Mitigation Potential of Agricultural Emissions using a Variety of Options in the Tropics

The release of greenhouse gases, primarily methane<!–[if supportFields]> XE “methane (CH4)” <![endif]–><!–[if supportFields]><![endif]–> is an important issue that needs to be considered in the agricultural sector. However, other gases are released from the agricultural sector as well, including carbon dioxide and nitrous oxide<!–[if supportFields]> XE “nitrous oxide (N2O)” <![endif]–><!–[if supportFields]><![endif]–>. Furthermore, in the context of climate change, changes made in agricultural practices as well as changes made in livestock-related practices, can play a role in reducing greenhouse gas emissions. Thornton and Hererrero (2010) used a method that involved the estimation of four different types of adoption on the production of carbon dioxide and methane. Each adoption could be applied at two levels: complete adoption and optimistic, but plausible adoption rates. Furthermore, they used two different types of methods: carbon sequestration<!–[if supportFields]> XE “carbon sequestration” <![endif]–><!–[if supportFields]><![endif]–> of degraded rangelands and the usage of agroforestry practices. Both these methods were applied in tropical regions, namely in tropical Central and South America and sub-Saharan Africa<!–[if supportFields]> XE “Africa” <![endif]–><!–[if supportFields]><![endif]–>. The authors found that despite the mitigation potential rates having not much impact on the global total from agricultural greenhouse gas emissions, the resulting carbon payments from offsets in gas emissions could be a source of income for farmers who are not very well off.— Nitya Chhiber
Herrero, M. and Thornton, P.K. 2010. Potential for reduced methane<!–[if supportFields]> XE “methane (CH4)” <![endif]–><!–[if supportFields]><![endif]–> and carbon dioxide emissions from livestock and pasture management in the tropics. Proceedings of the National Academy of Sciences 16, 19667 – 19672, doi: 10.1073/pnas.0912890107

Thornton and Herrero used the RUMINANT model to provide estimates of production of methane<!–[if supportFields]> XE “methane (CH4)” <![endif]–><!–[if supportFields]><![endif]–>, milk, and meat. This model is structured around inputs and outputs. The inputs are the fermentable nutrients and the outputs are the products of fermentation, which include methane. The study involved analyzing four different mitigation options under two different types of adoption rates: complete adoption and optimistic but plausible adoption. The four mitigation options mainly had an impact on the production of carbon dioxide and methane gases.
The highest mitigation potential for greenhouse gas emissions was the one associated with the method of restoration of the degraded rangelands in sub-Saharan Africa<!–[if supportFields]> XE “Africa” <![endif]–><!–[if supportFields]><![endif]–> and Central and South America at observed or plausible adoption rates. The next two methods, which are beneficial in terms of their mitigation potential, are the agroforestry option and improvements in the use of improved pastures and crop residue digestibility. It is interesting to note that despite having one of the highest mitigation potentials of all options, the agroforestry option, which involves the sequestration<!–[if supportFields]> XE “sequestration” <![endif]–><!–[if supportFields]><![endif]–> of carbon due to the replacement of concentrates by leaves of Leucaena leucocephal<!–[if supportFields]> XE “Leucaena leucocephal” <![endif]–><!–[if supportFields]><![endif]–> in their diet, there are cultural manifestations. In countries in the developing world, the number of livestock is a form of symbolic capital but this method is related to the reduction in livestock numbers.

Increasing Yields Decreases Green-house Gas Emissions

Interest in agricultural practices peaked around 1961, a time period which was eventually known as the Green Revolution. Currently, we are living during a time when a variety of methods is being sought to limit climate change, and agricultural practices also need to be considered as they also release greenhouse gases, which are the drivers for anthropogenic climate change. Burney et al. (2010) have considered three agricultural development scenarios. One (RW) is based on the real world situation, the second (AW1) focused on land expansion, and the third (AW2) is characterized by increased yield. The final recommendation was that if agricultural practices are carried out so that there is emphasis on the quantity of output rather than the quantity of input, there will be lower greenhouse gas emissions, thus making the third scenario the most beneficial for the climate. Nitya Chhiber
Burney, J.A.,Davis, S.J.,Lobell,D.B.,2010. Greenhouse gas mitigation by agricultural intensification. PNAS 107, 12052–12057.

