Lesson 2: Human Population Growth Big Question Why Is Human Population Growth the Underlying Environmental Problem?

Lesson 2 / ESRM100 / University of Washington The Prophecy of Malthus “the power of population growth” is “greater than the power of Earth to produce subsistence.”

Lesson 2 / ESRM100 / University of Washington Thomas Malthus: Essay on the Principle of Overpopulation-1798 Malthus was the first to notice the issue of there being more people than could be supported by the food supply. He noticed farming improvements could raise food production by a certain amount each year – in an arithmetic rate of increase..1, 2, 3, 4, 5, 6…… Whereas population tends to increase at a ‘exponential rate’ with each generation…1, 2, 4, 8, 16, 32……. So he concluded there must come a point when there are too many people for the available food supply.

Lesson 2 / ESRM100 / University of Washington The Malthusian Dilemma Malthus believed that when the population level rose above the food supply – then nature would regulate population growth by responding with: PESTILENCE, PLAGUE, FAMINE, WAR Malthus suggested that population growth should be limited by people marrying later – and abstinence until marriage. (he basically wanted to cut the birth rate of the poorer classes)

Lesson 2 / ESRM100 / University of Washington Exponential Growth Growth is exponential when it occurs at a constant rate per time period. Exponential growth produces a J-shaped growth curve. The human population has mostly grown exponentially.

Lesson 2 / ESRM100 / University of Washington Reaching the Carrying Capacity Malthus believed that the earth would reach it’s carrying capacity if populations continued to grow exponentially. The maximum number of organisms of a species that can be supported indefinitely in a given environment. Once capacity had been reached equilibrium would be thrown off and natural and human disasters would occur.

Lesson 2 / ESRM100 / University of Washington Esther Boserup (1965) / Julian Simons (1981): Belief in human ingenuity. These two theorists claim that rising populations are not a problem. In fact, Boserup suggested that it was at times when there were food shortages following periods of population growth, that people were forced to come up with better ways of producing food in order to survive. Summed up best by the phrase : Necessity is the mother of invention. Julian Simons supported this approach and suggested that governments should NOT try to influence populations. As resources become scarce, humans use their brain power to develop new technologies, substitute materials, or more efficient ways of using resources – so they don’t run out. As a result, mankind is better off after periods of resource shortage as we develop better ways – or ‘innovation’.

Lesson 2 / ESRM100 / University of Washington Which theorist do you most agree with and why?

Lesson 2 / ESRM100 / University of Washington Major Periods of Human History The early period of hunters and gatherers - less than a few million people The rise of agriculture - first major increase in the human population The Industrial Revolution - improvements in the food supply and health care led to a rapid population growth Today -growth has slowed in industrialized nations but is increasing rapidly in many less developed nations

Lesson 2 / ESRM100 / University of Washington Population Change, cont. Kenya has pyramid shape with many young people – rapid growth United States has column shape – slow growth Italy is slightly top-heavy – slow/negative growth

Lesson 2 / ESRM100 / University of Washington The Demographic Transition Stage I - birth and death rates are high until industrialization reduces death rates Stage II - gap between birth and death rates results in high population growth Stage III - birth rate drops toward death rate and population growth declines

Lesson 2 / ESRM100 / University of Washington The Demographic Transition, cont. Some nations are slow to move from stage II to stage III Medical advances can affect the demographic transition by decreasing death rates

Lesson 2 / ESRM100 / University of Washington Longevity and Its Effect on Population Growth The maximum lifetime (longevity) is the genetically determined maximum possible age to which an individual can live. Life expectancy is the average number of years an individual can expect to actually live. The human population has grown despite little or no change in longevity.

Lesson 2 / ESRM100 / University of Washington Limiting Factors to Population Growth Short-term factors: drought, disruption to energy supply, disease Intermediate-term factors: desertification, pollutants, disruption to supply of non-renewable resources Long-term factors: Soil erosion, groundwater, climate change

Lesson 2 / ESRM100 / University of Washington Quality of Life and the Human Carrying Capacity of the Earth What is the human carrying capacity of Earth? Logistic curve predictions Packing space Deep Ecology – moral imperative to preserve the biosphere by limiting human population The higher the quality of life, the lower the Earth’s carrying capacity

Lesson 2 / ESRM100 / University of Washington How Can We Achieve Zero Population Growth? Raise the age of first childbearing Social pressures to delay marriage Birth control Breast feeding Family planning

Lesson 2 / ESRM100 / University of Washington National Programs to Reduce Birth Rates The first country to adopt an official population policy was India in Many countries now have a family-planning program. China has one of the oldest and most effective family- planning programs: encourages couples to have only one child. relies on education, family planning control, and a system of rewards and penalties. Should governments force people to limit family size?

Lesson 2 / ESRM100 / University of Washington How Many People Can Earth Support? Estimates range from 2.5 billion to 40 billion. Critical factors are Food supply Land and soil resources Water resources Population density Technology

Chapter 2: Human Population Growth Questions? your TA.