1. Population & Environment
Lecture 6
Population & Environment

2. Population Growth Population Ecology
- the study of the number of individuals of a particular species that are found in an area and how and why those numbers change over time

3. Population Growth cont’d
Population Density
- the number of individuals of a population found in a certain place at a given time
- the number of individuals of a population per unit of habitat area
- e.g., the number of Grassquits per hectare
- e.g., the number of snapper per litre of sea water

4. Population Growth cont’d
Population Size
- the number of individuals making up a population
Population size changes due to:
• births
• deaths
• immigration
• emigration

5. Population Growth cont’d
Birth Rate (b)
- also called crude birth rate
- number of births per 1,000 individuals in a population in a given year
Death Rate (d)
- also called crude death rate
- number of deaths per 1,000 individuals in a population in a given year

6. Population Growth cont’d
Immigration (i)
- movement of individuals into a population
Emigration (e)
- movement of individuals out of a population

7. Population Growth cont’d
Growth Rate (r)
- also called annual rate of natural population change
- r = b – d
- r = (b + i) – (d + e)
Biotic Potential
- maximum rate at which a population can increase when there are no limits on its growth

8. Population Growth cont’d
Exponential Growth
- growth in population size increases by a fixed percentage of the whole in a given time period
- yields a J-shaped curve

9. Exponential Growth cont’d
J-shaped Growth Curve

10. Population Growth cont’d
Environmental Resistance
- all the factors jointly acting to limit the growth of a population
Carrying Capacity
- number of individuals of a given species that can be sustained indefinitely in a given area

11. S-shaped Growth Curve

12. S-shaped Growth Curve cont’d

13. Population Ecology Cont’d
A population grows exponentially (green line) until it is acted on by limiting factors that cause the growth to level off at the carrying capacity (yellow line).

14. Regulation of Population Size
Density Dependent Checks on Population Growth
- where some limiting factors become more influential as a population’s density increases
- examples:
• competition for resources
• predation
• parasitism
• disease

15. Regulation of Population Size
Density Independent Checks on Population Growth
- exert their effects on population regardless of population density
- examples:
• floods
• hurricanes
• severe droughts
• fire
• unseasonal temperature change
                

16. Overpopulation also called environmental unsustainability
more people than can live on Earth or a geographic region in comfort, health & happiness
leaves the planet or region unfit for future generations
occurs when people exceed the carrying capacity of an area

17. Overpopulation cont’d
There are 2 types of overpopulation:
1. People Overpopulation
2. Consumption Overpopulation

18. People Overpopulation
there are more people in the world or in a geographic region than available vital resources can support
causes the absolute poverty of 1.2 billion people each year in Less Developed Countries
causes 40 million people in Less Developed Countries to die prematurely each year

19. Consumption Overpopulation
high rates of resource use per person
high levels of pollution and environmental degradation per person
exists in More Developed Countries, where 1/5 of the world’s people cause significant resource depletion

20. Population Distribution: Urban Living
Urbanisation
- process in which people increasingly move from rural areas to densely populated cities
Cities are the main centres for new jobs, education, innovation, culture & trade

21. Effects of Urbanisation include:
Vegetation Loss
Urban Microclimate
Water Demands, Increased Runoff & Flooding
Solid Waste and Pollution
Noise Pollution
Land Conversion & Social Disruption

22. Improving Urban Life (Some Solutions)
reduce population growth
increase investments & social services in rural areas
repair and revitalise existing cities
grow food in abandoned lots & community garden plots

23. Age Structure Diagram
a diagram representing the percentage (or number of people) of the population at each age level in a population
plots the percentage or numbers of males & females in the total population

24. Demographic Transition
hypothesis that countries, as they become industrialised, have declines in death rates followed by declines in birth rates
the transition takes place in 4 stages
1. Pre-Industrial
2. Transitional
3. Industrial
4. Post-Industrial

25. - harsh living conditions - high birth rate - high death rate
1) Pre-Industrial Stage
- harsh living conditions
- high birth rate
- high death rate
2) Transitional Stage
- industrialisation begins
- death rate drops
- birth rate remains high

26. - birth rate approaches death rate - population growth slows
3) Industrial Stage
- birth rate drops
- birth rate approaches death rate
- population growth slows
4) Post-Industrial Stage
- birth rate equals death rate
- zero population growth

27. Pre-Industrial Stage – Little Population Growth

28. Transitional Stage – Rapid Population Growth

29. Industrial Stage – Population Growth Slows

30. Post-Industrial Stage – Negative Population Growth

31. 2001 Population Data For Selected Countries
Country
Population
Births
Per 1000
Pop.
Deaths
Per 1000 Pop.
Net Migration
Population Change
Aids Deaths
in 1999
(Adult prevalence)
Botswana
1,586,119
28.85
24.18
4.7
15.13
(35.8%)
Haiti
6,964,549
31.68 15
-2.64 14
3.3
(5.17%)
Jamaica
2,665,636
18.12
5.48
-7.52
5.1
0.24
(1.2%)
Barbados
275,330
13.47
8.53
-0.32
4.6
0.47
(1.17%)
United States
278,058,881
14.2
8.7
3.5 9
0.07
(0.61%)
Germany
83,029,536
9.16
10.42 4
2.7
0.007
(0.1%)
Source: CIA World Factbook

32. Fertility Rate
- the number of children born to a woman

33. Factors Affecting Birth & Fertility Rates
Average level of education & affluence
Importance of children as part of family labour force
Cost or raising & educating children
Urbanisation
Educational & employment opportunities for women

34. Factors Affecting Birth & Fertility Rates cont’d
6. Infant mortality rate
7. Average marriage age
8. Availability of private & public pension systems
9. Availability or reliable methods of birth control
10. Religious beliefs, tradition, cultural norms

35. Factors Affecting Death Rates
Better nutrition
Improvements in medical & public health technology

36. Population Control Methods
vary from culture to culture
include:
∙ family planning programmes
∙ laws
∙ educating women