Urban Agriculture Lecture Notes PDF

Chapter 7 Urban Agriculture This lecture will help you understand: Challenges of feeding a growing human population Traditional, industrial, and sustainable agriculture The Green Revolution The importance of soil Soil erosion and degradation Irrigation, fertilizers, and pest management...

Chapter 7 Urban Agriculture This lecture will help you understand: Challenges of feeding a growing human population Traditional, industrial, and sustainable agriculture The Green Revolution The importance of soil Soil erosion and degradation Irrigation, fertilizers, and pest management Genetic engineering Raising animals for food Organic agriculture The Race to Feed the World Industrial agriculture has boosted worldwide Figure 7.1 Global production of most foods has production of food and fiber risen more quickly than the world population. immensely, but has also brought increased pollution and resource depletion. – Organic farming decreases efficiency, but also has far fewer environmental impacts. We face undernutrition, overnutrition, and malnutrition (1 of 3) Despite improved food production, 800 million people suffer from undernutrition, receiving fewer calories than the minimum dietary requirement. Most people who are undernourished live in developing countries, although 49 million people are classified as “food insecure.” – Food security is the guarantee of an adequate, safe, nutritious, and reliable food supply. We face undernutrition, overnutrition, and malnutrition (2 of 3) The number of people suffering Figure 7.2 The number and the from food insecurity has percentage of people in the developing world who suffer undernutrition have decreased since the 1960s. each been declining. Overnutrition, receiving too many calories per day, has grown in developing countries due to the abundance of cheap junk food and sedentary lifestyles. – Excess weight leads to heart disease, diabetes, stroke, some forms of cancer, and other health issues. Malnutrition is a shortage of specific nutrients, such as lipids, proteins, vitamins, or minerals. The Changing Face of Agriculture Agriculture provides our most basic daily needs – from the cotton in our clothes to the food on our plates. Agriculture is also responsible for some of our biggest impacts on the environment, making the development of sustainable practices essential. Several factors underpin agriculture Agriculture is the practice of raising crops and livestock for human use and consumption. – Most of our food and fiber is obtained from cropland, land used to raise crops for human use. – Rangeland, or pasture, is land used for grazing livestock. Urban agriculture includes the cultivating, processing and distributing agricultural products in urban and suburban areas. Growing crops and raising animals require inputs of resources – soil, sunlight, water, nutrients, and pollinators. Today, more than 1 out of every 3 acres of land on Earth is used to produce food and fiber. Industrial agriculture is a recent human invention (2 of 2) In traditional agriculture, the work of cultivating, harvesting, and distributing crops was performed by human and animal muscle power. – Most farmers planted polycultures, mixtures of different crops in small plots of land. Industrial agriculture introduced large-scale mechanization and fossil fuel consumption into agriculture. – Higher rates of irrigation, synthetic fertilizers, and chemical pesticides – Greater prevalence of monocultures, where farmers grow vast areas of single crops in orderly rows Sustainable agriculture reduces environmental impacts Sustainable agriculture maintains healthy soil, clean water, pollinators, and other vital resources. – Mimic the way natural ecosystems function. – Low-input agriculture is an approach that uses less amounts of fossil fuels, water, pesticides, fertilizers, growth hormones, and antibiotics than are used in industrial agriculture. Requires an understanding of the soil, water, nutrients, and pollinators that underpin agriculture. Soils Figure 7.6 Mature soil consists of layers, or horizons, that have different attributes. Soil is a system consisting of disintegrated rock, organic matter, water, gases, nutrients, and microorganisms. – Soil is derived from rock, but shaped by microorganisms. – 50% mineral matter, 5% organic matter, and 45% pore space. Minerals dissolved or suspended in water can be transported downward in a process called leaching. Soil is renewable, but at a very slow rate (centuries, decades, or millennia). Watering and Fertilizing Crops The artificial provision of water beyond Figure 7.8 Irrigation methods vary in their water use. what is received by precipitation is irrigation. – Irrigation is necessary with water- intensive crops (like rice) and in areas with dry climates. – Irrigation is the largest use of water by humans, making up 70% of all fresh water withdrawn. Waterlogging occurs when irrigation oversaturates the soil to the point where water drowns plant roots, depriving them of gases. Fertilizers boost crop yields but can be overapplied (1 of 2) Fertilizers are substances that contain essential nutrients for plant growth. Inorganic fertilizers are mined or synthetically manufactured. Organic fertilizers are made of the remains or wastes from organisms, including manure, crop residue, charcoal, fresh vegetation, and compost. – Compost is