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In this paper, we present the results of a Global Sensitivity Analysis (GSA) proving that Animal Agriculture is the leading cause of climate change, responsible for 87% of human-made greenhouse gas emissions. The burning of fossil fuels is currently the leading source of human-made Carbon diOxide (CO2) emissions. However, climate change is caused by cumulative human-made greenhouse gas and aerosol emissions and not just current CO2 emissions alone. While humans have been burning fossil fuels for a little over 200 years, we have been burning down forests for Animal Agriculture for well over 8,000 years! For the GSA analysis, we use factual data from the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) and other peer-reviewed scientific sources. We show that we need to transition to a global plant-based economy first and that blindly eliminating fossil fuel usage first will accelerate the warming of the planet. We show that the annual methane emissions from Animal Agriculture alone causes more incremental global warming than the annual CO2 emissions from all fossil fuel sources combined. We further show that the transition to a global plant-based economy has the potential to sequester over 2000 Giga tons (Gt) of CO2 in regenerating soils and vegetation, returning atmospheric greenhouse gas levels to the “safe zone” of under 350 parts per million (ppm) of CO2 equivalent, while restoring the biodiversity of the planet and healing its climate. This paper clearly illustrates why the scientific community, government institutions, corporations and news media, who vastly underestimate the role of Animal Agriculture and focus primarily on reducing fossil fuel use, need to urgently change their priorities in order to be effective.
The burning of fossil fuels is undoubtedly the leading source of human-made Carbon diOxide (CO2) emissions today. CO2 is the most powerful human-made greenhouse gas in terms of its radiative forcing, the average energy trapped by the greenhouse gas per unit time per unit area of the Earth’s surface, relative to the base year, 1750. In the absence of active reforestation efforts, CO2 is a long-lived greenhouse gas as it persists in the atmosphere for hundreds of years to even tens of thousands of years. The Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) estimates the mean radiative forcing of human-made CO2 to be 1.68 Watts/square meter (W/m2). The next most powerful human-made greenhouse gas, methane, with a mean radiative forcing of 0.97 W/m2, lingers in the atmosphere for an average of 10-12 years before it reacts with oxygen free radicals and also converts into CO2. As such, it is tempting to conclude that a single-minded focus on the reduction of fossil fuel burning to minimize future human-made CO2 emissions is the best strategy to address climate change. Indeed, the global scientific community, government institutions, corporations and news media have adopted this strategy without much questioning. They have also unquestioningly accepted the United Nations (UN) Food and Agricultural Organization (FAO)’s estimate that the lifecycle emissions of the Animal Agriculture industry sector is a mere 14.5% of global human-made greenhouse gas emissions, which justifies their urgency of reducing fossil fuel burning over dealing with the Animal Agriculture sector.
In this paper, we will show that this strategy of focusing exclusively on the reduction of fossil fuel burning will accelerate climate change, potentially to the point of no return. Using a Global Sensitivity Analysis (GSA) method, we will show that the UN FAO’s 14.5% estimate for the lifecycle emissions of Animal Agriculture is incorrect and that the correct estimate is at least 51% as calculated by Goodland and Anhang and likely around 87% of global greenhouse gas emissions. Therefore, Animal Agriculture is the leading cause of climate change. Furthermore, we will show that a global transition to a plant-based economy has the potential to sequester over 2000 Giga tons (Gt) of CO2 in regenerating soils and vegetation, returning atmospheric greenhouse gas levels to the “safe zone” of under 350 parts per million (ppm) of CO2 equivalent (CO2e), while restoring the biodiversity of the planet and healing its climate.
The organization of this paper is as follows:
In Section 2, we will examine how waste “exhaust” from human activities changes the earth’s climate. The exhaust can be classified as either greenhouse gases, which heat up the Earth’s atmosphere, or aerosols, which are atmospheric particles that generally cool the Earth’s atmosphere. The main human-made greenhouse gases are CO2 and methane, which are both carbon-based gases and the main human-made aerosols are sulphates, which are primarily produced when we burn coal and oil.
