Estimating carbon capture in perennial crop systems

I think it's pretty clear that perennial agricultural systems can sequester more carbon than the alternatives, at least when done properly, but something is emerging from my own thinking on an attempt to conceptualise these systems, which is how we go about measuring, or at least presenting decent range estimates, for our ecosystems, which can then be used to calculate balances against other factors (for production and delivery of inputs using fossil fuels, CH4 and CO2 output by any ruminants and other livestock and so on).

One of the reasons agriculture is in the mess it's in is because farmers and others made assumptions that turned out to be wrong (or were just flat out lazy and short-sighted), but we are in a position where we can't afford to make such mistakes.

Clearly some systems are going to be better than others from a carbon perspective. How do we quantify it? How do we know our management regime is in some sense optimised (perhaps for carbon; perhaps for multiple functions)? This means we can then compare management in Patch A with that in Patch B (with, of course, the additional headache of the interactions between Patch A and Patch B, but let's leave that to one side for the moment).

There are also some wild and inaccurate claims being bandied around (see, for example: http://www.realclimate.org/index.php/archives/2013/11/cows-carbon-and-the-anthropocene-commentary-on-savory-ted-video/, and remember, of course, the ambiguous mess that was biochar).

In terms of rangelands, can we produce more protein/more food and lock up more carbon by the creation of food forests and turning the rest back over to the wolves and bison, perhaps with greater biodiversity? These are the kinds of questions we need to be answering.

As this article http://virtualorchard.net/IDFTA/cft/2000/july/cftjuly2000p82.pdf makes clear, even estimating carbon capture from a simple orchard is tricky enough:

"Whole-canopy photosynthesis depends on leaf photosynthetic rates, whole-canopy light interception and leaf area. These factors are in turn influenced by crop characteristics (genetics, stage of development), environment (light, temperature, water relation, carbon dioxide concentration) and cultural practices (nutrition, irrigation, pest management)."

Even in cases where we can measure soil carbon we'd need to work out what management practices were responsible for any changes (cover cropping (and which crops were used), changes in tilling regimes, presence and types of fungi present, type and intensity of grazing regimes, and so on).

Even if we can work out the photosynthetic yield of the habitat, and then subtract any food yield taken off site and lost, as this paper shows http://www.symbio.co.uk/files/Independant%20Research%20Papers/Arbuscular%20Mycorrhizal%20Fungi%20Lei%20Cheng%20et%20al%202012.pdf (summary: https://www.newscientist.com/article/dn22228-fungi-could-thwart-carbon-capture-efforts/) arbuscular mycorrhizal fungi can become a carbon source, not a carbon sink in the soil.

The list of variables goes on. I suppose what we need to know is what we need to measure and how we go about measuring it, without necessarily having access to a lab.

I'm in danger of getting distracted from what I was concentrating on and just getting sidetracked. I don't know, so I'm going to ask the question, and shut up and listen.

Neil Layton wrote:
In terms of rangelands, can we produce more protein/more food and lock up more carbon by the creation of food forests and turning the rest back over to the wolves and bison, perhaps with greater biodiversity?

From what I have read, forests are the most efficient system we know of for sequestering carbon. The North American Prairie ecosystem, a very special type of ecosystem, may have been equal or superior to forests - however, I think people too often confuse the prairie with "rangeland" or any other grassland when it was not that, it was a very particular confluence of factors which produced an ecosystem with biodiversity second only to the Brazilian rainforest. I don't think people just anywhere there is grassland can hope to emulate this prairie system without an awful lot of work and very different ideas about the place of humans in the ecosystem. I'm not convinced you can have a prairie without the factors which created it; particular rainfall, bison, wolves, fire, and (possibly) semi-nomadic humans. The present culture in North America is antithetical to this system. Even many permaculturists appear to be antithetical to this system, because they don't tolerate the presence of predators, and they certainly don't want to be nomadic or semi-nomadic. Could something like a prairie be created with cows and settled humans? Maybe, but I'm not convinced it would become such a vast carbon sink, certainly not in the short period that we need to create such sinks. Most of the prairie region "wants" to become forest - this is the case where I am at the Southern end of the prairie, where all the land is growing into low forest after having been overgrazed by domestic livestock for over a century. It would take a lot of work to change this forest back to prairie, and I think it might reverse the good work the forest is doing to capture carbon. This isn't to say that managed grazing systems are a bad idea, if people insist on raising cattle; I'm just not convinced we can assume they will be as efficient at capturing carbon as forests are.

