agriculture were already livestock producers, that seems fine, but if they were croppers before, that would be a step backwards from a climate-change perspective.
People confusing led and lead is one of my pet peeves, so it’s pretty embarrassing to mess it up myself! Thanks for noticing.
@David, thanks for summarising these arguments against the value of paying for soil carbon sequestration and I understand that you are making these arguments in an Australian context. You will be aware that in Europe the European Commission has described carbon farming in its Farm to Fork Strategy as a new business model and plans a new carbon farming initiative (by end 2021) and a regulatory framework to certify carbon removals. It has just published a Technical Guidance Handbook on on how to set up and implement carbon farming in the EU (links via https://ec.europa.eu/clima/content/carbon-farming_en). Whatever about the difficulties around monitoring, permanence, saturation and additionality with respect to mineral soils, there does seem to be good potential to sequester carbon by rewetting drained organic soils and restoring peatlands, of which there is a lot in northwestern Europe. Problems here seem to be more the collective action issue of getting a group of farmers in an area to buy into the project.
Hi Alan. Thanks for responding (and Tweeting). I wasn’t aware of these specific policy developments in the EU. That’s a very interesting and quite a good report (although I have some reservations – see below).
Re-wetting and restoring peatland is very different from the sorts of farming options I’m focusing on here. It is more of the nature of reducing emissions, rather than increasing sequestration. I know little about peatlands, but from a quick bit of reading, it is clear that the potential to reduce emissions is large. If the policy could be designed well, maybe it could work in that context.
The web site you linked to does include reference to the sorts of farming practices that make me much more worried, specifically “Enhancing soil organic carbon in depleted arable land, which also improves the productivity and resilience of farming activities”. It’s much more difficult to see a policy with that focus working out as a cost-effective contributor to mitigation of climate change.
The Technical Guidance Handbook is, in many respects, a very good report. It identifies a daunting list of challenges to making the policy work (e.g. in Box 1), and then reading what they say about the challenges, it is clear that they will be formidable. But then the authors become remarkably complaisant about them. In their “Overall conclusions” on page 148, they start with “Despite the challenges, …” and then say no more about them. I think they should have been highlighting the challenges, not skipping over them.
All of the challenges they identify will be difficult to address, but I’m especially worried about additionality – perhaps not on peatland but definitely on arable land. I’ll spell out my concerns in the next PD, but for now I’ll comment on their two suggested approaches for assessing additionality. (a) “If additionality is to be achieved and demonstrated, then it will be important that the scheme allows for the measurement of the baseline at the start of the scheme’s period of operation.” For arable land, that will not work. Management of arable land is constantly changing over time. Just like in Benefit: Cost Analysis, the relevant comparison is with-versus-without the policy, not before-versus-after the start of the policy. But you cannot observe the without-policy scenario once the policy is in place. (b) “the additionality of a restoration project can be determined by an assessment of its profitability in the absence of climate finance but with the access to CAP pillar 1 payments.” For this approach to work, you would have to do detailed financial analysis of each farm at periodic intervals. Surely the cost of doing that would be prohibitive. I would also have serious doubts about the reliability of the results, knowing how easy it is to manipulate this sort of analysis to get a desired result.
Thanks for response, Dave, I will look forward to your Part II.
Thanks for very helpful paper. Table 2 on p28 of the EU technical guidance seems like a good summary of where we are just now. Let’s hope we don’t stumble into a get rich quick scheme just because there’s so much money looking for a home.. remember biofuels seemed like a plan once
Dave raises an important point about methane emissions from livestock reducing the GHG abatement potential of permanent pastures. They also reduce the abatement potential of permanent pastures compared with cropping. There is surprisingly little information on this topic. We looked at the extent to which emissions from livestock reduce the soil C sequestration benefits of permanent pastures in Australia and, as Dave suggested, grazing really reduces/negates the benefits.
Meier et al (2020) Simulated greenhouse gas emissions from cropped lands match those from permanent pastures after accounting for livestock emissions. Frontiers in Sustainable Food Systems 3, paper 121 doi: 10.3389/fsufs.2019.00121
Thanks Peter. I had not seen that paper. Very relevant and useful!
Very interesting David, thank you. I would question the assumption that you – and many before you – have made about the harmful effects of grazed livestock.
1. For every kg of carbon they emit into the atmosphere, a kg of carbon has been removed from the atmosphere by the photosynthesising plants. Most people forget there are two sides to the equation
2. They emit the carbon as methane which breaks down after c.10 years to carbon dioxide, to be reused by the grass plants
3. There were as many enteric-fermenting (ie methane-emitting) animals on the planet 100m years ago as there are today. Atmospheric methane levels from animal sources are no higher today than they were then (due to point 2, above).
4. Price fluctuations and supply and demand mean that livestock are switched out of CAFO systems and into grass-based systems, rather than being “extra” animals in the meat production chain. The reduction in fossil fuels needed to produce a kg of protein under a grazing system compared to a CAFO system (no feed to grow, harvest, transport, no bedding to grow, harvest, remove and spread), plus the additional sequestration of carbon you referred to, means there is a real reduction in net emissions gained from the switchover.
A beautiful side benefit is that such properly managed grazed areas are wonderful for wildlife too, from the lowliest creatures to the top of the food web.
Thanks for the comments Tom. Let me respond to each of those issues.