Burney et al. (2010) wanted to understand the best combination of factors for ensuring the least impact of agricultural practices on climate. As certain parameters were difficult to measure quantitatively, they were converted to other units; for example, yield was measured using monetary values in the form of global spending on yield investment between 1961 and 2005. In this study other parameters that contributed to yield improvement, such as fuel use and transport were not considered. Graphs were drawn depicting emissions of nitrous oxide, methane, carbon dioxide that corresponded to levels of yield improvement.

Focus on outputs produced the least impact on climate. For example, increased yields that resulted from an increase in efficiency of fertilizer usage, was more effective in reducing emissions than increasing yields by agricultural land area. It was also found that the AW2 scenario minimized greenhouse emissions, not because AW2 was marked by yield improvements, but because it maintained 1961 standards of living and thus was characterized by an overall lower pressure on land by the population. Therefore land expansion, also known as extensification, was lessened in this particular scenario. 

Impact of Crop Straw and Other Conditions on the Release of Green-house Gases from a Wheat-Maize Rotation Site

The economy in China<!–[if supportFields]> XE “China” <![endif]–><!–[if supportFields]><![endif]–> is very much based on agriculture<!–[if supportFields]> XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–> and therefore this was the ideal location to carry out a study on means for reducing greenhouse gas emissions from soil. Lui et al (2011) wanted to study the emissions of nitrous oxide<!–[if supportFields]>XE “nitrous oxide (N2O)”<![endif]–><!–[if supportFields]><![endif]–> and nitric oxide from soil by observing the reaction of organic residue in the form of both wheat and maize<!–[if supportFields]> XE “maize” <![endif]–><!–[if supportFields]><![endif]–> straw that were applied to the soil along with the amount of N<!–[if supportFields]>XE “nitrogen, N”<![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “nitrogen” <![endif]–><!–[if supportFields]><![endif]–> fertilization<!–[if supportFields]> XE “fertilization” <![endif]–><!–[if supportFields]><![endif]–> applied. They found that nitrous oxide and nitric oxide emissions did decreased along with yield. Furthermore, the level of N fertilization under the improved treatment was better vis-à-vis the greenhouse gas emissions and yield as opposed to the level of N fertilization under the conventional treatment.Nitya Chhiber
Chen, D., Han, S., Liu, C., Meng, S., Yang, Z., Zheng, X., Zhou, Z., 2011. Effects of irrigation, fertilization<!–[if supportFields]>XE “fertilization” <![endif]–><!–[if supportFields]><![endif]–> and crop straw management on nitrous oxide<!–[if supportFields]> XE “nitrous oxide (N2O)” <![endif]–><!–[if supportFields]><![endif]–> and nitric oxide emissions from a wheat–maize<!–[if supportFields]> XE “maize” <![endif]–><!–[if supportFields]><![endif]–> rotation field in northern China<!–[if supportFields]> XE “China” <![endif]–><!–[if supportFields]><![endif]–>.Agriculture, Ecosystems & Environment 140, 226–233. doi:10.1016/j.agee.2010.12.009

