ENERGY AND THE ENVIRONMENT
ENERGY AND THE ENVIRONMENT PHSC 1014
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This 10 page Class Notes was uploaded by Kitty Reinger on Friday October 2, 2015. The Class Notes belongs to PHSC 1014 at Arkansas State University taught by John Pratte in Fall. Since its upload, it has received 36 views. For similar materials see /class/217717/phsc-1014-arkansas-state-university in Physical Science at Arkansas State University.
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Date Created: 10/02/15
Population Introduction On October 12 1999 the Earth welcomed a newborn child that brought our planet39s population up to the 6 billion mark according to the UN Population Fund While this is an astoundingly large number of people to have on Earth what makes this figure even more remarkable is that as recent as 1960 there were only a little over 3 billion people on the planet For the last century we have been averaging a rate of increase in the world39s population that would double it about every 50 years lfthis continues it means that we will have close to 12 billion people on the planet by the middle of this century By some people39s estimates this would amount to complete environmental devastation if it were to happen While the world39s population has been growing at a staggering pace it has not been a homogenous global growth Some areas of the world are not experiencing any growth at all In fact some areas of Europe are actually experiencing a decline in their population Other areas ofthe world offset these declines by growing at a rapid clip Both of these situations bring about their own unique set of problems In this chapter we will look at the factors that affect population and discuss how global population might change over the coming century Before we do that we need to define a few terms and formulae that are important to this discussion Demographic Basics Demography is the study of populations whether they be human plant or animal Human demography is that subdiscipline that looks specifically at humans and it relies very heavily on statistics geography psychology and sociology Like any area of study it has its own unique terms that while they exist in everyday language describe something very specific that might be different from their everyday definitions For example demographers have several terms that they use to describe how a population can change The terms that they use are birth rate death rate natural growth rate growth rate replacementlevel fertilim and total fertiliy rate The first two ofthese are quite simple and are what you would expect Birth rate Commonly used as the crude birth rate this is the number of births per 1000 people within a certain population Death rate Commonly used as the crude death rate this is the number of deaths per 1 000 people within a certain population The formulae for determining crude birth rate and crude death rate for a given time interval such as a year are as follows total number of births in a population x 1000 crude birth rate total population total number of deaths in a population x 1000 crude death rate total population The next two terms are not quite as obvious but are easily explained The natural growth rate is just the crude birth rate minus the crude death rate ie the number of people who are born minus the number that died per 1000 people Many people who read this think quotWell that is obvious The growth is just how many new babies are born minus the number of people who diequot However this neglects the effect of immigration and emigration and it is why this term is called the natural growth rate The term growth rate includes the effects of immigration people entering a country and emigration people leaving a country and is defined as the natural growth rate plus the migration rate immigration minus emigration To explain this another way let us look at an example Suppose that a country of 100000 people has 15000 births in a year in which 10000 people die At the same time 540 people move into the country to settle and 780 leave the country live in the Arctic tundra of Canada With these values the terms we have defined so far are birthrate xIDOO 150 100000 deathrate 161000 100 100000 naturalg rowthrate 150 100 50 migrationrate 540 Jxl000 24 100000 growthrate natmalg rowthrate migrationrate 50 24 476 Thus this country has a total growth rate of 476 people for every 1000 citizens that it has At this rate of growth it would take 21 years for the population to double as 476 people per year times 21 years is equal to 1000 people actually 9996 people but there is no such thing as 6 of a person We must recognize that this way of expressing the growth is a little different than some other ways of expressing it In some instances we express the growth as a percentage ofthe population It is easy to convert between the two as all one needs to do is to divide the crude growth rate by 1000 people and then multiply by 100 In our example this is 476 people 1000 people x100 476 percentagegrowth We need to note though that ifthe population continues to grow at this percentage then the amount of time to double will not be 21 years it will be less The reason for this is quite simple as growth at a fixed percentage means that each year sees greater overall growth than the year before In our example growth at 476 means that 4760 people are added to the country the first year The next year the number of people who are added will be 476 of 104760 or 4762 While this is only 2 people more this will continue to grow in succeeding years which means that doubling will be reached sooner as we will show below Replacementlevel fertility This is the average number of births that couples in a population must have in order to keep the population stable At first glance one might think that this number is 20 as it is a simple matter of each member of a couple replacing himself or herself However not all children will survive until they reach puberty when they could legitimately take part in