This is probably more opinion and less technical a response than you wanted.

While personally I prefer to not 'science the hell out of' this subject (to quote from The Martian), I think it's a worthy question, especially for those brave souls focusing on communicating this to a science-addicted world. (And to be clear, I'm not anti-science, but also wary of the use of 'science' as a weapon (to quote Paul Wheaton).)

Mostly in response to Tyler:

After reading Savory's book Holistic Management, I see the suggestion to use electric fence as an analogue to wolves as predators as a very promising option to assist in re-creating something like a prairie ecosystem, in regions that it's a appropriate to do so. In terms of the actual numbers - I look forward to browsing Eric's new book. Apparently the science so far is pretty inconclusive, especially on grazing.

Incidentally, Holistic Management is actually a decision-making system more than anything else - and as such, even for those who don't intend to raise animals at all, is an approach very complimentary to permaculture.

My inclination is to science the hell out of most such questions, even while I recognise that ecology is a very squishy science. I'd much rather have some good, generalisable studies than someone's opinion. The application of opinion and poorly thought out assumptions is what got us into this mess in the first place. I'm quite happy to "use science as a weapon" if it's going to stop us from doing something else completely stupid.

In response to Tyler, I've heard it suggested that one of the reasons for the so-called Little Ice Age in the nineteenth century was the removal of millions upon millions of ruminant methane-belching bison and the regeneration of woodland after the removal of all those grazers. I can't find the source (anybody?) or any good science backing up the assumption, so take that with a pinch of salt, please.

Is the answer, then, to remove the grazers and create food forests and otherwise allow succession to some sort of semi-natural woodland? Are there studies?

Tyler Ludens wrote:From what I have read, forests are the most efficient system we know of for sequestering carbon. The North American Prairie ecosystem, a very special type of ecosystem, may have been equal or superior to forests - however, I think people too often confuse the prairie with "rangeland" or any other grassland when it was not that, it was a very particular confluence of factors which produced an ecosystem with biodiversity second only to the Brazilian rainforest.

For long term sequestration of carbon, I would guess that the most efficient systems for sequestering carbon are the systems in nature where we observe coal forming. Peat turns into coal with time and pressure, so peat bogs are probably the most efficient systems for sequestering carbon.

John Wolfram wrote:For long term sequestration of carbon, I would guess that the most efficient systems for sequestering carbon are the systems in nature where we observe coal forming. Peat turns into coal with time and pressure, so peat bogs are probably the most efficient systems for sequestering carbon.

Scotland's Flow Country (basically one huge peat bog) stores vast amounts of carbon. It's not much use for agriculture. You'd need to drain it, which would destroy the bog, releasing the carbon. It's not a solution.

I don't see it as that difficult to work out how much a tree captures Carbon.
We know that plants are mostly multiples of carbohydrates and water and we could measure how much a tree adds in weight a year and there fore how much carbon from this we should be able to have a formula giving the hight of a tree how much it grown and how much carbon it's added . This would work as long as the tree grows
It's some work but doable and expressed as an average you could then work how much a forest / orchard has captured
David
David

David Livingston wrote:I don't see it as that difficult to work out how much a tree captures Carbon.
We know that plants are mostly multiples of carbohydrates and water and we could measure how much a tree adds in weight a year and there fore how much carbon from this we should be able to have a formula giving the hight of a tree how much it grown and how much carbon it's added . This would work as long as the tree grows
It's some work but doable and expressed as an average you could then work how much a forest / orchard has captured
David
David

That would work for short term calculations of carbon sequestration, but for longer term view (~100 years or more) the carbon released when the tree rots needs to be considered as well.

I accept that which is why I mentioned while the tree is growing . I am willing to accept any Fruitwood furniture anyone may wish to donate as my own part in holding the carbon from the atmosphere

David

Neil Layton wrote:

Is the answer, then, to remove the grazers and create food forests and otherwise allow succession to some sort of semi-natural woodland? Are there studies?

