Table 1. The six GIS raster datasets representing the landscape features thought to affect possum dispersal, the ecological justification for their choice, and the associated weight ranges that represent the perceived relative importance of each landscape feature.

GIS dataset	Dispersal affect	Weight range
Elevation	Aversion to higher colder elevations.	0.1–10
Plan curvature	Preference for drier ridges over wetter gullies.	0.1–10
Tree and scrub cover	The absence of cover provided by tree and scrub appears to modify movement behaviour.	0.1–10
Highway traffic volume	Highways with higher traffic volumes present an obstacle to dispersal that acts through behavioural aversion and direct mortality.	10–100
River order	While possums can swim, and have dispersed across rivers, they are disinclined to enter water, so high order river are thought to be a serious obstacle dispersal.	100–1000
Bridge length	Bridges enable possums to avoid the cost associated with crossing a river, but they may also increase the risk of mortality associated with highways as a function of length.	0.1–100