a mixture produced when decomposers break down organic matter in a controlled environment. Fertilizers boost crop yields but can be overapplied (2 of 2) Since the Green Revolution, Figure 7.9 Use of synthetic, inorganic fertilizers has risen sharply over the past farmers have increasingly half-century. relied on nutrients from inorganic fertilizers. – These nutrients are more quickly leached, creating other environmental problems. Sustainable fertilizer use involves monitoring and targeting nutrients Farmers who use drip irrigation can add fertilizer directly to the water, thereby releasing it only at the plant roots. Precision agriculture involves monitoring soil nutrient levels and only applying specific types of fertilizer when needed. Organic fertilizer use is embraced, because it provides additional benefits, such as improving soil structure, nutrient retention, and water-retaining capacity. Conserving Agricultural Resources Soil degradation is the deterioration in quality and productivity of soil. Erosion is the removal of material from one place and its transport to another by wind or water. – When eroded material is left at a new location, it is called deposition. – Overcultivating fields or excessive tilling (plowing), excessive grazing, and clearing forests on steep slopes. One study determined that U.S. croplands lose about 2.5 cm (1 in.) of topsoil every 15–30 years. The Dust Bowl prompted the United States to fight erosion In the late 19th and early 20th centuries, farmers moving into the Western Plains of the United States began plowing up native grassland plants in favor of wheat. A severe drought in the 1930s worsened the impacts, causing the region’s strong winds to erode millions of tons of topsoil. Figure 7.10 Drought and poor agricultural practices devastated millions of U.S. farmers in the 1930s in the Dust Bowl. Policy can promote conservation measures in agriculture (1 of 2) Many nations spend billions in subsidies to promote unsustainable practices, such as growing water-thirsty crops in desert regions. – In the United States, one-fifth of an average farmer’s income comes from subsidies. Subsidies help to stabilize and secure the income of farmers, but they also lead to land being cultivated that otherwise would not be. – This artificially increases food production, lowering prices for other farmers. Policy can promote conservation measures in agriculture (2 of 2) Every 5–6 years, the U.S. Congress passes legislation called the Farm Bill that guides agricultural policy. The Conservation Reserve Program, first established in the 1985 Farm Bill, pays farmers to convert damaged cropland to conservation reserves. In response to the Dust Bowl, the U.S. government passed the Soil Conservation Act of 1935, which established an agency (Natural Resources Conservation Service)that worked with farmers to combat erosion. Controlling Pests, Preserving Pollinators A pest is any organism that damages crops or livestock. A weed is any plant that competes with crops. Industrial monocultures limit the ability of natural enemies to control pest populations, causing farmers to turn to chemical suppression. We have developed thousands of chemical pesticides Pesticides include synthetic chemicals that kill insects (insecticides), plants (herbicides), and fungi (fungicides). – Nearly 400 million kg of ingredients from pesticides are applied in the United States each year. Pesticides also kill nontarget organisms, including predators and parasites of pests and pollinators. Pests evolve resistance to pesticides (1 of 2) Chemical pesticides tend to become less effective over time as pests evolve resistance to them. Most pests occur in huge numbers, so it is likely that a few have genes that detoxify or metabolize a given pesticide. Figure 7.12 Through the process of natural selection, crop pests often evolve resistance to the poisons we apply to kill them.  Pests evolve resistance to pesticides (2 of 2) Individuals with the gene will survive and reproduce at greater rates, creating a new generation with a much higher rate of carrying the gene. – Eventually the pesticide becomes ineffective and must be replaced by a new one. This is called the “pesticide treadmill.” [Figure 7.12 Continued] Biological control pits one organism against another The most obvious alternative to chemical pesticides is biological control or biocontrol, where natural predators or parasites are introduced to eliminate the pest. – Parasitoid wasps, for example, are natural enemies of many caterpillars. Integrated pest management combines biochemical and chemical methods Integrated pest management (IPM) combines biocontrol, chemical pesticides, habitat alteration, crop rotation, transgenic crops, alternative tillage methods, and mechanical pest removal. – This has been highly effective in Indonesia, which increased rice production while cutting pesticide subsidies and overall pesticide use. Pollinators are beneficial “bugs” worth preserving (1 of 2) Pollination is the process by which male plant sex cells (pollen) fertilize female plant sex cells (ova, or egg cells). – Grasses and conifer trees are pollinated by wind. – Plants with bright flowers attract animals (pollinators), which transfer pollen as they move from flower to flower. Pollinators are beneficial “bugs” worth preserving (2 of 2) Today, many pollinating insects are dwindling