The letter calls on the Government to accept advice that it protect 103,000 hectares of forest, including creating five new national parks and establishing a regional park from Wodonga to past Mildura.

But an angry rally in Echuca yesterday heard an opposing view: that timber workers, farmers and hunters also want forest management improved, but believe banning forestry and cattle grazing would be a disaster for the local environment and economy.

The Government is yet to formally respond to a three-year investigation by the Victorian Environmental Assessment Council, which in July reported that river red gum floodplains — home to 300 threatened or near-threatened species — would be lost without increased water flows.

Citing research that found up to 75pc of red gum forest was under stress, the council's advice included boosting protection for the internationally listed Barmah Forest wetlands. It estimated its recommendations would cost about 50 jobs.

The scientists' letter, seen by The Age, describes the Murray forests as an ecosystem in decline, degraded by current use. "It's a beautiful place that is suffering from the way we are currently managing it," Monash University hydrologist Dr Tony Ladson said.

The Echuca rally, attended by about 1000 people, was told the council had ignored research suggesting properly managed grazing and logging would lead to healthier forests.