Population & Environment Lecture 6 Population & Environment

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

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

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

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

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

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

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

Exponential Growth cont’d J-shaped Growth Curve

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

S-shaped Growth Curve

S-shaped Growth Curve cont’d

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).

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

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                 

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

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

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

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

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

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

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

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

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

- 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

- 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

Pre-Industrial Stage – Little Population Growth

Transitional Stage – Rapid Population Growth

Industrial Stage – Population Growth Slows

Post-Industrial Stage – Negative Population Growth

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

Fertility Rate - the number of children born to a woman

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

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

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

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