Chapter 2
Define and give an example of a limiting factor.
limiting factors -Single factor that limits the growth, abundance, or distribution of the population of a species in an ecosystem. Example These include the availability of resources necessary for survival, such as water, food, and space, as well as environmental threats to survival, such as diseases and predators.
State the demographic transition hypothesis and describe the four phases of the demographic transition.
demographic transition: a four-phase process in which a country's birth and death rates change as the country becomes industrialized, and its population growth rate declines. 1. Pre-Industrial 2. Transitional 3. Industrial 4. Post-Industrial
What are the world's three most populous countries?
1. In 2012, China had the world's largest population, with almost 1.4 billion people, or one of every 5 people on the planet. 2. India ranked second with almost 1.3 billion people. Together, China and India were home for 38% of the earth's people. 3. The United States, with 313 million people, was the third most populous country with 4.5% of the world's people.
Explain why a population with a large percentage of young people will keep growing for many decades even if its women have only one or two children, on average.
Aging can affect a population. Baby Boomers get older, their decade keeps growing. A large percentage of the population. Another effect is that the population of a country can decline as the percentage of its people aged 65 or older rises and the percentage of its people aged 15 and younger falls
How can empowering women help to slow population growth?
Also, a number of studies have shown that women tend to have fewer children when they have the ability to control their fertility and when they have paying jobs outside the home. In many of the world's less-developed countries, women are learning how to gain these advantages through family planning, including birth control, and through employment outside their homes. Increasingly, women in these countries are getting small loans to start businesses and work their way out of poverty. Many experts believe these trends will help to slow population growth and reduce poverty and environmental degradation.
Summarize the differences between the age structures of a typical less-developed country and a typical more-developed country.
Because many less-developed countries like Guatemala have large pre-reproductive populations, there are dramatic differences between the age structures of a typical more-developed country and a typical less-developed country. These differences help to explain why all but a small percentage of the projected population growth in this century will occur in less-developed countries. About 29% of the people in less-developed countries are younger than age 15, compared to 16% in the more-developed countries. pre-reproductive (ages 0-14), reproductive (ages 15-44), and post-reproductive (ages 45 and older).
Why is the issue of environmental refugees an urgent issue that the international community should deal with now, even though it is largely a future problem?
Growing numbers of environmental refugees could soon start to pose new threats to international stability, especially if many of them try to find shelter in the more-developed nations. According to many experts, the refusal to recognize the existing number of environmental refugees, as well as the potential for much larger numbers to come, is a recipe for disaster. The U.S. Central Intelligence Agency and several U.S. military experts see this problem as a major threat to global peace and social and economic stability. To these and many other experts, it is a humanitarian problem that deserves immediate attention from the international community.
What is the IPAT model, and how can we use it to estimate environmental impacts?
IPAT model A simple model that brings together three major factors that impact the environment: population size (P), resource consumption per person, or affluence (A), and the harmful and beneficial environmental effects of technologies (T). The IPAT model shows that the environmental impact (I) of human activities depends primarily on how these three factors interact, as represented by this simple equation: Impact (I) = Population (P) × Affluence (A) × Technology (T). While the ecological footprint model focuses on the environmental impact of the human use of renewable resources, the IPAT model shows the environmental impact of the per capita use of renewable and nonrenewable resources.
How were the people who were added to the population in 2012 distributed between more-developed and less-developed countries?
In 2012, about 82% of the world's people lived in less-developed countries. Many of these people live in encampments or crowded slums in cities such as Rio de Janeiro. During 2012, only 1 of every 80 infants was born in one of the world's more-developed countries.
Describe China's one-child policy and how it is implemented.
In the 1960s, China's large population was growing so rapidly that there was a serious threat of mass starvation. To avoid this, government officials decided to establish a family planning and birth control program. It became the world's most comprehensive, strict, and intrusive of such efforts. China's goal is to sharply reduce fertility by promoting one-child families.
Describe two problems that hinder family planning efforts.
