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Tille Human Population and Its Impact Applyin.g Population Ecology: TIlle Human Population and Its Impact ers it is the number of people in developed countries E CASE STUDY such as the United States where high resource con- e World Overpopulated? sumption rates magnify the environmental impact of each person (Figure 1-7, P: 13 and Figure 1-14, bot- orld's human population is projected to in- tom, p. 20). efram 6.6 to 9.2 billion or more between 2006 Those who do not believe the world is overpopu- 050 (Figure 1-1, P: 6), with much of this growth lated point out that the average life span of the ring in several rapidly developing countries world's 6.6 billion people is longer today than at any as India and China (Figure 9-1). Are there too time in the past and is projected to increase. According ypeople on the earth? to them, the world can support billions more people :Some argue that the planet has too many people as a result of human technological ingenuity in pro- iectively degrading the earth's natural capital. To viding food and other resources. They also see more p;e the problem is the sheer number of people in people as the world's most valuable resource for solv- ~yeloping countries (Figure 1-14, top, P: 20). To oth- ing environmental and other problems and for stimu- lating economic growth by increasing the number of consumers. Some view any form of population regulation as a violation of their religious or moral beliefs. Others see it as an intrusion into their privacy and personal free- dom to have as many children as they want. Some de- veloping countries and some members of minorities in developed countries regard population control as a form of genocide to keep their numbers and political power from growing. Proponents of slowing and eventually stopping population growth ask if we cannot or will not pro- vide basic support for about one of every five peo- ple-about 1.4 billion people today, how will we be able to do so for the projected 2.6 billion more people by 2050? They also warn that if we do not sharply lower birth rates, the death rate may increase because of de- clining health and environmental conditions in some areas, as is already happening in parts of Africa. They also warn that resource use and environmental degra- dation may intensify as more consumers increase their already large ecological footprint in developed coun- tries and in rapidly developing countries, such as China and India. This debate over interactions among population growth, economic growth, politics, and moral beliefs is one of the most important and controversial issues in environmental science. Figure 9-1 Crowded street in China. Together, China and India QY-I f/Ot//f!l/O{/LD YO{/ VOTE? Should the population of the have 37% of the world's population and the resource use per country where you live be stabilized as soon as possible? person in these countries is projected to grow rapidly as they Cast your vote online www.thomsonedu.com/biology/miller. become more modernized (Case Study, p. 15). ----------------------------- Tlu: proincm: io be faced O(C vast and comptex, b!!{"come there are 6.6 billion of us. It took from the time we ar- do~;./n .\;- [,.i;.j.'.j,' 5.6 billion people ate iJreeding exponcntiati». The rived until about 1927 to add the first 2 billion people procrss /illt]iling their wants atul neeii: is stripping eortl: o( to the planet; less than 50 years to add the next 2 billion iis biotic capacity to produce lire; a climactic burst ofcon- (by 1974); and just 25 years to add the next 2 billion (by sumprior: by (j single species is cverwhelmi.ig the skies, earth. 1999)-an illustration of the power of exponential waters, a:id [auna. growth. Such growth raises the question of whether ,., the earth is overpopulated (Core Case Study, p. 171). This chapter looks at the factors that affect the growth and decline of the human population. It addresses the Population Growth Today: Slowing but Still following questions: Growing (Science and Economics) The rate or po~:n~~IZitiong~,~0V\/t~1.:1215 slewed but is still !II What is the history of human population growth, gro';,vlng ~·Ci.pidly, and how many people are likely to be here by 2050? During 2006, about 81 million people were added to the world's population-79.5 million in developing l!I How is population size affected by birth, death, countries and 1.2 million in developed countries. At fertility, and migration rates? this exponential growth rate of 1.23% a year, we share I1J How is population size affected by the percentages the earth and its resources with about 222,000 more of males and females at each age level? people each day and 2.4 more people every time your heart beats. 