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Population and Community Ecology > Harvesting > Flashcards

Flashcards in Harvesting Deck (21):
1

How do humans act as a predator?

-Harvesting many species
-Can decide how many individuals are taken from a population

2

What is the ideal outcome of harvesting?

-Maximize long-term yield
-Highest possible removals that do not exceed replenishment

3

What are megafaunal extinctions?

-Human arrivals often 
followed by extinction
of many large mammals

4

Whats deforestation?

-Population expansion
accompanied by
widespread forest
loss

5

Whats poaching? Example?

-Illegal harvesting endangers wildlife species
-Rhino populations

6

Whats overfishing?

-Widespread collapse of marine ecosystems

7

How can we estimate maximum sustainable yield?

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

8

Whats fixed quota harvesting?

- q
-

9

Can we find maximum sustainable yield if we know K?

Hard to do
-environmental stochasticity and overestimation

10

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

11

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

12

How can we achieve maximum sustainable yield?

-Varying effort
-Find where the peak is

13

Do we need carrying capacity to find optimal effort?

No

14

How to find optimum E?

Look at how yield varied with effort

15

What produces a stable equilibrium?

Fixed-Effort harvesting

16

What does fixed effort produce if the population fluctuates?

Variable yields

17

How can political and economic pressure result in collapses?

-When yield is low
-Increase yield of source will cause collapse

18

Whats a cause of instability in harvesting?

1. Type III functional response
2. Allee effects- pop an go extinct if it passes lower threshold

19

Whats the tragedy of the commons?

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

20

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

21

Tragedy of the commons examples.

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