Feeding Global Warming: Assessing the Impact of Agriculture on Climate Change


Feeding Global Warming: Assessing the Impact of Agriculture on Climate Change

Emma Layman
Published by the PIT Journal: 


This essay examines the ways in which agricultural practices have influenced global climate change. Beginning with the Neolithic Revolution (12,000 years ago), and continuing through the Columbian Exchange (1492), Industrial Revolution (1760-1820s), and Green Revolution (1940s- ‘60s), agricultural practices have expanded and intensified. As these revolutions led to the domestication, diversification, and plant reliance on fertilizers and pesticides, the emission of greenhouse gases increased, and is still rising. Although it is known that these greenhouse gases, like carbon dioxide, methane, and nitrous oxide, contribute to climate change, many people believe they only come from industrial developments like factories and cars. However, since these gases are also emitted from agricultural practices, global warming may be influenced by more factors than the general public is aware. It can be concluded that previous agricultural advancements have been beneficial in supplying food, but while they are feeding the growing human population, agricultural practices are also feeding global climate change.


Agriculture has always been essential to human life but is becoming detrimental to the environment. Food is one of the most basic needs for people around the world, but it may be contributing to climate change more than the general public is aware. Agriculture has been fundamental to civilization since our nomadic ancestors discovered how to domesticate crops and live off the land. However, with agricultural revolutions, including the Neolithic Revolution (12,000 years ago) and the Green Revolution (1940s-’60s), agricultural practices have become destructive. Other historical events including the Columbian Exchange (1492) and the Industrial Revolution (1760-1820, 1840s) have increased agricultural output, but have also increased greenhouse gas output. Today’s expansive and intensive agricultural practices are contributing to global climate change through increased emissions of greenhouse gases.
Global warming can be attributed to three primary greenhouse gases: carbon dioxide, methane, and nitrous oxide. While research has proved that fossil fuels are responsible for most of the recent carbon dioxide in the atmosphere, fossil fuels are not the only contributors. An increasing number of studies in Nature, a respected research journal, argue that agricultural practices contribute large amounts of methane and nitrous dioxide to the atmosphere; these gases will have longer lasting effects on the environment than carbon dioxide. While it cannot be denied that agriculture emits these gases, few researchers have looked at the root of these practices so that we can better understand the increased rate of these emissions. Researchers like W. Neil Adger and Katrina Brown argue that most of the greenhouse gases produced by agriculture come from mass production of livestock, manure use, and fertilizer use. Deforestation and soil degradation, both results of agricultural expansion, emit greenhouse gases like carbon dioxide. Livestock, manure, and fertilizers contain large amounts of methane and nitrous oxide, making them primary emitters of these gases (Foley et al.). The harmful impact agriculture has on the environment will only increase with time, especially since the world population is continuing to rise, and with it rises the danger of food scarcity.
Before debating this topic in greater depth, it is important to understand basic agricultural practices. For example, intensive agricultural practices refer to systems of cultivation that use “large amounts of labor and capital relative to land area” (Encyclopedia Britannica). Labor and capital are required for the large amounts of fertilizers, pesticides, and water that maintain the land. Capital is also required to purchase and maintain high-efficiency machinery. Intensive agriculture is practiced primarily in developed countries. In developing countries or lower-income regions of the world, subsistence agriculture is the primary cultivation technique. Subsistence farmers are “those who produce only enough crops to feed their family” (Rosenberg). This type of farming uses minimal amounts of fertilizers and relies on small amounts of labor. Intensive and subsistence agriculture differ primarily in their goals—to make a commercial gain versus to make dinner.
Past Research and Research Gaps
The events I plan on analyzing have been discussed in previous research. Because the Neolithic Revolution marks the beginning of agriculture, it is cited by many scientists as the starting point for current agricultural practices (Ruddiman; Adger and Brown). Prior to the Neolithic Revolution, humans were hunters and gatherers. Although this lifestyle did have some impact on the environment, it was not until the domestication of crops that carbon dioxide and nitrous oxide began to be released from the soil (Ruddiman). The results of the Neolithic Revolution’s innovations are major factors of greenhouse gas emissions (Ruddiman). Although researchers agree on this topic, my research will connect this event with other events that have had larger impacts on climate change.