One is that about 42% of all pregnancies in less-developed countries are unplanned, and more than half of them end with abortion. The other is that in less-developed countries, family planning programs are not available to an estimated 160 million couples that want them.
Explain the importance of microloans for the poor in reducing poverty and slowing population growth.
One very promising way to help poor people who want to work their way out of poverty is to provide them with small loans for purposes such as starting a small business or buying seeds and fertilizer for growing food crops. Most of the world's poor people do not have a credit record or the means to qualify for conventional loans. In 1983, economist Muhammad Yunus (Figure 2.A) started the Grameen (Village) Bank in Bangladesh, a country with a high poverty rate and a rapidly growing population. Since then, the bank has provided a total of $7.4 billion in microloans of $100 to $1,000 at very low interest rates to 7.6 million impoverished people (97% of them women) who cannot qualify for loans at traditional banks. Almost all of these loans have been used by women to plant crops, to start small businesses, or to buy livestock, bicycles for transportation, or small irrigation pumps. To promote loan repayment, the bank puts borrowers into groups of five. If a group member fails to make a weekly payment, other members have to make it instead. As a result, the bank has made a solid profit and the average repayment rate on its microloans has been 95% or higher—much higher than the average repayment rate for loans by conventional banks. About half of the bank's microborrowers have moved above the poverty line and improved their lives within 5 years. Between 1975 and 2005, this innovative approach, along with the hard work of the people receiving the microloans, helped to reduce the poverty rate in Bangladesh from 74% to 40%. In addition, birth rates are generally lower among most of the borrowers.
What is the tragedy of the commons? Give two examples of this effect.
Resource depletion is an example of what biologist Garrett Hardin (1915-2003) called the tragedy of the commons. Historically, most users of widely available renewable resources such as ocean fish have assumed that the supplies of such resources are unlimited. They have also assumed that their own small use of any resource will not affect the resource's supply, especially since it is renewable anyway. This kind of reasoning works when there are a small number of users; however, as the number of users grows and their total rate of resource use outpaces the resource's rate of replenishment, the resource can eventually be depleted. Then it is no longer available to anyone, and that is the tragedy of the commons. Today with 7 billion people using growing amounts of resources and producing more wastes and pollution, humanity faces the ultimate tragedy of the commons—the degradation of the planet's life-support system. -the degradation of the planet's life-support system. -resources no longer available
Explain how a population can crash.
Sometimes, populations grow so rapidly that they temporarily exceed their environment's carrying capacity. In such a case, the population dies back in a population crash because its environment cannot support it.
What is the current size of the human population?
The human population on our planetary home now stands at 7 billion and every year it grows by about 83 million. By 2050, there may be 9.3 billion of us. This means that in less than four decades, we could be adding almost twice the number of people now living in China to the earth's population.
Why should we care about the growth of the human population?
There are two major reasons. First, each of us depends on the earth's life-support systems for food, shelter, clean water and air, energy, and other vital resources such as wood, iron, and aluminum. Adding more people to the population increases the need for these natural resources as well as natural services such as chemical cycling and renewal of topsoil. Also, average income per person is rising in many countries, and most of the world's more affluent consumers tend to use more of the earth's natural resources and services. As a result, average per-person, or per capita, natural resource use is very high in wealthy countries such as the United States and much lower in poorer countries such as India . The second major reason for caring about population growth is the strong and growing scientific evidence that we are degrading our life-support system with our rapidly growing ecological footprints (see Module 1, Figure 1.23). Each newcomer adds to this planetary stress, especially in areas of the world where people are using a lot of resources. While our ecological footprints are growing larger, we are not meeting the basic needs for many of the people alive today.
Why is it that no population can keep growing forever?
There is a combination of limiting factors that act together to control the growth of a population . Scientific research has shown that every growing population eventually reaches some size limit imposed by one or more limiting factors. Because there are not enough resources to sustain an ever-growing population of any species.
What is the total fertility rate (TFR)? How does it affect population growth?