18 How can we slow population growth? An exponential growth rate of 1.23% may seem IB What success have India and China had in slowing small, but compare the 81 million people added to the population growth? world's population in 2006 to the 69 million added in tII What are the major impacts of human activities on 1963, when the world's population growth reached its the world's natural ecosystems? peak. This increase of 81 million people per year is roughly equal to adding another New York City (USA) every month or another Germany every year. Also, there is a big difference between population HUMAN POPULATION GROWTH: growth rates in developed and developing countries. A BRIEF HISTORY In 2006, the population of developed countries was growing exponentially at a rate of 0.1% per year. That Population Growth in the Past (Science of the developing countries was 1.5% per year-15 and Economics) times faster. VVehave kept the 11111.J.12f1 population gr()yving Thus, population growth in recent decades is a re- by expanding into ecosystems throughout the sult of keeping more people alive by increasing life ex- world and using technologica! innovations to pectancy and reducing death rates. This is a good thing. expand the food supply and lower death rates, But coupled with increased resource consumption per For most of history, the human population grew slowly person this can to lead increased environmental degra- (Figure 1-1, left part of curve, p. 6). But for the past 200 dation as the human ecological footprint spreads across years, the human population has experienced rapid ex- the.planet (Figure 1-7, p. 13, and Figure 3 on pp. S12-513 ponential growth reflected in the characteristic [-curve. in Supplement 4). To those arguing that both developed (Figure 8-3, left side, p. 163 and Figure 1-1, right part of and developing countries are overpopulated, the solu- curve, p. 6). tion is to focus on sharply reducing birth rates. Three major factors explain this population in- crease. First, humans developed the ability to expand Where Are We Headed? (Science, Economics, into diverse new habitats and different climate zones. and Politics) Second, the emergence of early and modern agriculture allowed more people to be fed per unit of land area. "VVedo not know how long live CC'!Xlcontinue ir:.cE·(:::~~,~,ii}.1g..... Third, we developed sanitation systems, antibi- the earth' 5 carrying capacity for bl.UT!.3~:'S. otics, and vaccines to help control infectious disease Scientific studies of populations of other species, agents, and we tapped into concentrated sources of en- (Chapter 8), tell us that no population can continue gl'OW--' ergy (mostly fossil fuels, Case Study, P: 42). As a result, ing indefinitely. How long can we continue increasing. death rates dropped sharply below birth rates. the earth's carrying capacity for our species by side-. About 10,000 years ago when agriculture began stepping many of the factors that sooner or later lirnit: there were about 5 million humans on the planet; now the growth of any population? . 172 CHAPTER 9 Applying Population Ecology: The Human Population and Its Impact rfii_iiiiii~-:-------------------------. (The debate over this important question has been vide an adequate standard of living for the medium projec- g on since 1798 when Thomas Malthus, a British tion of 8.9 billion people in 2050 without causing wide- rtornist, hypothesized that the human population spread environmental damage?" In other words, how ds to increase exponentially, while food supplies many people can the earth support indefinitely? Some d to increase more slowly at a linear rate. So far, say about 2 billion. Others say as many as 30 billion. 'tthus has been proven wrong. Food production has Some analysts believe this is the wrong question. 'wn at an exponen~ial rate instead of at a linear rate Instead, they say, we should ask what the optimum ;'cause of genetic and technological advances in in- sustainable population of the earth might be, based on "strialized food production. the planet's cultural carrying capacity. Such an opti- '. No one knows how close we are to the environ- mum level would allow most people to live in rea- -ntallimits that sooner or later will control the popu- sonable comfort and freedom without impairing the ~tion size of the human species, but the evidence is ability of the planet to sustain future generations. (See 'rowing that we are steadily degrading the natural the Guest Essay by Garrett Hardin on this topic on apital that keeps us and other species alive and sup- the website for this chapter.) There is disagreement on :orts our economies-one of the arguments support- what the optimum sustainable population size for the ,fig the idea that the world is overpopulated (Core world is.
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