I think the answer is to remove annual crop systems and replace them with perennial systems, which might include grazers, though browsers might be more appropriate in reforesting systems. In my region, better grazing management and management of native and exotic browsers could lead to a much more biologically diverse and productive landscape.

http://www.perennialsolutions.org/carbon-farming-practices

http://www.chiefscientist.gov.au/2009/12/which-plants-store-more-carbon-in-australia-forests-or-grasses/

John Wolfram wrote:
That would work for short term calculations of carbon sequestration, but for longer term view (~100 years or more) the carbon released when the tree rots needs to be considered as well.

I think the idea is that new trees grow upon the old trees. If the new trees capture all of the carbon released by the rotting old tree, then it can be considered sequestered, it seems to me.

John Wolfram wrote: peat bogs are probably the most efficient systems for sequestering carbon.

Are they efficient? How quickly do they sequester the carbon? How resilient are they to changing climate?

http://www.bayceer.uni-bayreuth.de/biogeomon2014/en/prog/bayconf/beitrag_detail.php?id_obj=11322

http://www.nature.com/ngeo/journal/v1/n11/full/ngeo331.html

Tyler Ludens wrote:

Neil Layton wrote:

Is the answer, then, to remove the grazers and create food forests and otherwise allow succession to some sort of semi-natural woodland? Are there studies?

I think the answer is to remove annual crop systems and replace them with perennial systems, which might include grazers, though browsers might be more appropriate in reforesting systems. In my region, better grazing management and management of native and exotic browsers could lead to a much more biologically diverse and productive landscape.

http://www.perennialsolutions.org/carbon-farming-practices

http://www.chiefscientist.gov.au/2009/12/which-plants-store-more-carbon-in-australia-forests-or-grasses/

In other words, yes there are studies, and forestry is clearly the way to go, with pasture tending to be pretty poor, even in ideal conditions. I do note there are massive ranges for the amounts of carbon stored, however, which brings me back to my question. Are there ways of estimating the amount of carbon captured on any given site?

What an excellent thread. These are exactly the kinds of questions I set out to answer in my book. I do provide lots of data from individual studies, scientific reviews, and expert estimations, estimate the sequestration rates above and below ground of a variety of farming systems. They vary widely between and within practices as you might expect. I also look at the long term soil carbon storage potential which also varies widely between practices.

The general trend is that systems with trees sequester more than systems without, both above and below ground. This goes for annual crops vs. annual crop agroforestry, pasture vs. silvopasture, and annual crops vs. perennial crops. Multistrata perennial systems (including the permaculture "food forest") are in the highest category.

Estimating the carbon in aboveground biomass is fairly simple and well – understood, in that about half of the aboveground biomass is carbon on a dry weight basis, and there are well – established methods of measuring and or estimating aboveground biomass. It's when you want to measure or estimate carbon in the soil that things become a bit more challenging. Scientists have yet to agree on a standard method for doing so, one even finds that studies are measuring 10 cm or 30 cm or a full meter or even to full meters. This makes comparison very difficult. Lots of the key people working on this understand that it is a key issue holding back the wider implementation and financing of carbon farming, and they are hard at work on developing standardized systems that will be both accurate and cost – effective. As far as I know we're not there yet though.

Eric Toensmeier wrote:Multistrata perennial systems (including the permaculture "food forest") are in the highest category.

I feel so validated. Thank you, Eric.

Eric Toensmeier wrote:What an excellent thread. These are exactly the kinds of questions I set out to answer in my book. I do provide lots of data from individual studies, scientific reviews, and expert estimations, estimate the sequestration rates above and below ground of a variety of farming systems. They vary widely between and within practices as you might expect. I also look at the long term soil carbon storage potential which also varies widely between practices.

Many, many geek points, Eric. (You can take that as the compliment it's intended as.)

Eric Toensmeier wrote:The general trend is that systems with trees sequester more than systems without, both above and below ground. This goes for annual crops vs. annual crop agroforestry, pasture vs. silvopasture, and annual crops vs. perennial crops. Multistrata perennial systems (including the permaculture "food forest") are in the highest category.

This suggests I'm thinking along the right lines. Good.

