Invasive weeds and overgrazing are being blamed for a rising number of sick and malnourished southern hairy-nosed wombats in the Murraylands region of eastern South Australia.

Adelaide University researchers have confirmed the species is starving to death because the feed has disappeared.

Across the Murraylands, from Murray Bridge to Blanchetown, the wombats are too emaciated to stand.

Wildlife rescuer Brigitte Stevens said she frequently found dead animals.

"We see animals lying on their side, eating dirt and falling down holes," she said.

"We're seeing animals falling over and we're also finding about 20 to 30 dead every time we go out there."

Preliminary study findings suggested a mystery liver disease was causing the deaths.

But final results show limited food supply has left wombats to starve, said researcher Lucy Woolford.

"The overwhelming finding was that these animals were under severe nutritional stress which we believe is due to land degradation in the areas they were found," she said.

Toxic

Dr Woolford said the areas had been taken over by invasive plants, including onion weed, which could be toxic if eaten by the wombats.

"I think it's an example of when land mismanagement and land degradation has a particularly adverse effect on a native species and certainly this is an extreme welfare issue in the wombats that are affected," she said.

The SA Environment Department is working with conservation groups to rejuvenate the land along the River Murray.

One trial is revegetating a reserve near Blanchetown, which is owned by the Natural History Society.

Peter Clements explains the work being done.

"We've got lots of small plots, trial plots, to see what's the best way of doing that and whether we have to get rid of the weeds first," he said.

"There's a huge problem with weeds on the reserve and that's part of the problem."

Adelaide University is doing additional research on which specific weeds are poisonous to wombats.