The plots of land that were chosen in this study were based in a province in China<!–[if supportFields]> XE “China” <![endif]–><!–[if supportFields]><![endif]–> that had cinnamon soil, and a temperate, continental climate. During this study, the land on which these plots were located was going through a cycle of cultivation from wheat to maize<!–[if supportFields]> XE “maize” <![endif]–><!–[if supportFields]><![endif]–>. Half of the plots did not receive any straw whereas the other half did. There were five different scenarios in total: two scenarios were characterized by different levels of N<!–[if supportFields]> XE “nitrogen, N” <![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “nitrogen” <![endif]–><!–[if supportFields]><![endif]–> fertlisation, two scenarios were related to straw – the lack or the presence of straw. Finally the last scenario was characterized by no fertilization<!–[if supportFields]> XE “fertilization” <![endif]–><!–[if supportFields]><![endif]–> and the presence of straw. Finally, the emissions of nitric oxides and nitrous oxide<!–[if supportFields]> XE “nitrous oxide (N2O)” <![endif]–><!–[if supportFields]><![endif]–>s were measured using chambers in an automated measuring system. The relationship between conditions in soil such as soil temperature, soil moisture and the emissions of nitrous oxides and nitric oxides was described by using non-linear regression.
The presence of organic residue increased yields of both wheat and maize<!–[if supportFields]> XE “maize” <![endif]–><!–[if supportFields]><![endif]–>, and  the lack of any fertilizer<!–[if supportFields]> XE “fertilizer” <![endif]–><!–[if supportFields]><![endif]–> decreased them. The overall water management and N<!–[if supportFields]> XE “nitrogen, N” <![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “nitrogen” <![endif]–><!–[if supportFields]><![endif]–> fertilization<!–[if supportFields]> XE “fertilization” <![endif]–><!–[if supportFields]><![endif]–> application levels under the improved treatment condition were better for the soil and especially for the level of maize yields than under conventional treatment. Furthermore, the level of nitric oxide and nitrous oxide<!–[if supportFields]> XE “nitrous oxide (N2O)” <![endif]–><!–[if supportFields]><![endif]–> emissions decreased under improved treatment. Both nitric oxide and nitrous oxide emission levels increased in the presence of high soil temperature, which could be explained by the fact that higher soil temperatures allow a greater level of activity by nitrifiers and denitrifiers.
It is not only the addition or the application of materials that can be used in agriculture<!–[if supportFields]> XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–>. The effect of increasing yields should also be studied. Furthermore, one should note that agricultural sequestration<!–[if supportFields]>XE “sequestration” <![endif]–><!–[if supportFields]><![endif]–> is a process but concepts such as that of carbon footprint do exist, which provide a parallel type of application of this same process.

Biochar’s Impact on Greenhouse Gas Fluxes: Different Gas Fluxes are Cor-related with Different Parameters

The release of greenhouse gases from agricultural soil is important in the light of climate change. However, at the same time, the study of emissions from agriculture needs to take into account many variables, increasing the difficulty of pinpointing exactly what is causing the agricultural flux of greenhouse gases. Kurhu et al. (2011) wanted to study the impact of biochar on the release of greenhouse gases from soil in Southern Finland. They found that there were differences between the levels of carbon dioxide and nitrous oxide emissions between soils to which biochar had been added and soils to which it had not. Furthermore, although they found that biochar increased methane uptake, and also became aware of many limitations of studying biochar’s impact on the level of greenhouse gases released into the atmosphere.Nitya Chhiber
Bergstrom,I.,Karhu, K.,Matila,T.,Regina,K.,2011. Biochar addition to agricultural soil increased CH4 uptake and water holding capacity – Results from a short-term pilot field study. Agriculture, Ecosystems & Environment 140, 309–313.

Karhu et al. studied the affect of biochar on agricultural soil that was undergoing a process of five-year crop rotation. Plots were of mainly of two types: those with the addition of biochar and those without the addition of biochar. Fluxes of carbon dioxide, nitrous oxide, and methane were measured, and using linear method, related to soil water holding capacity, soil temperature, air temperature, and  grain yield.
Carbon dioxide emissions were positively correlated with temperature, however, the addition of biochar increased methane uptake by a great deal but had no effect on nitrous oxide and carbon dioxide fluxes.
Methane was an interesting case as it responded greatly to rainfall; when it rained and there was higher soil water content, there was a higher methane flux from soil into the atmosphere, especially when the soil was wet and there was no biochar in the soil.
In the literature, no pattern can be found between biochar and the fluxes of carbon dioxide and nitrous oxide across experiments due to the fact that the type of biochar used in each experiment varies. Other reasons that there may be no pattern is that nitrous oxide can be produced under both aerobic and anaerobic conditions, and that higher applications of biochar may be needed in soil to actually see a difference in the fluxes of these two gases.

