Chapter 12 Agriculture and the Environment

Chapter 12 Outline:

12.1 Introduction and Food Security

12.2 Conventional versus Sustainable Agriculture

12.3 Agriculture and Soil

12.4 Agriculture and Pest Management

12.5 Fertilizers – Challenges for the Environment

12.6 Biotechnology and Genetic Engineering in Agriculture

12.7 From Family Farms to an Uncertain Future

12.8 Summary of Chapter 12

Learning Outcomes:

After studying this chapter, each student should be able to:

• 12.1 Understand that the food one chooses may affect the environment
• 12.2 Differentiate between conventional and sustainable agricultural practices
• 12.3 Describe the role of soil and how agricultural methods vary in their effects on soil
• 12.4 Understand the challenges related to using pesticides to control plant pests, and describe sustainable alternatives to pesticide use
• 12.5 Describe how fertilizers, so important for plant growth, may have other, more deleterious effects
• 12.6 Explain the role of biotechnology in agriculture, and environmental challenges this poses
• 12.7 Explore other potential threats to the environment posed by agricultural practices, as well as the changing role of farming in the United States
•     12.8 To be able to summarize this chapter

12.1 Introduction and Food Security

Have you ever considered how the food you eat impacts the environment? As the human population increases and people move away from agricultural land towards more urban environments, the connection between people and the food they eat is growing increasingly distant. The food you choose to eat affects your body due to its nutritional content and calories – factors necessary for your body to produce the energy it needs to survive and perform activities. The food you choose to eat also affects the environment and potentially your access to future food sources, due to the resources needed to grow, process, transport, and package the food. These resources may include water, sunlight, land, fertilizer, pesticides, vehicles, gasoline, packaging materials, and energy and may produce harmful waste and pollution that enters the soil, air, and water. With this in mind, is it possible to sustainably feed the growing human population?

Food Security

Food security means that a person has both physical and economic access to sufficient food to meet dietary needs for a productive and healthy life. Progress continues in the fight against hunger, yet a large number of people lack the food they need for an active and healthy life (Figure 1). The latest available estimates indicate that almost one in nine humans go to bed hungry every night, and an even greater number live in poverty, defined as living on less than $1.25 per day. Poverty (lack of economic access), not food availability, is the major driver of food insecurity. Food security not only requires an adequate supply of food but also entails availability, access, and utilization by all—people of all ages, gender, ethnicity, religion, and socioeconomic levels.

Figure 1. This graph shows the number of people affected by food insecurity in 2019  (by region – in millions). (Credit: Jayati Ghosh,  Research Gate)

Agriculture and food security are inextricably linked. The agricultural sector in each country is dependent on the available natural resources, as well as the politics that govern those resources. Staple food crops are the main source of dietary energy in the human diet and include rice, wheat, sweet potatoes, maize, and cassava.

World population continues to grow exponentially (Figure 2). According to recent United Nations population projections, the world population will grow to 9.7 billion by 2050 and 11.2 billion by 2100. The rate of population increase is especially high in many developing countries, where food insecurity is most acute. In these countries, the fast-growing population, combined with rapid industrialization, poverty, political instability, large food imports and debt burdens, make long-term food security especially urgent.

Figure 2. Human population growth since 1000 AD is exponential (dark blue line). Notice that while the population in Asia (yellow line), which has many economically underdeveloped countries, is increasing exponentially, the population in Europe (light blue line), where most of the countries are economically developed, is growing much more slowly. (Credit: “Human Population Growth” by OpenStax Biology, 2nd ed. is licensed under CC BY 4.0)

The following video gives information and an update on worldwide food security from the United Nations:

Food and Agriculture Organization of the United Nations (2022, July 6) State of food security and nutrition in the world, 2022 [Video- YouTube] https://youtu.be/9rkE-gAUhBk

12.2 Conventional versus Sustainable Agriculture

Agriculture, which includes the cultivation of plants and animals, is constantly evolving. The prevailing agricultural system, variously called “conventional farming,” “modern agriculture,” or “industrial farming,” is typically characterized by rapid technological innovation and large capital investments in equipment and technology (Figure 3). Farms tend to be large-scale, with single crops (monocultures) which favor uniform high-yield hybrid varieties. Raising a monoculture crop increases the risk of disease and pest outbreaks because of the lack of genetic diversity. Most industrial farms depend on highly mechanized farm work, and extensive use of pesticides, fertilizers, and herbicides. In the case of livestock, most production comes from systems where animals are highly concentrated and confined.

Figure 3. Conventional agriculture is dependent on large investments in mechanized equipment powered mostly by fossil fuels. This has made agriculture efficient, but has had an impact on the environment. (Credit: Cotton Harvest by Kimberly Vardeman is licensed under CC BY 4.0.)

In contrast, “sustainable agriculture” is an ecological production management system that promotes and enhances biodiversity, biological cycles and soil biological activity. Organic food is produced by farmers who emphasize the use of renewable resources and the conservation of soil and water to enhance environmental quality for future generations. Organic meat, poultry, eggs, and dairy products come from animals that are given no antibiotics or growth hormones. Organic food is produced without using most conventional pesticides, fertilizers made with synthetic ingredients or sewage sludge, or genetically modified organisms (GMOs).

