The Parliamentary Commissioner for the Environment has released a heavy hitting report that says New Zealand is too reliant on forest offsets, calling it a "risky" short term fix to climate change challenges.
However, despite calling the report "thought-provoking", the Government said it is "committed to retaining the use of forestry off-sets for carbon dioxide and other greenhouse gas emissions".
Commissioner Simon Upton said the report focuses on "dealing with our agricultural greenhouse gases and forest sinks together, while dealing with fossil carbon dioxide emissions separately".
"We could store carbon in forest over large areas of New Zealand and score a net zero accounting triumph around mid-century; or adopt a more ambitious approach to reducing fossil emissions and make a clear statement about how far biological emissions should be reduced."
The report proposes dealing with emissions reduction targets and climate policies by grouping biological greenhouse gases from farming with the carbon uptake of forests. It would then have a separate target for reducing carbon dioxide emissions from the burning of fossil fuels.
"Since carbon dioxide is the main driver of global temperature rise, serious climate action to tackle New Zealand's gross fossil carbon dioxide emissions can be delayed no longer."
He said New Zealand relies heavily on forest to offset the emissions. "Forests are at risk from fire, disease and climate change itself. Managing a long-term problem with a short-term 'fix' is risky."
Climate Change Minister James Shaw said "for the sake of providing policy stability and predictability for emitters and the forestry sector, the Government is committed to retaining the use of forestry off-sets for carbon dioxide and other greenhouse gas emissions".
"Commissioner Upton is correct that trees only retain sequestered carbon for the life of the tree whereas emitted CO2 remains in the atmosphere for hundreds of years.
He said the New Zealand Emission Trading Scheme reforms that are set to be introduced this year "will provide necessary incentives to bring down domestic emissions".
Federated Farmers' Andrew Hoggard said the report recognised the "fundamental difference between the permanent conversion of inert, long-term fossil fuels into carbon dioxide and shorter term biological emissions from livestock (methane and nitrous oxide)".
He said it does not let farmers off the hook. "The agricultural sector is also a heavy user of fossil fuels in food processing and for transport to markets, and farmers will also be required to reduce methane and nitrous oxide, albeit at a lesser, and perhaps slower, rate than we all must tackle carbon dioxide emissions."
However, Greenpeace did not support the recommendation that nitrous oxide be combined with methane in climate policy.
"Nitrous oxide is a long-lived greenhouse gas, 298 times worse for the climate than carbon dioxide. It is also the most problematic gas for depletion of the ozone layer," said Steve Abel.
"Both methane and nitrous oxide emissions from agriculture must be urgently reduced at their source. That can only be done through eliminating synthetic nitrogen and heavily reducing cow numbers. We cannot primarily rely on offsetting these emissions through tree planting."