In Section 3, we will examine how the carbon cycle of the planet has been impacted by two main human activities over the past 8,000 years: land clearing or land use change, primarily for agriculture, and fossil fuel burning.
In Section 4, we will examine current agricultural land use and biomass flows to establish that Animal Agriculture is the primary sector necessitating land clearing, causing climate change. Next, we will compare Local Sensitivity Analysis (LSA) vs. Global Sensitivity Analysis (GSA) on the two main human activities causing climate change: Animal Agriculture and fossil fuel burning. While the LSA is useful for determining the impact of local variations in the current emissions scenario, it can lead to inaccurate results when extrapolated out on a global scale. In contrast, the GSA is based on analyzing a global change directly and will lead to more accurate results for that change. Using the GSA method, we will reveal the inaccuracies in the UN FAO’s 14.5% estimate on the greenhouse gas emissions contribution of the Animal Agriculture sector. Next, we will show that the Goodland-Anhang estimate of 51% is truly just a lower bound on the greenhouse gas emissions contribution of the Animal Agriculture sector. We will then tighten this lower bound using the Carbon Opportunity Cost (COC) estimates of Searchinger et. al. and show that the correct estimate for the greenhouse gas emissions contribution of Animal Agriculture is likely to be around 87%.
Finally in Section 5, we will estimate the CO2 sequestration potential and the resultant climate mitigation that can occur with the global transition to a plant-based economy.
In what follows, for the sake of simplicity, we have used the specified statistical mean or the midpoint of uncertainty ranges in the data found in the IPCC reports and other peer-reviewed sources. Our conclusions do not change if we include the underlying uncertainty ranges and other nuances, but we will likely lose clarity in our presentation.
2. How Humans Change Climate
Almost everything humans do changes the Earth’s climate. The waste “exhaust” from human activities can either heat up the Earth or cool it. Therefore, the question is not whether humans change the Earth’s climate, but how much and in what direction. When billions of humans drive cars, burn coal and natural gas for electricity and consume animal products, the exhaust gases and particles from these activities heat or cool the Earth. Exhaust gases such as CO2, methane and Nitrous Oxide (N2O) heat the Earth. Exhaust particles such as sulphates and nitrates cool the Earth. Other exhaust particles, such as black carbon, heat the Earth.
The UN IPCC has quantified the impact of each of these exhaust gases and particles in terms of radiative forcing measured relative to their levels that existed in the year 1750 as the base year (see FIg. 2.1). CO2 is the main human-made exhaust gas that heats the Earth and it is estimated to provide an additional 1.68 W/m2 of heating power relative to its atmospheric concentration in 1750. In other words, the impact of the additional CO2 in the atmosphere since 1750 is like adding a 1.68 Watt continuous heater on every square meter of the Earth’s surface.
The next most significant human-made exhaust gas is methane, which has the chemical formula CH4. Methane is estimated to have a mean radiative forcing of 0.97 W/m2 and it lingers in the atmosphere for an average of 10-12 years before it reacts with oxygen free radicals and also converts into CO2. The number one cause of methane emissions is Animal Agriculture, which contributes 37% of it. Even though the radiative forcing of methane (0.97 W/m2) is less than that of CO2 (1.68 W/m2), the annual emissions of methane has a more significant impact on net radiative forcing than the annual emissions of CO2. For a first order approximation, imagine that all the excess methane in the atmosphere was emitted over the past 10 years. Then, the emissions each year is responsible for 0.097 W/m2 of radiative forcing. In contrast, the annual emissions of CO2 (39 Gt Co2) is about 4% of the excess CO2 in the atmosphere since 1750, and therefore responsible for an additional 1.68X0.04 = 0.07 W/m2 of radiative forcing. Since we expect just 45% of that emitted CO2 to stay in the atmosphere each year, the additional radiative forcing for the annual CO2 emissions is only 0.45X0.07 = 0.03 W/m2, about one-third the impact of annual methane emissions.
