Harvesting

Question 1

How do humans act as a predator?

Answer 1

• Harvesting many species

- Can decide how many individuals are taken from a population

Question 2

What is the ideal outcome of harvesting?

Answer 2

• Maximize long-term yield

- Highest possible removals that do not exceed replenishment

Question 3

What are megafaunal extinctions?

Answer 3

-Human arrivals often 
followed by extinction
of many large mammals

Question 4

Whats deforestation?

Answer 4

-Population expansion
accompanied by
widespread forest
loss

Question 5

Whats poaching? Example?

Answer 5

• Illegal harvesting endangers wildlife species

- Rhino populations

Question 6

Whats overfishing?

Answer 6

-Widespread collapse of marine ecosystems

Question 7

How can we estimate maximum sustainable yield?

Answer 7

• Logistic growth model

- Population is growing fastest at 50% of carrying capacity (K)

Question 8

Whats fixed quota harvesting?

Answer 8

• q

-

Question 9

Can we find maximum sustainable yield if we know K?

Answer 9

Hard to do

-environmental stochasticity and overestimation

Question 10

Is the N equilibrium stable?

Answer 10

• Problem is that equilibrium for N is not stable
• If pop drops below K/2, removals will exceed growth
• Leads to population extinction

Question 11

What can we do instead of a fixed harvesting quota? What functional response is it equivalent to? X and Y axis?

Answer 11

• Fixed effort to harvesting (E)
• Type I functional response
• y axis- harvest rate per prey
• x axis- N

Question 12

How can we achieve maximum sustainable yield?

Answer 12

• Varying effort

- Find where the peak is

Question 13

Do we need carrying capacity to find optimal effort?

Answer 13

No

Question 14

How to find optimum E?

Answer 14

Look at how yield varied with effort

Question 15

What produces a stable equilibrium?

Answer 15

Fixed-Effort harvesting

Question 16

What does fixed effort produce if the population fluctuates?

Answer 16

Variable yields

Question 17

How can political and economic pressure result in collapses?

Answer 17

• When yield is low

- Increase yield of source will cause collapse

Question 18

Whats a cause of instability in harvesting?

Answer 18

1. Type III functional response

2. Allee effects- pop an go extinct if it passes lower threshold

Question 19

Whats the tragedy of the commons?

Answer 19

-Unregulated common resources can be overexploited when individuals act in their self-interest

Question 20

Should a herder graze his sheep on common land that is already at capacity?

Answer 20

• 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

Question 21

Tragedy of the commons examples.

Answer 21

-Clean air, groundwater, forests, wildlife, fisheries, and carbon