Eric Toensmeier wrote:Estimating the carbon in aboveground biomass is fairly simple and well – understood, in that about half of the aboveground biomass is carbon on a dry weight basis, and there are well – established methods of measuring and or estimating aboveground biomass. It's when you want to measure or estimate carbon in the soil that things become a bit more challenging. Scientists have yet to agree on a standard method for doing so, one even finds that studies are measuring 10 cm or 30 cm or a full meter or even to full meters. This makes comparison very difficult. Lots of the key people working on this understand that it is a key issue holding back the wider implementation and financing of carbon farming, and they are hard at work on developing standardized systems that will be both accurate and cost – effective. As far as I know we're not there yet though.

I think that pretty much answers the question. Thank you. I need to find out what those methods for estimating aboveground biomass are (which should be fairly straightforward) and keep an eye on the development of those standardised systems for soil carbon. That's very much appreciated.

Here are some links to methods of estimating standing carbon:

http://www.nrs.fs.fed.us/pubs/gtr/gtr_nrs88.pdf

https://www.broward.org/NaturalResources/ClimateChange/Documents/Calculating%20CO2%20Sequestration%20by%20Trees.pdf

https://www3.epa.gov/climatechange/Downloads/method-calculating-carbon-sequestration-trees-urban-and-suburban-settings.pdf

I think that MOST plant have the same sunlight to carbohydrate conversion ratio.
The difference is what type of carbohydrate aka how fast it breaks down (simple glucose, simple starch, complex starch, cellulose, lignin, etc).
Next is what happens to the eaten carbohydrate.
If it is used mostly to fuel non-moving fungi then, then it gets saved as bio-mass almost an extension of the tree roots
Instead if it is used by birds to fly, then most of it gets used up for motion and less gets stored as bio-mass.

So if we want to store carbon:
Long lived trees vs annuals (carbon stored as living primary bio-mass)
Trees that create the most dense, hardest to digest carbohydrate (carbon stored as dead primary bio-mass)
Plant eaters that move the least (fungi vs bird)
Plant eaters that trade the most (fungi/nitrogen-fixing bacteria)
Plant eaters that create the most favorable environment for plants to grow long term long-term.

You star, Tyler. That's a useful resource for any of us planting trees.

Tyler Ludens wrote:

John Wolfram wrote: peat bogs are probably the most efficient systems for sequestering carbon.

Are they efficient? How quickly do they sequester the carbon? How resilient are they to changing climate?

The Carboniferous period is known for its swampy peat bogs, so I would say they are fairly resilient to a warming earth with high CO2 levels. Speed and efficiency of carbon sequestration really seems to be dependent on the time scale you are talking about. With the right time scale / time period,* a strong argument could probably be made that mono-crop corn is the fastest way to sequester carbon.


***The time scale = 1 week
The time period = The last week in July.

John Wolfram wrote: I would say they are fairly resilient to a warming earth with high CO2 levels.

Or not:

"In our long-term simulation, an experimental warming of 4 °C causes a 40% loss of soil organic carbon from the shallow peat and 86% from the deep peat."

http://www.nature.com/ngeo/journal/v1/n11/full/ngeo331.html (repeating link above)

Tyler Ludens wrote:

John Wolfram wrote: I would say they are fairly resilient to a warming earth with high CO2 levels.

Or not:
"In our long-term simulation, an experimental warming of 4 °C causes a 40% loss of soil organic carbon from the shallow peat and 86% from the deep peat."
http://www.nature.com/ngeo/journal/v1/n11/full/ngeo331.html (repeating link above)

Or so...

The carbon people are worried about sequestering wasn't originally put deep into the ground by prairies. It was put there by bogs and swamps. Computer simulations are nice and all, but observing what nature has actually done is better.

Carboniferous coal was produced by bark-bearing trees that grew in vast lowland swamp forests. Vegetation included giant club mosses, tree ferns, great horsetails, and towering trees with strap-shaped leaves. Over millions of years, the organic deposits of this plant debris formed the world's first extensive coal deposits—coal that humans are still burning today.

http://science.nationalgeographic.com/science/prehistoric-world/carboniferous/

John Wolfram wrote: It was put there by bogs and swamps.