Both conventional and sustainable agriculture has pros and cons associated with their practices. Conventional agriculture has delivered tremendous gains in the productivity and efficiency of food production worldwide in the past 50 years, which is significant when trying to feed the world’s growing population. However, this increase in productivity often comes at an ecological cost, including soil degradation and the need for large amounts of fertilizers, herbicides, and pesticides.

Sustainable production, with the corresponding practices to maintain soil fertility and soil health is a more ecologically benign alternative to conventional horticulture, but may fall short in providing enough food for everyone. In reality, there is a continuum of agricultural practices used around the world and both conventional and sustainable agricultural practices are likely needed to balance the need for providing sustenance to people while maintaining a healthy environment – also necessary for survival and quality of life.

The following video explores various features of effective sustainable agriculture:

Sustainable Agriculture Research and Education – SARE Outreach (2023, Apr 25)  What is sustainable agriculture? [Video – YouTube] https://youtu.be/iloAQmroRK0?list=PLWlltQ6Oy0zpgxVhd2vZqTDvVXpPhSVd0

12.3 Agriculture and Soil

Soil is a material found at the earth’s surface which is composed of five ingredients — minerals, organic matter, living organisms, gases, and water. Of course soil, water, and sunlight are needed to grow foods, but have you ever wondered why these resources are needed? Water and light are needed for plants to conduct photosynthesis, which uses light energy to power a series of chemical reactions that produces oxygen and sugars. Plants use these sugars for maintenance and growth and to produce ATP, the molecule that fuels all living processes. But what is the role of soil?

In agriculture and horticulture, soil generally refers to the medium for plant growth, typically material found near the surface of the ground (Figure 4). Soil consists predominantly of mineral matter, but also contains organic matter (humus) and living organisms. Water and air fill the spaces between the mineral grains.

Figure 4. Soil-Plant Nutrient Cycle. This figure illustrates the uptake of nutrients by plants in the forest-soil ecosystem. (Credit: U.S. Geological Survey)

Soil plays a role in nearly all biogeochemical cycles, or ways in which elements or compounds move between living and nonliving forms and locations. Global cycling of key elements such as carbon (C), nitrogen (N), sulfur (S), and phosphorus (P), and the compound water all pass through soil and play important roles in allowing plant life to thrive in soil. In the hydrologic cycle, soil helps to mediate the flow of precipitation from the surface into the groundwater. Microorganisms living in soil can also be important components of biogeochemical cycles through the action of decomposition and other processes such as nitrogen fixation.

Soil use and conservation is one factor that needs to be considered when comparing and contrasting conventional and sustainable agricultural practices. Conventional agriculture practices often lead to a decline in soil productivity. Soil is lost overtime due to wind and water erosion as the topsoil is exposed (Figure 5). Salinization (increased salinity) of soils occurs in highly-irrigated farming areas since all water sources contain at least some dissolved salts – some amount of salt is  left behind in the soil after the plants are watered. Desertification, or the conversion of grassland to desert, can be caused by overgrazing of livestock. This is a growing problem across many marginal growing areas, but is especially severe in sub-Saharan Africa, where the desert is expanding south.  These two processes slow or cease biological activity in the soil (and ultimately reduce the amount of organic matter present), which has a severe negative effects on any future plant growth.

Figure 5. Agricultural lands abut the Yellow River, just outside of Touzha in Pingluo County, China. This is part of the Ningxia Hui Autonomous Region in Northwestern China, where a desertification control project is under way to preserve agricultural lands. (Credit: “Desertification Control Project, Ningxia, China” by Planet Labs, Inc. is licensed under CC BY-SA 4.0)

Soil compaction is the increase in density of soil, and occurs when soil particles are pressed together, reducing the pore spaces between them. This compaction limits root penetration depth and may inhibit proper plant growth. Conventional agriculture, using heavy machinery to prepare the seedbed for planting, to control weeds, and to harvest the crop, can cause compaction of soil and disrupts the healthy functioning of  natural soil organisms. Another aspect of mechanical soil tillage is that it may lead to more rapid decomposition of organic matter due to greater soil aeration. Over large areas of farmland, this has the unintended consequence of releasing more carbon and nitrous oxides (greenhouse gases) into the atmosphere, thereby contributing to global warming effects.

Alternative practices associated with sustainable agriculture generally encourage minimal tillage or no tillage methods. With proper planning, removing the need for heavy farm equipment to till can simultaneously limit compaction, protect soil organisms, reduce costs, promote water infiltration, and help to prevent topsoil erosion (Figure 6). In no-till farming, carbon can actually become sequestered into the soil. Thus, no-till farming may be advantageous to sustainability issues on the local scale and the global scale. No-till systems of conservation farming have proved a major success in Latin America and are being used in South Asia and Africa.

Figure 6. Farmers should consider no-till farming as an important tool to prevent loss of soil moisture. (Credit: Pressbooks – University Libraries – Introduction to Environmental Sciences and Sustainability, Creative Commons)

12.4 Agriculture and Pest Management

Pests are organisms that occur where they are not wanted or that cause damage to crops or humans or other animals (Figure 7.). Thus, the term “pest” is a highly subjective term. A pesticide is a term for any substance intended for preventing, destroying, repelling, or mitigating any pest. Though often misunderstood to refer only to insecticides, the term pesticide also applies to herbicides, fungicides, and various other substances used to control pests. By their very nature, most pesticides create some risk of harm —pesticides can cause harm to humans, animals, and/or the environment because they are designed to kill or otherwise adversely affect living things. At the same time, pesticides are useful to society because they can kill potential disease-causing organisms and control insects, weeds, worms, and fungi.

