Environmentalist Mark Selmes (dressed as a platypus) said the removal of the willows from the area was a good thing for platypus, native fish and other river creatures.

"The willows had overtaken from native she-oaks from along our banks as well as river bottle-brushes and other native plants," Mr Selmes said.

"These plants used to drop food into the rivers and streams and provide shade without choking the river.

"Willows are not native and do not provide food. They block the river until oxygen is taken out of the water, so when natives are planted after the removal of willows they provide food again to the river invertebrates, which in turn feed the platypus and our native fish and the Rakali (native the water rat).

"If these waterways are allowed to revitalize - platypuses will breed and they will come back and our grandchildren will be able to see them right here in the Wollondilly again."

Spokesperson for LachLandcare Inc, Mary Bonet said it was great to see the willows being removed.

"We are going to see some great things happening along the waterways and hopefully bring back the platypus," she said.

Goulburn Mulware operations director Matt O'Rourke said the tree removalists had been contracted as part of a general clean-up of the area.

"They will finish the work this week after a few more days' work," Mr O'Rourke said.