It is important to point out that the IPCC has consistently undercounted the impact of methane by averaging its impact over a 100 year period. Even as it warns humanity that catastrophic climate change is imminent within the next 11 years, not 100 years! In the latest report issued in August 2019, the IPCC is still using a Global Warming Potential (GWP) of 28 for converting methane emissions to a CO2 equivalent (CO2e), which corresponds to averaging its impact over 100 years, while excluding cloud effects. For a more appropriate 10-year averaging, including cloud effects, the GWP of methane would be 130. If we used GWP of 130 for methane, then the annual emissions of methane would be 10.1 X 130/28 = 46.9 Gt CO2e, which exceeds the annual emissions of CO2 (39 Gt CO2). Besides only about 45% of the annual CO2 emissions stays airborne each year and therefore, the comparison of methane (46.9 Gt CO2e) should be with respect to 0.45 X 39 = 18 Gt CO2, which is about one-third the impact of annual methane emissions, just as we calculated above. Indeed, the impact of methane from Animal Agriculture alone (46.9 X 0.37 = 17.3 Gt CO2e) exceeds the impact of all fossil fuel based CO2 emissions (18 X 0.85 = 15.3 Gt CO2). For reference, please see Table on Page 9 of the latest IPCC report.
The third most significant human-made exhaust particles are sulphate aerosols, created mainly during the burning of coal and oil. According to NASA, “the sulfate aerosols absorb no sunlight but they reflect it, thereby reducing the amount of sunlight reaching the Earth’s surface. Sulfate aerosols are believed to survive in the atmosphere for about 3-5 days.
The sulfate aerosols also enter clouds where they cause the number of cloud droplets to increase but make the droplet sizes smaller. The net effect is to make the clouds reflect more sunlight than they would without the presence of the sulfate aerosols. Pollution from the stacks of ships at sea has been seen to modify the low-lying clouds above them. These changes in the cloud droplets, due to the sulfate aerosols from the ships, have been seen in pictures from weather satellites as a track through a layer of clouds. In addition to making the clouds more reflective, it is also believed that the additional aerosols cause polluted clouds to last longer and reflect more sunlight than non-polluted clouds.”
The radiative cooling effect of human-made sulphate aerosols together with their cloud adjustments is estimated to be -0.95 W/m2.
The fourth most significant human-made exhaust are black carbon particles, which cause a radiative heating effect of 0.6 W/m2. These are formed due to the incomplete combustion of fossil fuels, biofuels and biomass. The main emissions sources are diesel engines, wood burning cookstoves and forest fires that humans ignite to clear land for Animal Agriculture and other sundry purposes. Fig 2.2 shows a map of the world depicting forest fires seen from space by the NASA MODIS Satellite during a 10 day period in May of 2019! Such forest fires are a significant source of black carbon emissions.
CO2 is absorbed by trees and plants during photosynthesis and it is stored away permanently in vegetation and soil in regenerating forests. However, in the absence of active reforestation efforts, CO2 is a long-lived greenhouse gas that lingers in the atmosphere for hundreds to even tens of thousands of years. At present, almost 85% of human-made CO2 emissions are from burning fossil fuels, i.e., coal, oil and natural gas. The remaining 15% is mainly from burning down forests to clear land, i.e., land-use changes.