The Columbian Exchange is a unique event in terms of greenhouse gas emissions. While researchers do not think the event itself was a cause of negative agricultural practices, the spread of crops caused by the exchange pushed us toward intensive agriculture (Shmoop). However, this subject is controversial as some researchers disagree that the Columbian Exchange contributed to global warming. There are differing opinions about the effects of the exchange. Some researchers believe the Columbian Exchange led to intensive agriculture, but the significance of their studies is minimal.  
Researchers analyzing this topic argue that the Columbian Exchange caused agriculture to become more intensive as farmers grew crops that were not indigenous to their respective regions. As continental drift occurred, so did the evolution of crops (Richmond). Therefore, the plants traded in the Columbian Exchange required more intensive agriculture in order to meet wanted yields. 
Researchers agree that the Industrial Revolution is one of the greatest causes of global warming, although only some relate this to greenhouse gases emitted from new agricultural practices (Adger and Brown; Grimm; Davidson). However, it is undeniable that the Industrial Revolution caused agriculture to expand into more rural areas as cities grew and caused agriculture to become more intensive in order to support the developed world’s growing population (Davidson). The Industrial Revolution was a step forward for humanity but a destructive force on the environment. The Earth is significantly hotter now than it would have been without the greenhouse gases emitted by the Industrial Revolution (Grimm). The Industrial Revolution’s effect on agriculture led to greenhouse gas emissions just as detrimental as the emissions of the factories being built at the same time.
The most recent shift in agricultural practices was caused by the Green Revolution, an agricultural renovation in the 1940s that incorporated manufactured fertilizers and high-yielding crops into existing agricultural practices (Andrews). Because this revolution is more recent, researchers have more data on how this event has begun to impact global warming than any other agricultural revolution. Without the increased yield of crops caused by the Green Revolution, the greenhouse gases that would have entered the planet’s atmosphere “would have been equal to as much as one third of the world’s total output of greenhouse gases since the dawn of the Industrial Revolution” (Hill). While this shows that the Green Revolution has reduced emission levels, this does not negate the intensive agriculture practices it caused. These practices include the use of fertilizers and pesticides that emit greenhouse gasses.
Agriculture has undergone many changes since the Neolithic Revolution as a result of technological advances, although some of these advances may be costly down the road. The Neolithic Revolution brought about the widespread practice of agriculture, the Columbian Exchange facilitated the spread of nonindigenous crops to many regions around the world, the Industrial Revolution led to agricultural expansion into forests, and the Green Revolution increased the amount of fertilizers and reduced crop diversity. All these events contributed to global warming. Agriculture’s role in greenhouse gas emissions is an indirect result of revolutions that brought about positive change for humans but negative change for the environment.
The Neolithic Revolution
The history of agriculture begins with the Neolithic Revolution, an event that occurred around 12,000 years ago but is still having lasting impacts. The warming of the Earth in this post-Ice Age period allowed humans to stay in one place where crops were planted and animals were domesticated (Gascoigne). Although the Neolithic Revolution allowed populations to flourish and cities to develop, it can also be held accountable for the beginning of poor agricultural practices.
The Neolithic Revolution was sparked by climate change. The earth warmed up; as a result, plants were more abundant and animals migrated to colder regions. Some humans began cultivating the surplus of crops, while others continued the practice of hunting and gathering. Jericho is the first known region where crop cultivation occurred, and it is also the first known town, with a population of 2,000 people (Gascoigne). While the adoption of crop cultivation helped civilizations like Jericho develop and increase their populations, there is a negative side to crop cultivation. The change in land use from forests to farmland released carbon into the atmosphere. Because trees absorb carbon, tearing them down causes their stored carbon to be released into the atmosphere. Once in the atmosphere, this carbon can undergo a chemical reaction and become carbon dioxide (Adger and Brown). Jericho is one example of how agricultural practices led to increased populations, further contributing to global warming through deforestation.
Another type of agricultural change caused by the Neolithic Revolution was the domestication of livestock, which allowed humans to become less nomadic. Villages and towns were able to develop and survive off of nearby resources. However, the domestication of livestock caused resources to go to animals instead of humans, meaning more crops had to be produced (Foley et al.). Another negative result of livestock is the amount of manure produced, which contains large amounts of methane. While carbon dioxide and nitrous oxide levels were not severely influenced by the Neolithic Revolution, they have experienced increases in the past 8,000 years that have caused the Earth to be warmer than it would have been without anthropogenic influences (Ruddiman). This revolution marks the beginning of a rise in anthropogenic gases and also created the groundwork for future agricultural practices that have had greater impacts on global warming.
