New Zealanders will have to plant new forests, boost the use of existing forests as carbon sinks, and increase the use of wood in construction to significantly cut the nation's greenhouse gas emissions, researchers say.

"In order to avoid a serious problem in our future national greenhouse gas accounts, we need to increase the rate of new planting right now," said two experts at Canterbury University's forestry school, Associate Professor Euan Mason and senior lecturer David Evison.

Ministry of Economic Development figures released last week showed the nation's total greenhouse gas -- primarily carbondioxide, methane and nitrous oxide -- jumped nearly 24 percent between 1990 and 2008.

The Government plans to set an emissions target for 2020 early next month so that Trade Minister Tim Groser can take the figure to negotiations at a United Nations climate change meeting in Germany on August 10.

Climate Change Minister Nick Smith said at the weekend that while decisions were yet to be made, targets of a 40 percent reduction on 1990 emissions -- the figure international scientists say is necessary to keep global warming to around 2degC -- would have too great an economic impact, which he claimed would cost $15 billion a year by 2015.

National campaigned in last year's general election on a 50 percent cut by 2050, which would equate to about 15 percent by 2020.

The Canterbury academics said new forestry plantation establishment is at an "extremely low" level, but with the right planting policies, the nation could meet its international commitments on reducing emissions. "This could be done solely through afforestation," they said.

"If we consistently achieved a new planting rate of 50,000 hectares a year, it would take the best part of a century before we established forest on all our eroding landscapes, and meanwhile we would have carbon credits to sell to others on the international market."

If owners of pre-1990 forests were allowed to claim credits for increased carbon storage, the amount of atmospheric carbon "sunk" would be even greater, even if Kyoto Protocol rules might not allow sale of credits from such forests in the international market.

"Our goal should be to solve the problem, not to just make money from credits," the academics said.

Developing new building technologies that used wood, and promoting the benefits of timber construction, could also reduce greenhouse gas emissions.

Dr Smith said recent satellite data had confirmed the area of post-1989 forests was sufficient to offset New Zealand's increase in emissions and meet Kyoto obligations in the first commitment period from 2008 to 2012 -- which only requires a reduction to the 1990 level of emissions.

But an international aid group, Oxfam, yesterday called for New Zealand and Australia to take urgent action against climate change to stop neighbouring nations on Pacific islands becoming uninhabitable.

"Some island nations in the Pacific face the very real threat of becoming uninhabitable in the decades ahead," Oxfam said in a report that called for New Zealand and Australia to reduce carbon emissions by 40 percent by 2020 and by 95 percent by 2050.

Allowing global temperatures to rise more than 2degC would reduce the displacement of people in the Pacific due to rising sea levels.

By 2050, 8 million people in the Pacific Islands may need to find new places to live, along with 75 million people in the Asia Pacific region.