in number due to pesticide use and habitat loss. Colony collapse disorder is a phenomenon where a majority of worker bees in a hive disappear, endangering the queen and developing larvae. Restoring bee populations will require establishing more wildflowers and flowering shrubs near farm fields and highways and decreasing the use of chemical insecticides. Raising Animals for Food As global wealth and commerce have increased, so have the production and consumption of meat, milk, eggs, and other animal products. – Meat production has grown more than fivefold since 1950, and per capita meat consumption has doubled. Figure 7.13 Per-person production of meat from farmed animals and of seafood has risen steadily worldwide. Our food choices are resource choices (1 of 3) Every time that one organism consumes another, only about 10% of the energy moves to the next trophic level. – Feeding grain to a cow and eating beef from the cow result in loss of most of the grain’s energy to the cow’s metabolism. Eating lower on the food chain (a more vegetarian diet) is more energy-efficient and reduces our ecological footprint. Our food choices are resource choices (2 of 3) Some animals convert grain feed into milk, meat, or eggs more efficiently than others. Figure 7.14 Producing different animal food products requires different amounts of animal feed. Our food choices are resource choices (3 of 3) Based on these difference in energy conversion efficiencies, a footprint of land area, water weight, and CO2 equilvants has been calculated for producing 1 kg of edible protein for each animal. – Animal agriculture accounts for 14.5% of our greenhouse gas emissions—more than driving. Figure 7.15 Producing different types of animal products requires different amounts of (a) land and (b) water—and releases different amounts of (c) greenhouse gas emissions. Feedlots have benefits and costs (1 of 2) Feedlots are huge pens designed to provide high-energy feed to animals living in high densities. – These are also known as factory farms or confined animal feeding operations (CAFOs). Feedlots have the benefit of being more economically efficient and reducing grazing impacts by the animals. Feedlots have benefits and costs (2 of 2) Feedlots can also produce more intensive pollution due to the release of highly concentrated waste. – Pollution is rich in nitrogen and phosphorous, so it contributes to eutrophication. – Feedlot waste contains bacterial and viral pathogens. – Hormones, antibiotics, and other drugs administered to animals may also be excreted. We raise seafood with aquaculture (1 of 2) Due to plummeting wild fish populations and increasing demand for seafood, aquaculture, the cultivation of aquatic organisms in controlled environments, may be the answer. Aquaculture increases food supplies and protein sources, increasing overall food security. – Pros: reduces overfishing of wild fish and the unintended catch of other organisms called bycatch. – Cons: antibiotic overuse, degradation of coastal ecosystems, and spreading disease or invasive species into nearby ecosystems. We raise seafood with aquaculture (2 of 2) The first genetically modified animal to become approved for human consumption is a salmon that can grow faster and reach larger sizes than wild salmon. Figure 7.16 Transgenic salmon (top) grow faster than wild salmon of the same species. Genetically Modified Food (1 of 4) Genetic engineering refers to any process where scientists directly manipulate an organism’s genetic material (DNA). Genetically modified (GM) organisms (GMOs) contain recombinant DNA, meaning it has been produced from multiple organisms. Genetically Modified Food (2 of 4) An organism that contains DNA from another species is called a transgenic organism. – The genes that move between them are called transgenes. Biotechnology creates products derived from organisms. Figure 7.17 To create recombinant DNA, scientists follow several steps. Biotechnology is transforming the products around us (1 of 2) Sales of GM seeds have increased in the United States and other countries. Figure 7.18 GM crops have spread with remarkable speed since their commercial introduction in 1996. Biotechnology is transforming the products around us (2 of 2) Soybeans account for more than half of the GM crops grown worldwide. The United States, Brazil, Argentina, India, and Canada accounted for 90% of production in 2017. Figure 7.19 So far, genetic engineering has mainly involved common crops grown in industrialized nations.  The Growth of Sustainable Agriculture One approach is organic agriculture, including practices that do not include synthetic pesticides, fertilizers, hormones, or antibiotics. Figure 7.21 Organic agriculture is growing. About 80% of Americans buy organic food at least occasionally, and most retail groceries offer it. The average food product sold in a U.S. supermarket travels at least 1600 km (1000 mi) from the farm. At farmers’ markets, consumers buy meats and produce from local producers. Urban Agriculture Sustainable agriculture provides a roadmap for the future Sustainable agriculture must meet the triple bottom line of social, economic, and environmental dimensions: – Provide food security – Be profitable to famers and ranchers – Conserve resources for future agriculture Let’s Start Our Plant Experiments Today, we will prep for our 6-week plant experiments!