Winemaker, author, critic and wine show judge James Halliday issues the warning in his latest Australian Wine Companion 2010, launched today.
In the book Mr Halliday writes that the global recession, wine glut, exchange rate fluctuations, drought and the prospect of climate change is making the "future of the Murray Darling almost impossible to predict".
"Out of these and other issues, the view has emerged that the annual crush should be permanently reduced by up to 400,000 tonnes ... so 46,500ha have to be removed" he writes.
However, he said if the annual crush was cut while record low inflows into the Murray Darling became permanent, the worst case scenario would emerge.
"We (would) have removed 45,000ha from cool regions and suddenly find the Murray Darling's capacity has been permanently crippled.
"In this nightmare scenario all of the massive gains the industry has made since 1985 will evaporate, and - in wine terms - we would be a Third World producer."
Speaking to The Weekly Times this week at his Yarra Valley home, Mr Halliday said while he was unconvinced about the science of climate change, the continuing drought did not bode well.
Read more at weeklytimesnow.com.au