Total fertility rate (TFR): the average number of children born to the women in a population during their reproductive years. - This number is important because it helps to determine the rate of growth of a population. ----------- If a population has a TFR of well over 2.0, it will grow, because each couple is having more than enough children to replace themselves when they die. If the TFR is lower than 2.0, the population will eventually start to decline, because not enough people will be born to replace each couple. ------------ TFRs have generally been dropping in most countries of the world.
What is the age structure of a population and how does it influence the future size of a population?
age structure: -the numbers or percentages of people in its young, middle, and older age groups. -Percentage of the population (or number of people of each gender) at each age level in a population. Determines how fast the population will grow or decline.
Give three reasons why it can make sense for couples living in poverty to have a large number of children.
1. In poorer cultures, large families are common because many poor couples rely on their children to care for them in their old age. (In countries with old-age pension programs, there is less of a tendency for people to have large families.) 2. Infants are more likely to die in poorer countries, so having several children might insure the survival of at least a few. 3. Also, in these cultures, larger numbers of children can provide more help by hauling daily drinking water, gathering wood for heating and cooking, or tending crops and livestock.
What three factors caused the world's population to grow exponentially?
1. We learned to use energy from coal, oil, and other fuels and developed a variety of machines and other technologies. These advances have allowed us to expand into almost all of earth's climate zones. 2. Modern agriculture has allowed us to produce larger and longer-lasting food supplies by using technologies such as farm machinery, irrigation, chemical fertilizers and pesticides, and factory fishing boats. 3. Human death rates dropped sharply below birth rates as we improved sanitation and health care and developed medicines to help control infectious diseases.
What are two possible effects of a rapid decline in the population of a country due to aging?
1.Government budgets are strained as expenses for public services such as health care rise. At the same time, there are fewer workers paying the taxes needed to support the growing number of older people. 2.A country with a rapidly declining population can also experience a labor shortage unless it encourages immigration of young workers from other countries. Another effect is that the population of a country can decline as the percentage of its people aged 65 or older rises and the percentage of its people aged 15 and younger falls (Figure 2.11, right). For example, in 2012, Japan had the world's highest percentage of elderly people and the world's lowest percentage of young people, and Japan severely restricts immigration. As a result, its population is projected to drop by 24% from 128 million to 95 million people between 2012 and 2050. A slow population decline can usually be managed. But rapid population decline can cause serious economic and social problems.
How does population growth affect resource depletion and other forms of environmental degradation? Give four examples.
A growing population and growing per capita ecological footprints can also lead to other forms of environmental degradation and depletion. -One example is deforestation, the extensive cutting and burning of forests to make way for crops, grazing land, settlement, and the expansion of cities. Often, the result is erosion of a forest's topsoil to the point where the forest cannot grow back. Clearing a forest or grassland and replacing it with roads, parking lots, houses, and other buildings have the same effect. -The processes of mining and producing mineral resources also degrade vast areas of land, pollute air and water, and destroy wildlife habitat. - the rising global average level of carbon dioxide (CO2) in the atmosphere. This has resulted primarily from the large-scale burning of fossil fuels and the removal of forests that absorb CO2 from the atmosphere, as both the human population and resource use per person have grown. Higher atmospheric levels of CO2 and other greenhouse gases are adding to the problem of atmospheric warming, which is projected to disrupt the earth's climate during this century. -In some cases, we can deplete a renewable resource to the point where it cannot recover.
Summarize the projections for U.S. population growth. How does U.S. population growth compare with that of other more-developed countries?
According to the U.S. Census Bureau, the U.S. population grew in 2012 by about 3.2 million, an average of 1 additional person every 10 seconds. Most of these newcomers were newborn babies, but around 1 million were immigrants, mostly from Latin America, Asia, and Europe. The U.S. Census Bureau projects that between 2012 and 2050, the U.S. population will grow from 313 million to 423 million. Immigration is projected to account for at least a third of this projected growth. -------------- The rate of population growth in the United States slowed because of this drop in the TFR. But the U.S. population is still growing faster than the populations of all other more-developed countries and of China, and it shows no sign of leveling off.
