Population Ecology

Population Ecology

  • Definition: Ecological study focused on populations.

  • Population: All individuals of one species inhabiting the same geographic area, capable of interbreeding.

  • Example Research Question: What percentage of a sockeye salmon population can be harvested by humans annually without causing long-term decline?

Human Population Change Over Time

  • Long-term Patterns:

    • Increase from 0.3 billion in 1804 to 7 billion in 2011.

    • Significant growth observed in the 20th century.

Ecological Changes Associated with Human Population Growth

  1. Declining Resource Availability:

    • Caused by overconsumption and unsustainable ecosystem destruction.

  2. Biosphere Degradation:

    • Resulting from pollution.

  3. Climate Change:

    • Increased greenhouse gases leading to higher temperatures, droughts, and storms.

  4. Reduced Ecosystem Services:

    • Declining biodiversity and biological production impacts air and water purification and carbon sequestration.

Predicting Population Change

  • Logistic Growth Model:

    • Formula: Nt+1 = rmaxNt[(K-Nt)/K] + Nt

    • Variables:

      • Nt = current population size

      • rmax = intrinsic rate of increase

      • K = carrying capacity (maximum population size supported by environment)

      • Nt+1 = projected population size

Population Growth using Logistic Model

  • Example Calculations:

    • Generation 1: Nt = 10, population size in generation 10 is calculated based on logistic growth model.

Density Dependence in Population Growth

  • Characteristics:

    • Growth rate slows at high density, eventually plateauing at carrying capacity.

    • Early Growth: Rapid, then slows down as resources dwindle.

Life History Strategies

  1. r-selected Strategy:

    • High reproduction rates, low survivorship, subject to density-independent factors.

  2. K-selected Strategy:

    • Low reproduction rates, high survivorship, density-dependent factors maintain population near carrying capacity.

Factors Regulating Population Change

  1. Density-Independent Factors:

    • Effects unrelated to population density, usually abiotic (e.g., severe weather events).

  2. Density-Dependent Factors:

    • Effects increase with population density, include competition and predation.

Carrying Capacity

  • Consequences of Exceeding K:

    • Potential long-term impacts on population viability.

Applications of Population Ecology

  1. Sustainable Resource Management:

    • Establishing sustainable harvesting practices, such as in fisheries.

  2. Metapopulation Theory:

    • Preservation of populations in fragmented habitats; managing connections to reduce extinction risks.

  3. Wildlife Corridors:

    • Facilitating movement between isolated populations, maintaining population sizes and genetic diversity.

Conclusion

  • Understanding population ecology is crucial for sustainable resource use and biodiversity preservation.