A report by the Asian Development Bank has found some Pacific countries will have to spend up to $800 million per year by the end of the century to combat climate change.
The report looked at the effects of climate change on the economies of Papua New Guinea, Vanuatu, Solomon Islands, Fiji, Samoa and East Timor up to 2100.
The bank found they all need to spend between $225 - $775 million annually - or between 3% - 15% of their GDP on this.
Most of the economic losses will be related to the impact on fishing and agriculture.
Papua New Guinea is expected to experience the most signficant loss - up to 15% of GDP by 2100.
The report did not include Kiribati.