Population Change

Overview of Chapter 8 o Principles of Population Ecology o Reproductive Strategies o The Human Population o Demographics of Countries o Demographics of United States

Principles of Population Ecology o Population Ecology Study of populations and why their numbers change over time Study of populations and why their numbers change over time Important for Important for Endangered species Endangered species Invasive species Invasive species o Population Group of individuals of same species living in the same geographic area at the same time Group of individuals of same species living in the same geographic area at the same time

Population Density o Population density The number of individuals of a species per unit area or volume at a given time The number of individuals of a species per unit area or volume at a given time Ex: minnows per Liter of pond water Ex: minnows per Liter of pond water o Ovals below have same population, and different densities

Change in Population Size

Principles of Population Ecology o How Do Populations Change in Size? o Global scale: r = b – d Growth rate Birth rate Death rate *remember that when calculating growth rates you always use per 1000 individuals in the population unless specifically stated otherwise!

Practice Problem: “Global Population Change” o You have a human population of 10, 000 where there are 200 births per year and 100 deaths per year. Calculate the natural growth rate of this population (Hint: remember that we always calculate per 1000…reduce!) o Use r = b – d

Answer o 200/10,000 = 20/1000 = 0.02 o 100/10,000 = 10/1000 = 0.01 o R = b – d = 0.02 – 0.01 = 0.01 or 1% per year o More examples can be found at the end of chapter 8

Calculating Population Change: “Local Population” Birth (b), Death (d), Immigration (i) and Emigration (e) are calculated per 1000 people Growth rate Birth rate Death rate Immigration rate Emigration rate r = (b – d) + (i – e)

Practice Calculating Local Population Growth o Calculate the growth of a population of 10, 000, that has 100 births, 50 deaths, 10 immigrants, and 100 emigrants o Use equation: r = (b - d) + ( i – e ) o REDUCE!

Answer o b =100/10,000 = 10/1000 =.010 o d =50/10,000 = 5/1000 = o i =10/10,000 = 1/1000 = o e = 100/10,000 = 10/1000 = 0.01 o So, r = (0.010 – 0.005) + (0.001 – 0.010) o r = – = , or -0.4% per year

Maximum Population Growth o Intrinsic Rate of Growth (Biotic Potential) Growth rate under ideal conditions Growth rate under ideal conditions J- Shaped Curve (exponential growth) J- Shaped Curve (exponential growth)

Environmental Resistance o Environmental limits (resistance) Prevent indefinite reproduction Prevent indefinite reproduction Unfavorable food, water, shelter, predation, etc. Unfavorable food, water, shelter, predation, etc. o Carrying Capacity (K) Maximum # of individuals an environment can support Maximum # of individuals an environment can support Causes leveling off of exponential growth Causes leveling off of exponential growth S- shaped curve of logistic population growth S- shaped curve of logistic population growth

Population Crash o Overshooting carrying capacity can lead to population crash Abrupt decline in population density Abrupt decline in population density

Factors That Affect Population Size o Density Dependent Factor Factor whose effect on population changes as population density changes Factor whose effect on population changes as population density changes Examples: Examples: Predation Predation Disease Disease Competition Competition Sometimes cause Boom-or-Bust Population Cycles Sometimes cause Boom-or-Bust Population Cycles

Boom-Or-Bust Population Cycles

Case Study- Predator Prey Dynamics on Moose and Wolf Isle Royale o As wolf population increases, moose population decreases (and vice versa)

Factors That Affect Population Size o Density Independent Factors Factors that affects population size, but is not influenced by changes in population density Factors that affects population size, but is not influenced by changes in population density Examples: Examples: Killing frost Killing frost Severe blizzard Severe blizzard Fire Fire

Reproductive Strategies r-selected species k-selected species -Small body size - Early maturity - Short life span - Large broods - Little or no parental care - Probability of long term survival is low - Mosquitoes and Dandelions - Small broods - Long life span - Slow development - Large body size - Late reproduction - Low reproductive rate - Redwood trees and human beings

Survivorship

Some populations fit two curves o Herring Gulls o Type III (as chicks) & Type II (as adults)

Human Population o Demography Science of population structure and growth Science of population structure and growth o Human Population since 1980 is J- shaped curve (exponential) Population experts believe that this graph will level out during the 21 century and represent an S-shaped curve. When this happens which individuals will be those dying and which will be those surviving???

