L19. Conventional Agriculture: Impacts & Alternatives
In the last lesson, we learned about the vast quantity of corn produced in the United States, and the expansive amount of land that is dedicated to agriculture. We have over 391 million acres of cropland in the US, covering about 20% of the 48 contiguous states (source Links to an external site.). Globally, this number is an astounding 3.9 billion acres, or the equivalent area of the entire continent of South America. Global pastureland (land used for grazing livestock) covers another 7.4 billion acres, an area the size of Africa (source Links to an external site.).
Figure 1. Percent of global land area covered in cropland and pastureland.
This cropland and pastureland produces the meat, milk, eggs, fruits, nuts, and vegetables that feed the ever-growing human population, and well as the cotton, flax, jute, and hemp we use for cloth. We are also starting to use this land for crops that will be converted to biofuels and bioproducts. Being able to produce enough food, fiber, and fuel for 7.5 billion people through agriculture is an incredible success story, but it has also completely reshaped the surface of our planet. Converting all of this land area to agriculture is not without consequences.
Problems with Conventional Agriculture
When we talk about producing herbaceous biomass from agriculture, we are almost referring to conventional cropping systems. In the following video, Professor Andrew Friedland from Dartmouth College explains some of the negative environmental effects associated with conventional agriculture.
Professor Friedland moved through the issues associated with large-scale conventional agriculture fairly quickly, so let’s take a moment to summarize and expand upon them. The main, overarching problem is the disruption of natural ecosystem processes. Natural vegetation communities change and develop over time. But in agriculture, we force nature to abide by an annual cycle, which means the landscape is disturbed every single year. Typically, native vegetation communities are also fairly diverse, meaning there is a mixture of different plant species. Conventional agriculture grows one species at a time (e.g. corn, soybeans), which is called a monoculture. This disruption of natural processes has several consequences.
Pest-related issues
First, we learned from the video that monocultures are more susceptible to pests. Why is that? Let’s say a pest’s favorite food is corn (Pictured: Corn Rootworm Beetle). If that pest stumbled upon a corn monoculture, it would be like an all-you-can-eat buffet with only its very favorite dish. If instead that same pest found itself in a diverse field filled with all different types of plants, it would be much harder for it to find the dish it wants to eat. You can see, then, how it is much easier for a pest to feed, grow, and multiply in a monoculture of its favorite plant than in a diverse cropping system. Hypothetically, a single pest could take out the entirety of the nation’s corn crop in one fell swoop. To protect our crops from this disaster, we use a lot of pesticides. This is not ideal because some pesticides can remain in the environment for a long time, harming animals that are high on the food chain. Pesticides can 
also have negative health effects on agricultural workers.
But applying all of this pesticide can actually have the reverse effect of what was intended. Have you ever heard of pesticide resistance? This happens because some of the insects in the population naturally are stronger and more resistant to the pesticide (just like some humans can digest lactose while others are intolerant). When the pesticide is applied to the first generation of insects, the individuals that are most sensitive die off, while the strongest survive and go on to reproduce. That means that the next generation will have more insects that are resistant to the pesticide. After repeated applications, resistant pests may comprise the majority of the population. In the illustration, the naturally pesticide-resistant individuals are red. After multiple applications of a pesticide, a greater proportion of the later generation is resistant.
Soil health issues
Second, conventional agriculture removes the plants from the system at the end of each growing season by harvesting them. If you remember from the “How Plants Grow” lesson, plants uptake nutrients from the soil via their roots, and use these nutrients to grow biomass. When we harvest crops, then, we remove all of the nutrients that are stored in the plant’s biomass, leaving behind soil that is less productive. To make up for removing all of this nutrient-rich organic material, we apply a lot of synthetic fertilizers. It’s important to note that synthetic fertilizers don’t add any organic matter to the soil, just a concentration of nutrients (namely nitrogren, phosphorus, and potassium). The issue with fertilizers is that these nutrients are highly mobile in water, and therefore susceptible to runoff. Of the 125-160 pounds of nitrogen a farmer applies to each acre of their corn field, somewhere around 13 pounds will be lost as water running over the surface of the land transports the nitrogen into 
the nearest water body. Excess nitrogen in our surface waters can cause a range of issues such as Blue Baby Syndrome (blood can’t properly carry oxygen) and eutrophication. Eutrophication occurs when waters are overly enriched with nutrients, leading to the excessive growth of algae. As the algae decomposes, the water becomes depleted of oxygen and larger animals suffocate to death. This is what causes the Dead Zone and fish kills in the Gulf of Mexico.