Give an example of how a resource can be depleted.
However, renewable resources such as forests and the fresh water in streams can be replenished as long as we do not use or pollute them faster than natural processes can renew them. When we do misuse them in these ways, they can become degraded and possibly depleted examples - much of the water we use to irrigate crops and to supply cities, factories, and homes comes from underground deposits of water, called groundwater, stored in formations called aquifers. Most aquifers are renewed by rain that percolates down through the soil. However, if we drill wells and remove water from this type of aquifer faster than it is replenished, the available supply of water can shrink. In this way, we can deplete the aquifer. -topsoil. Wherever farmers grow crops year after year to feed more mouths without adding nutrients to replace those that are taken up by their crops, those topsoil nutrients provided by nature become exhausted. Then, to replace nature's free soil nutrients, farmers are forced to use costly fertilizers, which can cause water pollution. -mineral resources. As populations grow and as resource use per person increases, several countries have exhausted their stocks of important minerals such as copper and gold, and must rely on other countries to supply these resources at great cost. Today, the United States imports all or nearly all of its supplies of 25 key nonrenewable mineral resources. -overexploitation of many wild species. Numerous ocean fish species have been overfished to the point where their populations are depleted. Rare and endangered plants and animals are being collected, captured, or killed for use as food or as part of the global trade (illegal as well as legal) in ornamental plants, exotic pets, and animal hides, horns, and other body parts. This is a growing factor in the sharply rising rate of biodiversity loss. ((This scarlet macaw is found in several of the tropical rain forests of Central and South America. These birds are endangered due to loss of habitat and because they are captured and sold as pets, often illegally.))
Describe some of the inequalities that women, especially poor women, face throughout most of the world.
In most countries, women have fewer rights and educational and economic opportunities than men have. Yet within their families, women provide more unpaid health care, globally, than that provided by all of the world's organized health services. In rural areas of Asia, Africa, and Latin America, women and girls do well over half of the daily work devoted to growing food, finding and hauling water, and gathering and carrying firewood. Women account for about two-thirds of all the hours of work performed every day throughout the world but receive only a tenth of the world's income and own less than 2% of its land. In many societies, sons are valued more than daughters, and parents often make their school-age daughters work at home instead of sending them to school. As a result, about 900 million girls—almost 3 times the entire U.S. population—do not attend elementary school. And almost 2 of every 3 illiterate adults and 7 of every 10 people in the world who suffer from poverty are women.
Explain why some countries may have difficulty in making such a transition
In recent years, several nations have climbed out of poverty in a short time through economic development. For example, within two decades, South Korea transformed itself from a poor nation with a rapidly growing population to a modern, industrialized nation with a slowly growing population. Some experts believe that, over the next several decades, most of the world's developing countries will undergo a demographic transition, mostly through a combination of economic development and family planning. But other analysts warn that some extremely poor countries with fast-growing populations could become mired in the transitional phase of the demographic transition. This can occur if environmental degradation becomes too devastating to allow for improvements in health care and food production that are part of Stage 2.
How successful have these efforts been?
India has undergone rapid economic growth. As members of its growing middle class use more resources per person, the country's total and per capita ecological footprints will grow. On the other hand, further economic growth could help the country to slow its population growth by making a demographic transition bad
Define and distinguish between overpopulation impacts and overconsumption impacts. Which of these is likely to be larger in a more-developed country?
Overpopulation impacts The results of population size being the biggest factor in a country's total environmental impact, common in less-developed countries where environmental degradation, such as deforestation and depletion of topsoil, often results from a growing number of poor people trying to survive by using these resources; while average resource use per person in these countries is low, the total resource use is high because of the large and growing population. overconsumption impacts In more-developed countries, the environmental degradation that typically results when affluence is the biggest factor in a country's total environmental impact. In these countries, the high rate of resource use per person leads to high levels of waste, pollution, and resource depletion and degradation. ---------- Some forms of technology have a high environmental impact because they increase the T factor. Examples are gas-guzzling motor vehicles and farm machinery, polluting factories and power plants that burn coal. Other technologies can lower an environmental impact by decreasing the T factor. Examples of technologies that prevent or reduce pollution are air pollution control systems, solar cells, and wind turbines
Define poverty and list three ways in which businesses and governments can help to reduce it.