Usage of Biochar Leads to Higher Yields and Methane Levels but Lower Nitrogen Dioxide Levels

Rice is a staple crop in many Asian countries, including China<!–[if supportFields]> XE “China” <![endif]–><!–[if supportFields]><![endif]–>. However, like many other crops, rice<!–[if supportFields]> XE “Oryza sativa (rice)” <![endif]–><!–[if supportFields]><![endif]–> also releases greenhouse gases. In fact, rice paddies are one of the biggest anthropogenic sources of greenhouse gas production and so there is a great need to be concerned about them vis-à-vis climate change. In order to decrease the amount of greenhouse gases released from the soil, the application of biochar, which is a form of charcoal, was tried. Zhang et al. (2010) also changed soil conditions by the application of N<!–[if supportFields]> XE “nitrogen, N” <![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “nitrogen” <![endif]–><!–[if supportFields]><![endif]–> fertilizer<!–[if supportFields]> XE “fertilizer” <![endif]–><!–[if supportFields]><![endif]–>.  There was interaction between biochar, N fertilization<!–[if supportFields]> XE “fertilization” <![endif]–><!–[if supportFields]><![endif]–>, and the inherent soil conditions, and methane<!–[if supportFields]> XE “methane (CH4)” <![endif]–><!–[if supportFields]><![endif]–> emissions were sensitive to the interaction in soil between biochar and N fertilization. The authors conclude that there is still some hesitation about the usage of biochar, but found increased yield level and methane emissions with the application of biochar and decreased nitrous oxide<!–[if supportFields]> XE “nitrous oxide (N2O)” <![endif]–><!–[if supportFields]><![endif]–> emissions.—<!–[if supportFields]> TC ” Nitya Chhiber “\l 3 \n <![endif]–><!–[if supportFields]><![endif]–> Nitya Chhiber

Zhang et al. generated data for this study from a plot of land that was divided into three parts and all treatments were implemented in triplicate. Some sub-plots received N<!–[if supportFields]> XE “nitrogen, N” <![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “nitrogen” <![endif]–><!–[if supportFields]><![endif]–> fertilization<!–[if supportFields]> XE “fertilization” <![endif]–><!–[if supportFields]><![endif]–> and biochar, whilst others were controls. The concentration of nitrous oxide<!–[if supportFields]> XE “nitrous oxide (N2O)” <![endif]–><!–[if supportFields]><![endif]–> and methane<!–[if supportFields]> XE “methane (CH4)” <![endif]–><!–[if supportFields]><![endif]–> released was measured by gas chromatography throughout one whole rice<!–[if supportFields]> XE “Oryza sativa (rice)” <![endif]–><!–[if supportFields]><![endif]–>-growing season in southeast China<!–[if supportFields]> XE “China” <![endif]–><!–[if supportFields]><![endif]–>.
The addition of biochar decreased nitrous dioxide emissions. On the other hand, methane<!–[if supportFields]> XE “methane (CH4)” <![endif]–><!–[if supportFields]><![endif]–> emissions increased. Another difference between nitrous oxide<!–[if supportFields]> XE “nitrous oxide (N2O)” <![endif]–><!–[if supportFields]><![endif]–> and methane emissions was such that nitrous oxide emission levels decreased regardless of the presence of N<!–[if supportFields]> XE “nitrogen, N” <![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “nitrogen” <![endif]–><!–[if supportFields]><![endif]–> fertilization<!–[if supportFields]> XE “fertilization” <![endif]–><!–[if supportFields]><![endif]–>; on the other hand, methane emission levels were sensitive to the interaction of biochar with N fertilization. However, in the case of carbon dioxide, the addition of biochar in soil increased carbon dioxide emissions. There is still some uncertainty with regards to carbon emission, which can be the basis of future studies. Furthermore, in soils containing biochar and no fertilizers, there were higher yields compared to soils containing biochar and N fertilization.

The Usage of Organic Waste can lead to an increase of Greenhouse gas emissions including fluxes from soil

Agricultural production of greenhouse gases is a big issue that contributes to climate change. So, it is important to study what changes must be made to agricultural practices to minimize greenhouse gas release. Heller et al. (2010) carried out a study of different tilling and soil fertilization practices, which mainly consisted of adding different types of organic waste. The aim of the study that was carried out by the authors was to understand how different types of organic waste impact soil. It was found out that there is a correlation between ammonia in soil and the emissions of nitrogen oxide and carbon dioxide into the air. In addition, carbon dioxide fluxes correlated with soil water content, where as nitrogen oxide fluxes correlated with air temperature. – Nitya Chhiber
Heller, H. (2010). Effects of Manure and Cultivation on Carbon Dioxide and Nitrous Oxide Emissions from a Corn Field under Mediterranean Conditions. Journal of Environmental Quality 39, 437 – 448.

