ESS notes

• Economic value


  the worth of a resource in terms of its ability to contribute to economic activities (production, consumption or trade)
• Ecological value


  importance of a resource, species or ecosystem for maintaining ecological balance and function
• Aesthetic value


  subjective appreciation or beauty that individuals find in a resource, object or natural scenery
• Intrinsic value


  inherent worth of something, regardless of its utility to humans or other external factors
• System


  assemblage of parts and the relationships between the, which together constitute an entity or a whole
• Open system


  energy and matter can flow in and out of the systems (applies for most systems)
• Closed system


  only energy can flow in and out of the system (most are artificially constructed often for experimental process, but the entire planet can be thought of as a closed system)
• Isolated system


  nothing can flow in or out of the system (hypothetical systems but you can describe the entire universe as an isolated system)
• Storages


  stores of matter or energy (shown as box, or other shapes) - box size represents storage size
• Flows


  transfers or transformations between storages or outside of the model (shown as arrows with its direction indicating the flow direction) - arrow size represents flow size
• Inputs


  Flows coming into a system or storage
• Outputs


  Flows going out of a system or storage
• Boundaries


  dividing line between two systems shown by a line through flows (e.g. atmosphere and ground)
• Transfers


  flow through a system, involve a change in location
• Transformations


  involve a change in state (e.g. photosynthesis)
• Models


  simplified description showing structure or workings of an object, system or concept
• Strengths of a model


  simplification, visualization, hypothesis testing
• Weaknesses of a model


  uncertainty, lack of validation, oversimplification, hard to model human factors
• First law of thermodynamics


  conservation of energy - energy in an isolated system can be transformed but not created or destroyed
• Second law of thermodynamics


  entropy (amount of disorder in a system) increases over time - energy is lost during transformation
• Resilience


  capacity to withstand or to recover quickly from difficulties (tendency of a system to avoid tipping points and maintain stability through steady-state equilibrium)
• Tipping points


  minimum amount of change in a system that will destabilize it, leading to a new equilibrium
• Stable equilibrium


  tendency for a system to return to the previous equilibrium following a tipping point
• Steady-state equilibrium


  no changes over the long term, but oscillations in the short term in an open system
• Positive feedback


  when a change in a system's state leads to increased change (amplifies change)
• Negative feedback


  feedback that counteracts change away from equilibrium, contributing to stability
• Pollution


  the addition of a substance or agent to the environment by human activity, at a rate greater than at which it can be rendered harmless by the environment
• Primary pollutants


  active on emission
• Secondary pollutants


  formed by primary pollutants, undergoing physical or chemical change
• Point-source pollution


  only one source of origin of the pollutant - single, clearly identifiable site
• Non-point source pollution


  numerous widely dispersed origins of the pollutant; difficult to identify
• Biodegradable pollutants


  substances that can be broken down by natural processes into simpler, harmless compounds over time
• Persistent pollutants


  harmful chemicals that remain in the environment for a long time without breaking down naturally
• First level of pollution management


  altering human activities to reduce pollutant's production
• Second level of pollution management

  control release of pollutants
• Third level of pollution management


  clean-up/restoration of the damaged ecosystem
• Direct measurement of pollution


  recording the amount of a pollutant in water, air or soil
• Indirect measurement of pollution


  recording changes in abiotic or biotic factors
• DDT


  pesticide used to combat insect-borne diseases
• Bioaccumulation


  gradual build-up of substances in an organism's body over time, often from the environment