Population Ecology and Human Population Issues

population a group of individuals of the same species living in a certain area

Factors Affecting Populations natality – the number of individuals added to a population through reproduction mortality – the number of deaths in a population over time

sex ratio – the relative numbers of males and females age distribution – the number of individuals in each age group pre-reproductive reproductive post-reproductive

Population Density and Spatial Distribution population density – the # of organisms per unit area dispersal – movement away from densely populated areas immigration – movement in to an area emigration – movement out of an area

Population Growth biotic potential – how fast a species can increase its population if no limiting factors exist recruitment – the percent of a population that lives long enough to reproduce

Reproductive Strategies in Nature r-strategists – organisms with high biotic potential but low recruitment – small, fast-growing, short-lived K-strategists – organisms with low biotic potential but high recruitment – large, longer lifespan

Estimating Population in the Wild sampling- counting the population in a small area and projecting that density over the entire area mark and recapture- capturing, tagging, releasing, and recapturing a segment of a mobile population

Assumptions for validity of mark and recapture techniques tagging does not change the behavior of the animal tagged animals must have time to freely mix with the rest of the population animals must be captured randomly

Population Growth exponential growth – growth at an ever-increasing rate

Population Growth logistic growth – growth with limits

Limits to Growth carrying capacity – the maximum size of a population that can be supported over the long term environmental resistance – abiotic and biotic factors that tend to reduce populations

Demography the study of human population growth and its consequences

Human Population Growth why was human population growth relatively stable for 50,000 years (until the early 1800’s) why has the population explosion occurred? when will our population stabilize? what is the planet’s carrying capacity for humans?

Survival Rates longevity- the maximum age of death of a population – biologically determined life expectancy- the average age of death – mathematically determined survival rates- the % of a population living past a certain age

the two most important historical/scientific events that lead to the human population explosion 1800’s – after the discovery of bacteria, connections were made between sanitation, personal hygiene, and disease 1930’s - antibiotics

Why is human population growth an environmental issue?

rapid population growth leads to … environmental stress Major Global Environmental Issues water pollution, water shortages atmospheric change (air pollution, global warming, ozone loss, acid rain) soil degradation (erosion and loss of fertility) loss of biodiversity (extinctions)

Industrialization developed countries – fully industrialized, modern, high GDP developing countries – various stages of modernization, lower GDP

where population growth is occurring 95 % of population growth today is occurring in developing countries

demographic statistics total fertility rate – the average # of children a woman has in her lifetime infant mortality rate – the part of a population that dies before age one replacement fertility rate – the fertility rate that will yield a stable population (2.1) age distribution – the number of people in each age bracket

changing populations crude birth rate (CBR) – # of births/1000 people crude death rate (CDR) – # of deaths/1000 people population growth rate % = CBR – CDR/10 doubling time: the # of years it takes for a population to double rule of 70: doubling time = 70/pop growth rate

social factors affecting population growth … historically high infant mortality combined with lack of social security in old age child labor needs for rural lifestyle lack of education/work opportunity for women cost of child raising in urban lifestyle

political factors affecting population growth … China one child policy incentives/disincentives for having children

why is it desirable to control human population growth? many humans live in poverty all environmental problems made worse with increasing population running out of resources other species

What are some arguments against controlling human population growth? more people, more ideas, creativity, technology birth control is immoral it’s not population, it’s consumption population will level off naturally within Earth’s carrying capacity population control is “social engineering”

two schools of thought regarding the population problem control population through biological means encourage development in poor countries where population is growing the fastest

demographic transition theory as a country industrializes, it goes through a series of changes leading to a stable population

stages of the demographic transition stage I - high CBR, high CDR … stable population stage II - high CBR, lowering CDR … rapid growth stage III - with increased industrialization, CBR begins to lower stage IV - full industrialization, low CDR, low CBR … stable population

Demographic Transition Theory

Encouraging development world bank lending – U.N. lending large sums of $$ to governments microlending – small banks lending small amounts of $$ to individuals

Why the shift? many World Bank projects (agriculture and energy) were mishandled by inept and/or corrupt governments resulting in increased debt for developing countries and little improvement in standard of living micro-loans have a 98% payback and have resulted in progress for individuals

Predicting Future Population Growth population profile – a model showing relative age distribution of a population in five-year increments

Profiles what would a rapidly growing country’s population profile look like? what would the population profile look like for a country whose population is stable? what would the population profile look like for a country whose population is declining with each new generation?

ecological footprint The amount of biologically productive land necessary to support your lifestyle what goes into this measurement?

Per Capita Ecological Footprint Total Ecological Footprint (Hectares per person) Country United States The Netherlands India 9.6 3.8 0.8 Total Ecological Footprint (Hectares) Country United States The Netherlands India 3 billion hectares 62 million hectares 880 million hectares Fig. 1-7a, p. 11

Ecological Footprint Fig. 1-7b, p. 11 1.5 Earth's Ecological Capacity 1.2 0.9 Humanity's Ecological Footprint Number of Earths 0.6 0.3 1960 1970 1980 1990 2000 2010 Year Fig. 1-7b, p. 11