hef: Human Ecological Footprint
Variable
World3 03 indicators sector
Human Ecological Footprint [Dmnl]
hef = ( algha + ulgha + ablgha )/ tl

hef in the updating graph: ( how to read )
In nodes
ablgha : “Absorption Land (GHA)”
algha : “Arable Land in Gigahectares (GHA)”
tl : Total Land
ulgha : “Urban Land (GHA)”