Removing the crop at the end of the growing season has another negative effect. In Minnesota, corn is typically planted in May and harvested in October or November. That means for at least 5 months of the year, the field is barren. Without the roots of the plants to hold it in place, the soil is extremely vulnerable to erosion from wind and water.
Resources are required
As we mentioned in the last lesson, large-scale industrial agriculture requires a lot of fossil fuel consumption throughout each step of the process. This includes producing the synthetic fertilizer, running the tractors and other machinery, transportation, and pumping water for irrigation. In fact, about a quarter of all greenhouse gas emissions come from agriculture-related activities.
In addition to energy, conventional agriculture consumes a lot of water. Globally, we use 2,800 cubic kilometers of water on crops every year. That’s enough to fill the Empire State Building 7,305 times every single day of the year (source Links to an external site.). Intensive irrigation can result in the depletion of major water bodies; the most famous examples being the Colorado river (which no longer flows to the sea) and the Aral Sea (which has shrunk to a tiny fraction of its original size).
The dried up river bed of the Colorado River in San Luis Río Colorado, Mexico.
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Satellite photos showing how the Aral Sea has shrunk over time. The two major rivers that once fed the Aral Sea were largest diverted for irrigation.
It's not all bad
We’ve been talking about bioproducts and biofuels as an eco-friendly alternative to mineral-based products (fossil fuels, sand, cement, etc.), but it is clear that agricultural production is not without negative impacts. However, how bad is it, really? Is 25% of all GHG emissions really that surprising when you think about an industry that feeds, clothes, and provides energy to 7.5 billion people? Water used for food production is probably a good use of resources. It’s important to keep in mind that agriculture is an absolute necessity, and we cannot simply stop farming because of the impacts. There is nothing more essential to our survival on Earth than our ability to grow food, fiber, and fuel in a highly efficient and productive manner.
But if we want more of our products and fuels to be bio-based, we will have to grow more biomass. At the same time, we will need to feed more and more people who have higher and higher levels of consumption (think back to Lesson 2). If this is the case, how can the world possibly sustain this level of agricultural production? And perhaps more importantly, how can we do it without further contributing to climate change and environmental degradation?
Fortunately, many of the issues described above are not unavoidable. There are many practices and alternative growing systems that focus on reducing the environmental impact of agriculture. Let’s dive in!
Best Management Practices for Conventional Agriculture
There are a multitude of practices that farmers are implementing to reduce the impacts of conventional agriculture, even when we’re talking about large-scale, industrial production. We are only going to highlight a few, so if you’re interested in learning about other Best Management Practices (BMPs) check out the Agricultural BMP Handbook for Minnesota Links to an external site.. The following information is taken directly from this Handbook.
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Cover crops - the use of winter rye, oats, alfalfa, buckwheat, and other small grains planted with annual cash crops (e.g. corn, soy) to provide seasonal soil cover on cropland when the soil would otherwise be bare. Water quality and soil health benefits of cover crops come from three processes. The first is the reduction of erosion from raindrop impact and by slowing the flow of water. The second is the potential for the cover crop to take up nutrients that would otherwise be lost from the field through surface or drainage water, and the third is increasing soil infiltration.
- Nutrient management - the management of the application rate, timing, source, and placement of fertilizers, manure, and other soil amendments. In other words, making sure the right type of nutrient is applied at the right place at the right time. Among all BMPs, nutrient management BMPs are one of the most effective ways to improve water quality.
- Crop rotation - a system for growing several different crops in planned succession on the same field, including at least one soil-conserving crop such as perennial hay. In Minnesota, this practice usually consists of a corn-soybean-alfalfa rotation or a corn-soybean-small grain rotation. Crop rotations have many benefits to the producer including reduced erosion, improved soil quality, and improved wildlife habitat.
- Conservation tillage - any tillage practice that leaves additional residue on the soil surface for purposes of erosion control and moisture conservation. Crop residue is the most important factor affecting erosion from different tillage systems. The more residue on the land following tillage, the less erosion from the field.