Figure 7. The cotton boll weevil is considered a major pest because of the damage it does to cotton plants. (Credit: This work by Jimmy Smith is licensed under CC BY-NC-ND 4.0.)

The management of pests is an essential part of agriculture and public health. Conventional agriculture relies heavily on chemical pest management, which has helped to reduce losses in agriculture and to limit human exposure to disease vectors, such as mosquitoes, saving many lives. Chemical pesticides can be effective, fast acting, adaptable to all crops and situations. When first applied, pesticides can result in impressive production gains of crops. However, despite these initial gains, excessive use of pesticides can be ecologically unsound, leading to (1) the destruction of natural enemies of the pests, (2) an increase in pesticide resistance as pests evolve defenses against the pesticides, and (3) outbreaks of secondary pests. formerly insignificant pests that replace the original target pest as an economic problem

These consequences have often resulted in higher production costs as well as environmental and human health costs. Pesticides from every chemical class have been detected in groundwater and they are widespread in surface waters. Prolonged exposure to pesticides has been associated with several chronic and acute health effects like non-Hodgkin’s lymphoma, Parkinson’s Disease, leukemia, as well as cardiopulmonary disorders, neurological and hematological symptoms, and skin diseases. Ecologically, pesticide use has led to over 400 insects and mite pests and more than 70 fungal pathogens becoming resistant to one or more pesticides. Pesticides also negatively impact pollinators and other beneficial insect species.

Persistent Organic Pollutants

Persistent organic pollutants (POPs) are a group of long lasting organic chemicals, such as DDT, that have been widely used as pesticides or industrial chemicals and continue to pose risks to human health and ecosystems (Figure 8). POPs have been produced and released into the environment by human activity. POPs are also sometimes referred to PBTs, because they have the following three characteristics:

  Persistent: POPs are pesticides or other chemicals that last a long time in the environment. Some may resist breakdown for years and even decades while others could potentially break down into other toxic substances.

  Bioaccumulative: POPs can accumulate in animals and humans, usually in fatty tissues and largely from the food they consume. As these compounds move up the food chain, they concentrate to levels that could be thousands of times higher than acceptable limits.

  Toxic: POPs can cause a wide range of negative health effects in humans, wildlife and fish. They have been linked to damage to various organ systems, such as the nervous, reproductive, endocrine, and immune systems. Toxic POPS have also been tied to developmental (normal growth) problems and various forms of cancer. 

Figure 8. In 1958, The United States’ National Malaria Eradication Program used an entirely new approach implementing DDT for spraying of mosquitoes. DDT, first developed during the early stages of WWII, was very effective in combating vector-borne diseases such as malaria and typhus, but was banned by the Environmental Protection Agency in June, 1972, from general use in the United States, due to its negative effect on birds and other wildlife. (Credit: “DDT Spray 1958” by Centers for Disease Control and Prevention is in the Public Domain, CC0)

The production and use of most POPs has been banned around the world, with some exceptions made for human health considerations (e.g., DDT for malaria control) or in very specific cases where alternative chemicals have not been identified. However, the illegal production and current use of some POPs continue to be an issue of global concern. Also, even though most POPs have not been manufactured or used for decades, they continue to be present in the environment and thus potentially harmful. The same properties that originally made them so effective, particularly their stability, make them difficult to eradicate from the environment.

The relationship between exposure to environmental contaminants such as POPs and human health is complex. There is mounting evidence that these persistent, bioaccumulative and toxic chemicals cause long-term harm to human health and the environment. Drawing a direct link, however, between exposure to these chemicals and health effects is complicated, particularly since humans are exposed on a daily basis to many different environmental contaminants through the air they breathe, the water they drink, and the food they eat. Numerous studies link POPs with a number of adverse effects in humans. These include effects on the nervous system, problems related to reproduction and development, cancer, and genetic impacts. Moreover, there is mounting public concern over the environmental contaminants that mimic hormones in the human body (endocrine disruptors).

Biomagnification   

Biomagnification is the process by which a compound (such as a pollutant or pesticide) increases its concentration in the tissues of organisms as this compound travels up the food chain. As with humans, animals are exposed to POPs in the environment through air, water and food. For example POPs can remain in aquatic sediments for years, where bottom-dwelling creatures consume them and are then eaten by ever larger organisms and fish. Because tissue concentrations can increase or biomagnify at each level of the food chain, top predators (like largemouth bass or walleye in freshwater) may have a million times greater concentrations of POPs than the sediments contain (Figure 9) . In the oceans, the animals most vulnerable to POP contaminants are those higher up the food web such as marine mammals (whales, seals, polar bears, etc.)  and birds of prey (ospreys, bald eagles, etc.), in addition to large fish species such as tuna and swordfish. Once POPs are released into the environment, they may be transported within a specific region and across international boundaries transferring among air, water, and land.