However, since CO2 is a long-lived greenhouse gas, it is the cumulative emissions of CO2 over time that impacts its radiative forcing, not current emissions alone. In 1850, land use changes were the main source of human-made CO2 emissions, while at present, it is fossil fuels (see Fig. 2.3). Integrating the annual CO2 emissions components over time, we see in Fig. 2.4 that between 1850 and 2011, cumulative CO2 emissions due to land use changes is second only to that from coal burning. Besides, land use changes have been occurring for over 8,000 years, whereas fossil fuel burning only started in the industrial era, around 200 years ago. Since the long-range time constant of CO2 rock weathering sequestration is on the order of tens of thousands of years, it is relevant to consider the cumulative CO2 emissions from land use changes over the past 8000 years. Kaplan et al. has estimated the CO2 emissions due to land use changes in the pre-industrial era to be 1250 Gt CO2. This implies that if we integrate from 8000 years ago to 2011, CO2 emissions from land-use changes (1850 Gt CO2) exceeds the CO2 emissions from all fossil fuel sources combined (1200 Gt CO2). Therefore, land use changes are the leading cause of human-made CO2 emissions over the years and not fossil fuel burning.
In summary, of the four main human-made exhaust gases and particles impacting climate change,
1) Land use changes, primarily for Agriculture, is the leading cause of CO2 emissions, a global heating component with the largest radiative forcing;
2) Animal Agriculture is the leading cause of methane emissions, the global heating component contributing the most incremental heating on an annual basis;
3) Fossil fuel burning is the leading cause of sulphate emissions, a global cooling component; and
4) Animal Agriculture is a leading cause of black carbon emissions, a global heating component.
With the lone exception of sulphate aerosols, which are mainly a by-product of fossil fuel combustion, the other three main exhaust gases and particles causing climate change – CO2, methane and black carbon – are molecular forms of carbon. Therefore, let us now take a closer look at how humans have altered the carbon composition of the planet.
3. How Humans Changed Carbon
Carbon is stored on land in vegetation and soils. Roughly half the weight of a tree is carbon. Half the weight of a tree is below ground and half above ground and therefore, the above ground weight of a tree is a good measure of the amount of carbon stored by the tree. In general, soil contains three times as much carbon as the vegetation it holds.
Carbon is stored deep underground in the form of fossil fuels. It is also stored under permafrost land in the form of ancient vegetation that got frozen and preserved at the dawn of the ice ages 3 million years ago.
Carbon is stored in the ocean in surface, intermediate and deep sea sediments. It is also stored in the ocean as dissolved carbon. Finally, carbon is found in the atmosphere, primarily as CO2, methane, organic carbon and black carbon.
For at least 8000 years, humans have been displacing carbon by clearing land for agriculture and by burning fossil fuels (see Fig. 3.1). Most of that displaced carbon has returned back to land, while some has dissolved into the ocean and 240 GtC of it has remained in the atmosphere in the form of greenhouse gases causing climate change. It is estimated that in the pre-industrial era, humans displaced around 300 GtC of carbon on land, but this barely made a dent in the atmospheric CO2 levels as most of it returned back to land in the form of peat moss. Since then, humans have combusted 365 GtC of carbon from the planet’s fossil reserves and displaced 164 GtC from vegetation and soil on land. Of that total of 529 GtC of carbon, 45% or 240 GtC has remained airborne in the form of CO2, methane, etc., in the atmosphere, while 155 GtC has dissolved into the ocean and 134 GtC has returned back to land.
Humans have cut down about 46% of the trees on land since the dawn of civilization. This corresponds to displacing an estimated 464 GtC from vegetation and soils and sending it up into the air. While the pre-industrial clearing of land was compensated by carbon storage in Arctic peat moss, the industrial-era clearing has been mostly compensated with additional storage in forests due to the so-called CO2 fertilization effect. Since the land clearing in the industrial era was accompanied by fossil fuel burning, it raised the atmospheric CO2 levels, which spurred plant-growth due to more efficient photosynthesis. Therefore, even though the cleared land is storing very little carbon as we shall see below, the remaining forests now have a greater density of carbon than in pre-industrial times, which partially offsets the carbon lost due to land clearing.