Heller et al. (2010) exposed soil to a variety of different scenarios, including variations in the intensity of tillage, type of organic residue applied and whether the plot was planted in corn. In control cases of no tillage (NT), no organic residue (NR) soils were included. Emissions of carbon dioxide and nitrogen oxide from the soil were measured and the soil organic content was monitored.
The results show that the most carbon dioxide was released after the addition of pasteurized chicken manure and after irrigation, even under the no-tillage system scenario. Nitrogen dioxide emissions also increased with the addition of pasteurized chicken manure, as well as with tillage. The occurrence of rainfall, which increased soil moisture content, led to peaks of carbon dioxide and nitrogen oxide release. Therefore, concentrations of carbon dioxide emissions from soil are related to the percentage of water content. Nitrogen oxide fluxes were higher only if there was rainfall after the application of inorganic fertilizer. Nitrous oxide emissions were reduced when crops were growing on the plots owing to the competition for ammonium ions from the crops. Furthermore, there is a strong correlation between the content of ammonia in soil and the emissions of carbon dioxide and nitrogen oxide; ammonia in soil forms due to the combination of nitrogen fertilizers and carbon from organic waste.

Impact of rainfall on Soil co2 flux should be considered in Agriculture

It is well known that agricultural practices release carbon dioxide. Tillage is a type of activity carried out in agriculture that loosens the soil and therefore causes soil co2 flux. The impact of different degrees of tillage in terms of soil co2 flux was studied keeping in mind the fact that soil conditions are affected by fertilization and precipitation.  Alvaro-Fuentes et al. (2010) used a method that depended on collecting data on which statistical analyses of variance were applied. It was found out that soil co2 flux increased with rainfall and therefore co2 emissions depended on how wet or dry the soil is. – Nitya Chhiber
Alvaro-Fuentes, J.,Cantero-Martinez, C., J.,Lampurlanes, Morell, F.J., 2010. Soil co2 fluxes following tillage and rainfall events in a semiarid Mediterranean agroecosystem: Effects of tillage systems and nitrogen fertilization. Agriculture, Ecosystems and Environment 139, 167–173. 

Alvaro-Fuentes et al. (2010) wanted to understand the impact of soil tillage, vis-a-vis the process of soil co2 fluxes. They applied a method that was spread over three years. It must be noted that the climatic conditions used during the period of this study could be described as being of the Mediterranean type. Different tillage systems were used, namely no-tillage system (NT), conservation tillage system (MT) and finally conventional tillage (CT).  To ensure a fair test, the soil co2 flux was measured five times each year. Three abiotic factors that affected the soil were also measured; which were soil temperature, soil water content, and fertilization. As water content was to be considered, measurements of the soil were only carried out during fallow periods. Finally, statistical analysis of data was carried out using the system of analyses of variance.

It was found out that tillage caused an increase in the soil c co2 fluxes, as there was an increase of the air transport coefficient from soil loosening. Precipitation also influenced the soil co2 flux, which increased after rainfall. Soil co2 fluxes also increased when there was increased substrate availability, which in turn occurs when there is soil organic content accumulation, crop residue production and fertilization. Most importantly, the level of soil co2 flux levels was caused by the fluctuation of the soil between dry and wet points. Furthermore, the combination of rainfall with either a no-tillage system or conservation tillage system led to increased co2 fluxes.

Carbon Footprint and the Production of Potatoes Requires Taking Note of Uncertainties

A carbon footprint is a concept that is being applied in a variety of contexts, including agriculture. This concept is important because it relates to climate change. The potato was chosen to be studied by Roos et al. (2010), because it was a staple national crop. The study showed that it was not an easy task finding out the carbon footprint of potatoes due to the high uncertainty levels involved with parameters. The researchers found out that there are limitations associated with the implementation of the concept of carbon footprint, namely the uncertainty levels associated with variables. They concluded by stating that the Climate Labelling for Food had the best value in terms of production of carbon dioxide but encourage the on-going use of uncertainty analysis. Furthermore, they recommend the usage of uncertainty analysis to ensure further understanding of carbon footprint as a concept. – Nitya Chhiber

Roos, E., Sundberg, C., Hansson, P., 2010. Uncertainties in the carbon footprint of food products: a case study on table potatoes. The International Journal of Life Cycle Assessment 15, 478–488.