producing the next generation of children For this reason replacementlevel fertility RLF is higher than 20 and depends greatly upon the infant and childhood mortality rates of a country In more developed countries this number is approximately 21 while in developing countries with poor medical care the number can be as high as about 23 Total fertility rate This is the average number of children a woman in a population has in her lifetime Excluding immigration and emigration from the equation ifthe total fertility rate exceeds the replacement level fertility in a population then the population is growing lfthe total fertility rate is below the replacementlevel fertility then the population is reducing Germany in 2007 for example had a total fertility rate of 14 which is well below the RLF With this rate the population of Germany should be shrinking yet it is actually stable The reason for this is in two parts First of all Germany is experiencing a net immigration influx of 2 people per 1000 people which is causing a small increase to offset the low TFR The second reason is due to population inertia which a country experiences even as it is goes below RLF This can happen for a number of reasons but is usually due to the large number of kids who were born when the TFR was greater than the RLF getting older and maturing past the age of childrearing It can take a country up to 3040 years past the date at which TFR goes below RLF before its population actually begins to level off and decline because ofthis An excellent web site for finding statistics related to population is the following httpwwwgeographyigcom When you arrive at the site click on where it says Rankings on the menu at the upper left When you arrive at the next web page scroll down until you see the Population topic heading You will see categories related to population such as birth rate death rate and total fertility rate listed Statistics for each country in the world are provided Doubling Time and the Rule of 70 As we stated above there is a difference between growth at a constant amount and growth at a constant percentage rate The constant amount growth always adds the same number of people each year while the constant percentage rate growth increases the number of people that are added each year This growth at a constant percentage rate is called exponential growth because it is exactly explained by an exponential function Because of this relationship we can very accurately define how long it will take a population to double in size by performing some simple mathematics which we will not do here but will leave either to your professor or to a good economics textbook to explain It turns out that the doubling time is approximately 70 years divided by the percentage growth in a given years Example Ougadougastan has a population of 20 million people that is growing at 20 per year If it continues to grow at this same rate every year how many years would it take for the population to reach 40 million 70 35 years 20 As you can see this is much fewer than the projected 50 years it would take if the population only grew at 400000 each year which is 20 ofthe original 20 million Growth Factors John Eli Miller versus Jules Francis Pratte What causes growth in a population There are numerous factors that affect growth some of which limit it and some of which cause it to increase One can divide most ofthese factors into two categories basic necessities for life and sociologicalpsychological factors of life An example of the first of these is the availability of food and water If there is not enough of these two things the population will starve or die of thirst which will cause the total number of people to decrease lfthere is more than enough of these two then the population can grow although it does not have to do so Another example would be the availability of clothing and shelter without which people will be left to the elements and possibly die of exposure While the basic necessities for life often set upper bounds on the population they do not necessarily cause a population to grow as we can see from the following example Afterthe basic necessities are met there are numerous factors that will cause a population to grow be stable or shrink For instance take the example of the John Eli Millerfamily Millerwas a farmer born in the mid 180039s who had 5 children 61 grandchildren and 338 greatgrandchildren alive when he died Some environmental textbooks use this example to show that a population can bloom quickly ie it can experience exponential growth forgetthough quot 39 quot L r quot John EliMillerandhis quot Miller quot39 r4 1 raised in an agrarian community in a developing country the US was not a Jlly developed country in the 1800 s Lquot 39 39 quot39 39 39 39 39 iine one would nd in a Jlly developed country like America Europe and Japan today or even a semiindustrialized As a contrary example let us look at the Jules Francis Pratte family Jules was born in the late 18 39 n near St ouis Like John Eli Mmquot Vs39 Prat Miller he had a irly large brood of children Miller had 7 in total Pratte had 6 However Pratte39s six children only produced 14 grandchildren much less than the 63 ofMiller These 14 grandchildren only pro uced 21 greatgrandchildren which is a fa ry he 341 greatgrandchildren ofMiller As Figure 1 shows while Miller s family growth is exponential increase by same percentage Pratte s is an example of linear growth increase by same nt Number of Offspring 13 2 2 3 3 3 Generation The difference is that all of Pratte39s family have had occupations in the industrial or professional sector of the e ican ec This has a profound difference in the rate of r h fa population In an agrarian society especially one without modern fossil Jel driven machinery every child you have is another 39ee eld an 39 39 39 a e 39 39 for producing more food than they eat This results in a net income for the family In an industrial society Fig 1 N ller circles versus Pram diamonds iaw bring in any additional income In a very