Subject: Earth Science: Text: Environmental Science: A Global Concern (11th ed.) by William Cunningham and Mary Ann Cunningham. Environmental Case Study: What Is Earths Carrying Capacity for Humans? Human numbers are doubling about every 40 years. At that rate there would be an astounding 170 quadrillion people 600 years from now. That would put one person on each square meter over the entire land surface of the earth. Carrying capacity reflects the limits imposed on population growth by finite space and finite resources. Earths resources would never support such ludicrous numbers. So, what is the carrying capacity of the earth for humans? That question cannot be meaningfully addressed without clarifying a basic assumption: the type of lifestyle on which to develop the estimates. Different lifestyles have different resource requirements. Are people to be vegetarians or will meat be a significant part of the diet? Will the earths resources be counted upon to provide additional amenities beyond food? The answers to those questions have a profound effect on the numbers of people the earth can sustain. For illustration purposes imagine a miniature planet we could call Terrabase. Consider the following scenarios to see how lifestyle affects carrying capacity. Scenario 1 In this scenario, the humans living on Terrabase are vegetarians, and 100 percent of the planets space is devoted to raising human food. Lets assume that under these conditions 1,000 people can be sustained. Carrying capacity equals 1,000. Scenario 2 Most people enjoy meat in the diet. Assume that the people of Terrabase do not live as vegetarians, but obtain half their calories by eating herbivores such as beef cattle. This would require a significant amount of plant mass to be fed to animals. But, as you learned in chapter 3, much energy is lost in transfer between trophic levels. It takes about 10 calories of plant food to produce one calorie of beef. After doing the calculations, it turns out that under these conditions, Terrabase will produce enough food to sustain only 180 people. Simply by eating meat, the carrying capacity has been reduced by over 80 percent. Scenario 3 In both scenarios 1 and 2, all of the land has been used exclusively for humanfood production. But people have consumer needs as well: cars, parking spaces, televisions, washers, dryers, clothing, shopping centers, and much more, all of which require space that would have to be subtracted from that used to produce food. Recreational space is also important to us. We want athletic fields, golf courses, bird sanctuaries, nature preserves, and hunting lands. All of which divert even more land away from food production. Assume the residents of Terrabase had the high living standard of industrialized nations, requiring the immense and continuous input of chemicals, energy, paper, and other raw materials, as well as requiring land for waste disposal. How much of Terrabase would be devoted to these uses? If it is 20 percent, the carrying capacity is reduced to 140. Wild organisms also play ecological roles important to our well-being. Leaving space for wild nature further reduces land available to produce human food. What is the earths carrying capacity for humans? is not a meaningful question until the cultural context within which people are to live has been clarified. The magnitude of the cultural impact on carrying capacity is underlined by information provided by Robert Goodland and others. It is estimated that the continuous production of 10 to 15 acres are necessary to sustain just one person at our affluent lifestyle. To support all of the earths 5.6 billion humans at such a lifestyle would require three times as much productive land as is available. Defined in those terms, the carrying capacity of the earth is around 1.8 billion people, one-third the worlds current numbers. On the other hand, if carrying capacity is defined as the number of humans the planet could adequately feed without providing other amenities, that number is obviously much larger. Questions for Discussion: 1. Reflect on your personal Ecological footprint from Unit one and describe what you learned about your impact on the carrying capacity of the Earth from this case study. 2. What small lifestyle changes can the average American make that would greatly impact the resource usage? TOPIC 2: Environmental Case Study - Murray County, Minnesota The Prairie Wetlands of Southwest Minnesota Log on to the text book website and find the above mentioned case study or use the link : http://www.mhhe.com/Enviro-Sci/CaseStudyLibrary/Regional/North/CaseStudy_ThePrairieWetlandsO.pdf Introduction The Great Plains region of North America is part of one of the most intense and most productive agricultural efforts in the world. Vast acres of corn, soybeans, hay, and wheat dominate the landscape. Drive for an hour on a county road in any direction and you are likely to pass at least one grain elevator. At various times during the year, you will also pass (or be passed by) millions of dollars worth of agricultural machinery, highly specialized to till, plant, spray, or harvest. Great Plains farmers feed much of the world. The grains produced in this region feed untold numbers of livestock, and are also used in the production of ethanol, oils, fertilizers, and a host of other products. The effort, ingenuity, and technology that have gone into this production make it truly one of the great accomplishments of the human race. Along with agricultural developments of the last century, a way of life has developed on the Great Plains. It is based on the relationship of people with the land, particularly through the production, processing, and marketing of food. Scattered among the acres of corn and beans are clusters of homes, sometimes numerous enough to form towns or cities. Necessarily tied to the land and the process of agriculture, most citizens of these towns are conscious of the weather, the current agricultural economy, the recent growing conditions, and the lay of the land. These communities are not without their problems, but they are the backbone of a nation. This incredible production and this reliance upon the land have been forged at a considerable ecological cost. Indeed, if this region is known for anything, it is known for (1) agriculture, (2) the rural way of life, and (3) the ecosystems that used to exist here. The tall-grass and short-grass prairies that must have seemed endless to early European settlers have been all but lost to cultivation, and many areas that have managed to evade the plow are grazed by livestock. This region, although it generally receives less rainfall than eastern North America, was also home to a great number of small depressional wetlands, termed prairie potholes in the northern Great Plains. Potholes are freshwater marshes, many of which may be small and ephemeral. North America's Prairie Pothole region includes 300,000 square miles extending from Eastern Alberta to Western Manitoba in Canada, south to the Dakotas and Southwest Minnesota.1 Potholes are particularly important for migratory waterfowl; although this region contains only about 10 percent of the waterfowl nesting habitat on the continent, it produces 50 to 75 percent of all North American waterfowl.2,3 Prairie wetlands may have fared better than uplands in the early stages of European settlement, but as population density increased and drainage techniques were improved and encouraged, many potholes were incorporated into the agricultural effort. The prairie wetlands that remain, like the remnant prairie grasslands, are tiny islands in a sea of agriculture and are invariably influenced by the surrounding land management practices. Finish examining the case study including the maps and graphs and then answer the following questions. Ethical Considerations 1. What are the benefits of devoting our land so completely to agriculture? 2. What are the consequences of devoting our land so completely to agriculture? 3. Explain if the costs and benefits of ecosystem destruction have been ignored when land is used for agriculture? 4. What is the value of agricultural alternatives that do not destroy prairies? 5. Can you find examples where wetland restoration has been a success