L8 Population viability analysis

Question 1

What does triage mean? and in conservation?

Answer 1

rating priority based on urgency and potential for recovery. Originated from first aiders in war.
In conservation, triage refers to approaches which abandon some species or subpopulations to extinction, in order to focus resources on others with higher chances of survival.

Question 2

Arguments for triage in conservation?

Answer 2

Deal with an issue in a quick manner. Resources for conservation are limited. (IUCN 2010)
Resources should not be wasted on species that require, for example, expensive captive breeding and reintroduction programmes, but instead be allocated for cheaper conservation actions that will prevent several other species from becoming extinct, or from becoming threatened to begin with (Arponen, 2012)
Bottrill et al. 2008).

Question 3

Arguments against triage in conservation?

Answer 3

There are success stories where the the future was very dim. 97% of Mauritius’ original habitat had been lost and was ecologically devastated. Many species including the Dodo were exterminated and several highly endangered/ on the brink of extinction. A mix of conservation efforts have brought Mauritius back from the bleak and have saved many species including the endemic Mauritian pink pigeon and numerous plants. (Hambler and Canney 2013, p. 343) funadmental concept in conservation biology: extinction is unacceptable (Soule, 1985)

Question 4

When using the triage approach to conservation what do we need to assess? (6)

Answer 4

1) Vulnerability – where is a population in the triage categories?
2) Value of the biodiversity in question
3) The benefit to biodiversity of an action
4) The probability the action will succeed
5) The cost of the action
6) Return on investment

Question 5

What are the triage categories? (3)

Answer 5

1. Some species will become extinct even if we try to conserve them
2. Some species are threatened but will benefit from conservation intervention
3. Some species do not require conservation interventions.
   Those who accept the idea of conservation triage believe that we should focus on 2 and not on 1. Others think that species very close to extinction drive innovation in conservation practice and sometimes conservation actions are successful for those species.

Question 6

In terms of population viability wha should we measure?

Answer 6

• range size
• no. of individuals
• is there a threshold for these values?
• ratio of variance in population growth rate to mean growth rate
• body size, litter size
  …everything!

Question 7

How is population viability analysis (PVA) defined?

Answer 7

Application of data and models to estimate probabilities that a population will persist for a specified time (Mills 2012, p.254)
It is used to confront the extinction vortex.

Question 8

Population viability analyses includes 3 central concepts making it better than the minimum viable population (MVP) analysis which focuses on one number. What are the 3 concepts?

Answer 8

1) Persistence - not extinct, above 0 individuals (1 mating pair)
2) Time - becomes less reliable further in future so short term evaluated against long term goals.
3) Probabilities - cumulative distribution of reaching a quasi-extinction threshold over a range of time periods

Question 9

What is minimum viable population?

Answer 9

minimum number of individuals that is sufficient to sustain 99% probability of population persistence in 100 years5.
cannot correctly establish the exact minimum no. of individuals because of stochasticity.

Question 10

what is a quasi-extinction curve/threshold?

Answer 10

When the population size reaches a given lower density a quasi-extinction could occur where the population is not viable.

When a population becomes so low it may not be able to rebound

Question 11

To analyse the viability of a pop you must? (3)

Answer 11

1) Gather a population census data
2) Gather biological data including: survival rate, dispersal, frequency of breeding etc but this may not be readily available
3) Use a complex mathematical model that looks at trends in growth rates and its variance

Question 12

What is vortex?

Answer 12

A population viability analysis model. Simulates of the effects of deterministic forces as well as
demographic, environmental and genetic stochastic events on wildlife populations.

Question 13

what is and give examples of catastrophic variation?

Answer 13

Catastrophic variation is the extreme of environmental variation examples include:
-epidemic disease
-hurricanes
-large-scale fires
-floods
they are analysed separately from seasonal environmental variation/stochasticity.

Question 14

When is vortex the best analysis to use? (6)

Answer 14

Diploid organism 
there are changes in the genetic variation of interest
a local pop of less than 500
less than 20 pops modelled
low fecundity 
long lifespan

Question 15

What are the main difficulties when use PVA?

Answer 15

Omission of critical parameters
Untested assumptions
Lack of independent model verification
Tuning to preconceived management strategy?

Question 16

Go to final slide in presentation for module summary

Answer 16

Go to final slide in presentation for module summary