Can we talk about the practicality and efficiency of sequestering carbon in bogs and swamps? Is it actually occurring now, or are we losing carbon from swamps? Conditions during the Carboniferous period were very different from what we have now, and it took, as you point out, millions of years for those deposits of carbon to form. What is the practical benefit of talking about the Carboniferous period now? Is it suggested that we create vast bogs and swamps in which to sequester carbon?

@John; @Tyler

Can I first make the point this is off topic?

Secondly, I become very suspicious whenever someone raises the subject of the Carboniferous in any discussion related to the subject of climate change.

All too often it's someone attempting to cast doubt on the severity of the problem we face by drawing false comparisons with the climate situation during the Carboniferous, a period in which CO2 levels dropped from roughly 4000 parts per million by volume to around the current 400, and average global temperatures dropped relatively slowly (over millions of years) from around 20C to around 12C.

This ignores the extreme rapidity with which human activity is adding greenhouse gases to the atmosphere, which is unprecedented in at least tens of millions of years, and is likely to lead to climate disruption and the kind of severe pressure on ecosystems that results in a major extinction event, with massive impacts on agriculture.

Discussion of the Carboniferous simply isn't relevant, because conditions were different, and the decline in greenhouse gases happened much more slowly - many millions of years - than the rate at which we are pumping them back in. Plants ("giant club mosses, tree ferns, great horsetails, and towering trees with strap-shaped leaves" that are extinct) during the Carboniferous were adapted to warmer temperatures, higher levels of humidity, weaker sunlight and higher carbon dioxide levels than are plants today.

The question is not whether we are in trouble, but how much trouble we are in, and what we can do about it - and the point of this discussion is to address the question of how we measure the success of what we are doing about it.

Methods for estimating aboveground biomass are helpful. Raising false comparisons and jumping to conclusions is not helpful. It's derailing the conversation.

So it looks like the evidence indicates that forests are far more efficient at sequestering carbon than any other system. How can we encourage more people to plant or allow more forests to grow? Even on permies, for example, how can we encourage people not to clear their forests for pasture? What specific models can we offer that allow them to pursue their goals of farming, while allowing the maximum amount of forest to grow?

I think we need to give more value to wood as a fuel / crop / resource so farmers have more economic benefit from farming wood .
The more I think about this the more I think this great topic should be it's own thread
How about it Tyler fancy starting a new thread ?

David

Tyler you might take a look at Brett Chedzoy of Angus Glen Farm, he's done some very nice work on converting secondary forest to silvopasture. he says that you have two choices with the secondary forest ( relatively young regrowth of relatively low quality), first you could preserve your best trees for future timber use and manage the rest for firewood. The other option is to keep the good quality trees as in the first option, but thin out the rest and seed in shade – tolerant pasture species for conversion to silvopasture. quite interesting.

Eric Toensmeier wrote:The other option is to keep the good quality trees as in the first option, but thin out the rest and seed in shade – tolerant pasture species for conversion to silvopasture. quite interesting.

To me this looks like encouraging pasture rather than encouraging forest.

Here's a thread in which I hope we can discuss how to encourage farmers to choose forest systems over pasture systems: https://permies.com/t/54801//Encouraging-forests

Eric Toensmeier wrote:Tyler you might take a look at Brett Chedzoy of Angus Glen Farm, he's done some very nice work on converting secondary forest to silvopasture. he says that you have two choices with the secondary forest ( relatively young regrowth of relatively low quality), first you could preserve your best trees for future timber use and manage the rest for firewood. The other option is to keep the good quality trees as in the first option, but thin out the rest and seed in shade – tolerant pasture species for conversion to silvopasture. quite interesting.

Presumably this assumes the objective is pasture of some description?

By my understanding of what we discussed above, using the existing canopy for shade-grown crops would sequester more carbon, and would not have the secondary effects of livestock on the climate?

