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Agriculture

Published on July 14th, 2019 | by Guest Contributor

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A Pathway To 350 PPM, Part 2: Carbon Farming Can Deliver

July 14th, 2019 by  


In the previous article, I argued the case that we would need to sequester at least 20 gigatonnes CO​2​ or 36% of our current emissions each year (even after we stopped burning fossil carbon) to reduce atmospheric CO​2​ levels down to a safe level of ​350 PPM​. Scientists have also ​argued that although GEO-CCS has the potential to sequester CO​2,​ it is impractical to do this until we have excess clean energy resources to put towards this task. I showed that biological carbon capture and storage (BIO-CCS) also known as carbon farming, could sequester this amount, however, it would require a massive amount of land and much of the world’s suitable lands are already being used for other needs — namely agriculture.

In the second part of this two part series, I’ll show how the inefficiency of how we obtain the energy to power the human body provides a lifeline for getting us out of this climate crisis.

We have the land, we just need to use it better

LED light bulbs, heat-pumps, and electric cars all have something in common: they represent an efficiency improvement of 300% or greater over their predecessors (incandescent lights, resistive heating, and gas-powered vehicles). This drive towards efficiency and reducing costs is ongoing and encouraging. Even in the agricultural sector, farmers and businesses have implemented techniques to improve crop yields, and in the past 30 years American wheat crop yields have increased by ​39%​, soybean yields by 5​1%​, and corn yields by ​65%​.

Unlike LED light bulbs, heat-pumps, and electric cars, the efficiency improvements witnessed in the agricultural sector have been incremental. The paradigm shift that awaits the agricultural sector are not the incremental improvements seen for existing food sources, but a dietary shift away from the most land-inefficient food sources.

Take protein for example. Humans need protein to survive, but rather than obtain protein through efficient sources like legumes, we focus most of our attention and diet on animal proteins like beef.​ The land required to produce 1 kilogram of protein from beef is ​14 times greater​ than the land required to produce 1 kilogram of equivalent protein from beans, corn, or potatoes. With nearly ​60​%​ ​or 3.3 billion hectares of the world’s agricultural land devoted to raising beef, we could produce the same amount of protein from plant sources using only 260 million hectares of land, a 93% reduction in land area.

Animal-based foods are more resource-intensive than plant-based foods

Sources: ​WRI​, GlobAgri model (land use and greenhouse gas emissions), authors’ calculations from Mekonnen and Hoekstra (2011, 2012) (freshwater consumption), and Waite et al. (2014) (Farmed fish freshwater consumption).

If we were to substitute land-inefficient food sources, such as cattle, with efficient, plant-based alternatives — ideally using regenerative, no-till, and agroforestry practices — we would free up an area of land equal to the entire continent of Africa (over 3 billion hectares) that could be put to work performing other services, like farming carbon out of the atmosphere. Although much of this land wouldn’t be suitable for trees, a ​recent study​ released by the Crowther lab in Switzerland has indicated that up to 1.8 billion hectares of land, much of it coming from existing pasture lands, could be forested.

As stated in the first part of this essay, afforestation of pasture land in the USA could sequester 8.4 tonnes CO​2/​hectare/year​. To sequester 20 gigatonnes would require the planting of 2.4 billion hectares of land.

In the tropics, with a year-round growing season, sequestration potential jumps to ​25 tonnes CO​2/​hectare per year​ and 20 gigatonnes could be sequestered by planting trees on 800 million hectares of land.

Reforesting the tropics

Since 1950, we have lost approximately ​50% (7.5 billion hectares)​ of our tropical forests, and scientists estimate that number will increase to ​80% by 2030​ unless significant action is taken to stop deforestation. More than ​80% of deforestation​ of tropical forests has been for agriculture, with a significant amount being to support livestock. In the Amazon alone, ​91% of the 700 million hectares​ of land deforested since 1970 has been for livestock pasture. By converting this pasture land in the Amazon back to forests, potentially ​15.9 billion tonnes​ of CO​2e​ q/year or 29% of our current GHG emissions could be sequestered.

A teak, coffee and soursop agroforestry plantation in Nicaragua on lands once used for cattle grazing. © Ryan Logtenberg

Afforestation of grasslands

The creation of new forests on lands that never were or have not been for a very long time is called afforestation. Scientists have determined that over ​20% (730 million hectares)​ of the world’s grasslands have enough rainfall to support trees, and they also determined that afforestation of pasture land in the USA could sequester on average ​8.4 tonnes of CO​2e​q/hectare per year​. Those values would equate to the potential for 6.1 billion tonnes of CO​2e​q to be sequestered each year from afforestation of these suitable grasslands globally. Some will argue that managed cattle grazing techniques that mimics historical migratory herds is the way forward for carbon sequestration of grasslands. Although beneficial, managed grazing provides about ​1⁄2 the sequestration potential​ of afforestation and after 20-30 years, a saturation point is reached where ​off-gassing of N​2O​ offsets CO​2​ being sequestered. Although carbon saturation is an issue for all carbon farming practices, mature trees can be harvested and replaced with new ones which prevent carbon saturation from occurring. Managed grazing also doesn’t address the substantial methane emissions generated from the digestive processes of ruminants (cattle, sheep etc.) or their manure. The livestock industry is responsible for ​14.5% (7.1 billion tonnes CO​2e​q/year)​ of total anthropogenic GHG emissions and methane from ruminant livestock like cattle is the largest contributor. This is slightly more than the emissions from the entire transportation sector which is responsible for ​14% of GHG emissions​.

Carbon farming solves many of the world’s problems

Both afforestation and reforestation of cattle pasture lands will not only relieve logging pressure on existing natural forests which themselves are important carbon sinks and harbor much of the world’s ​terrestrial biodiversity​, they would also provide the raw materials to supply a growing trend away from the use of ​CO​2-​ intensive steel and concrete​ in building construction in favor of wood-based alternatives like ​laminated timber.​

Laminated timber replaces steel and concrete in building construction. ​© Structurlam

Drastically improving the efficiency of how much land is used to produce our protein and calories by switching to plant-based or more land-efficient animal sources, will also make it much easier to sustainably produce enough food to feed the world’s growing population.

Aside from a dietary shift and global tree planting effort, this pathway to 350 PPM requires that we eliminate fossil carbon consumption. The generation that is alive today will determine the future of humanity. Therefore, we must act accordingly and clean up our carbon footprints by reducing consumption. Specifically, we need to stop the use of fossil carbon to power our transportation, home heating, cooking appliances, and other power tools. When feasible and available, install solar on our roofs or buy our electricity from green energy sources. We must buy less, share more, practice repairing over replacing, and avoiding disposable consumer goods. Lastly, we need to shift our diets towards land-efficient food sources so we create the space for trees. This is one of the most powerful tools we have for returning atmospheric greenhouse gases to non life-threatening levels, solving a host of anthropocentric environmental problems, and getting us out of this mess.

About the author: Ryan Logtenberg is a director of the 2 Degrees Institute. The 2° Institute mission is to develop and support strategies that empower people to make the behavioral and lifestyle changes needed to prevent our planet from warming by 2 degrees Celsius. 
 
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