At present, 2470 GtC is stored in 130 Million square kilometers (MKm2) of the ice-free land area of the planet, for an average carbon storage density of 19,000 tons per sq. km (t/Km2). According to the IPCC Land Use Block diagram (see Fig. 11.9, page 836), 46 MKm2 or 35% of that land is used as grazing land for Animal Agriculture. The Integrated Science Assessment Model (ISAM) at the University of Illinois estimates that this grazing land is currently storing 53 GtC, for an average of 1,150 t/Km2, or just 6% of the global average. This is reflected in the global land carbon stock map of Fig 3.2, which shows vast swathes of the planet with low carbon density corresponding to where human and farmed animal population is dense.
4. Sensitivity Analysis for Human Activities Causing Climate Change
In the previous sections, we have established that land clearing, primarily for Agriculture, and fossil fuel burning are the two main human activities causing climate change. In this section, we will compare the climate change impact of eliminating fossil fuel burning with the impact of eliminating Animal Agriculture, a sub-sector of Agriculture.
At the dawn of the Agricultural revolution, 10,000 years ago, human biomass was negligible compared to the biomass of large wild animals (> 44kg in weight) and humans could afford to lead a predatory existence, cooking and eating animal foods (see Fig. 4.1). However, in the Industrial era, by 1970, human biomass alone was equal to the biomass of all large wild animals from 10,000 years ago. In addition, humans were now farming animals whose total biomass was roughly double that of humans, but who were consuming three times as much food as all humans. As far as the planet was concerned, our farmed animals were presenting the profile of a biomass that was triple the biomass of all the large wild animals from 10K years ago. Meanwhile, the biomass of large wild animals had declined by 60%.
Fast forward another 40 years and by 2010, human biomass had doubled from 1970 levels. Our farmed animals were now eating 4.5 times as much food as all humans thereby presenting the profile of a biomass that is NINE times the biomass of all large wild animals from 10,000 years ago. The biomass of wild animals had declined by 52% from 1970 levels and therefore down by 81% from 10K years ago. The decline in the biomass of wild animals was also accelerating exponentially to be 58% from 1970 levels by 2012 and 60% by 2014. The primary driver for this decline is human land clearing for agriculture, since 80% of mass extinction is due to habitat loss.
In terms of dry matter biomass, our “livestock” or farmed animals consume more than 80% of the food that we extract from the planet in order to provide just 15% of the food (including “seafood”) that humans consume (see Fig. 4.2). That is, in terms of dry weight, 85% of the food that we consume today is already plant-based! Poore and Nemecek have calculated that 82% of the calories and 63% of the protein that we consume is already plant-based as well. Therefore, it is not too far-fetched to ask the question, how much can we mitigate climate change if we eliminated the Animal Agriculture sector altogether and relied entirely on plant-based foods and products? Indeed, this is a much more immediate, practical scenario than eliminating fossil fuel burning altogether. Of course, this would require us to not use animal products for any purpose whatsoever, i.e., to adopt a “Vegan” ethic, since at present, the Animal Agriculture industry is providing 190 million tons of “food” for human consumption along with 140 million tons of “other raw materials” such as skin, blood and bones. If we only change our diets, the industry is perfectly capable of raising animals just to produce the “other raw materials” and therefore, we may not be making much of a dent in its environmental impact.
In its Fifth Assessment Report, the UN IPCC had calculated that the “Agriculture, Forestry and Land Use” (AFOLU) sector was responsible for 12 Gt CO2e or 25% of the global greenhouse gas emissions by industry sector, including indirect emissions from the electricity and heat production sector (see Fig. 4.3). Since Animal Agriculture is a sub-sector under AFOLU, its contribution must be strictly less than 25%. In contrast, fossil fuel burning was calculated to produce 32 Gt of CO2 or 65% of the total greenhouse gas emissions (49 Gt CO2e) in 2010. Therefore it is tempting to conclude that eliminating fossil fuel burning is a more effective climate mitigation strategy than eliminating the Animal Agriculture sector.
