by Judith Curry
Some interesting new ideas about the role of soils, farming and livestock in fighting global warming.
For context, here are some previous posts on this topic:
- Livestock’s long shadow
- Soil carbon: permanent pasture as an approach to CO2 sequestration (by Robert Ellison)
Summary of the problem
From an article We can reverse climate change by the way we grow food:
The overall global food system — including land-use changes, feed, fertilizer, transportation, refrigeration, processing and waste — is estimated to be responsible for 30 to 50 percent of global greenhouse gas emissions. Over the last decade, agricultural emissions have increased by approximately 1 percent per year.
Researchers at the World Bank Group estimated intensive livestock production alone is the largest single contributing factor to climate change. Industrial animal agriculture is also one of the largest polluter of air, water and land, and the largest consumers of fossil fuels and water and yet feed only a relatively small percentage of the world’s population, compared with those fed by small-scale farmers who continue to be the major producers of the world.
Healthy soils store vast quantities of atmospheric carbon. Improving soil health is therefore an integral part of reversing CO2 levels.
Regenerative Organic Agriculture and Climate Change
From the same article:
According to cutting edge agricultural research, including that outlined in the Rodale Institute’s white paper, Regenerative Organic Agriculture and Climate Change, “recent data from farming systems and pasture trials around the globe show that we could sequester more than 100 percent of current annual CO2 emissions with a switch to widely available and inexpensive organic management practices, which we term “regenerative organic agriculture.”
As well as sequestering carbon, regenerative organic and agro-ecological systems can mitigate the chaotic effects brought about by climate change, such as flooding. Healthy soils have structure that allows them to retain large quantities of water. This structure not only holds soil in place preventing erosion, it also allows plants to be more tolerant of weather extremes. Regenerative systems increase the amount of carbon in soil while maintaining yields. In fact, research shows that yields under organic systems are more resilient to the extreme weather which accompanies climate change.
Conventional agricultural practices have resulted in a loss of 30-75 percent of original organic soil carbon, as well as being heavily reliant upon synthetic fossil fuel-based nitrogen fertilizer, mono cropping and toxic pesticides. Regenerative, organic agriculture on the other hand refrains from using fossil-fuel based inputs and instead utilizes cover crops, integrated pest management systems, residue mulching, composting, and crop rotation, and conservation tillage. Organic agriculture also uses 30-50 percent less fossil fuel energy than industrial farms.
Growing wheat might help fight climate change
Civil Eats has an article If grown right, wheat might help fight climate change. Excerpts:
Conventional farming usually gets a bad climate rap. But a new paper, published today in the journal Nature Communications, offers a slice of good news. The study found that a combination of a few basic farming practices boosted wheat production and put heaps of carbon back into the soil–more than enough to compensate for the GHGs emitted in the process of growing it.
Roots and stems left in the ground at the end of the growing season return carbon to the soil, offsetting emissions. That means reducing the climate impact of wheat hinges on maximizing soil carbon storage and minimizing inputs, all while growing as much grain as possible.
As it turns out, keeping crops in the ground as much as possible, rather than letting fields lay fallow, played an important role in decreasing wheat’s carbon footprint. Fallowing leads to the loss of carbon-rich organic matter–bad for soil and for climate–and produces less food.
On the other hand, planting fields continuously requires more carbon-intensive inputs, like fertilizers and pesticides. That’s where the lentils come in. Lentils belong to a class of plants called legumes that can convert useless atmospheric nitrogen into plant food, some of which remains in the soil through the next year. On average, fields planted with lentils required 30 percent less fertilizer than fields planted continuously with wheat, and produced just as much grain.
In effect, the lentil rotation works like cover cropping, another similar approach, which involves planting (often inedible) legumes in the off-season. Cover cropping is common on organic farms, which forgo synthetic nitrogen fertilizer, and must devise other ways of adding nitrogen to the soil. It has also been making headway as a sustainable option within in conventional systems.
The researchers found that, in the fields where all these practices were applied together, carbon built up in the soil at staggering rates. Overall, the scientists estimated that for each kilogram of wheat they harvested, the soil removed up to a third of a kilogram of CO2 from the atmosphere.