I mean, ecosystems without human intervention would have grazers or browsers of some description, but that doesn't change the fact that livestock are a major contributor to GHG emissions, whether they are stalled or pastured. This article contains some interesting conclusions, including the fact that the higher the amount of carbon in the soil, the greater the quantities of GHG released when it's grazed, and the fact that GHG emissions from pastured livestock can be surprisingly high: http://www.monbiot.com/2015/12/22/sacrifice/

just to be clear: there are ways to raise livestock that have a net sequestration and net mitigation impact. AND most of us in the wealthy countries need to eat much less meat in order to have a better climate impact. My personal proposal is as follows. Stop feeding the annual grains to livestock (one third of all annual cropland goes to feed livestock and annual cropland is a huge part of the problem); produce livestock on the land not suited to annual agriculture (too steep, too rocky, too remote); convert pasture to silvopasture wherever there is sufficient water to allow this; manage the remaining grasslands with holistic raising and other managed grazing practices. Note that scientists do not yet remotely agree on whether or how this sort of manage grazing is possible and whether it is appropriate on all kinds of grasslands.

Eric Toensmeier wrote: produce livestock on the land not suited to annual agriculture (too steep, too rocky, too remote)

I hate to be a nit-picker, but this may give the impression that it's appropriate to raise livestock on steep, remote land. It's my understanding that steep land should be in forest, because livestock can damage steep land, especially under conditions of alternating drought and flood that we're likely to experience more of in the future. From a permacultural point of view, remote land should be left to wild nature (Zone 5). Of course I'm not talking about the few peoples who live in remote places who depend on raising livestock on steep terrain because that's all there is, I'm talking about the bulk of the human population and how we get our food.

Eric Toensmeier wrote: just to be clear: there are ways to raise livestock that have a net sequestration and net mitigation impact. AND most of us in the wealthy countries need to eat much less meat in order to have a better climate impact. My personal proposal is as follows. Stop feeding the annual grains to livestock (one third of all annual cropland goes to feed livestock and annual cropland is a huge part of the problem); produce livestock on the land not suited to annual agriculture (too steep, too rocky, too remote); convert pasture to silvopasture wherever there is sufficient water to allow this; manage the remaining grasslands with holistic raising and other managed grazing practices. Note that scientists do not yet remotely agree on whether or how this sort of manage grazing is possible and whether it is appropriate on all kinds of grasslands.

I'm not seeing this, Eric. We're agreed on feeding grain to livestock. That has to stop.

Plants convert carbon dioxide and water into sugars, complex carbohydrates and proteins. Animals eat the plants, and convert around 90% of that consumed biomass back into carbon dioxide and water. How can you conceivably get net carbon sequestration from this process?

The only process I can see is that you are then left with biomatter which has an increased biological availability (i.e. manure) which I suppose could accelerate the activity of microorganisms and improve soil fertility, at least over the short term, but many of those microorganisms also convert soil carbon into CO2 and CH4.

I don't see how this could possibly counterbalance the GHG emissions by the livestock.

There have been some, shall we say, wild and inaccurate, claims over this, that don't seem to stack up mathematically: http://www.realclimate.org/index.php/archives/2013/11/cows-carbon-and-the-anthropocene-commentary-on-savory-ted-video/

It looks to me like you are advocating "holistic management" while acknowledging that "scientists do not yet remotely agree on whether or how this sort of manage grazing is possible and whether it is appropriate on all kinds of grasslands." If scientists don't agree on whether it's even possible, never mind appropriate, why advocate it? I'm seeing people on here who seem to be bringing it down to "intensive systems bad, mob stocking good". At best the latter seems ambiguous, at worst simple wishful thinking.

Even Savory's original trial involved substantial supplementary feeding (which brings us back to feeding annual grains to livestock, on which we're agreed).

As for producing livestock on land not suited to agriculture, surely this is taking land in what permaculturalists call zone 5, and producing more methane and CO2 in a means that is as inefficient as you can possibly get for producing food (see the Monbiot link above)?

Neil Layton wrote:
As for producing livestock on land not suited to agriculture, surely this is taking land in what permaculturalists call zone 5, and producing more methane and CO2 in a means that is as inefficient as you can possibly get for producing food (see the Monbiot link above)?

This is what jumped out at me. It seems to me that we should be withdrawing production from marginal lands and returning those to wild nature. We don't need to produce food on them, so why do it? There are a few peoples who depend on pastoralism on marginal lands as their traditional way of life, but the majority of humans don't get their food that way, and I feel strongly that we should not advocate it.

Oops - removing my post in case it belongs in the cider press (was "doubting" science as the right tool for any of this) - I don't want to cause problems