Key Themes

• Population Growth
• Sustainability
• Global Perspective
• Urbanizing World
• People and Nature
• Science and Values

Human Population Growth

• 35,000 years ago: ~3,000,000
• 12,000 ya: ~15,000,000
• 2,000 ya: ~100,000,000
• Malthusian Population Growth
• Population growth in the absence of resource limitation
• Growth is proportional to the population
• Equivalent to doubling at fixed intervals
• Natural populations grow exponentially until they reach their carrying capacity
• Carrying Capacity: the number of people, other living, or crops that a region can support

What Happens When a Population Reaches this Capacity

• It reaches a logistic curve, staying under carrying capacity
• If shot over then a rapid decline will occur
• Carrying capacity is the maximum number of plants, animals, bacteria, etc that an environment can sustain
• Carrying Capacity is not fixed
  • health of ecosystem
  • resource utilization
  • technology
  • quality of life
• Humans carrying capacity estimates are variable (1-40 billion)

Sustainability

• Sustainability of a resource
  • Harvesting no more than is replaced
• Sustainability of an ecosystem
  • Human stressors
  • Natural disturbances
  • Ecosystem resilience
  • Biodiversity
• What would sustainability look like?
  • Live without conflict with nature
  • Minimize pollution and risk
  • Restrained use of resources
  • Political system support
  • Minimize use of non renewable resources

A Global Perspective

• Local actions have distant consequences
• Remote regions are linked by atmosphere and water
• DDT - 1962
  • Industrial Pesticide
  • Long half life in soils
  • Transported by runoff and rivers
  • Bio-accumulates
  • Linked to declines in aquatic life and birds
  • Human toxicity
• The ozone hole
  • Protects from UV rays
  • Destroyed by refrigerants
  • Over Antarctica

An Urban World

• Worldwide cities growing rapidly
• Positives and negatives for environment
• Can be more efficient
• Less land per person
• Reshapes land drastically

People and Nature

• Humans are a product of nature, and have been shaped by and have always shaped nature
• Prehistoric humans likely drove most large mammal species in North America to extinction
• Invented agriculture, reshaped ecosystems
• What is the natural world
  • Nature is always in a form of flux
  • What is the natural form?
  • Changed over time
• What steps should we take to protect

Science and Values

• Decision making relys on:
  • Personal values
  • Human equality
  • Economic Progress
  • Future Generations
  • Science
  • Assessing uncertain outcomes
• Scientific knowledge is always being challenged
• Theories can be disprove, but never proven
• The classic scientific method is:
  • Observe phenomena
  • Formulate a question
  • Develop a hypothesis
  • Make predictions from hypothesis
  • Conduct experiment (tests) with potential to disprove hypothesis
  • Analyze results
• The Precautionary Principle
  • States when there is a threat of serious, irreversible environmental damage we should not wait for proof before taking precautionary actions
  • It is better to err on the side of not destroying the earth
  • Why do we value the earth?