Risk of Climate Variability
The reference scenario:

Assuming the global climate changes will continue, what is the impact of climate variability on the ability to maintain a population of at least 20 whooping cranes?

Global change affects the variability of climate. The standard deviation is a measure which reflects the variability in climate. Therefore, to demonstrate the variability in climate and to determine if it would have an effect on the whooping crane persistence, we guessed at a 0.5 variability. We killed off the cranes at that level of variability so we ran the simulation over a range of standard deviations.

Using the following parameters, the simulation was run to show results when using values for standard deviation ranging from 0 through .75, increasing by .05.

PARAMETERS
    initial population
180
    growth rate
1.04
   survival rate
70%
   standard deviation
0 - .75
density dependent
contest
    carrying capacity
180
habitat change (trend in K)
0

 

Data Table
 
SD  p20 p50 p100
0 0 0.001 0.059
0.05 0 0.003 0.198
0.1 0.002 0.061 0.487
0.15 0.043 0.272 0.74
0.2 0.152 0.501 0.889
0.25 0.385 0.719 0.94
0.3 0.555 0.824 0.974
0.35 0.712 0.916 0.99
0.4 0.796 0.955 0.995
0.45 0.902 0.987 1
0.5 0.926 0.989 0.999
0.55 0.946 0.993 1
0.6 0.979 0.997 0.998
0.65 0.99 0.998 0.999
0.7 0.994 0.999 1
0.75 1 1  1

Graph


 

The data show that the standard deviation does change and must be considered as a serious parameter in our simulations. Therefore, we chose a standard deviation of 0.25 as our best guess. That value is included as a baseline data for the other scenarios we developed.

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