Human Population 1 Billion Billion Billion Billion Billion Billion Billion 2006

Population Increase in Mexico High D.R. due to Mexican revolution Analysis: death rate declined much more than the birth rate so there was a high population growth during the 20 th century

Doubling Time o One Way to express population growth of a country is to determine it’s doubling time o Doubling Time = The amount of time it takes for a population to double in size (assuming that it’s growth rate (r) doesn’t change) o Doubling time can identify a country as highly, moderate, or less developed. o The shorter the doubling time the less developed the country! o Formula (simplified): TD (time double) or DT (doubling time) = 70/r

Replacement Level Fertility o Replacement-level-fertility: The number of children that a couple must produce in order to “replace” themselves o It usually given as 2.1 children o The number is greater than 2 b/c some children die before they hit reproductive age

Total Fertility Level (global) o Total-Fertility-Level: The global average number of children born to each woman o Currently we are at 2.8! o This is way above the replacement level fertility rate!

Projecting Future Global Human Populations o Population is increasing o Growth rate (r) has started to decline o Projections for 2050 Low = 7.7 billion Low = 7.7 billion High = 10.6 billion High = 10.6 billion Most likely = 9.1 billion Most likely = 9.1 billion

Demographics of Countries

Demographic Stages o Pre-industrial Stage Birth and death rates high Birth and death rates high Modest population growth Modest population growth o Transitional Stage Lowered death rate Lowered death rate Rapid population growth Rapid population growth o Industrial Stage Birth rate decline Birth rate decline Population growth slow Population growth slow o Post Industrial Stage Low birth and death rates Low birth and death rates Population growth very slow Population growth very slow

Demographic Stages

Age Structure Diagrams (or Pyramids) Explained o A countries age structure helps us predict the future growth of a country o The number of males/females at each age from birth to death is represented o It is especially important to look at the pre-reproductive and reproductive years (generally speaking if they are larger then the population is expanding

Age Structure Diagrams o The number and proportion of people at each age in a population

Demographics of Specific Countries

World-wide Population Statistics o 29% of human population is under age 15 o The higher the % the higher the likelihood of growth o Could cause large increase in birth rates

Education of Immigrants into US See envirobrief on pg. 179 of your text

Addressing Population Issues Women in Egypt learning about family planning. Egypts TFR’s declined to 3.5, which was at 7.0 in the 1960’s

Overview o Population and Quality of Life Population and Chronic Hunger Population and Chronic Hunger Economic Effects of Population Growth Economic Effects of Population Growth o Reducing the Total Fertility Rate Culture and Fertility Culture and Fertility Social and Economic Status of Women Social and Economic Status of Women Family Planning Services Family Planning Services o Government Policies and Fertility China, India, Mexico, Nigeria, Europe China, India, Mexico, Nigeria, Europe o Achieving Population Stabilization

Population and Quality of Life o Difficult to meet basic needs in developing countries o Problems associated with overpopulation: Environmental degradation Environmental degradation Hunger Hunger Persistent poverty Persistent poverty Economic stagnation Economic stagnation Urban deterioration Urban deterioration Health issues Health issues

Carrying Capacity o Carrying Capacity (K) The maximum number of individuals of a given species that a particular environment can support for an indefinite period, assuming no changes in the environment The maximum number of individuals of a given species that a particular environment can support for an indefinite period, assuming no changes in the environment o Overuse of land can cause a decrease in carrying capacity o Uncertain what the carrying capacity of the earth is for humans

Population and Chronic Hunger o Food security Condition in which people live with chronic hunger and malnutrition Condition in which people live with chronic hunger and malnutrition o Effects of Chronic Hunger Weakened immune system Weakened immune system Increased susceptibility to illness and disease such as Increased susceptibility to illness and disease such as Malaria Malaria Measles Measles Diarrhea Diarrhea Acute respiratory illness Acute respiratory illness

