[MUSIC] Hello and welcome, this is Brent Kim. Here to kick things off with soil, the stuff where our food system begins and ends. In the words of farmer, author and poet, Wendell Berry, the soil is a great connector of our lives. The source and destination of all. In 400 BCE, Athenian scholar and soldier Xenophon wrote that to be a successful farmer, one must first know the nature of the soil. In this lesson, I'll begin with an overview of the prevailing industrial approach to crop production. We'll also talk about an alternative approach called agroecology and I'll also briefly touch upon some of the major public health, and ecological challenges associated with industrial crop production. However, since covering all those challenges in detail could be the subject of an entire course and we'd be here all day. The rest of the lesson will instead zoom in on the topic of soil, the foundation of our food supply. Specifically, I'll be covering soil composition. So, what soil is made of. We'll talk about soil ecosystem services, which is how soil benefits humans and why this resource that we often take for granted is pivotal for our health. I'll talk about some of the public health and ecological challenges associated with something called soil degradation. And finally, we'll cover some policy and technological intervention. Aimed at conserving soil, this important resource that is essential to our health. So, let's talk about crop production. Here, I listed nine major public health and ecological challenges associated with crop production. Mind you, it's not a comprehensive list, but it covers at least most of the big ones that keep me up at night. And so, we're not covering all of these in detail with the exception of soil degradation which we'll talk about later. Most of these challenges are predominantly associated with the industrial approach to crop production. An approach characterized by specialization, mechanization, consolidation which is the shift towards fewer and larger farms famously illustrated in the 1950s by the then Secretary of Agriculture Ezra Taft Benson when he called on farmers to quote, get big or get out. And finally, the heavy use of chemical inputs. This person here in the hazmat suit is preparing an herbicide called alachlor. This is the second most widely used herbicide in the United States, but it's actually banned or been banned in the European Union since 2006. So, these are the four prevailing characteristics of industrial crop production. The industrialization of crop production has been problematic on many fronts. It contributes to those nine major challenges that we saw earlier, but industrialization has also been greatly beneficial in some regards. Mechanization, for example, brought enormous gains in labor efficiency. By hand, a person can thresh roughly 15 to 40 kilograms of grain per hour, usually by beating the harvested crop against a hard surface over and over again to shake that grain loose from the inedible chaff that surrounds it. In that same hour, a mechanized pressure can process 450 to 600 kilograms of rice, sorghum or beans or 1,500 to 2,000 kilograms of corn. That's 100-fold increase in efficiency. And personally, this looks like good exercise, but surely backbreaking work. Pictured here is a combine harvester going through a field of wheat, performing two processes at once. Reaping or cutting the grain and threshing, which is removing the grain from the inedible chaff. So, mechanization in agriculture greatly reduced the need for human animal labor. Between 1950 and 200, production on US farms more than doubled with less than one-third of the labor force. Let's talk about another innovation associated with industrialization. This graph shows fertilizer applications on major US crops from 1964 to 1992 and you can see that corn represented here by the dotted yellow line on the top accounts for the largest share of fertilizer use. Synthetic nitrogen fertilizers introduced in the early 1900s, greatly increased crop yields per acre and have been credited with feeding the lion's share of a global population that grew from 1.6 to 6 billion over the course of the 20th century. So, it's been clear that industrialization has been a mixed blessing. On one hand, you have contributions to those nine major challenges that we showed earlier. But on the other hand, there have been certain aspects of industrial crop production that have greatly increased productivity at least in the short-term. So, returning again to our list of challenges. We're faced with this question of how to address these nine problems while at the same time maintaining or hopefully, increasing our agricultural productivity. Now, how can we do that? With a low hanging fruit solution, so to speak would be for us to eat far fewer animal products. The average American consumes over three times more meat, milk and eggs compared to the global average. The red bar on the far right illustrates per capita intake of meat, milk, eggs and seafood combined for the average US citizen and the dark gray bar next to it shows you the same statistic for the average global citizen. The reason that cutting back on meat intake and production by association would allow us to increase our food supply is that the fresh water and land use, and other resources required to grow feed for these animals represents a highly inefficient use of finite resources. For example, only 40% of North American cropland is devoted to growing food for direct human consumption. The remainder is devoted to feed crops and ethanol production. When we're using limited agricultural land to grow feed to feed animals, this represents a net drain on our food supply. The reason being that the vast majority of calories and protein in feed crops are lost when they are converted to animal products. Because of these inefficient feed conversion ratios, all of the aforementioned problems that we saw earlier associated with industrial crop production are amplified by the use of cropland for animal feed. In addition to cutting back on our intake of animal products, what else can we do to address those challenges? Well, many of the world's leading thinkers on sustainable agriculture are calling for something called agroecology as a proven alternative to industrial agriculture. Agroecology is a holistic, systems-based approach that looks to nature as a model. Essentially, ask the question, how can we apply the qualities of natural ecosystems through farm in order to produce more food sustainably? I'll give you some examples of qualities that you find in natural ecosystems that can be applied to farms. So here's one, efficiency. The concept of waste does not apply in nature. Rainfall, organic matter and so on are continually recycled by natural systems. Nothing is thrown away. There's no away, so to speak and one way farmers can reduce waste and use resources more efficiently is by composting. When your crop residues and food wastes, returning it to soil. Improving soil health in the process and increasing productivity, and we'll talk more about soil health in the next section. Another quality of natural ecosystems is self-sufficiency while terrestrial ecosystems require only sunlight and rainfall. Farms generally involve hard working many different resources from fossil fuels to agricultural chemicals, but farming can be made less demanding by letting nature do some of the work. Cultivating healthy soil as we'll discuss later in this lesson can lessen or even do away with the need for irrigation, pesticides, synthetic fertilizers and so on. Let's talk about diversity. In contrast to the specialized nature of industrial agriculture, farmers who cultivated diversity of different plant and animal species together can benefit from the relationships among them. The classic example of synergistic diversity on a farm is combining corn, beans and squash called the Three Sisters by the Seneca Nation. The leguminous beans picks nitrogen from the atmosphere, providing nutrients for the other crops. The corn provides a scaffolding for the beans to climb on. Meanwhile, the squash, those squash leaves, a broad squash leaves act as a living mulch retaining soil moisture and deterring weed growth. Crop diversity also offers an ecological alternative to relying on pesticides and here's why. Insect pests, such as say, corn earworms and cabbage loopers. They tend to favor certain crops, which you can probably tell by their names. Growing the same crop over a large area, something called monoculture presents the opportunity for these beasties to thrive and multiply on a bonanza on their favorite crop. In contrast, growing a variety of different crop and rotating them over time helps keep these pests in check. Finally, let's talk about resilience. Resilience is the ability of an ecosystem to withstand or recover from floods, hurricanes, droughts and other shocks. Farmland can be made more resilient against soil erosion during heavy storms, for example, by planting trees and using other barriers to block heavy winds and by plowing and planting crops perpendicular to sloping land. A practice called couture farming pictured here, which slows rainwater runoff. When Hurricane Mitch struck Nicaragua in 1998, those farms that used agroecological methods, such as planting trees and contour farming retained 40% more topsoil compared to a conventional farm. So you may have noticed that conserving soil quality is a recurring theme in agroecology and that's because what farmers call healthy soil is the literal, and figurative foundation of sustainable agriculture. And while healthy soil can't solve all of the problems in our food system, it can certainly help with many of them. So, stick around for the next section. When we come back, we'll take a closer look at exactly what soil is made of. See you soon.