In the last 30 years there have been two big outflows of Hong Kong people moving to other countries. Both were driven by fear. The first followed the Chinese Communist Party's massacre of unarmed students in Tiananmen Square. The reason was plain – it was eight years before Britain was due to hand the city back to Beijing's control. The second exodus came just before that handover of sovereignty.

Based on those precedents, we should be expecting a third. In fact there are signs that it may be beginning already. At core, the political crisis engulfing Hong Kong today is galvanised by exactly the same fear – that the city's long-standing autonomy is to be lost in a creeping authoritarian takeover. If so, how should Australia be positioning itself in anticipation? A debate is already under way behind the scenes in Canberra.

The Greens have proposed one idea – to allow Hong Kong people currently living in Australia on various temporary visas to be allowed to stay permanently. There are some 19,000 such people, students, workers, tourists. "It is now absolutely clear that any Hong Kong resident currently in Australia faces a genuine risk of harm should they return home," Greens leader Richard Di Natale said. "We have a legal and a moral obligation to offer them safe haven."

Prime Minister Scott Morrison described the idea as "premature". Not necessarily – Germany has granted asylum to two Hong Kong democracy activists. And within his government, a number of MPs and senators think that the Coalition should get more active in helping Hong Kongers to migrate. They think it could represent a great opportunity for Australia.