The head of Victoria's zoos says the scale of logging in the state's central highland forests is environmentally unsustainable and has backed the creation of a new national park as giving key endangered species the best chance of survival.

A letter sent by Zoos Victoria chief executive Jenny Gray to the state-owned timber company VicForests in January says recent scientific modelling had led the zoos to form the view that rates of highland harvesting could not be viewed as "ecologically sustainable".

A Leadbeater's possum, which Zoos Victoria says will become extinct unless logging in Victoria's central highlands decreases. Credit:Joe Armao

The rules for logging in the central highlands would not save the state's critically endangered faunal emblem, the Leadbeater's possum, from extinction, she said.

Conservationists want clearfell logging to end in the highlands to protect the possum an other threatened forests species They are also campaigning for a "Great Forest National Park" to be established.