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Contour Buffer Strips - strips of perennial vegetation planted in-field and on the contour (perpendicular to the slope) and regularly spaced between wider crop strips. Contour buffer strips slow the flow of water, which reduces erosion and the transport of sediment and associated contaminants to downstream water bodies.
Alternative Production Systems
In addition to improving the environmental impacts of conventional agriculture, there is also the option to grow crops using alternative, more eco-centered production systems. Again, this is not a comprehensive list, but rather a description of a handful of selected systems.
Organic Agriculture & Permaculture
In conventional agriculture, implementing BMPs is voluntary. The farmer can choose which practices they wish to implement, if any. In contrast, many of these practices are mandatory for organic agriculture. For example, organic requires non-chemical methods of soil management such as crop rotation, cover crops, and the application of plant and animal materials. Organic also prohibits artificial pesticides and instead encourages alternative practices.
Permaculture takes organic agriculture to the next level. Bill Mollison, who coined the term, describes permaculture as “The conscious design and maintenance of agriculturally productive systems which have the diversity, stability, and resilience of natural ecosystems. It is the harmonious integration of the landscape with people providing their food, energy, shelter and other material and non-material needs in a sustainable way.”
In the following video, Austin talks about her experiences with organic agriculture and permaculture. While she focuses on food production (because this is what typically comes to mind when we think of agriculture), brainstorm ways these ideas could be applied to biomass production systems for bioproducts and bioenergy. There will be quiz questions from the first 3 minutes or so, the rest of the video is just for fun.
Perennial Crops
Many of the issues with conventional agriculture stem from the fact that we grow crops on an annual cycle. As you learned in the last lesson, most of the bioproducts produced today come from corn, an annual crop. But what if we could make biofuel and bioproducts out of a perennial crop instead?
A perennial plant is any plant that lives more than two years. Some perennial crops that are considered important to the future of biomass production are switchgrass and miscanthus. As with any other crop, planting these grasses requires time and money, but unlike annual crops where these costs are incurred each year, planting perennial crops is a one-time cost. Once 
the switchgrass or miscanthus is established, they can grow for 15-20 years without having to disturb the soil, thereby mitigating soil erosion. Both species are drought tolerant and have low nutrient requirements, and therefore do not require a lot of water or nutrient application. Neither switchgrass nor miscanthus have issues with pests, so there is also no need to apply pesticides.
Sound too good to be true? The main issue with these crops is that they produce biomass with a high cellulose content. In the current economy it is really only profitable to make bioproducts and biofuels from starch, which is why corn dominates the bioindustry. In the next lesson we will explain why we do not currently make more bioproducts from cellulose.
Tradeoffs
If we're aware of the environmental impacts of conventional agriculture, why do we still use it? It gets back to our need to provide for a continuously growing population. Conventional agriculture is extraordinarily productive, meaning we get very high yields (amount of crop per area). Every aspect of conventional production is mechanized and optimized for efficiency. A key issue in the debate on the role of organic agriculture in the future of world agriculture is whether organic agriculture can produce sufficient food/fiber/fuel to feed the world. Surveys conducted by the USDA showed that organic systems had 20-25% lower yield and higher total economic costs than conventional systems. (USDA McBride 2015 Links to an external site.)
This is the reason organic food costs more at the grocery store; in an organic system, it costs more money to produce less product. If we want to produce a large volume of cheap food, manual labor-intensive systems like organic and permaculture may not be the solution. On the other hand, our current food prices do not take into account the environmental costs of conventional production. Food is cheap because fossil fuels are cheap, which makes large-scale, industrial agriculture cheap. If we added in the costs to the environment and our health, the price of organically and conventionally produced crops might not be so different.
With perennial cropping systems, we run into similar issues. We may be able to someday produce much of our biofuels and bioproducts from switchgrass or miscanthus, but we cannot eat grass. To grow food, we might be able to use a perennial agroforestry system in which trees or shrubs are grown around or among crops, like the fruit-coffee forest Austin discussed in the video. But again, is this efficient enough to provide for 7.5 billion people?
As continues to happen in this course, we arrive at the conclusion that there are no easy solutions to our our consumption of resources.
Conclusion
In this lesson we learned about the environmental issues associated with producing biomass via conventional agriculture and some alternative practices and production systems that can mitigate these problems. In the next lesson, we will begin discussing the pathways and processes used to convert the biomass we grow into useful bioproducts and bioenergy.