Slashing pastoral stock numbers by up to 35 per cent has been suggested among ways to push New Zealand's greenhouse gas emissions down to zero by 2100.
A cross-party group of MPs have commissioned UK consultants Vivid Economics to look at the options, which have been presented as four bold scenarios for the country in a new report launched today.
Under the first scenario, the country would further slash the emissions intensity of its economic activity through technological advances, such as cost reductions in electric vehicles for freight, electric heating technologies for high temperature applications and a vaccine to reduce methane emissions from pastoral agriculture.
This would be accompanied by a structural shift away from pastoral agriculture - with animal numbers around 20 to 35 per cent lower than today - to less emissions-intensive activity.
The country would instead support a diverse range of land uses, including horticulture and crops, alongside extensive planting of forests, covering an extra million hectares of land by 2050.
This scenario could result in a 70 to 80 per cent reduction in net emissions compared with current levels, however the authors said this option still relied upon breakthroughs like high-grade heat and non-passenger transport, along with extra tech in the agriculture sector.
Under a second scenario, an extra 1.6 million hectares of forest planted by 2050 would "substantially reduce emissions" - a 65 to 75 per cent reduction - and provide opportunities in a significantly enhanced forest products industry.
"However, changed land uses may require a difficult transition for rural economies, as well as represent a lost opportunity to reintroduce native habitat."
The third scenario predicted increasingly efficient economic activity, yet without any significant land-use change, and the point of zero emissions occurring well after 2100.
The report authors said realising the fourth scenario - zero emissions by 2050 - could be possible, although a detailed economic analysis had not been done.
The authors concluded any pathway to reducing the country's domestic emissions would involve substantial change to patterns of energy supply and use, including moving towards a 100 per cent renewables grid and substantial electrification of the passenger vehicle fleet and low-grade heat.
"It is possible for New Zealand to move onto a pathway consistent with domestic net zero emissions in the second half of the century, but only if it alters its land-use patterns."
If New Zealand could substantially plant new forest, and it could benefit from extensive availability of new technologies, it may be possible for the country to achieve domestic net zero emissions by 2050, they said.
"Although afforestation will likely be an important element of any strategy to move to a net zero emissions trajectory in the period to 2050, in the second half of the century alternative strategies will be needed."
The authors made a raft of recommendations, including that the Government develop a trajectory for emissions price policy values, to apply to all government assessments and analyses, that were consistent with what is required to deliver the objectives of the Paris Agreement.
"This would imply significantly higher values than seen in the New Zealand Emissions Trading System today."
Green MP Kennedy Graham, chairman of GLOBE-NZ - the national cross-party chapter of parliamentarians climate change effort GLOBE-International - was pleased with the report.
"It has produced what we as a cross-party group were looking for - an independent and insightful analysis of New Zealand's mitigation potential, which we can share and use to debate the merits of the various options open to us," he said.
"It gives an unprecedented opportunity for us to move forward with national climate policy, complemented with practical action by the private sector and local communities.
It should enable us move towards the ambition level required of us in the Paris Agreement.
"Our children and grandchildren deserve no less. We parliamentarians have to deliver."
Parliament would schedule a debate on the report as soon as can be agreed by its business committee.
New Zealand and climate change
• Under present projections, the sea level around New Zealand is expected to rise between 50cm and 100cm this century, while temperatures could also increase by several degrees by 2100.
• Climate change would bring more floods (about two-thirds of Kiwis live in areas prone to flooding); make our freshwater problems worse and put more pressure on rivers and lakes; acidify our oceans; put even more species at risk and bring problems from the rest of the world.
• Climate change is also expected to result in more large storms compounding the effects of sea level rise.
• New Zealand, which reported a 23 per cent increase in greenhouse gas emissions between 1990 and 2014, has pledged to slash its greenhouse gas emissions by 30 per cent from 2005 levels and 11 per cent from 1990 levels by 2030.