Poverty is the set of conditions that people endure when they are not able to meet their basic needs. Every day, the world's desperately poor people struggle to get enough water, firewood, food, and money to survive. As a result, some of these people unintentionally degrade renewable forests, grasslands, soil, and wildlife. 1.UN Millennium Development Goals—for sharply reducing poverty and hunger, improving health care, achieving primary education for everyone, empowering women, and moving toward environmental sustainability by 2015. 2.Businesses and governments can help to cut poverty and reduce population growth by providing funds and other assistance toward achieving the UN Millennium Development Goals. Governments and businesses could fund solar energy technology to provide electricity for many of these villages, and they could also help poor people to work themselves out of poverty by providing small loans. 3. More-developed countries agreed in 1979 to devote 0.7% of their annual national income toward achieving these goals. But the average amount donated in most years has been 0.25% of national income. The United States, the world's richest nation, has been donating only 0.16% of its national income.
Summarize the story of India's efforts to slow its population growth.
Some of India's family planning program supporters argue that the results of the programs have been disappointing for several reasons, including poor planning, bureaucratic inefficiency, the low status of women (despite constitutional guarantees of equality), extreme poverty, and lack of administrative and financial support. Two factors help to account for larger families in India. Because of extensive poverty, most poor couples decide to have several children to help them survive and to take care of them in old age. In addition, a strong cultural preference for male children in parts of India encourages couples to keep having children until they have one or more boys.
What are the major benefits of China's policy and what are some problems resulting from it?
The government provides contraceptives, sterilizations, and abortions for married couples. In addition, married couples pledging to have no more than one child receive a number of benefits including better housing, more food, free health care, salary bonuses, and preferential job opportunities for their child. Many (but not all) couples who break their pledge lose these benefits. The one-child policy has presented other problems. Because of a strong preference for male children, China has a rapidly growing bride shortage. Young girls in some rural areas of China are being kidnapped and sold in other parts of the country as brides for single men. In some cases, pregnant Chinese women get abortions if their ultrasound scans show that their fetus is female. Also, because there are fewer children, the average age of China's population is increasing rapidly. This shift in age structure means that there will be fewer children and grandchildren to care for the growing number of older people, and there will be fewer workers to support the economy. These factors may lead to some relaxation of the government's one-child population policy.
Summarize the debate about the earth's carrying capacity for humans. What are two possible consequences of failing to slow population growth and lessen the harmful impacts of consumption?
There is growing concern that as our ecological footprints grow and spread across the earth's surface, we are likely to reach several ecological tipping points and overwhelm the carrying capacity of more and more of the planet's natural systems. The exact size of the earth's carrying capacity for the human population is a subject of debate. The estimates of experts range from about 2 billion to as many as 50 billion people. The high-end estimates carry the assumption that humans will develop technologies that will allow more and more people to live on the planet at higher levels of resource use without increasing our overall environmental impact. ------------ Such technological optimism could be dangerous if we continue to expand the population and its resource use per person, and fail to develop environmentally beneficial technologies to offset our resulting harmful environmental impacts. They suggest that, given the environmental problems we face today with a population of 7 billion, we may be nearing the earth's carrying capacity. Some argue that we already have exceeded it and will eventually face a dieback of the human population imposed by natural processes that have always controlled the populations of other species that exceeded the carrying capacities of their environment. Other experts, including some economists, believe that continued economic growth can provide enough resources for tens of billions of people without serious environmental harm. ---------- two serious consequences if we fail to slow and eventually halt human population growth by sharply lowering birth rates, and fail to find ways to reduce the harmful environmental impacts of resource consumption. 1. In some areas, health and environmental conditions will deteriorate, and death rates will rise. This is already happening in parts of Africa and southern Asia, partly because of a combination of eroding soils, lower food production, water shortages, severe poverty, and conflicts over control of vital resources. 2. A growing population of consumers will expand the already large ecological footprints in more-developed countries such as the United States and in rapidly developing countries, such as China and India. This will likely lead to spreading resource depletion and environmental degradation.