However, this is like inferring the Earth is flat based on local, line-of-sight observations. Such “Local Sensitivity Analysis” can be notoriously misleading. Firstly, the above comparison is based on current emissions and not on cumulative emissions or radiative forcing, which are more appropriate for measuring climate change impact. Secondly, the IPCC is using a 100 year time frame for calculating the CO2 equivalence of methane, which undercounts its more relevant 10-year impact by nearly a factor of 5. Thirdly, it is not just greenhouse gas emissions, but also aerosol cooling effects that need to be taken into account for comparing climate change impact. Fourthly, the IPCC is allocating each molecule of emission to one sector alone. Therefore, if a truck is transporting agricultural products, its emissions is being assigned to the transportation sector and not to the AFOLU sector. Finally, the UN IPCC is relying on the UN Food and Agricultural Organization (FAO) for its AFOLU data, while the FAO has publicly partnered with the International Meat Secretariat and the International Dairy Federation to promote intensive “livestock” farming. How reliable can the FAO’s analysis be, when it is wedded to industry interests? Indeed, here’s a timeline of events debunking the FAO’s reports:
2005 – Alan Calverd published an estimate of GHG emissions from “Livestock” breathing alone is 8.8 Gt CO2e or 21% of total. “Livestock” breathing is a proxy for the avoided carbon sequestration while consuming animal products.
2006 – FAO published Livestock’s Long Shadow (LLS) calculating lifecycle emissions from the “Livestock” sector to be 7.5 Gt CO2e or 18% of total, i.e., less than the breathing contribution alone!
2009 – Goodland and Anhang published WorldWatch report correcting errors in LLS and calculating lifecycle emissions of the “Livestock” sector to be 32.6 Gt CO2e or 51% of total. This 32.6 Gt CO2e can be split into actual emissions of 21.1 Gt CO2e plus avoided carbon sequestration of 11.5 Gt CO2e (see Fig. 4.4) on the land that would be freed up when Animal Agriculture is eliminated. The latter is their estimate of the “Carbon Opportunity Cost” of Animal Agriculture, to use the terminology of Searchinger et al. In the former, Goodland and Anhang used a 20-year timeframe for averaging the impact of methane instead of the 100 year timeframe used in the FAO’s analysis.
2011 – FAO scientists published critique of Goodland and Anhang’s estimate in Animal Feed Science and Technology (AFST) Journal.
2012 – Goodland and Anhang published refutation in AFST Journal and reiterated their estimate. FAO scientists declined to continue the debate despite AFST Editor’s invitation.
2013 – FAO publicly partnered with International Meat Secretariat and the International Dairy Federation and published revision to LLS, calculating lifecycle emissions of the “Livestock” sector to be 7.1 Gt CO2e or 14.5% of total, without addressing any of the egregious errors pointed out in Goodland and Anhang’s report or in the ensuing peer-reviewed debate.
Therefore, relying on the FAO’s analysis is like relying on a Philip Morris scientific paper that extols the cancer healing benefits of smoking Marlboro Lights. In its lifecycle analysis of Animal Agriculture, the FAO had calculated the Carbon Opportunity Cost of Animal Agriculture to be ZERO, which is blatantly incorrect. In addition, it appears that Goodland and Anhang may have also vastly undercounted the Carbon Opportunity Cost of Animal Agriculture since they only included CO2 stored in above ground vegetation and did not include CO2 stored in soil. Searchinger et al. calculate the Carbon Opportunity Cost to be an average of 5 tons of CO2 per person per year, which works out to a total of 34.5 Gt CO2 for a human population of 6.9 billion in 2010. Therefore, the true Lifecycle emissions of Animal Agriculture was closer to 55.6 Gt CO2e in 2010, i.e., 87% of the total.
In contrast to “Local Sensitivity Analysis,” a “Global Sensitivity Analysis” works by considering the thought experiment: how will the human-caused radiative forcing change in the two scenarios:
a) Clean Energy Economy: if we eliminate fossil fuel burning and replace it with clean energy sources, keeping all else the same vs.
b) Plant Based Economy: if we eliminate the Animal Agriculture sector and replace it with plant-based sources, keeping all else the same?
