Pacific islander Ioane Teitiota - whose homeland is threatened by rising seas - has failed in an attempt to become the world's first climate change refugee.

A New Zealand judge dismissing his against deportation case as "novel but unconvincing."

Mr Teitiota argued New Zealand should not deport him even though his visa had expired, because climate change was destroying his low-lying home in Kiribati.

The tiny nation consists of about 30 atolls - most only a few metres above sea level.

High Court judge John Priestley acknowledged Kiribati was suffering environmental degradation attributable to climate change.

But he said millions of other people in low-lying countries were in a similar situation and ruled that Mr Teitiota did not qualify as a refugee.

"Novel and optimistic though these submissions are, they are unconvincing and must fail," Judge Priestley wrote.

"Were they to succeed and be adopted in other jurisdictions, millions of people facing medium-term economic deprivation or ... hardships caused by climate change would be entitled to protection under the refugee convention."

"It is not for the High Court of New Zealand to alter the scope of the convention in that regard."

Kiribati's government has raised the prospect of relocating the entire population or building man-made islands to rehouse them if predictions that the sea will rise by a metre prove accurate.

It has also bought 5,000 acres of land in Fiji to act as a farm for Kiribati if salt-water pollution means the islands can no longer produce crops.