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Are Predicted 1798 Food Shortages Coming True?


Malthus Theory Critiques


Advances in technology can keep production rising ahead of population.

Demographic transition- societies move from conditions of high fertility rates roughly offset by high mortality rates to conditions of low fertility rates together with low mortality rates.


(Article in Scientific American by Jeffrey D. Sachs)


Did he have a point?

Sub-Saharan Africa- total fertility rate of 5.1 children per woman

Global population continues to rise by about 79 million per year, with much of the increase in the world’s poorest places.

According to the medium-fertility forecast of the United Nations Population Division we are on course for 9.2 billion people by mid-century.


(Article in Scientific American by Jeffrey D. Sachs)


Factors Affecting Human Population Change


Major Periods (Stages)

Stage 1- Early period of Hunters and Gatherers (total world population and rate of growth were very low).

Stage 2- Agricultural settlement (first major increase in total world population).

Stage 3- Industrial Revolution (rapid increase in the human population resulting from improvements in healthcare and food).

Stage 4- Urbanized World (rate of population growth has declined for wealthy industrialized nations, but has continued to rise rapidly in poorer, developing countries).


Cultural Factors


Many cultures of the world- positive value on large families.

Reasoning: a large family provides such benefits as protection from enemies, a greater chance of leaving descendants, and a type of social security/insurance for retirement.

Other cultural arguments are offered for large families.

Africa Examples.


Consider This…


The number of people on Earth combined with the level of consumption and technological capability largely determines ecological resource exploitation. Is population control, decreased consumptionor technological innovationthe most effective way to conserve our natural resources?

By 2050, global population is expected to reach 7.9-10.9 billion people with most expected to be living in urban areas. What types of social changes might take place from this increased urbanization?


Population, Sustainability, and Earth’s Carrying Capacity


Gretchen C. Daily and Paul R. Ehrlich- 1992


Carrying Capacity Defined


Carrying capacity is defined as “the maximal population size of a given species that an area can support without reducing its ability to support the same species in the future.”(62)

More specifically, it means “a measure of the amount of renewable resources in the environment in units of the number of organisms these resources can support.”(62)


Population Projections (1992)

“The current estimate for the 2025 population is 8.5 billion, with growth eventually leveling off at approximately 11.6 billion around 2150. These projections are based on optimistic assumptions of continued declines in the population growth rate”. (62)

Why don’t we notice?

The authors claim that “the negative impact of human activity on the planet usually manifests itself first to those whose lives are tightly dependent on the health of fragile, local ecosystems”.


One Planet, How Many People?


A Review of Earth’s Carrying Capacity


We are adding roughly one million more people to our world population of 7 billion almost every 4.8 days.

Speculation about the ultimate carrying capacity of the earth dates back to at least the 17th century (1632-1723).


Tipping Points


Exceeding the Earth System thresholds risks triggering abrupt environmental change- this is known as the “tipping point”.

Think of the Earth System as a bus that is overloaded (tipping point- one passenger equals an overturned bus).


Contributing Factors


Global freshwater use

Change in land use

Biodiversity loss

Chemical pollution

Climate change

Ocean acidification

Ozone depletion

Date: 2015-12-24; view: 1794

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