In the Clean Energy Economy scenario, we assume that all energy sources have been transitioned to clean, zero emissions sources, but we will be continuing to burn down forests to grow more animal foods as before. Therefore, land use change emissions would continue to add CO2 to the atmosphere. The CO2 component of the radiative forcing would continue to increase but at a slower pace than before. Since we are no longer burning coal and oil, sulphate aerosols would disappear within 3-5 days, which means that the net radiative forcing would increase by 0.95 W/m2 due to this component. Finally, Other Heating Effects would remain the same so that the net radiative forcing would increase to 3.24 W/m2 from the present 2.29 W/m2, exacerbating numerous catastrophic climate feedback loops.
In the Plant Based Economy scenario, we assume that all animal products have been replaced with plant-based equivalents and that Animal Agriculture has been eliminated, but we continue to burn fossil fuels as necessary. From Fig. 4.2, we see that we can now supply all the plant-based food and product requirements from the cropland output alone, freeing up the grazing land for reforestation and carbon sequestration. This grazing land will begin sequestering 34.5 Gt CO2 per year, reducing CO2 levels in the atmosphere. In addition, a good chunk of the fossil fuel burning would disappear as we reduce our need for transporting vast amounts of food to animals, killing them in industrial settings, refrigerating their carcasses, treating diseased people, etc. About 40% of the methane in the atmosphere would disappear in 10-12 years, reducing the radiative forcing by 0.4 W/m2. The Black Carbon component of 0.6 W/m2. would reduce as we stop burning forests to create grazing land for animals. Therefore, we can expect the net radiative forcing to decrease to 1.3-1.7 W/m2 from the current 2.29 W/m2. within 10-12 years. As the net radiative forcing decreases, we can start gradually switching out the fossil fuel infrastructure for clean energy sources without exacerbating catastrophic climate feedback loops.
The choice between these two scenarios should now be obvious. This shows that Animal Agriculture is indeed the leading cause of climate change.
5. CO2 Sequestration Potential in a Plant-Based Economy
At present, grazing lands store just 6% of the carbon per unit area when compared to the average for all land. In our Lifestyle Carbon Dividend poster paper presented at the AGU Fall Meeting in 2015, we reported that 41% of this grazing land used to be forests in 1800 and that if we can return the original forests on that land, the carbon storage on land would increase by 265 GtC from its present value. Our analysis was conducted using 2014 HYDE land use data, assuming that grazing land is reverted to native biomes that existed in 1800.
Here are the supporting calculations and extrapolations assuming that all grazing land can be regenerated to store the same carbon sequestration per unit area as the reverted lands:
Total area of grazing lands in 2014: 47.3 M Km2
Total carbon stored in that land (soil + vegetation): 52.8 GtC
Total area of grazing lands reverted to forests: 19.6 M Km2
Carbon sequestered in reverted lands at maturity: 292.7 GtC
Carbon sequestered per unit area at maturity: 14,930 t/Km2
Potential Carbon sequestration in all lands at maturity: 706.2 GtC
Net Carbon sequestration in all lands at maturity: 653.4 GtC
Net CO2 sequestration in all lands at maturity: 2396 Gt CO2
Please note that as CO2 sequestration occurs on such a massive scale, we can expect the ocean to release its dissolved CO2 and the CO2 fertilization effect to decrease on land. Then the potential CO2 sequestration will also decline proportionally, because we would be literally reducing the CO2 levels in the atmosphere, an outcome devoutly to be wished.
In this paper, we established that Animal Agriculture is the leading cause of climate change accounting for an estimated 87% of annual greenhouse gas emissions. We also illustrated the need to transition to a global plant-based economy first and that blindly eliminating fossil fuel usage first will accelerate the warming of the planet. The necessary global transition to a plant-based economy can be achieved through concerted, grassroots action, with or without the active cooperation of governments, scientific institutions, corporations and the news media.
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