Figure 9. Bioaccumulation and biomagnification of POPs such as PCBs (polychlorinated biphenyls, a highly carcinogenic chemical). Note that PCBs were at low concentrations in zooplankton and phytoplankton (less than 0.123 ppm) but bioaccumulate to levels of 124 ppm (over 1000 times more concentrated) in the eggs of herring gulls.  (Credit: U.S. EPA. Great Lakes: The Great Lakes Atlas: Chapter Four the Great Lakes Today – Concerns. January 2009)

Sustainable agriculture aims to avoid or limit chemical pesticide use through Integrated Pest Management (IPM). IPM refers to a mix of farmer-driven, ecologically-based pest control practices that seeks to reduce reliance on synthetic chemical pesticides. It involves:

(1) managing pests (keeping them below economically damaging levels) rather than seeking to eradicate them;

(2) relying on a variety of non-chemical measures to keep pest populations low; and

(3) selecting and applying pesticides, when they have to be used, in a way that minimizes adverse effects on beneficial organisms, humans, and the environment.

It is commonly understood that applying an IPM approach does not necessarily mean eliminating pesticide use, although this is often the case because pesticides are often over-used for a variety of reasons. The IPM approach regards pesticides as mainly short-term corrective measures when more ecologically based control measures are not working adequately (sometimes referred to as using pesticides as the “last resort”). In those cases when pesticides are used, they should be selected and applied in such a manner as to minimize the amount of disruption that they cause to the environment, such as using products that are non-persistent and applying them in the most targeted way possible). Non-chemical pesticide pest management practices often used in sustainable agriculture include biological control, intercropping, and crop rotation

Biological control (biocontrol) is one form of non-chemical pest management that uses one biological species (organism) to reduce populations of a different, usually pest species (Figure 10). There has been a substantial increase in commercialization of biocontrol products, such as beneficial insects, cultivated predators and natural or non-toxic pest control products.

Figure 10. The ladybird beetle eats aphids which can destroy plant life. Each adult lady beetle can destroy about 5,000 aphids while the beetle larvae can consume nearly 400 aphids in a week. (Credit: Utah State University – Utah Pest Extension)

Biocontrol is being mainstreamed to major agricultural commodities, such as cotton, corn and most commonly vegetable crops. Biocontrol is also slowly emerging in vector control in public health and in areas that for a long time mainly focused on chemical vector control in mosquito (malaria) and black fly (onchocerciasis) control programs. Successful and commercialized examples of biocontrol include ladybugs to depress aphid populations and parasitic wasps to reduce moth populations. At the microorganismal level, the bacteria Bacillus thuringenensis has been used to kill mosquito and moth larvae, and fungi, such as Trichoderma, have been used to suppress fungal-caused plant diseases. the leaf beetle (Galerucella calmariensis) has been successfully released to suppress the growth and spread of purple loosestrife, a noxious weed. In all of these cases, the idea is not to completely destroy the pathogen or pest, but rather to reduce the damage below economically significant values.

Intercropping refers to growing two or more crops in close proximity to each other during part or all of their life cycles to promote soil improvement, biodiversity, and pest management. Incorporating intercropping principles into an agricultural operation increases diversity and interaction between plants, arthropods, mammals, birds and microorganisms resulting in a more stable crop-ecosystem and a more efficient use of space, water, sunlight, and nutrients (Figure 11). This collaborative type of crop management mimics nature and is subject to fewer pest outbreaks, improved nutrient cycling and crop nutrient uptake, and increased water infiltration and moisture retention. Soil quality, water quality and wildlife habitat all benefit.

Figure 11. Intercropping alyssum (the flowering plants shown center left) with organic romaine lettuce for aphid control. (Credit: : Pressbooks – University Libraries – Introduction to Environmental Sciences and Sustainability; Creative Commons)

Crop rotation is the planned sequence of crop planting over time in the same field, as illustrated in Figure 12. Rotating crops provides productivity benefits by improving soil nutrient levels and breaking crop pest cycles.

Figure 12. Illustration of a three-field crop rotation. (Credit: “Crop Rotation Graphic” by Hakvoort is licensed under CC BY-SA 3.0)

Farmers may also choose to rotate crops in order to reduce risks to their production  through diversification or to manage scarce resources, such as labor, during planting and harvesting timing  (Figure 13.). . This strategy reduces the pesticide costs by naturally breaking the cycle of weeds, insects and diseases. Also, grass and legumes in a rotation protect water quality by preventing excess nutrients or chemicals from entering water supplies.

Figure 13. Cotton in a crop rotation, protected by wheat and grain sorghum stubble, near Lubbock, TX. (Credit: “Cotton in a crop rotation” is in the Public Domain, CC0)

12.5 Fertilizers – Challenges for the Environment

Artificial fertilizers are primarily made up of the soil nutrients nitrogen (N), phosphorus (P) and potassium (K). Plants, like all living organisms, require nutrients to grow, reproduce, and survive, and when the same soil is used year after year to grow the same crop, these nutrients must be replaced artificially,  if techniques such as crop rotation or intercropping are not being used.

Plants get needed nutrients from the soil, air, and water. Macronutrients are needed by plants in large amounts, and include carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S). The macronutrients of nitrogen and phosphorus, in particular, are often limiting factors in the growth of plants, which is why they are major components of artificial fertilizers.

