Lecture 15 - Human Populations

Ecotoxicology

The study of toxic pollutants (natural or synthetic) to the constituents of ecosystems

ED50

Concentration of toxicant at which 50% of a population exhibits response of interest

LD50

Concentration of toxicant at which 50% of a population dies

Demography

Study of size, composition, and distribution of human populations

Demographers seek to:

• Identify causes/consequences of changes in populations

• Project future population characteristics

• Understand dynamics in population growth rates

Population Growth Formula

dN/dT = rN(1 - N/K)

Intrinsic Population Growth

The maximum rate a population can increase under ideal conditions

Intrinsic Growth Formula

r = (b-d) +(i - e)

Replacement rate

average number of children a couple must produce to replace themselves so that there is a zero growth rate. ~2.1 is global replacement rate

Stage 1 - Preindustrial stage

• Birth and death rates are high

• High infant mortality rates

• Plagues, famines, wars common

• Very slow population growth

Stage 2 - Transitional

• Improved healthcare, reliable food, etc. becoming industrial

• Lowered death rates

• Birth rates still high

• Population grows rapidly

Stage 3 - Industrial

• Industry!

• Decline in birth rate

• Low death rate

• Population slows

Stage 4 - Post-Industrial

• Industry!

• Low birth and death rates

• Education, affluence

• Smaller families, limited family size

• Population slowly grows or not at all

Earth’s carrying capacity

Estimates of Earth’s carrying capacity range from 2 billion to 1 trillion, with a median of 8-16 billion

Techno-optimism

• New technology might allow us to innovate out of these issues (ex: bioengineering, carbon capture, nuclear fusion, lab-grown meat)

Contentions with techno-optimism

• Waiting on new technology might be a gamble

• Can solve one environmental issues and can create even bigger ones

• Innovation might not be distributed equitably

Degrowth

An economic theory focused on reducing total throughput of energy and resources by reducing less-necessary production, improving public services, and reducing work time

Contentions with Degrowth

• GDP and sustainable development are not mutually exclusive

• Reduced GDP growth will reduce innovation and technological advancement

• Reducing throughput is challenging, and cap standards of living in developing countries