Although Gan is cautious about generalizing his results beyond wheat, he said the techniques recommended in the study may hold promise for other crops. Prime candidates are those grown in degraded soils that have lost carbon due to poor management, and corn and oilseeds, which require large amounts of nitrogen.
The Virgin Earth Challenge is about removing CO2 from the atmosphere. As far as I can tell, this is part of Richard Branson’s Virgin brand. Two article are of particular relevance
Can cows help save the planet? is a post written by Judith Schwartz, author of the book Cows Save The Planet and other improbable ways of restoring soil to heal the Earth. Excerpts:
Few people realize that there is more carbon in the world’s soil than in the atmosphere and all plant life put together and that cultivated soils are estimated to have lost 50 to 70 percent of their carbon. Or that some scientists say regenerative agricultural practices that return carbon to the soil could bring atmospheric carbon concentrations back to 350 ppm.
Enter Holistic Management, developed over several decades by Zimbabwean wildlife biologist Allan Savory. The core of HM is Holistic Planned Grazing, in which livestock are used as a tool for large-scale land restoration. Savory’s insight was that grasslands and grazing animals evolved together—that the land needs the animals in the same way that the animals need the land. Specifically, the land needs animal impact: herbivores act so as to kickstart biological processes that would otherwise stall. Just as land might suffer from being overgrazed, it can also be undergrazed.
A quick snapshot of how it works: animals nibble grasses in a way that stimulates plant growth; their waste adds fertility to the soil; and as herds in the wild bunch up and flee en masse to avoid predators, their trampling breaks capped earth, pushes down dead plant matter so it’s in contact with microorganisms and other soil-dwellers that will break it down, and presses in seeds so that a diversity of species can germinate. The perennial grasses, plant residues and animal waste build carbon, which makes soil less prone to dry out and the rain that falls is more effective. In practice, the rancher takes on the role that the predator does in nature, keeping animals on the move so that land is neither under- nor overgrazed.
The point is that Holistic Planned Grazing has reinvigorated the land, and functioning land is potentially storing a lot of carbon (bolstering soil fertility), moderating against temperature extremes (thanks to plant cover and transpiration), holding water (enhancing resilience to floods and droughts) and supporting life (above and below ground).
Reviving land ecosystems, in which the hydrological, carbon and nitrogen cycles are restored, belong in our discussions of climate. The upside here is that we can make this happen. And by working holistically, the benefits, which include the potential to sustainably draw down a significant amount of atmospheric CO2, could greatly exceed the sum of all the parts.
A second post critically evaluates Savory’s claims. Excerpts:
For events like this conference to translate into wider adoption for Savory’s techniques, the Savory Institute will need to start targeting a new, more mainstream “customer.” Scientific data will need to start replacing the anecdotes as the primary substance of the event, and the circle of partners for the Savory Institute will need to widen considerably to include more investors, ag tech companies, large established companies and financiers, and regulators and policy makers. Most importantly, it will be critical for the Savory Institute to further integrate with the other communities seeking to advance systemic approaches to managing land with the goal of regenerating depleted ecosystems (e.g. no-till, bio-dynamic, etc.) in order to build the most effective coalition of organizations seeking similar end goals.
In conclusion, the Savory Conference demonstrated the positive progress that holistic land management is making towards unlocking its potentially vast CDR potential, but also showed that the road to achieving this potential remains long and fraught with obstacles.
The ideas presented here are particularly appealing since they seem to have little downside, and potentially have ancillary favorable impacts on the environment and food production.
Assessing the effect of agricultural practices on soil carbon requires that we have a better understanding of the relevant processes, see e.g. this recent press release As Temperatures Rise, Soil Will Relinquish Less Carbon to the Atmosphere Than Currently Predicted.
Seems like working to understand/address the soil carbon issue would be much less contentious than international energy policy treaties. The idea of exploiting natural carbon sequestration (what VirginEarth is promoting) seems to me like it has received far too little attention.