Micronutrients are essential elements that are needed only in small quantities, but are still critical to plant growth and survival. Micronutrients include iron (Fe), manganese (Mn), boron (B), molybdenum (Mo), chlorine (Cl), zinc (Zn), and copper (Cu), and are also included in many fertilizers.

Recall that soil, air, and water are all components of the nitrogen and phosphorus biogeochemical cycles. To speed up plant growth, farmers often use artificial fertilizers (which contain nitrogen and phosphorus compounds) in agriculture, thereby altering the natural nitrogen and phosphorus cycles. While fertilizer use is beneficial to crop production, it is detrimental to aquatic ecosystems, when that fertilizer runs off into nearby water resources. A major negative effect of fertilizer runoff into saltwater and freshwater ecosystems is eutrophication, which may lead to the formation of dead zones, as was explored in chapter 11.

Sustainable agriculture aims to eliminate or reduce artificial fertilizer use to reduce these ecological challenges. Many of the sustainable agriculture practices already discussed, including crop rotation, intercropping, and minimal tillage all allow for a reduction in fertilizer use.

The following video further explores why fertilizers, although useful, can be problematic for the environment:

Environmental Defense Fund (2015, Jul 14) Why fertilizer matters to the environment, and to  your bottom line. [Video – YouTube] https://youtu.be/5TzzPOy1T3g

12.6 Biotechnology and Genetic Engineering in Agriculture

The development of a new strain of crop is an example of agricultural biotechnology, a range of tools that include both traditional breeding techniques and more modern lab-based methods. Any discussion about modern-day agriculture would not be complete without considering the potentially controversial topic of lab based genetically modified crops.  Traditional breeding methods date back thousands of years, as farmers used seeds of the best producing crops and bred animals that provided the most meat, milk, or eggs for future generations.

Today’s controversy related to agricultural changes primarily surrounds a form of modern biotechnology that uses the tools of genetic engineering to develop new strains of organisms. Genetic engineering is the name for the methods that scientists use to introduce new traits into an organism, often by inserting genes from one organism into a different organism. This process results in genetically modified organisms, or GMOs. For example, plants may be genetically engineered to produce characteristics to enhance the growth or nutritional value of food crops. GMOs that are crop species are commonly called genetically engineered crops, or GE crops for short.

The History of Genetic Modification of Crops

Nearly all the fruits and vegetables found in your local market would not occur naturally. In fact, they exist only because of human intervention that began thousands of years ago. Humans created the vast majority of crop species by using traditional breeding practices on naturally-occurring, wild plants. These practices rely upon selective breeding (human assisted-breeding of individuals with desirable traits). Traditional breeding practices, although low-tech and simple to perform, have the practical outcome of modifying an organism’s genetic information, thus favoring positive traits for human use.

An interesting example of selective breeding for particular traits is corn (Figure 14.). Biologists have discovered that corn (sometimes called maize) was developed from a wild plant called teosinte. Through traditional breeding practices, humans living thousands of years ago in what is now Southern Mexico began selecting for desirable traits until they were able to breed the plant into what is now known as corn. In doing so, they kept genetic instructions that were most favorable, keeping traits like large and sweet kernels.  

Figure 14. Wild forms of Zea mays are called ‘Teosinte’. Image description: Over time, selective breeding modifies teosinte’s few fruitcases (left) into modern corn’s rows of exposed kernels (right). (Credit: “Teosinte” by John Doebley is licensed under CC BY 2.5)

This history of genetic modification is common to nearly all crop species. For example, cabbage, broccoli, brussel sprouts, cauliflower, and kale were all developed from a single species of wild mustard plant (Figure 15.). Wild nightshade was the source of tomatoes, eggplant, tobacco, and potatoes, the latter developed by humans 7,000 – 10,000 years ago in South America.

Figure 15. Selective breeding favored certain desired traits of the wild mustard plant (Brassica oleracea) over hundreds of years, resulting in dozens of today’s agricultural crops. Cabbage, kale, broccoli, and cauliflower are all cultivars of this plant. (Credit: “Wild Mustard Plant Selective Breeding” by Liwnoc is licensed under CC BY-SA 4.0)

Traditional Breeding v. Modern Genetic Engineering

To produce new traits in livestock, pets, crops, or other types of organisms, there almost always has to be an underlying change in that organism’s genetic instructions.  As noted, traditional breeding practices result in permanent genetic changes and is therefore a type of genetic modification that has been occurring since agriculture has been used by humans.   But traditional breeding practices do not require sophisticated laboratory equipment or any knowledge of genetics, a perquisite for laboratory based genetic engineering.

How do traditional breeding practices compare to modern genetic engineering? Both result in changes to an organism’s genetic information, but these variations between the two techniques of course exist! Traditional breeding shuffles all of the genes between the two organisms being bred, which can number into the tens of thousands (maize, for example, has 32,000 genes). When mixing a large number of genes, the results can sometimes be unpredictable. Modern genetic engineering allows biologists to focus on and modify a single gene. Also, genetic engineering can introduce a gene between two distantly-related species, such as inserting a bacterial gene into a plant. Such a transfer has a rare but significant equivalent in nature, a process called horizontal gene transfer.  DNA from one species  (usually a prokaryote) can be inserted into other prokaryotes or even some eukaryotes by various natural phenomena, such as when a prokaryotic cell or genes are engulfed by another cell.