The Columbian Exchange
Most of the world’s crop diversity is a result of evolution and the Columbian Exchange. To fully understand the evolution of agriculture, it is necessary to look back at a pre-agriculture environment. Approximately 200-270 million years ago, the same species of certain plants and animals were present on multiple continents. An example of this is Glossopteris, a tropical forest fern that has been found fossilized in South America, Africa, India, and Australia (Richmond). However, today there is no plant like Glossopteris; there are no single plant species that inhabit multiple regions of the world. Some plants may be closely related, but none are the exact same species (Akioyamen). Species that are present on multiple continents were indigenous to one area and then transported around the world by humans.
Darwin’s theories of natural selection and evolution are most commonly used to explain the diversity of animals and other active creatures. However, Darwin’s theories can also be used to analyze the idea that crops have adapted and evolved to be successful in their environments. This idea is supported by the plant Brassica oleracea. By selecting for certain traits like leaf size and amount of flower development, this plant has been used to create broccoli, cabbage, kale, and cauliflower (Courteau). This can be applied to the wide variety of crops present today. At some point in time, there may have been similar crops like Glossopteris on multiple continents, but the differing environments after the split of Pangaea most likely selected different traits for each plant so that, after many generations, the plants became unique species distinct from similar crops in other regions of the world (Darwin).   
When Columbus arrived to the “New World” in 1492 there were new exotic crops that had very small resemblance to the plants grown in the “Old World.” Therefore, it follows that the crops present in the “New World” and “Old World” were the best suited for their environments and should have been cultivated there, and only there (Foley et al.). While it may be argued that some crops are able to produce higher yields in nonindigenous areas, it is important to consider the technology available in different regions of the world. For example, developed countries have more access to fertilizers and large plows than developing countries. Therefore, developed countries are able to produce higher yields, but at a greater environmental cost.
Expanding different crops to more regions of the world has caused intensification to become necessary to keep yields high. Because the Columbian Exchange was responsible for spreading crops to regions where they were not as successful, agriculture expanded to produce the needed yields and caused increased deforestation. Therefore, the Columbian Exchange increased emissions of carbon dioxide. While the Columbian Exchange has been identified as an extremely important event in facilitating trade between two worlds, recent research regarding intensification and expansion of agriculture supports the claim that, in some ways, the Columbian Exchange caused the use of land practices that have contributed to global warming.
The Industrial Revolution
The Industrial Revolution began in Great Britain in 1750 and spread to the entire US in the 1860s. This introduced new agricultural technology, including more efficient plows and devices that allowed more seeds to be planted at one time. The time saved on preparation allowed larger amounts of crops to be planted at one time. The development of meat processing factories that occurred after the Industrial Revolution caused livestock production to increase. Both crop and meat production led to the expansion and intensification of agriculture. As the population increased, urban sprawl also occurred and more areas were deforested to make room for croplands and living spaces. All of these events caused methane, carbon dioxide, and nitrous oxide levels to increase.
The Industrial Revolutions of Britain and the United States are known for increasing carbon dioxide emissions; however, it is possible that they led to the emission of other greenhouse gases through expansion and intensification of agriculture. The Industrial Revolution caused cities to expand and populations to increase.  As a result, agriculture was moved further from cities and spread into more rural areas. During the Industrial Revolution the population reached 1 billion people, making more intensive agricultural practices necessary (McLamb). From 1960 to 1999 methane concentrations grew six times faster than during any other 40 year span. This was a result of human influences including emissions from natural gases and livestock production (“Greenhouse Gas Sources”). Following the Industrial Revolution, there was also an increase in nitrous oxide as agriculture was adapted to meet population needs, although the increase was not as great as the change in methane emissions. The use of nitrogen-based fertilizers and the cultivation of soils in tropical regions have been the primary contributors to nitrous oxide emissions (Davidson). However, without these practices food production would not be as efficient and more people would go hungry.
The Green Revolution
While the Green Revolution is known for increasing crop yields in developing regions where populations were growing faster than food production, the Green Revolution is also responsible for the emission of greenhouse gases. During the time of the Green Revolution, India was close to a major famine, but a modified type of rice allowed more food to be produced with less land. So how can something so beneficial be so detrimental? The real debate on this topic is whether the impact of greenhouse gases is greater now, after the Green Revolution, or if it would have been worse without the Green Revolution, if we had just maintained post-industrial land use practices.
