Feedback in Nature's Orchestra

Introduction

• Feedback is a core concept in understanding natural systems, social science, and sound.
• Defined as mutual causal interaction: x affects y, y affects x.
• Creates feedback loops which are ubiquitous in nature.

Positive Feedback

• Amplifies changes or effects.
• Example: Plant growth and humus formation.
  • Dead plant material enriches soil with humus.
  • Humus promotes more plant growth.
  • Cycle repeats, amplifying the abundance of plant life.
• Can be harmful: Deforestation and erosion.
  • Removal of forest leads to erosion.
  • Loss of soil nutrients and organic matter.
  • Less plant growth to anchor soil, leading to more erosion.

Negative Feedback

• Diminishes or counteracts changes to maintain stability.
• Example: Predator-prey relationships.
  • Lynx and snowshoe hares.
  • Lynx reduce hare population.
  • Decline in hares leads to reduced lynx population.
  • Fewer lynx allows hare population to recover.
  • Cycle maintains ecological equilibrium over time.

Complex Interactions

• Feedback vs. linear cause and effect.
• Pesticide example: Spraying insects can reduce predator population, causing insect population to rise again.
• Each feedback loop is the product of links.
  • Adding/removing links can reverse or diminish feedback effects.
• Natural communities have networks of interactions, not separate chains.
  • Can have numerous feedback loops involving many links.
  • Loops create regular patterns, forming a complex but balanced system.

Ecosystem Dynamics

• Wide-ranging negative feedbacks stabilize positive feedbacks.
  • Example: Ecosystem rhythms like musical instruments in an orchestra.
• Different ecosystems have unique feedback patterns:
  • Oceans: Strong predator-prey interactions, loud and powerful with many oscillations.
  • Deserts: Slow biomass turn over, constant and droning.
  • Rainforests: High diversity, strong feedbacks, rich and complex sounds.
• Ecosystems change over time, altering their 'harmonies'.
  • Deforestation example: Lush forest becoming barren.
  • Abandoned farmland becoming a forest over time.