real sense every child you have will be a serious drain on your nancial resources This societal difference accounts for a large portion ofthe difference that you will nd in the population quot 39 quot 439 quot cultu en 39 39 39 societies have a longer life span other Growth Factors While the exact reason a person has a child will vary it usually falls into one of several categories The most obvious reason is a biological imperative to procreate ie an innate desire to have children This is avery strong reason 39 quot However 39 39 39 quot other factors to stop having children become strong For example some people have babies for societal reasons such as to carry on the family name iiau uieii muuiei Ul iauiei going to get married settle down 39 39 wen 1quotquot 39 on the 39 39 g 39 quot quot4 China s One Baby Policyquot in which couples pay quot39 39 uiey quot quotquot 39 urban r4 1 quotI H resorted to abortion or giving their child up for adoption ifthey nd out it is a female in order for them to i L39l i 10a nuaiiuii more males under the age of 30 than there are females Even with the shorter lifespans of males this 39 39 ie erse quot quot L 39 39 problem for China in the Jture Some people have children for religious reasons For some faiths it is a matter of not doing anything to prevent having children For instance the Roman Catholic faith believes that it is immoral to use arti cial means to prevent conception For other faiths there are actual dictates to have more children as the 39 39 39 good place in the afterlife Th F larger 4 4 4 RLF These two reasons along with the basic instinct to procreate are probably the two strongest reasons for growth in the US and some other developed countries In developing countries where growth rates are the largest there are often many other very important reasons For instance a lack of education and economic opportunity for women has been very strongly correlated to increased birth rates Women in these situations generally do not have information about birth control The lack of economic opportunities further compounds the problem as their only job is to be married and have children This is a double edged sword lfthey are able to find employment then there is pressure not to have more children as each child means that they will have to be away from work and thus decrease the earnings for the family lfthere are no economic opportunities available then the only way for women to provide for themselves later in life is to have children who will take care of them as they age Hence ifthere are economic opportunities there is pressure to decrease family size while a lack ofthem causes pressure to t increase I Another very important factor in determining growth is the age at which women get married The average woman has about 30 years in which she can have children If she starts having children at an early age then she is much more likely to have a lot of children This factor is also tied to economic opportunities and education as these two things often delay the age at women get married Developed Countries and Immigration When George Washington started the first Presidency of the United States of America he was governing less than 4 million people who occupied an area of 2300000 square kilometers1 It was an agrarian society with 95 ofthe population living on farms and only 5 in cities or towns of more than 25002 There was plenty of land and a vast array of natural resources just waiting to be tapped Today we live in a country of over 300 million peoples While we are one of the major food HiStorical US POPUIation producers in the world it is no longer due to us being an agrarian society Today most people 35 live in towns and cities with less than 25 of m the population living in rural areas And even though we have grown to a physical size of over 98 million square kilometers our population density has increased from the 2 people per square kilometer of Washington s day to almost 30 people per square kilometer today Population Millions From where did all ofthese people come The increase in territory that we experienced over that time did increase the number of people in nan 13am l mun l man man the US from the simple fact that there were Year already people living there We have also 0 expanded by immigration with wave after wave of people entering this country to find new life Flg 2 Hlstoncal US Populatlon Data US Census and new opportunity Neither ofthese though accounts for the largest segment of growth Both put together still account for less than 80 million people The largest sector of people is here due to birth This same thing is true of most countries Immigration is often a small factor to the overall growth ofthe country However it can have a powerful effect on the growth of a country as the birthrate can be greatly affected by it In the early days of the US the growth from births came from all sectors of society However as the following story shows the growth of a developed country can come mostly from the descendents of immigrants Karen s Story by Matt Laposata It had been a bad day for Karen Christini After enduring paralyzing rushhour traffic following a miserable day at work she was ready for some hardeamed relaxation But no such opportunity availed itself for tonight was decision night While in college Karen had joined the Sierra Club a national organization dedicated to environmental preservation with her boyfriend Andrew Andrew lasted less than a semester but her Sierra Club membership was still going strong as she entered her midthirties And on this chilly April night it was the Sierra Club that demanded her attention The Sierra Club s budget political lobbying policy stances and preservation efforts are directed by a group of 15 elected board members Board elections were typically not national news but this election was anything but typical For some time the membership of the Sierra Club had been divided on the issue of US immigration and its relationship to human population growth In 1998 a movement within