Define life expectancy and infant mortality rate and explain how they can affect population growth.
Two other important factors in human population growth are related to the death factor of the equation ---------- life expectancy, the average number of years a person in a population can expect to live. It is calculated by statisticians who consider a host of factors such as diseases present in the population, occupations, accident rates, and other health hazards. The higher the life expectancy, the more likely a population is to remain stable or to grow. ---------- Infant mortality rate, or the number of babies, out of every 1,000 born, who die in their first year of life. Because infant mortality is related to a country's general level of health care and nutrition, it is viewed as one of the best measures of a society's quality of life. If this number is high, it can slow a population's rate of growth. The lower this rate is, the more likely the population is to remain stable or to grow.
Define carrying capacity.
carrying capacity - the maximum population of a given species that an area of land or a volume of water can sustain indefinitely. As the size of a population nears the carrying capacity of its environment, its rate of growth typically slows because of decreasing supplies of key resources such as food, water, and space.
Define and give an example of an ecological tipping point.
ecological tipping point Point at which an environmental problem reaches a threshold level, which causes an often irreversible shift in the behavior of a natural system. ex: some diverse tropical forests that have been cleared cannot grow back, largely because of a severe loss of topsoil. In such cases, where environmental degradation has caused an irreversible ecological change in a natural system,
What are environmental refugees? Summarize the threats they face.
environmental refugees—people who have been forced to leave their homes because of environmental degradation that has left them without the resources, such as soil, food, and water, that they need in order to survive and live well. Many of these people are forced to live in environments that are too wet or too dry, or where the land is too steep for sustainable agriculture. Many have had to flee their homes because of severe drought, excessive soil erosion, floods, and other environmental hazards.
Define and give an example of exponential growth.
exponential growth: -the growth of any quantity at a fixed percentage per unit of time -Growth in which some quantity, such as population size, increases at a constant rate per unit of time. Examples: - The growth sequence 2, 4, 8, 16, 32, 64, and so on, which increases by 100% at each interval. When the increase in quantity over time is plotted, this type of growth yields a curve shaped like the letter J. -a population can grow at 2% per year, a rate that will double its size every 35 years. --------------------------- Exponential population growth starts out slowly, but eventually, the population's size increases rapidly. This is because, even if the percentage of growth remains constant, at 2%, the number of people added every year gets larger because it is 2% of a larger and larger total. So the population grows by a much larger amount in each unit of time, and eventually it explodes
What is family planning and how has it affected population growth? How has it benefited the health of many people?
family planning, a set of programs designed to provide information and clinical services that can help couples to decide how many children to have and when to have them. These services usually take the form of information on birth control and birth spacing, and health care for pregnant women and infants. Family planning has played a major role in lowering birth rates in many countries, although it has met with certain challenges in other areas of the world. It has also played a role in reducing the number of abortions performed each year, as well as the number of deaths of mothers and fetuses during pregnancy. The UN Population Division and other population agencies have estimated that family planning has accounted for at least 55% of the drop in TFRs in the world's less-developed countries between 1960 and 2010, from 6.0 to 2.7.
Define migration, and write a simple equation to show how four key factors affect human population change.
migration- or the movement of people from one population to another Equation Population Change= (Births + Immigration) - (Death + Emigration) -immigration (the arrival of individuals from outside the population) -emigration (the departure of individuals from the population).
Define and distinguish between more-developed countries and less-developed countries.
more-developed countries— highly industrialized countries where the average level of income per person and rate of consumption are relatively high. less-developed countries—those countries with lower average levels of income and low rates of consumption.
