Scientists are still working to find a solution, but warn the dieback could rob the stressed Murray-Darling Basin of water, creating problems for farmers and wildlife well beyond the mountains of Victoria, NSW and the ACT.
Matthew Brookhouse, from the Australian National University, said many Australians were unaware snow gums played a vital role in capturing and feeding water into the Murray-Darling Basin.
"Something like 30 per cent of the basin's annual flow comes from these high-yielding areas at high elevation," he said.
"If you diminish the capacity of those areas to yield water by taking away tree cover … you are losing significant amounts of water."
Less water in the system could affect everything from food production to wildlife abundance in low-lying wetlands.
Climate change has contributed to the decline, as beetles emerge earlier in summer, giving them a longer window to mate, lay eggs and attack trees.
The larvae feed on sapwood, literally eating the snow gums alive.
Infestations that were once isolated and localised are now widespread, with entire stands of snow gums dying throughout NSW, Victoria and the ACT.
"This is not a minor issue that's playing out locally," Dr Brookhouse said.
"This is now occurring across every subalpine area from Mount Buffalo in Victoria, to Kosciuszko, and the Brindabella Range in the ACT.
"The insects hit these trees again and again until they die. At higher elevations, these are the only trees that can survive the harsh conditions, so that puts everything that depends on them in danger as well."
The challenge is to identify a landscape-scale solution, but achieving it will require ongoing partnerships among universities, parks and forest management agencies, private industry and the community.
Dr Brookhouse will address the Snow Gum Summit in Jindabyne on Saturday and Sunday.
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