Possums have become predators in New Zealand; they eat shoots of native trees and eggs of native birds. They also climb up poles and chew on the lines, (I wonder if they get electrocuted in the process) so we often see slippery metal sheetings covering any tall structures where we don't want possums climbing and chewing.
There are many country pubs that offer a free pint if you bring in a dead possum, but we haven't had the pleasure of encountering any customer collecting on that. (And I'd like to keep it that way.)
Possum fur is collected and used to create such wonderful products as these attractive attire or possom-blended yarns. It took me six years to try possum yarns because I could not get rid of the picture of a roadkill, but the yarns are nice.
And an update on the Kiwi water tank: Owner Tim said most of the water in his tank is from a well, but some collected from the roof goes into the tank also; his water is not treated nor filtered. And yes, he uses the water from this tank for everything. Knowing the quality of the water in Nelson City (bad!!), he's still drinking cleaner and nicer water than us, I can tell you.