(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).
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.
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).
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).