Potential Benefits of  the Genetic Engineering of Food Crops

Advances in biotechnology may provide consumers with foods that are nutritionally enriched, longer lasting, or that contain lower levels of certain naturally occurring toxins present in some food plants. For example, developers are using biotechnology to try to reduce saturated fats in cooking oils, reduce allergens in foods, and increase disease-fighting nutrients in foods. Biotechnology may also be used to conserve natural resources, enable animals to more effectively use nutrients present in feed, decrease nutrient runoff into rivers and bays, and help meet the increasing world food and land demands.

Biotechnology has helped to make both pest control and weed management safer and easier while safeguarding crops against disease. For example, some biotechnology crops can be engineered to tolerate specific herbicides, which make weed control simpler and more efficient. Herbicide-tolerant soybeans, cotton, and corn enable the use of reduced-risk herbicides that break down more quickly in soil and are non-toxic to wildlife and humans. Other crops have been engineered to be resistant to specific plant diseases and insect pests, which can make pest control more reliable and effective, and/or can decrease the use of synthetic pesticides. For example, genetically engineered insect-resistant cotton has allowed for a significant reduction in the use of persistent, synthetic pesticides that may contaminate groundwater and the environment. These crop production options can help countries keep pace with demands for food while reducing production costs.

One particularly compelling story in support of genetically engineered crops includes the Hawaiian Papaya industry. In the early 1990s, an emerging disease was destroying Hawaii’s production of papaya and threatening to decimate the $11 million industry (Figure 16.). Fortunately, a man named Dennis Gonsalves, who was raised on a sugar plantation and then became a plant physiologist at Cornell University, would develop papaya plants genetically engineered to resist the deadly virus. By the end of the decade, the Hawaiian papaya industry and the livelihoods of many farmers were saved thanks to the free distribution of Dr. Gonsalves seeds.

Figure 16. Image of Papaya Ringspot Virus symptoms on trees (a) and fruit (b). (Credit: “Papaya Ringspot Virus Symptoms” by APS is in the Public Domain, CC0)

Potential Concerns about Genetically Engineered Crops

Environmental Risks: Critics of GE crops warn that their cultivation should be carefully considered within the broader context of the ecosystems they are being introduced to,  because of their potential risks to the ecological balance of the environment. The complexity of ecological systems presents considerable challenges for experiments that assess the risks and benefits of GE crops. Assessing such risks is difficult, because both natural and human-modified systems are highly complex and have uncertainties that may not be clarified until long after an experimental introduction has been concluded. .

In addition to environmental risks, some people are concerned about potential human health risks of GE crops because genetic modification may alter the intrinsic properties, or essence, of an organism. As discussed above, however, it is known that both traditional breeding practices and modern genetic engineering may result in permanent genetic modifications.  Considering this, it is wise that both new GE crops and traditionally produced crops should be studied for potential human health risks.

Results of NASEM Report on Genetically Engineered Crops

To address these various concerns, the US National Academies of Sciences, Engineering, and Medicine (NASEM) published a comprehensive, 500-page report in 2016 that summarized the current scientific knowledge regarding GE crops. The report, titled Genetically Engineered Crops: Experiences and Prospects, reviewed more than 900 research articles, in addition to public comments and expert testimony.

Five major results from this seminal report, hereafter referred to as the “GE Crop Report” for brevity, is shared in the various subsections below:

1. Interbreeding with Native Species

Through interbreeding, or hybridization, GE crops might share their genetically-modified DNA with wild relatives. This could affect the genetics of those wild relatives and have unforeseen consequences on their populations, and could even have implications for the larger ecosystem. For example, if a gene engineered to confer herbicide resistance were to pass from a GE crop to a wild relative, it might transform the wild species into a ‘super weed’ – a species that could not be controlled by herbicide. Its rampant growth could then displace other wild species and the wildlife that depends on it, thus inflecting ecological harm.

NASEM’s GE Crop Report did find evidence of genetic transfer between GE crops and wild relatives. However, there was no evidence of ecological harm from that transfer. Clearly, continued monitoring, especially for newly-developed crops, is warranted.

 2. Cross-contamination Concerns

The International Federation of Organic Agriculture Movement has made stringent efforts to keep GE crops out of organic production (cross-contamination), yet some US organic farmers have found their corn (maize) crops, including seeds, contain detectable levels of genetically engineered DNA. The organic movement is firm in its opposition to any use of GE crops in agriculture, and organic standards explicitly prohibit their use (however, keep in mind that even “organic” maize has incurred significant genetic modification compared to its wild relative, teosinte). The farmers, whose seed is contaminated, have been under rigid organic certification, which assures that they did not use any kind of genetically modified materials on their farms.

Any trace of GE crops must have come from outside their production areas. While the exact origin is unclear at this time, it is likely that the contamination has been caused by pollen drift from GE crop fields in surrounding areas. Seed producers, who intended to supply GE crop-free seed, have also been confronted with genetic contamination and cannot guarantee that their seed is always 100% GE crop-free.

