Australia’s Defence chief has issued a climate change warning.

Defence chief Angus Campbell says a rise in climate change refugees may force Australia to increase its military patrols of the nation's northern waters.

Reports say he has also warned that China could take advantage of rising sea levels to occupy abandoned islands in the Pacific.

Foreign Minister Marise Payne says Australia is focused on tackling climate change.

She pointed to the signing of the Boe Declaration at the recent Pacific Islands Forum - which recognises climate change as the greatest risk to life and security in the Pacific - as evidence.

“We are very focused on our engagement on climate in the region,” she told the ABC.

She said the government has a multi-billion-dollar fund to pay for projects in the Pacific.

“Which will stream climate adaptation and resilience through its investment in energy, in transport, in communications and in water, reflects the priority we place on these issues,” Senator Payne said.