br: Birth Rate
Variable
Global
Birth Rate []
br = p * clip ( brn , brn1 , swt1 ,time)* brfm * brmm * brcm * brpm

br in the updating graph: ( how to read )
In nodes
brcm : birth-rate-from_crowding multiplier
brfm : birth-rate-from-food multiplier
brmm : birth-rate-from-material multiplier
brn :
brn1 :
brpm : birth-rate-from-pollution multiplier
swt1 :
p : population
Out nodes
p : population