In a similar vein to my previous post about the little German owl, I found another insightful gem about possums, from the official report of the 15th national conference of acclimatisation societies in 1926:
“The Government had appointed Professor Kirk to inquire into opossums and the Forestry Department had also appointed an independent man. Both had come to the conclusion, namely, that opossums did no damage to Native trees. [The President] knew himself that the boards looking after certain scenic reserves had been able to obtain quite a large revenue from the opossums,* and had been thus able to fence the reserves, so that in that way the opossums were doing good in the bush.”
This was indeed reassuring.
But evidently, the question was raised again, because the President had this to say at the 18th national conference in 1929 of a twelve month “examination of opossums” by Professor Kirk:
“The inquiries he had made showed that the opossums did no damage to forest, birds, or bird foods, as they took the berries from the ground. It was stated that on Stewart Island, where the kakas were in thousands, the opossums did not harm them.”
* Possums were introduced into New Zealand’s forests to establish a fur trade. The possum was introduced into the South Island in 1858, into Auckland district in 1869, and into the Wellington district in 1892 (from the Official report of the New Zealand Acclimatisation Societies’ Association 18th national conference, 1929).
See the furry money spinner – the history of the possum in New Zealand.
envirohistory NZ 
I don’t think I ever knew why possums were introduced to N.Z. The story confirms my mistrust of opinions regarding the enviroment expressed by anyone with a profit connection to that issue. This is on a par with the denials by the tobacco industry that smoking is a threat to health.
One has to wonder what kind of observations were made.