Planting pine trees is a stop gap but not the solution to the problem of rising greenhouse gas emissions.

That was one of the messages from GHG measurement, reporting and verification specialist Dr Carly Green at a deer industry seminar at Wanaka on Estimating GHG Emissions from Agriculture and Forestry.

“Offsets, such as tree planting are part of the short-term management solution, but we need to change our behaviour to bring about real progress,” she said.

Green overviewed the global and NZ GHG situation and projections; the proposed model for farm assessment and costing of emissions as well as some of the mitigations farmers could take.

New Zealand’s total GHG emissions from 1990 to 2018 increased 24% to 78.9 million tonnes of carbon dioxide equivalent. Almost half (48%) was from agriculture, and 41% from energy.

NZ agriculture is reducing emissions by 1% year-on-year in absolute terms, which is positive because that is how change is measured under the climate change framework. But complacency is not an option and efforts to drive that downward trend have to continue.

Methane is by far the major contributor to farm emissions, caused by ruminant animals and fertiliser use, so methane-busting strategies is where farmers should be focusing efforts, she said.

“Understand where emissions are coming from on your own farm and what drives them so that you can make the most meaningful changes.”

These changes were dependent on the development of strategies for lower-emission land uses, and farm systems that could maintain production with reduced stocking rates and inputs. She explained that the government’s Interim Climate Change Committee is looking towards a package of mitigations to lower emissions including methane inhibitors and vaccines; the breeding of lower-emission animals; reduced fertiliser use, low-emission seeds and crops; and genetically modified ryegrasses.

A farmer levy/rebate for GHG will be phased in by 2025, aligned with the price of carbon. The formula for calculation is:

Net obligations = (emissions – allocation) x levy rate.

The allocation – the ‘free’ amount excluded from net obligations – is set at 95%, and any reduction should be “well signaled and predictable”.

Farmers at the seminar calculated their likely obligations using their Overseer GHG number and the November 2020 carbon price of $35/tonne. The calculated amounts ranged from $700 to $3700 per/hectare.

NZ and global GHG emissions

New Zealand’s response and policy to GHG Emissions is aligned with the Paris 2016 Agreement. NZ is one of 197 signatory countries, all of which have committed to Nationally Determined Contributions (NDC) to address climate change.

NZ’s first stage NDC is the 2030 target of reducing GHG emissions by 30% below 2005 levels. The end goal is to be at a Net Zero emissions by 2050. We’re on target to meet the 2030 target, but the problem is our NDC and those of other signatory countries won’t achieve the Paris Accord’s goal of holding the global temperature increase within 1.5-2C.

A more realistic figure, based on current NDC’s is around 3-4C, which is why Paris Accord signatory countries have been asked to review and reconsider their NDCs.

NZ’s national response and policies to meet Paris Accord Obligations are the Emissions Trading Scheme, Zero Carbon Act and the Agriculture Sector Response.

The goals of the Zero Carbon Act are to be net zero in nitrous oxide and carbon dioxide by 2050, and reduce emissions of methane to 24-47 percent below 2017 levels by 2050, with an interim target of 10% below 2017 levels by 2030.

GHG 101

The greenhouse gases are Carbon dioxide (CO2), Nitrous Oxide (N2O) and Methane (CH4). As well as helping keep global temperatures within a biological reproduction and production range they act like an atmospheric blanket by trapping and retaining energy from the sun.

Not all GHG are equal in terms of trapping heat and retaining it in the atmosphere before it breaks down. Carbon dioxide is the least effective at trapping heat and breaks down over thousands of years. Methane is 25-times more effective at trapping heat and breaks down over about 12 years. Nitrous Oxide is almost 300-times more efficient than C02 at trapping heat. It has an atmospheric life of about 121 years.

Useful references:

Google: ‘Farm Carbon Footprint Calculator (Lincoln University) for a basic and free GHG estimation tool for on farm carbon calculation.

Go to: for reference tables showing carbon stock/ha for Pinus radiata, Douglas fir, exotic softwoods and hardwoods, and native forest.

International consultant

Dr Carly Green is a globally recognised greenhouse gas measurement, reporting and verification scientist with a PhD in International Climate Change Policy related to agriculture, forestry and other land use sectors.

From her home base at Hawea, near Wanaka, she consults for the United Nations and the Intergovernmental Panel on Climate Change (IPCC), and works with overseas governments and related organisations on how to reduce greenhouse emissions through land use planning and sustainable practices.