Lecture 1: Environmental Systems
a system: a collection of things (components) that:
1) have a relationship (linkage) between each other
Linkage:
any relationship between the components of a system
qualitative:
quantitative:
linkages should tell us a story about the relationship btw those two things
can be positive or negative
treat each connection separately (“as the first thing increases what happens to the next/other thing) as if they were independent from anything else
Direction of the arrow matters
How you draw the arrow also tells u if the linkage is a positive or negative linkage
2) are contained within an identifiably boundary (so that you dont keep making links between things for infinity bc you can)
have to define the limits of end of the system
3 diff types of system boundaries:
open system
both energy and matter (anything) can move across the system
closed system
only energy can move across the boundary (physical matter cannot)
rare in natural systems
isolated system
neither energy or matter can cross the boundary (nothing can pass)
mainly theoretial rn (none exist in nature rn as far as we know)
boundaries can change over time (when water came to earth from space it was a open boundary but now it is a closed boundary and no more physical matter (water) can come through or leave (we have what we have no more or less is going to come in or escape as of rn)
things that are outside the system that influence things inside it, go outside the boundary diagram
the type of line used to draw the boundary tells u what type of boundary it is (solid, dashed etc.)
system dynamics: the study of how systems / things change over time
state of a system: what condition is a system in at a specific period of time
two types of states:
transient state:
steady state:
input and output are equal / stable over long time periods
require this stable state for life to evolve and diversify in unchanged conditions
continuity equation:
stuff going in, stuff going out, how much is left over time?
where you draw your boundary matters in wether it is a steady state or not
resevoir time:
ex 1)
ex 3) focus on figureing out where each peice of data goes (what is means) (the math is not hard so dont focus on it)
equilobriums state:
trying to maintain the same state of that environment for a very long period of time
can be stable or unstable depending on how they react to external forces
stable ex) beaver repairing a small leak in the dam
unstable ex) a human puts a pipe through the dam (beaver cant repair that leak on its own)
an unstable state can be disrupted to such an extenet that it enters a new, irreversible stable state (completely and irreversibly change the ecosystem and landscape)
tipping point = point of now return
pushed so far into an unstable state that is becomes something entirely different (framework described as changing global systems- concerned abt when we pass tipping points, when we change it so much that the original thing cannot return to the state it was in before)
feedback loop: when the future of a system changes based on the past/current linkages and state if the system (all of your components feed back into itself) (end products must go back and influence the beginning of that system)
positive(amplifying):
amplifys whatever change is happening
changes are happening in whatever way to make the state more unstable - push towards the tipping point
indicated by a + near the system defined in a diagram
negative(balancing):
tries to balance the changes to return to stable state ?????
indicated by a - near the system defined in a diagram
ex) increased otters decrease the beaver population that have grown to then increase the lake/bodies of water and increase the otter population