The Green Revolution transformed agricultural practices by making them more intensive, thereby reducing the amount of land needed. However, the amount of gases being produced by intensive agricultural practices is still dangerous to the environment without the expansion of agriculture (Hill). Although decreasing the rate of deforestation is beneficial because it reduces carbon emissions, decreasing deforestation will not succeed long-term because the world population continues to grow. Even after the implementation of “green” practices which reduced deforestation, carbon dioxide has experienced a seasonal rise of 15% over the past five decades (Andrews). This can be attributed to the larger seasonal range in crop growth that was caused by the Green Revolution. With modified crops, farmers are able to produce crops for a longer period of time, meaning crops release more and absorb less carbon dioxide (Andrews).
If the Green Revolution had not occurred and the agricultural processes of the industrial age had continued, the emission of greenhouse gases would not have undergone severe fluctuation. The combination of agricultural practices and deforestation during the Industrial Revolution would have released slightly more greenhouse gases than the intensive agriculture of the Green Revolution. Even with this information, it is difficult to determine which agricultural practices are better. The use of modified crops and fertilizers is harmful to the environment, but for many developing countries, these practices are the only way to feed their nations. Developing new techniques that maintain the current level of crop production will be the only way to transition away from the harmful practices of the Green Revolution.
While agriculture’s impact on the environment cannot be completely prevented, researchers have proposed practices that would reduce the impact. Some of the most promising solutions are reducing waste by shifting diets and increasing agricultural resource efficiency (Foley et al.). The solutions differ between developed and developing countries because agricultural practices are dependent on the amount of technology. Different countries contribute different concentrations of each greenhouse gas to the atmosphere.
Because raising livestock contributes more harmful gases than producing crops, reducing the amount of meat-based diets would lessen the emission of greenhouse gases from agriculture and land use practices. Another solution that primarily targets developing countries is increasing resource efficiency or implementing more sustainable agricultural practices. Since fertilizers are responsible for polluting water and emitting nitrous oxide, using them more efficiently would reduce their impact (Foley et al.). There are many solutions for reducing agriculture’s emission levels, but they will only be effective when countries enforce new policies.
While these ideas seem feasible, many countries are unsuccessful in implementing policies because they are not sure if the benefits will outweigh the loss in food production. Foley et al. negates that argument by saying more people would be fed if less resources went to livestock. Because livestock must also be fed, large amounts of agricultural land is devoted to growing feed for cows, pigs, chickens, and other mass-produced animals. Redirecting this food to humans could counteract the decrease in calorie consumption caused by eliminating meat from one’s diet. Researchers agree that implementing policies to reduce emissions will be worth it in the future, but the short-term impacts turn many diplomats away from reform.
While the lasting effects of global warming are not fully understood, the causes are widely accepted to be the emission of greenhouse gases. Carbon dioxide, methane, and nitrous oxide have always been present in Earth’s current atmosphere; however, the concentration levels have undergone severe fluctuation. The advantages brought by the Neolithic Revolution, Columbian Exchange, Industrial Revolution, and Green Revolution must be weighed against their contributions to greenhouse gases.
The domestication, diversification, spread, and intensification of crops all contribute to greenhouse gas emissions. Some of the most successful, change-inducing events in human history are indirect causes of global warming. Is it possible to develop agricultural practices into something more environmentally friendly? Perhaps the cavemen of the Pliocene Epoch in the Tertiary Period (5 to 1.8 million years ago) were more aware of their impact on their surroundings than we are today. Our collective lack of empathy for the environment may lead to the end of our time on Earth. Of course, this apocalypse will not be experienced by our generation, or even our grandchildren. But one day, our descendants will face the consequences of our neglect. The earth is always changing, and we have only begun to understand it. Too often environmental scientists look at future emissions and the ways in which global warming has increased within the last decade. Maybe it is time to look deeper in the past. How have events only mentioned in textbooks influenced lifestyles today? Are we really better off than the hunters and gatherers of the pre-Neolithic age? At what point will our knowledge and technology become too great for our own good? We may never know, but our great-great grandchildren will surely face the impacts of the path we have chosen.
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