Roos et al. (2010)  had the desire to study the uncertainties associated with carbon footprint of the potato in order to apply the results on the real-world implementation of carbon footprint, which was via a labeling system. There were no uncertainties in the methods used; instead there were uncertainties associated with finding out the carbon footprint of the potato as there are so many variables, especially those categorized under Activity Data (AD) that affect it and that are in turn difficult to measure. As a result, there is a high degree of uncertainty associated with each variable. In the study, the variety of processes that contributed to the carbon footprint of the potato were the nitrogen dioxide content in soil, the carbon dioxide content in soil, fertilizer production, the packaging, seed distribution, fuel tillage and some others. In order to ensure that all parameters were considered from the agricultural aspect of growing the potato to the time the potato reaches the consumer, another category of parameters was also considered known as Emission Factors (EF), which consisting emissions from soil, emissions from transport and production of inputs, and finally emissions from the transport of the final goods.
It was found out that two parameters, yield and nitrogen content in soil, affected the carbon footprint. Furthermore, it was recognized that decreasing yield will reduce carbon footprint. The authors also acknowledged the need to set up a system that will take into account a variety of conditions that affect soil apart from nitrogen content. The results show that the amount of carbon released from a regular two-kilogram paper bag is higher than the amount of carbon released from packaging following the Climate Labeling Food Project guidelines. Such a discrepancy between the values of carbon highlights the drawbacks of using carbon footprint as a concept. Such a drawback needs to be considered when setting up a system identifying the carbon footprint of agricultural crops.

Increased Yields more beneficial for Decreasing Greenhouse Gases in the Atmosphere

Interest in agricultural practices peaked around 1961, a time period which was eventually known as the Green Revolution. Currently, we are living during a time when a variety of methods are being sought to limit climate change, and agricultural practices also need to be considered as they also release greenhouse gases, which are the drivers for anthropogenic climate change. Such practices need to be improved in order to limit the amount of greenhouse gases that are released into the atmosphere. Burney et al. (2010) have considered three agricultural development scenarios. One (RW) is based on the real world situation, the second (AW1)is such that it is focused on land expansion and finally, the third one (AW2)is characterized by increased yield. The final recommendation was that if agricultural practices are carried out so that there is emphasis on the quantity of output rather than the quantity of input, there will be lower greenhouse gas emissions and thus making the third scenario (AW2) the most beneficial for the climate.Nitya Chhiber
Burney, J.A.,Davis, S.J.,Lobell,D.B.,2010. Greenhouse gas mitigation by agricultural intensification. PNAS 107, 12052–12057.

Burney and his colleagues at Stanford wanted to understand the best combination of factors for ensuring the least minimal impact of agricultural practices on climate. They did this by describing three scenarios: one (RW) was based on the real world situation, the second (AW1) is characterized by an emphasis on land expansion and finally, the third (AW2) is characterized by yield gains. The last scenario was the control, which was used to compare with the former two scenarios. What must be noted that as certain parameters were difficult to be measured quantitatively, they were converted to other units; for example, yield was measured using monetary values in the form of global spending on yield investment. The timescale that was considered vis-à-vis yield improvements was between the years of 1961 and 2005. Furthermore, other parameters that contributed to yield improvement were not considered, such as fertilizer and irrigation. Finally, in order to ensure the existence of a fair test for more accurate results, the two scenarios (AW1 and AW2) had to be characterized by the same parameters and therefore, pesticides; fuel use and transport were not considered. Graphs were drawn depicting the amount of gigatons of gas emissions, namely pertaining to the gases of nitrogen dioxide, methane, carbon and finally, carbon dioxide, released that corresponded with the amount of yield improvement.
It was found out that the least impact on climate was when there was focus on outputs, for example, increased yields that resulted from an increase in efficiency of fertilizer usage rather than focusing on increasing inputs, such as in the form of expansion of land. It was also found that the AW2 scenario constituted of an overall lower amount of greenhouse emissions. This is not because AW2 was marked by yield improvements but because AW2 maintained 1961 standards of living and thus was characterized by an overall lower pressure on land by the population. Therefore, the existence of land expansion, also known as extensification was lessened in this particular scenario.