Last month's huge rain in New South Wales saw vast torrents pummel the land, in some cases, in areas that had already been savaged by the fierce 2019-20 bush fires.

There's an ongoing impact of that double assault.

Massive amounts of unstable soil has been swept away, draining into waterways, threatening river and wetland eco-systems and animal life, and wreaking havoc for farmers.

This story on ABC Radio's PM program features commentary by ANU Professors David Lindenmayer and Jamie Pittock.