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Chapter Six - Lecture 2 - Human Population.docx

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Environmental Science

Chapter 6 Human Population: Approaching 7 Billion  Nation population continue to grow, we are at 6.7 billion o China working to slow population growth o The rate of global growth is slowing The Human Population is growing nearly as fast as ever  Population increases as a quantity by a fixed percentage per unit time, like a compound interest accrues(积累) in a savings account. o A given percentage of a larger number is > than an equal percentage for a small number  Population growth hasn’t remained steady o Vary greatly from region to region  China instituted its one child population, as its growth was 2.8% o 2.8% = 25 years doubling time of population. Perspectives (远景)on human population have changed over time  In the 1700s population growth was regarded as a good thing o Parents thought of a high birth rate as more children to support them at an old age o For society, it meant a greater pool of labour for factory work.  Malthus (british economist) said the population growth had to be limited by laws or social controls or the number Chapter 6 of people would outgrow(出生) the food supply until starvation, war, or disease arose and reduced it. o Published essay on the principle of population Is population growth really ‘problem’ today?  The ongoing population growth has been made possible by technological innovations, improved sanitation, better medical care, increased agricultural output, and other factors that have led to a decline in death rates, particularly a drop in rates of infant mortality(死亡率). o Enormous increases in crop yields and advances in agricultural technology associated with the Green Revolution  Births have outpaced(超过。。的速度) deaths for many years now o Creating population problem.  Cornucopian(丰富的) thinkers believe we can find a way to replace depleted resources.(资源枯竭)  Not all resources can be replaced or reinvented(改造) once they have been depleted o Once species is extinct it is gone. o We can’t expand earth like a balloon.  Resource availability must keep pace with population growth o Otherwise in the future each person will have less space to live, eat and material wealth  In todays world population growth is strongly correlated with poverty than with wealth. Chapter 6  Outside of Europe 56% of national governments feel their birth rates are too high, and only 8% feel they are too low o In Europe 3 of every 5 European national governments say their birth rates are too low  Global population growth and resulting environmental scarcity have played a central role in causing famine, disease and social & political conflict around the world. Population is one of several factors that effect the environment  IPAT Model o I=PxAxT  Impact (I)  Impact is thought of in various ways o Pollution or resource consumption  Population (P)  Increased population means more individuals take up space, use natural resources and generate waste  Affluence (A)  Increased affluence magnifies(放大) environmental impact through the greater per capita resource consumption that generally has accompanied enhanced wealth.  Technology (T)  May decrease or increase human impact on the environment. Chapter 6  Can decrease impact if we reduce smokestack emissions, harness (renewable energy  Increase if we enhance our abilities to exploit minerals, fossil fuels, ocean fisheries.  We can add a sensitivity factor (S) to the equation o I=PxAxTxS  Sensitivity (S)  Denote how sensitive given environment is to human pressures o Disturbance of regions may slow down plant growth.  Technology advances to increase global agricultural production faster than our population his risen.  China is a window on what much of the rest of the world could soon become o World’s developing countries try to attain the level of material prosperity that industrialized nations enjoy. Demography(人口统计学)  The application of population ecology principles to the study of statistical change in human populations is the focus of the social science of demography The environment has a carrying capacity for humans  Environmental factors set limits on our population growth, and the environment has a carrying capacity for our species. Chapter 6  4 Significant periods of societal change appear to have fundamentally altered the human relationship with the environment and increased the carrying capacity, triggering remarkable increases in population size. o Paleolithic period (stone age旧石器时代  Humans gained control of fire and began to use stones as tools to modify the environment. o Nomadic Hunter-Gatherer lifestyle (agricultural way of life游牧狩猎采集的生活方式(农业生活方式)  Agricultural Revolution (new stone ageéneolithic) 农业革命(新石器时代新石器时代)  People began to grow their own crops, raise domestic animals and live settled, sedentary lives in villages, found it easier to meet nutritional needs.  Lived longer and had more children who survived to adulthood.  Industrial Revolution  Began in mid 1700s  Shifted rural life, animal powered agriculture and manufacturing by craftsmen to an urban society powered by fossil fuels  Introduced improvements in sanitation and medical technology  Introduction of fossil fuel enhanced agricultural production o Powered equipment, steam engines, and synthetic fertilizers. Chapter 6  We are in the midst of a fourth major transition o Medical-Technological Revolution  Involving the globalization of modern medical and technological advancements.  Marked by developments in medicine, sanitation and pharmaceuticals  Hopefully this transition will BE MORE SUSTAINABLE, RENEWABLE ENERGY SOURCES AND away from dependence on fossil fuels. Demography is the study of human population  Demographic data helps us understand how differences in population characteristics and related phenomena (e.g. decisions about reproduction) affect human communities and their environments.  Demographers study population size, density, distribution, age structure, sex ratio, and rates of birth, death, immigration, and emigration of humans, just as population ecologists study these characteristics in other organisms. Population Size  The size of the population doesn`t tell a whole story o A populations environmental impact depends on its density, distribution, and composition, as well as on affluence, technology level of consumption, and other factors outlined earlier. Population density and distribution Chapter 6  People are distributed very unevenly over the globe.  Population density is the number of people per unit of land area o High in regions with temperate, subtropical, and tropical climates  China, Europe, Mexico, Southern Africa, and India o Low in regions with extreme climate biomes  Desert, deep rainforest and tundra o Dense along seacoasts and rivers  Less dense at locations far from water.  This means that certain areas bear far more environmental impact than others.  Areas with low population density are often vulnerable to environmental impacts o The reason they have low population in the first place is because they are sensitive(S In IPAT) and cant support many people.  Deserts have low availability of water. o The artic tundra is another environment highly sensitive to environmental change and human impacts  Disturbance of vegetation (something as simple of a set of car tracks) can cause deep melting of permafrost and collapse of soil, the scars of which may last for years or even decades. Age structures Chapter 6  China guaranteed its population age structure would change by causing dramatic chnges the number of children born. o Shift in age structure as the number of people older than 65 will rise from 100 million in 2005 to 236 million in 2030. o Dramatic shift will challenge chinas economy, health care systems, military forces because fewer working age people ewill be available to support socil programs that ssist the increasing number of older people.  Shift in age structure also reduces the proportion of dependednt children.  Decrease in crime rate may occur because of reduced number of young adults. Sex Ratios  For every 100 female infants born, 105-106 male infants are born o Men are slightly more prone to death making it equal  Women then predominate as the population ages leading to a ratio of males to females that is slightly less than one-to-one.  A greatly distorted ratio can lead to problems but a slightly uneven is beneficial.  Lately, a male dominance in new born babies. (some provinces are 138 boys for every 100 girls) o Might be because females may abort foetuses after learning the child`s sex from ultrasound. Chapter 6  China want to have their only kid a son so he could carry on the family name.  This is the sex skewed ratio. Population growth depends on rates of birth, death, immigration and emigration.  Rates of birth, death, immigration, and emigration help determine whether a human population grows, shrinks or remains stable.  Crude Birth Rate & C
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