Lecture 36- Conservation tools II

Question 1

What are the 3 tools we will talk about?

Answer 1

Inferring risk of extinction - Solow’s equation - surrogates - PVA

Question 2

What is risk?

Answer 2

Three Components of Risk: 1. the probability that an event will occur in particular time frame 2. a measure of the consequences of the event 3. a time frame over which risk is considered • e.g. “there is a 5% probability that the population will become extinct within the next 50 years”

Question 3

What is a herbaria and a museum?

Answer 3

-collection of data about plant and animal species -information about species

Question 4

What is the Solow’s equation?

Answer 4

• equation to calculate probability of extinctions from obseravtions
• probability that a species is extant (still around)
• Tn is the date of the most recent sighting

Tn-1 is the date of the second most recent sighting

T is the date of the end of the observation period

Question 5

What is the example of using Solow’s equation?

Answer 5

• probability that species is extinct is 1-the probability that it is extant
• if p extant= 0.1 so the p extinct= 0.9
• what doesn’t the equation take into account is how hard it is to find the individuals etc.

Question 6

What can you measure if don’t have the data needed for Solow’s equation?

Answer 6

• We don’t always have the data at hand to calculate the risk of extinction… • Measures to represent risk of extinction can include: – Range contraction – Population decline – Changes in ecological processes – Changes in ecosystem composition – Changes in physico-chemical processes (flows of energy and nutrients) …How much change is acceptable?

Question 7

What are the IUCN red list categories?

Answer 7

-each 5 years the countries reasses the state of species on the red list -Extinct (EX) -Extinct in the wild (EW) -Threatened: Critically Endangered (CR) Endangered (EN) Vulnerable (VU) -Low Risk (LR) -Data Deficient (DD) -Not Evaluated (NE)

Question 8

What does critically endangered mean?

Answer 8

• Critically endangered = 50% chance of extinction over 10 years

Question 9

What does endangered mean?

Answer 9

• Endangered = 20% chance of extinction over 20 years

Question 10

What does vulnerable mean?

Answer 10

• Vulnerable = 10% chance of extinction over 100 years

Question 11

What rules does IUCN use to asses risk?

Answer 11

-(most) IUCN rules employ surrogates of extinction risk -A-D are surrogates of extinction risk -Rule A: Reduction in population size -Rule B: Restricted range and a combination of: - severely fragmented - continuing decline - extreme fluctuation -Rule C: Small population size with a continuing decline Rule D: Small population size -Rule E: Risk of Extinction (a direct measure using PVA)= can use mathematical data,skills to asses the risk -we have to be careful as they are not always tested

Question 12

What is PVA (population viability analysis)?

Answer 12

-A PVA is a mathematical representation of what we believe to be true about the ecology and dynamics of a species or population. -It has three main uses: 1. Guiding data collection(examine uncertainty) 2. Ranking threatened species 3. Assisting management decisions (e.g.payoff curves) -the thing it is the harder the PVA get the harder it is to scrutinize

Question 13

What is the basic population model?

Answer 13

• Nt+1= population next year
• Nt= population this year
• B= births
• D= deaths
• I= immigration
• E= emmigrants
• also need to take into account other forces that affect the extinction and survival (next question)

Question 14

What are the extinction processes?

Answer 14

1. Deterministic forces 2. Stochastic factors • demographic stochasticity (sth. about randomness about death and birth rates) • environmental stochasticity (can have good and bad years) • genetic stochasticity (have sublethal alleles, if combine can have lethal) • Spatial variation • catastrophes (floods, fire etc.)

Question 15

How can you model demographic stochasticty?

Answer 15

• really important for small populations
• N(t) = pop next year
• N(t+1) = pop. this year
• f = fecundity rate
• s = survival rate
• r = growth rate
• if r is 1 then population is constant, if greater than 1 then exponentially increasing population, when less than one then in decline

Question 16

What are the trade offs?

Answer 16

-advice from one group and another, scientific and social for example

Question 17

What is demographic stochasticity?

Answer 17

• Demographic stochasticity: variation in population size that is due to the random processes of birth and death. Important for small populations
• overall line is smooth
• but zoom in and have ups and downs
• this is crucial for small populations as the down can mean extinction

Question 18

What is environmental stochasticity?

Answer 18

-what environmental factors influence the rate of fecundity and survival -rainfall is a good example -

Question 19

What is the basic population model like?

Answer 19

-it is a deterministic model, if we didn’t take the stochasticity into account it would not be accurate -it would be naive as don’t include risk -use quasi extinction rates= use acceptable levels above or below the animal will not survive -if we include stochasticity in the model= get uncertain bounds, the population + 1 can be anywhere from the bottom to top, must account for uncertainty -the more stochasticity and risk your have the greater risk

Question 20

What would we do in a stochastic model?

Answer 20

-include as much environmental information into the model -the threats etc.

Question 21

What is a metapopulation?

Answer 21

• Metapopulations: a collection of discrete populations linked by dispersal -• Density dependence= the community is limited by resources, if highly dense population= then lower fecundity as • Harvesting, predation, competition, disease, catastrophes -trade off between model simplicity and realism

Question 22

What are the limitations of PVAs?

Answer 22

• PVAs suffer from a lack of data on – demographic rates – spatial distribution, habitat, dispersal – correlations – nature and magnitude of variation – validation/testing/assessment -hard to make, hard to understand, hard to scrutinize if they don’t do maths much -expensive and labor intensive

Question 23

Why use PVA?

Answer 23

• Internally consistent (left equals right) • Transparent • Explicit about assumptions • Repeatable • Free from linguistic ambiguity • Incorporates uncertainty