3. Long-Term Negative Ecological Effects

An early study indicated the pollen from a particular type of genetically modified corn may be harmful to the caterpillars of monarch butterflies (Figure 17). This type of corn, known as Bt corn, is genetically modified to produce a bacterial protein that acts as an insecticide. This trait has the positive effect of reducing the amount of insecticides used by farmers. But relatively high concentrations of pollen from Bt corn can be harmful to caterpillars. A large, multi-national study funded by the US and Canada found that a majority of Bt corn did not represent a risk to monarchs. However, one strain of Bt corn was particularly harmful, and it was consequently removed from the market.

Figure 17. Photograph of a female Monarch Butterfly (Danaus plexippus) on a Mexican Milkweed called Silky Gold (Asclepias curassavica). (Credit: Picture was taken in Aston Township, Pennsylvania. “Monarch Butterfly Danaus plexippus on Milkweed Hybrid” by Derek Ramsey is licensed under CC BY-NC 4.0)

The GE Crop Report also mentioned a separate threat to monarch: loss of milkweed, which is critical to the butterfly’s lifecycle. Some GE crops are engineered to resist the herbicide glyphosate. Farmers using these crops can spray their entire field with the herbicide, which kills milkweed but not their GE crop. This can lower the amount of milkweed growing within the habitat range of monarchs, and have a negative effect on monarch populations, that depend on the milkweed. 

4. Potential Human Health Risk

At least some of the genes used in GE crops may not have been used in the food supply before, so GM foods may pose a potential risk for human health, such as producing new allergens. But the UN’s Food and Agriculture Organization has concluded that risks to human and animal health from the use of GMOs are low to negligible. NASEM’s GE Crop Report found “no substantiated evidence of a difference in risks to human health between current commercially available genetically engineered (GE) crops and conventionally bred crops, nor did it find conclusive cause-and-effect evidence of environmental problems from the GE crops.” The American Medical Association’s Council on Science and Public Health, in 2012, stated that “Bioengineered foods have been consumed for close to 20 years, and during that time, no overt consequences on human health have been reported and/or substantiated in the peer-reviewed literature.” Similar statements have been made by the US National Resource Council and the American Association for the Advancement of Science, which publishes the preeminent scholarly journal, Science.

The potential of GE crops to be allergenic is a potential adverse health effects and should continue to be studied, especially because some scientific evidence indicates that animals fed GE crops have been harmed. NASEM’s GE Crop Report concluded that when developing new crops, it is the product that should be studied for potential health and environmental risks, with less emphasis on the process that achieved that product. What this means is, because both traditional breeding practices and modern genetic engineering produce new traits through genetic modification, they both present potential risks. Thus, for the safety of the environment and human health, both should be adequately studied.

5. Intellectual Property Rights

Intellectual property rights, or being able to patent new GE seeds, are one of the important factors in the current debate on GE crops. GE crops can be patented by Agri-businesses, which can lead to them controlling and potentially exploiting agricultural markets. Some accuse companies, such as Monsanto, of allegedly controlling seed production and pricing, much to the detriment of farmers. NASEM’s GE Crop Report recommends more research into how the concentration of seed-markets by a few companies, and the subsequent reduction of free market competition, may be affecting seed prices and farmers. In particular, fewer seed choices for farmers and restrictive rules for using GE seeds have often raised costs for farmers and narrowed their choice of products.

More information of genetically modified seeds, including their pros and cons,  are explored in the following video:

Dynamic Earth Learning (2020, Oct 14). Genetically Engineered Seeds: Pros and Cons. [Video – YouTube] https://youtu.be/Ao9Twt7ef9E

Are GE Crops the Solution We Need?

Significant resources, both financial and intellectual, have been allocated to answering the question: are GE crops safe? After many hundreds of scientific studies, the answer is yes. But a significant question still remains: are they necessary? Certainly, such as in instances like Hawaii’s papaya, which were threatened with eradication due to an aggressive disease, genetic engineering was a quick and effective solution that would have been extremely difficult, if not impossible, to solve using traditional breeding practices.

However, in many cases, the early promises of GE crops – that they would improve nutritional quality of foods, confer disease resistance, and provide unparalleled advances in crop yields – have largely failed to come to fruition. NASEM’s GE Crop Report states that while GE crops have resulted in the reduction of agricultural loss from pests, reduced pesticide use, and reduced rates of injury from insecticides for farm workers, they have not increased the rate at which crop yields are advancing when compared to non-GE crops. Additionally, while there are some notable exceptions like virus-resistant papayas, very few GE crops have been produced to increase nutritional capacity or to prevent plant disease that can devastate a farmer’s income and reduce food security. The vast majority of GE crops are developed for only two purposes: to introduce herbicide resistance or pest resistance.

Genetic engineering of crops represents an important tool in a world of rapidly changing climate and a burgeoning human population, but it is only one of many tools that agriculturists can use to produce enough food for all humans while simultaneously working to conserve the environment.

The following video, by the “Amoeba Sisters” gives a nice summary and update on genetic engineering in general:

Amoeba Sisters (2023, Oct 1) Genetic Engineering with the Amoeba Sisters. [Video – YouTube] https://youtu.be/CDw4WPng2iE

12.7 From Family Farms to an Uncertain Future

Other concerns associated with agriculture include potential impacts on global climate change, human health, and several economic, social, and philosophical issues explored below:

(1) Agriculture’s link to global climate change is just beginning to be appreciated. Destruction of tropical forests and other native vegetation for agricultural production has a role in elevated levels of carbon dioxide and other greenhouse gases. Recent studies have found that soils may be large reservoirs of carbon.