the organization put forth a proposal to replace the Sierra Club39s historic quotno positionquot stance on US immigration with one that advocated reductions in the number of immigrants admitted to the United States to reduce environmental impacts associated with growing populations Sixty percent of members rejected the proposal and the Sierra Club continued advocating controls on global human population growth with a neutral policy towards US immigration In the following years however three members that advocated a stance towards reduced immigration were elected to the board There were five open seats this year so the election of five reducedimmigration candidates would give the group a majority on the board and the power to steer the organization Karen had not come to a decision on her votes and the ballot had to be in the mail tomorrow As she had done many times over the past few weeks she sat at the kitchen table hunched over her Sierra Club ballot and began running her ngers through her hair trying to use the rhythmic motions to force a decision from her head She reviewed the major points of view one last time hoping yet another analysis would yield a conclusion On the one hand she thought the advocates of reduced immigration had a point The United States absorbs around one million legal immigrants and several hundred thousand illegal immigrants a year and these immigrants have average birth rates about double that of USbom citizens Unlike most industrialized nations the population of the United States is expected to grow from around 292 million in 2003 to about 422 million in 2050 7 and up to 70 of this growth is attributable to immigration Given the highconsumption lifestyle in modern America this population growth will lead to increased impacts on the local and global environment exactly the things the Sierra Club aims to reduce Proponents of immigration reduction also argue that international immigration causes talented and educated citizens of developing nations to leave for industrialized countries slowing the industrialization that leads to lower birth rates They further contend that immigration has economic costs when wages earned in the United States are sent home by immigrant workers But she thought those that support current immigration policies make several convincing arguments They argue that while international immigration increases the US population it slows the growth of the global human population as the children of immigrants have birth rates like that of other US born citizens 7 rates likely far lower than those in the immigrant s native country Immigration proponents also claim that immigration improves cultural awareness in the United States thereby promoting environmental sustainability in these countries through foreign aid initiatives Immigration advocates say that the United States should always be a quotsafe harborquot for victims of human rights abuses or armed con ict around the world They also claim that immigrants infuse skills and labor into the workforce and improve the economy of the host country Karen s family was a classic example Her grandparents emigrated from Sicily to the vibrant ItalianAmerican community in New Haven Connecticut in the early 1900s and prospered in subsequent generations through a dedication to education and hard work Karen sat back in the chair and sighed heavily The epiphany the tiebreaker or the revelation she sought had once again eluded her This wasn39t going to be easy She sat forward propped her elbows on the table stared at her ballot and began running her fingers through her hair If you were Karen what would you do Describe how your family s immigration history in the United States Did an understanding of this history a ect your views on the subject Do you think the current US immigration regulations are appropriate Explain why or why not If you think current immigration policies are inappropriate provide specific suggestions on how they should be modified Predicting the Future For all of its futuristic stylings the television show Star Trek was like most science fiction a commentary on the state of society at the time it was written late 1960s One ofthe more famous episodes ofthat series was the one entitled The Mark of Gideon which dealt with a planet that was so overpopulated that people did not have anywhere to sit down At the time of the show the Earth s population was at about 35 billion and was increasing at an incredible rate The effects of such a large population on the environment were beginning to become abundantly clear and people had begun to wonderjust how many more people the Earth could hold This Star Trek episode wasjust one of a number of television shows movies and books at that time ex Soyent Green that foretold of an ominous future if we did not begin to do something All ofthese shows were predicated on predictions made by demographers at the time of what the world s population would be at some point in the future Each generation has done this sometimes with startling accuracy and sometimes missing the mark completely For example in 1798 Thomas Malthus an English demographer and economist predicted that the world s population would one day outstrip mankind s ability to feed itself and that this would be reached when the population was 1 billion people Of course Malthus could not foresee the introduction ofthe internal combustion engine and the production of artificial fertilizers that have increase our capacity to feed We now have more than 65 billion occupants of Earth and we are continuing to grow As previously stated at current rates of growth we will reach 12 billion by the year 2050 However this prediction is most assuredly wrong as it relies on everything going along just as it is As Malthus shows us one cannot assume this In order to make a more sophisticated prediction we need to look deeper at the data to see what it is telling us One tool that aids in that regard is the age structure diagram also known as the population pyramid Demographic Profiles While