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ENV CHAPTER 9-1: STUDYING HUMAN POPULATIONS
Why we care about studying the human pop – the human pop grew faster in the 20th century than ever beforeIt created environmental problems around the worldSo we want to try to understand and predict pop changes The human pop over time:- Grew slowly for thousands of years, then started to grow fast in the 1800s.- It underwent exponential growth – due to increases in food production and hygiene – these things came along with the industrial and scientific revolutions and made for higher birth rates and lower death rates Earth can’t sustain this kind of growth forever Forecasting pop size:Demography – the study of popsThey study different 4 aspects of a pop to make pop predictions:1. Age structure – the distribution of ages in a pop at a certain timeIt can be graphed in a pop pyramid (a double-sided bar graph that shows ratio of males to females and older people to young people)A. High growth rate – the pop usually has more young people than old peopleB. Slow or no growth – usually an even distribution of ages in the popa. Rapid growth – least developed nations (highest birth rates)b. Slow growth – transitional nations c. Zero or declining growth – most developed nations 2. Survivorship – percentage of individuals that are likely to survive to a given age.Demographers study a group of people born at the same time and note when each one dies. You can plot the data to get a survivorship curve.a. type I curve – most people live to be very old – wealthy developed countriesb. type II curve – similar death rate at all agesc. type III – many children die – very poor human pops both I and III can result in pops that stay the same size 3. fertility rates – number of babies born each year per 1000 womenreplacement level – the number of children each parent must have in order to replace themselves in a pop (2). Since 1970 fertility rates have declined in both less-developed and more-developed countries 4. migration – the movement of individuals between areas. Immigration – movement into an area Emigration – movement out of an area Migration within and between countries is a big part of pop change The pops of many developed countries might be decreasing if it weren’t for immigration Also – Increase in the human pop b/c of declining death rates and increased life expectancy- Declining death rates – Dramatic increase in human pop in the last 200 years b/c death rates have declined faster than birth rates.- This has been due to adequate food, clean water, sewage disposal, medical advances. Life expectancy – the number of years a person is likely to live.- It’s most affected by infant mortality – death rate of babies less than 1 year old- Infant health is most affected by the parents’ access to education, food, fuel, clean water.- When infant mortality is low, life expectancy goes up The demographic transition – a model of how changes in a pop will occur.Theory behind it – industrial development causes economic and social progress that affects pop growth rates There are 4 different stages of the transition:1. society is pre-industrial – birth and death rates are high and pop is stable (most of the world was this before the scientific and industrial revolutions)2. pop explosion – death rate declines – b/c hygiene, nutrition and education improve. But the birth rate is still high so pop grows very quickly3. pop growth slows – b/c birth rate decreases. Birth and death rates get close and the pop stabilizes. Societal conditions favor smaller families.4. birth rate drops below replacement level – size of pop starts to decreasewomen and fertilitybirth rates have been most affected by increased education and economic independence for women
ENV CHAPTER 9-2: CHANGING POPULATION TRENDS
Infrastructure – facilities and services that support a community (water, sewer, power, transportation, education, medical services) Problems of rapid growth- People can’t live w/o a working infrastructure. - Breakdown of an infrastructure happens when people use up resources faster than they can be replaced by the environment The 3 resources most critically affected b/c of the increase in humans are fuelwood, water, and arable land.1. Wood – less developed nations use wood as fuel.when pops grow rapidly dead wood doesn’t accumulate fast enough to provide enough fuel.So people start to cut down living trees faster than it can be replaced. So it is like a limited resource. W/o fuel, food can’t be cooked, and water can’t be boiled.Many people suffer from disease and malnutrition. 2. Water – local water supply gets used for drinking, washing, and sewage disposal.Diseases – dysentery, cholera, typhoidFix – providing sewage treatment for growing pops 3. Land – people need space to live inAs popss grow, arable land is lost – land that can be used to grow crops.Urbanization – more people move into citiesSurbaban sprawl can result – people moving outside the city into suburban areasTraffic jams, land lost to development, inadequate infrastructure results
The world’s demographics are diverse – not every country is progressing through every step of the demographic transition The global community has started to focus on the least developed nations- they have given priority for foreign aid and development programs. - the goal is to help out the world environment ICPD – International Conference on Population and Development- It looks at relationships between pop, development, and environment- Many favor stabilizing pop growth through improvements in women’s status. Growth is slowing- Currently the world pop is 8 billion billion and growing- But fertility rates have been declining in many regions and so growth is slowing down. - If most countries achieve replacement levels of fertility, world pop growth would eventually stop Projections to 2050 – hoping for a medium growth rate, will reach 9-10 billion Factors that could change pop predictions: changes in economic trends, environmental disasters, war, changes in the status of women, government policies.
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