The region's instability could be forgotten momentarily in the warmth of the Pacific welcome, but reminders of the fractures in Pacific unity are plain to see, like Kiribati's empty seat.

Forum Secretary-General Henry Puna on Tuesday hinted at the tensions.

"Our region remains in a precarious position both in the short and in the long-term," he said.

Ardern relished the face-to-face time with fellow leaders after three years of Zoom diplomacy and the chance to show her climate change chops - allocating the first chunk of a $1.3 billion aid fund.

It's going towards a lab developing plant varieties more resistant to changing rainfall patterns or coastal flooding.

"You are literally our Noah's ark," Ardern said. "That is so important to us as a region when we are so reliant, of course, on our ability to provide our own food security but also given it's such an important part of our culture and identity."

Taking the Pacific's biggest threat seriously is a way Australia and New Zealand might keep the spectre of China at bay.

 READ MORE

• Fiji hit by coastal flooding; officials fear it could get worse
• China's whirlwind Pacific tour a slight success with several bilateral agreements signed
• China's Pacific push causing 'anxiety' - Fiji politician
• Pushback on China: US adds Fiji to its Indo-Pacific economic strategy

"If Australia wants to cement its place as the key security partner for the Pacific and if New Zealand wants to secure its place as a  security partner for the Pacific then both need to be taking real action on climate change," says Dr Wesley Morgan, a research fellow at Griffith University. 

Ardern got in before Australian Prime Minister Anthony Albanese with the $10 million climate aid, but she could be gazumped by her Aussie counterpart looking to make up for a lack of ambition.

"I expect the new Australian Government will come to this Pacific Islands Forum with new announcements for support for the Pacific," said Dr Morgan.

Ardern said "there's one area where I think the world would welcome some healthy competition: between New Zealand and Australia, and I think that would be climate action".

Ardern and the Aussies showing up after a three-year hiatus to say we're here, and we're not telling you what to do.

"Members of the Pacific family are capable of providing that security and we think that Pacific unity is important as we navigate a world where we confront climate, COVID, and strategic competition," said Australian Foreign Affairs Minister Penny Wong.

China is an example "of a development partner who's been around the Pacific for decades," Ardern said.

"But [it's] certainly increasing their activity and changing the way in which they engage."

Hoping this boost to the threat lapping at the Pacific's doorstep will reset the relationship away from Beijing.