it is sometimes called a population pyramid an age structure diagram does not have to have a pyramid shape What this diagram actually shows is the distribution by ages of females and males within a certain population in graphic form 7 V Figure 3 shows a diagram in which the ages and sexes for the United States population are arranged so that ages are grouped together such as 0 4 years 5 9 years and so on The population of each is group is represented as a bar extending from a central vertical line with the length of each bar dependent upon the population total for that particular group The centerline separates the females from the males The female and male populations for each group a represented by the distance from the centerline with females on the right and males on the left Fig 3 Age Structure diagram for the US Age and Sex Distribution By looking closely at the age structure diagram one will notice slightly more boys in the younger age groups than girls however the ratio tends to reverse in the upper age groups as females tend to outnumber males Many countries have a female majority as a result ofthe longer life expectancy for females In the United States this ratio change is clearly shown in the table below showing age and sex distribution in the census year 2000 Notice that at about age 35 the majority changes As stated before in China the age and sex distribution is a cause for alarm Efforts there to reduce the birth rate have apparently contributed to a prominent male majority Since the early 1980 s a thrust by the government to reduce population growth in the most populous country in the world has resulted in many parents actively trying to have Fig 4 Age structure diagram for China a male child if they are to have only one child Cultural traditions there tend to cause parents to see a male child as more beneficial to the family than a female child therefore a striking imbalance has resulted between the numbers of males and females There are concerns that the imbalance could lead to instabilities as these boys mature into men and find that there are not enough women to marry Constructing and Interpreting an Age Structure Diagram With age and sex distribution data from a certain population you can retrieve this for any country using the US Census Bureau s International Database it is easy to construct an age structure diagram All one has to do is to plot each value for the number of males or females in a given age bracket as a horizontal bar with older brackets being found higher on the diagram The reason for doing this is that this diagram gives a very visual representation of what is likely to occur to a country in the future barring a major catastrophe This can be interpreted just from the shape of the diagram For example if the diagram shows a pyramidal shape then one can expect a rapid rise in population If the diagram shows a generally straight up and down shape except for the older age groups a stable population is thus revealed If the diagram shows a topheavy shape then a decline is forecast for that population Why is this Figure 5 shows the age structure diagrams for Mexico Iceland and Japan from the year 2000 The different shapes seen in the diagrams reflect different population characteristics The diagram for Mexico shows the unmistakable pyramidal shape that will cause by everincreasing number of births This is because there are much larger numbers of children in the 04 age bracket than there are in the 2024 one Barring a major catastrophe most of these children will make it to the 2024 year range meaning that there will be many more people of childrearing age 20 years from now than there maxim 2mm FEMRLE 210012365 Iceland 2an ma mmz a WVF WW 3 Wmeegeeswamwa z 0 Japan zuna Fig 5 Age structure diagrams for Mexico Iceland and Japan US Census Bureau are today Unless they drastically cut back on the total fertility rate this means that there will be even more children in the 04 age bracket 20 years from now than there are today Thus the total population of the country will grow as all age brackets will have more people in them then than today Japan s diagram shows the opposite of this In it you should note how prereproductive age groups 0 14 years have smaller populations than the reproductive age groups 15 44 years Thus unless the total fertility rate increases there will be even fewer kids in the 014 age group 20 years from now than there are today which means that the population will decrease Of course this will present different problems for Japan as a shrinking younger age group means that there will be fewer and fewer younger workers to support the elderly One way to rectify this is to increase immigration at the lower age groups which will bring more workers into the country While this will provide the necessary workers to take care of the elderly it can be problematic to implement in a homogenous population like that found in Japan or ltaly another country that has this same problem Iceland on the other hand shows a more stable population Except for the postreproductive groups 45 years the populations for the age groups extend generally the same lengths There is a slight bulge outward but if you account for infant and childhood mortality the number of children in the 04 age range that make it to the 2024 age range should be just about the same as the number of adults in that age range today This means that there should be little to no growth with the possible exception of people living longer and increasing the raw numbers by essentially extending the diagram upwards Additional Reading Topic Population Projections for theU S Summary Information on projected po lation increases in the US Link httpwvvwcensusgovpopulatiohWvaprojectionsppl4739html References 1 httpwwwcensusgovpopulationcensusdatatable2pdf October 16 2004 2 httpwwwcensusgovpopulationcensusdatatable4pdf October 16 2004 3 httpwwwcensusuuwnmi 39 39 html October16 2004 4 httpehnetei 39 quot 39 39 LUS October 16 2004 wu
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