After Peter retired from the University of Canberra in 2002, he continued to speak for the rivers with his advocacy, notably as a founder of the Wentworth Group of Concerned Scientists.

Peter was known for his exploration of different ways of communicating complex science – he could explain systems approaches to environmental management in accessible ways to all in society, from the Prime Minister to community members living by our rivers. He greatly affected water and environmental policy in all tiers of government, by strong and effective leadership and accessible and evidence based science communication.