1. That is true, but the two carbons (on each side of the equation) are not equivalent. In the form of methane (emitted by livestock), it is approximately 25 times more potent as a cause of climate change. The way they calculate CO2 equivalents is certainly open to question/debate, but the difference in potency is so large that there is a lot of room for adjustment without changing the core point that methane is much worse for climate change than the CO2 it originally came from.
2. That is true, but the calculation of CO2 equivalents accounts for that. The 25 number is for a time frame of 100 years, and it accounts for the fact that methane only lasts about 10 years in the atmosphere.
3. That could be true, but it is irrelevant. It doesn’t change the fact that new methane emissions today add to the other emissions (from non-agricultural sources) to give us a climate problem.
4. This point could be relevant to some degree in some cases. A scheme that rewards switching from crop to pasture results in animals being grazed on that new pasture. But this is embedded in a complex interconnected system of supply and demand with multiple moving parts. The scheme lowers the marginal cost of grass-based production, so it moves the supply curve for that segment of the market vertically down. This results in a new aggregate supply curve (grass-based plus non-grass-based) that is lower than the original aggregate supply curve, leading to a lower market price and somewhat higher overall production of livestock products. The lower market price means that non-grass-based-production would be reduced to some degree, so in aggregate there would be partial substitution of grass-based for non-grass-based production. It would not be one-for-one. The final equilibrium level of increase in emissions would depend on the elasticity of demand, the elasticity of supply for grass-based production, the elasticity of supply for non-grass-based production, and the size of the shift in supply. Importantly, for a country that exports animal products, demand would in most cases be highly elastic. That means that the scheme would have little or no effect on price, and therefore little if any substitution between non-grass-based and grass-based production. Almost all of the production increase would be from newly bred animals, not from animals switched out of CAFO or other non-grass-based systems.
The comment about wildlife is interesting. Perspectives on this vary in different places. In Australia, we would not usually consider pastures as making any contribution to biodiversity conservation. The focus for that is primarily on habitat provision by native vegetation not being used by agriculture. I can see that you’re based in the UK, where appropriately managed pasture is seen as making a contribution to biodiversity. I suspect the difference results from differences in the length of time that European-style agriculture has been operating and the persistence (or not) of large areas of original native vegetation.
Well done David . The points you build on are sound . I sought to get my old university to say exactly what you have said over 15 years ago , They didn’t do that but took the money and finally after spending it ,said what you are saying . As you well know but our parliament does not , these false political expectations are discouraging competent decision making and productive soil science research in this country .
What, then, about regenerative agriculture projects whose entire purpose is to refertilize arid and otherwise unusable land? The untapped potential is MASSIVE, both from a carbon capture standpoint, but also in terms of increasing biodiversity, food security, and so on.
The title of this article is critical of soil carbon solutions as a whole, when you’re only really considering soil carbon as it relates to existing farming operations.
Some regenerative agriculture projects such as Greening the Earth focus on using hardy, desert-evolved plant species to restore fertility to drought-afflicted land. There are millions of square kilometers in the Australian outback which meet the requirements for implementation of these projects. Is there a single good reason not to push ahead in this direction? We can address atmospheric carbon, climate, food security, create jobs, etc etc all at the same time, without even interrupting the operations of a single Australian farmer.
Thanks Ed. The issues I raise in this post are also relevant to regen ag. It doesn’t mean regen ag itself is not a good idea. It just means that the existence of a soil carbon policy is going to make little difference to the amount of soil carbon sequestered by regen ag. I’ve addressed the issues in more depth in post number 371 and in a webinar you can see in post 374.
Hi David, I’m a little late to the party on this one. But I did have a question for you related to …. “but once farmers change their management to increase soil carbon, it increases up to a new equilibrium level after about 20-30 years and then stops.”
How does this relate to depth of topsoil? Are you referring to equilibrium reached within a certain depth profile of topsoil? i.e. equilibrium in the top 10cm?
I read a lot about “building” topsoil up and up, which challenges the notion of soil having a max SOC carrying capacity per Ha. Sure it may have a max % SOC, but does it have a max net SOC per Ha?
With improved soil (chemical, biological and physical) wouldn’t the assumed max SOC% capacity first be achieved in the top 10cm, then slowly work it’s way deeper and deeper into the soil profile.
Keen on your thoughts / recommended resources on this topic in particular? Cheers
My understanding is that the measurements that show saturation of soil C are for more than the soil surface. e.g. in Hoyle et al. (20130) they go to 30 cm, which seems to be pretty common.
A soils specialist could probably give more detail, but here is some literature to get you started.
West, T.O. and J. Six. 2007. “Considering the influence of sequestration duration and carbon saturation on estimates of soil carbon capacity.” Climatic Change 80(1): 25–41.
Stewart, C., K. Paustian, R. Conant. 2007. “Soil carbon saturation: concept, evidence and evaluation.” Biogeochemistry 86(1): 19–31.
West, T. O., Marland, G., King, A.W., Post,W. M., Jain, A. K., & Andrasko, K. (2004). Carbon management response curves: Estimates of temporal soil carbon dynamics. Environmental Management, 33, 507–518. doi:10.1007/s00267-003-9108-3
Hoyle, F. C., D’Antuono, M., Overheu, T.,& Murphy, D. V. (2013). Capacity for increasing soil organic carbon stocks in dryland agricultural systems. Soil Research, 51, 657–667. doi:10.1071/SR12373