In her fourth Boyer lecture, an extract of which is published in today's Saturday Age, Professor Langton attacked Professor Flannery - a distinguished scientist, explorer and conservationist - for comments in his recent Quarterly Essay, After the Future: Australia's New Extinction Crisis, which she said suggested he believed land was not ''safe'' if it was owned by Aboriginal people.

''Even under Labor governments with a strong green bent, national parks are not always safe. In 2010, the Queensland Bligh government began the process of degazetting a large part of Mungkan Kaanju National Park on Cape York Peninsula with a view to giving the land back to its traditional Aboriginal owners,'' Professor Flannery wrote in the essay.

Professor Langton, the foundation chair of Australian indigenous studies at the University of Melbourne, suggested Professor Flannery had succumbed to the ''environmental campaign ideology that Australia's first people are the enemies of nature''.

But Professor Flannery said Professor Langton had misunderstood his essay.

''In writing that national parks are not 'safe', I meant they are not secure as a permanent part of the national parks estate. I expressed no view whether biodiversity would be more or less secure under indigenous management, though in the essay I point out that biodiversity has done best where NGOs and indigenous groups have worked … '' he told Fairfax Media via email.

Professor Langton said the ''racist assumption in the green movement about Aboriginal people being the enemies of the wilderness'' had been a recurring theme in deals between conservation groups and state governments ''to colonise Aboriginal land under the green flag'', citing as an example the Bligh government's Wild Rivers Act to limit development on Cape York, since repealed by the Newman government.

Accusing conservationists and governments of ''racist chicanery'', Professor Langton said Aboriginal lands held a diversity of fauna and flora because of ancient Aboriginal systems of management, and because indigenous people had fought to protect their territories from white incursion.

''They are not wilderness areas. They are Aboriginal homelands, shaped over millennia by Aboriginal people. The presumption by conservationists that these areas need to be rescued from Aboriginal people - as made clear by Tim Flannery and in the Wild Rivers saga in Queensland - is a strange twist on the racist fiction of terra nullius overturned by the Mabo case,'' Professor Langton argued.