Flashcards in Harvesting Deck (21):
How do humans act as a predator?
-Harvesting many species
-Can decide how many individuals are taken from a population
What is the ideal outcome of harvesting?
-Maximize long-term yield
-Highest possible removals that do not exceed replenishment
What are megafaunal extinctions?
-Human arrivals often followed by extinction of many large mammals
-Population expansion accompanied by widespread forest loss
Whats poaching? Example?
-Illegal harvesting endangers wildlife species
-Widespread collapse of marine ecosystems
How can we estimate maximum sustainable yield?
-Logistic growth model
-Population is growing fastest at 50% of carrying capacity (K)
Whats fixed quota harvesting?
Can we find maximum sustainable yield if we know K?
Hard to do
-environmental stochasticity and overestimation
Is the N equilibrium stable?
-Problem is that equilibrium for N is not stable
-If pop drops below K/2, removals will exceed growth
-Leads to population extinction
What can we do instead of a fixed harvesting quota? What functional response is it equivalent to? X and Y axis?
-Fixed effort to harvesting (E)
-Type I functional response
-y axis- harvest rate per prey
-x axis- N
How can we achieve maximum sustainable yield?
-Find where the peak is
Do we need carrying capacity to find optimal effort?
How to find optimum E?
Look at how yield varied with effort
What produces a stable equilibrium?
What does fixed effort produce if the population fluctuates?
How can political and economic pressure result in collapses?
-When yield is low
-Increase yield of source will cause collapse
Whats a cause of instability in harvesting?
1. Type III functional response
2. Allee effects- pop an go extinct if it passes lower threshold
Whats the tragedy of the commons?
-Unregulated common resources can be overexploited when individuals act in their self-interest
Should a herder graze his sheep on common land that is already at capacity?
-Yes, because it benefits him in
the short term
-Subsequent overgrazing hurts
everyone in the long run
-Overgrazing and reduced food will hurt the sheep
-Not good in lone run