ch07

Chapter 7: Human Population Change and the Environment

India’s Population Pressures

• Average number of children decreased from 4.7 (1980) to 2.3 (2015).

• India is the world’s second most populous nation after China.

• Government initiatives include family planning, economic development, and adult literacy programs.

• Population growth has resulted in significant environmental degradation.

• More than 20% of the population lives below the poverty line, surviving on less than $2 a day.

Population Ecology

• Population: All individuals of a particular species in a defined area.

  • Study of these populations falls under Population Ecology.

• Population Ecology: Concerned with how populations increase or decrease due to factors like competition, disease, and predation.

Population Size Changes

• Growth Rate (r): A percentage change in a population’s size, calculated as:

  • r = Birth Rate (b) - Death Rate (d)

  • Conditions:

    • r > 0: More births than deaths (population increases).

    • r < 0: More deaths than births (population decreases).

    • r = 0: Births equal deaths (population stable).

Dispersal Effects on Population Size

• Dispersal: The movement of individuals affecting local populations.

• Two components:

  • Immigration (i): Arrival increases population size.

  • Emigration (e): Departure decreases population size.

• The equation for growth rate becomes:

  • r = (b - d) + (i - e)

Human Population Metrics

• Birth Rate (b): Births per 1,000 people per year.

• Death Rate (d): Deaths per 1,000 people per year.

• Natural Increase: Growth rate in human populations considered globally and locally.

Maximum Population Growth

• Biotic Potential: Maximum growth rate under ideal conditions, influenced by life history traits, including:

  • Age at first reproduction

  • Number of offspring per reproductive event

• Exponential Growth: Occurs when conditions allow constant reproductive rates, demonstrated by J-shaped curves in population growth graphs.

Environmental Resistance and Carrying Capacity

• Environmental Resistance: Limits placed on population growth due to environmental factors.

• As population grows, factors like food and resource availability decline, leading to:

  • Increased competition

  • Increased predation

• Carrying Capacity (K): Maximum sustainable population size impacted by changing environmental conditions; typically results in S-shaped growth curves in graphs.

Dynamics of Carrying Capacity

• Populations fluctuate around K, sometimes overshooting and experiencing crashes due to resource exhaustion.

  • Example: Reindeer population research shows significant population crashes post-peak.

Human Population Patterns

• Growth comparisons with other species; historical reference from Malthus’ 1798 work highlights death rate decreases as a significant factor in growth.

• Factors lowering death rates: Improved food production, accessible medical care, water quality, and sanitation.

Future Projections

• Continued human population growth with a declining growth rate:

  • 1960: (r) = 2.2%

  • 2010: (r) = 1.2%

• Average global number of children born per woman is currently 2.5.

• Different estimates of Earth’s carrying capacity (K) range from 4 billion to 16 billion.

Demographics of Countries

• Highly Developed Countries:

  • Lower birth rates and infant mortality rates.

  • Higher GNI PPP (Gross National Income in Purchasing Power Parity).

  • Example: US GNI PPP is approximately $55,860; global average is $15,030.

Moderately Developed and Less Developed Countries

• Moderately Developed Countries: Higher birth rates than highly developed but declining.

• Less Developed Countries: Highest birth and infant mortality rates.

• Example: Global Total Fertility Rate (TFR) decreased from 6.1 (1970) to 2.5.

The Demographic Transition

• Process of moving from high birth and death rates to low birth and death rates in four stages:

  • Stage 1: Preindustrial

  • Stage 2: Transitional

  • Stage 3: Industrial

  • Stage 4: Postindustrial

Age Structure of Countries

• Information on age distribution helps predict future growth patterns; represented in age structure diagrams.

  • Positive momentum occurs when a large prereproductive group exists.

  • Negative momentum occurs with fewer young individuals.

Social Dynamics Affecting Population

• Gender roles and cultural values affect fertility rates; high TFRs are common in societies with economic dependency on children.

• Lower status of women correlated with higher TFRs; improving women’s education and economic opportunities can decrease TFRs.

Family Planning and Education's Impact on TFR

• Family planning and education greatly influence fertility rates.

• Increased availability of contraceptives directly correlates with decreased TFR.

Urbanization Effects on Population Dynamics

• Urbanization trends showing significant migration to cities, driving the need for effective urban planning.

• 80% of the US population resides in urban areas, raising environmental and infrastructural challenges.

Environmental Challenges in Urban Areas

• Urban areas face unique challenges such as brownfields, suburban sprawl, air, and water pollution problems.

• Well-planned urban growth can mitigate some of these adverse effects.

Case Study: Urban Planning in Curitiba, Brazil

• Known for compact development and effective mass transit.

• Sustainable initiatives include:

  • Pedestrian-friendly city center

  • Use of clean-burning fuel and programs integrating waste collection with social benefits.

Conclusion

• Understanding and managing the dynamics of human population changes are crucial for establishing sustainable policies for future growth and environmental preservation.