ES 6 - Global Population & Environment

Topic 6 – Global Population & Environment

Demography

-          Study of populations.

Human Demography

-          Study of human population size, structure, and interrelated variables (births, deaths, where they live)

Population Dynamics

-          (population growth and change) reveal principles which apply to all species, human and non-human.

Growth Limit

-          Thomas Malthus 1798 wrote “An essay on the principle of population”

-          He said that human populations tend to increase at exponential rate while food production either remains stable or increases only slowly

-          Eventually human populations will outstrip food supply and eventually collapse

-          Malthus also said that diseases or famines that kill people are positive checks on population growth.

-          Neo-Malthusians believe that we are approaching or surpassed Earth’s carrying capacity

-          They say that surplus population must be addressed directly by birth control

-          One neo-malthusian said that by 2100 12 b people would be suffering life on earth. He argues that the optimum population is 2 billion which will allow a high standard of living

Environmental Limits

-          Exponential growth cannot continue indefinitely

-          Eventually populations come up against environmental limits to further increase

-          Population increase until the carrying capacity is reached

-          At carrying capacity, population size is constant so birth rate must equal death rate and thus population growth is zero

-          The concept of carrying says that a given environment can only support a certain number of individuals of a particular species

-          For example for African buffalo, carrying capacity is largely determined by amount of grass available as food

-          For barnacles (teritip) on a rocky shore, carrying capacity is determined by availability of space on the rocks

Carrying Capacity

-          Maximum population size that can be sustained indefinitely

-          A population in excess of its carrying capacity damages the environment's ability to support that population.

-          The carrying capacity for humans must take into account the desired average standard of living.

Growth Limiting Factors

-          Limiting factors are those which limit population growth; they may be short-term (limiting growth within one year of occurrence), intermediate-term (limiting growth after one year but before 10 years of occurrence) or long-term (limiting growth ten or more years after occurrence).

-          Food supply is short-term limiting factor; pollution medium term; global climate change is long-term factor

Modern Birth Reduction Pressures

-          Higher education and personal freedom for women often result in decisions to limit childbearing

-          High cost of education in many countries make parents more likely to have only 1 or 2 children for whom they can concentrate their time, energy and financial resources

Total Fertility Rate

-          Total fertility rate (TFR) or expected number of children per woman per lifetime has an important time-lag effect on human population growth; a high TFR implies future population growth; a low TFR, population decline.

-          When a population has a TFR of approximately 2.0, it has reached replacement level fertility, indicating the population will achieve stability.

-          The delay between a population's achievement of replacement level fertility and its growth rate reaching zero is termed population momentum or lag effect.

-          Populations continue to grow after reaching replacement level fertility (i.e., display the lag effect) not because women are having many children each, but because there are so many women of childbearing age.

Population Control

-          Continued rapid population growth in many poor countries will markedly increase environmental stress ( on water, land degradation, overhunting and overfishing, falling farm size, deforestation, other habitat destruction) on the planet. Africa is a good example

-          High fertility rates in poor countries also result in the children suffering from underinvestment in education, health, nutrition. So fewer children means healthier children…

-          So it is beneficial to control fertility in poorer countries

Population Control Strategy (JD Sachs, UN Millennium Project 2007)

-          Four steps to quickly reduce fertility rates from 5 or more children per fertile woman to 3 or less within 10-15 years:

o   Promote child survival. Parents choose to have fewer children if they can expect their children to survive

o   Promote gender equality and education for girls

o   Promote family planning and availability of contraceptives

o   Raise productivity on farms

Population, Consumption, & Our Ecological Footprint

-          Ever-accelerating human consumption of natural resources lies at the root of many of our global environmental problems.

-          Current consumption patterns stress limited natural resources, contribute to global warming, and create wasteful and even toxic byproducts that affect the quality of life and the health of communities around the world.

-          Add global population growth to the mix, and it becomes increasingly clear how the health of the ecosystems we depend on for survival are being compromised.

People overpopulation

-          Too many people in a geographic area

Consumption overpopulation

-          Each individual of population consumes too large shares of resources

Fact: In 2006, industrial countries, with less than 20% of the world's population, contributed roughly 40 percent of global carbon emissions, and they are responsible for more than 60% of the total carbon dioxide that fossil fuel combustion has added to the atmosphere since the Industrial Revolution began. But this picture is now changing rapidly, particularly in China, where emissions are now rising at 10 percent a year--10 times the average rate in industrial nations. By 2006, China's fossil fuel emissions were only 12 percent below the United States--and gaining rapidly.

Ecological Footprint

-          An amount of productive land, fresh water, and ocean required on a continuous basis to supply that person with food, wood, energy, water, housing, clothing, transportation, and waste disposal. In the

Population, consumption, and environmental impact

-          Biologist Paul R. Ehrlich and physicist John P.

-          Holdren proposed the IPAT model in the 1970s. It shows the mathematical relationship between environmental impacts and the forces that drive them

-          This method of assessment is usually referred to as the IPAT equation:  I = P x A x T.

o   P = number of people

o   A = affluence per person (consumption / resources used)

o   T = environmental effects (resources / wastes of technologies)

IPAT Benefits

-          Identify what we don’t know or understand about consumption and its environmental impact.

-          Which kinds of consumption have the greatest destructive impact on the environment?

-          Which groups in society are responsible for the greatest environmental disruption?

-          How can we alter the activities of these environmentally disruptive groups?

Global Issues of Population & Ecological Footprints

-          Climate change, threatened ocean, desertification, deforestation