Population and Chronic Hunger o Ways to Help Solve the Food Problem Control population growth Control population growth Promote economic development of developing countries without adequate food supplies Promote economic development of developing countries without adequate food supplies Provide access to food and land resources to those who live in areas without them Provide access to food and land resources to those who live in areas without them

Areas with Greatest Food Problems

Economic Effects of Population Growth o Two viewpoints from economists: Population growth stimulates economic development and technological innovation Population growth stimulates economic development and technological innovation Rapidly expanding hampers developmental efforts Rapidly expanding hampers developmental efforts o Most observations support the second viewpoint o Developmental efforts are also hampered by debt from past development attempts

Reducing the Total Fertility Rate Three major influences on total fertility rate 1. Cultural traditions 2. Social & economic status of women 3. Family planning (or the lack of)

Cultural Traditions o Culture influences and controls individuals’ behaviors o Marriage age o Couple is expected to have large number of children Due to high infant and child mortality rates Due to high infant and child mortality rates o Children often work in family business Provide support for aging parents Provide support for aging parents o Religious values

Social & Economic Status of Women o Gender inequality is common worldwide o Disparities Political participation Political participation Social status Social status Economic status Economic status Health status Health status Legal rights Legal rights Education Education Employment and Employment and earnings earnings Single most important factor affecting high total fertility rates is low status of women Illiteracy in 2002

Educational Opportunities and Fertility o Women with more education Marry later Marry later Have fewer children Have fewer children

Family Planning Services o In many countries men make reproductive decisions regarding contraceptives o Family planning services offer information to both men and women on: Sexuality Sexuality Contraception Contraception STDs STDs Parenting Parenting

Contraceptive Use Among Married Women of Reproductive Age

Government Policies and Fertility- China o Largest population in the world o Controversial Family Planning Policy Chinese Government pursued birth control seriously Chinese Government pursued birth control seriously Incentives to promote later marriages and one-child families Incentives to promote later marriages and one-child families Medical care, schooling for child, preferential housing, retirement funds Medical care, schooling for child, preferential housing, retirement funds Brought about rapid and drastic decrease in fertility Brought about rapid and drastic decrease in fertility

Government Policies and Fertility- China o Law – controversial and unpopular Compromised freedom of choice Compromised freedom of choice Social pressure to abort a second child Social pressure to abort a second child Pressure to abort/kill female first child Pressure to abort/kill female first child More boys than girls in China More boys than girls in China o Law more relaxed in rural China

Government Policy and Fertility- India o Severe population pressure first country with government- sponsored family planning first country with government- sponsored family planning Did not work due to language/cultural barriers Did not work due to language/cultural barriers introduced incentives and compulsory sterilization introduced incentives and compulsory sterilization Unpopular and failure Unpopular and failure Recent years- government focused on education Recent years- government focused on education Much more effective, but TFR still above replacement level (currently at 3.4) Much more effective, but TFR still above replacement level (currently at 3.4)

Government Policy and Fertility- Mexico o Young age structure Huge potential for population growth: 33% of population is under age 15 Huge potential for population growth: 33% of population is under age 15 Positive growth momentum Positive growth momentum o government imparted educational reform, family planning, health care Very successful Very successful

Government Policy and Fertility- Nigeria o Population challenge Largest population of any African country Largest population of any African country o Very high reproductive potential: 43% of population is less than age 15 o Current National Population Policy Improving health care Improving health care Population education Population education

Government Policy and Fertility- Europe o Population concern Proportion elderly people in population is increasing Proportion elderly people in population is increasing Due to low TFR Due to low TFR o Decrease in population could cause decrease economic growth

Achieving Population Stabilization o How can developing country governments help? Increase $$ allotted to pubic health and family planning services Increase $$ allotted to pubic health and family planning services Education on affordable, safe, effective methods of birth control Education on affordable, safe, effective methods of birth control Increase average level of education Increase average level of education Especially for women Especially for women o How can developed country governments help? Provide financial support Provide financial support Supporting research and development of new birth control methods Supporting research and development of new birth control methods