(2) In addition to human health risks associated with pesticide use explored earlier, the general public may be affected by the sub-therapeutic use of antibiotics in animal production and the contamination of food and water by pesticides and nitrates. These are areas of active research to determine the levels of risk. The health of farm workers is also of concern, as their risk of exposure is much higher.

(3) Economically, the U.S. agricultural sector includes a history of increasingly large federal expenditures. Also observed is a widening disparity among the income of farmers and the escalating concentration of agribusiness—industries involved with the manufacture, processing, and distribution of farm products—into fewer and fewer hands. Market competition is limited and farmers have little control over prices of their goods, and farmers continue to receive a smaller and smaller portion of consumer dollars spent on agricultural products.

(4) Economic pressures have led to a tremendous loss of farmers, farmland, and farms (particularly small farms), during the past few decades.  The US lost more than 100,000 farms between 2011 and 2018 (12,000 of those between 2017 and 2018 alone). Economically, it is very difficult for potential farmers to enter the business today because of the high cost of doing  business. Productive farmland also has been swallowed up by urban and suburban sprawl—since 1970, over 30 million acres have been lost to development.

(5) Historically, farming played an important role in our development and identity as a nation. From strongly agrarian roots, we have evolved into a culture with few farmers. Less than two percent of Americans now produce food for all U.S. citizens. This leads to the philosophical questions of whether sustainable and equitable food production can be established when most consumers have so little connection to the natural processes that produce their food and what intrinsically American values have changed and will change with the decline of rural life and farmland ownership.

Sustainable agriculture addresses many of the concerns outlined above. Therefore, there is a growing sense of urgency among scientific experts in this field to adopt sustainable agriculture practices. Sustainability has become an integral component of many government, commercial, and non-profit agriculture research efforts, and it is beginning to be woven into agricultural policy. Increasing numbers of farmers and ranchers have embarked on their own paths to sustainability, incorporating integrated and innovative approaches into their own enterprises.

The following video shows how a family farm in Maine has employed various techniques to run a sustainable farming business:

Consensus Digital Media (2022,  Feb 17) Regenerative agriculture on a family farm in Maine. [Video – YouTube]  https://youtu.be/mj3JkAG_XiU

12.8 Summary

The prevailing agricultural system has delivered tremendous gains in productivity and efficiency. Food production worldwide has risen in the past 50 years. On the other hand, agriculture profoundly affects many ecological systems. Negative effects of current practices include ecological concerns, economic and social concerns and human health concerns. Pesticides from every chemical class have been detected in groundwater and are commonly found in groundwater beneath agricultural areas. Despite impressive production gains, excessive use of pesticides has proven to be ecologically unsound, leading to the destruction of natural enemies, the increase of pest resistance pest resurgence and outbreaks of secondary pests. These consequences have often resulted in higher production costs and lost markets due to undesirable pesticide residue levels, as well as environmental and human health costs. Alternative and sustainable practices in farming and land use include organic agriculture, integrated pest management and biological control. Genetic modification of crops can benefit crop production, but is controversial due to known and unknown risks.

Attribution

Content in this chapter includes original work created by Lauren Roberts and Paul Bosch as well as from the following sources, with some modifications:

Bora, S., Ceccacci, I., Delgado, C. & Townsend, R. (2011). Food security and conflict. World Bank, Washington, DC. © World Bank. Retrieved from https://openknowledge.worldbank.org/handle/10986/11719. Available under Creative Commons Attribution License 3.0 (CC BY 3.0). Modified from original.

CK12. (2015). Food and nutrients. Accessed August 31, 2015 at http://www.ck12.org/user:a3F1aWNrQHdlYmIub3Jn/section/Food-and-Nutrients/. Available under Creative Commons Attribution-NonCommercial 3.0 Unported License. (CC BY-NC 3.0). Modified from original.

“Genetically Modified Foods and Social Concerns” by Behrokh Mohajer Maghari and Ali M. Ardekani is licensed under CC BY-NC 4.0. Modified from the original by Matthew R. Fisher.

Godheja, J. (2013). Impact of GMO’S on environment and human health. Recent Research In Science And Technology, 5(5). Retrieved from http://recent-science.com/index.php/rrst/article/view/17028. Available under Creative Commons Attribution License 3.0 (CC BY 3.0). Modified from original.

Maghari, B. M., & Ardekani, A. M. (2011). Genetically Modified Foods and Social Concerns. Avicenna Journal of Medical Biotechnology, 3(3), 109–117.

NASEM. 2016.Genetically Engineered Crops: Experiences and Prospects. http://nas-sites.org/ge-crops/category/report/

World Bank; Food and Agriculture Organization; International Fund for Agricultural Development. (2009). Gender in agriculture sourcebook. Washington, DC: World Bank. © World Bank. Retrieved from https://openknowledge.worldbank.org/handle/10986/6603. Available under Creative Commons Attribution License 3.0 (CC BY 3.0). Modified from original.

World Bank Group. (2015). Ending poverty and hunger by 2030: An agenda for the global food system. Washington, DC. © World Bank. Retrieved from https://openknowledge.worldbank.org/handle/10986/21771. Available under Creative Commons Attribution License 3.0 IGO (CC BY 3.0 IGO). Modified from original.