Agricultural methane emissions remain the sticking point for New Zealand to meet its Paris Accord targets, and it is unlikely technology will be arriving in time to help farmers pull those emissions down significantly.
The Climate Change Commission’s (CCC) draft advice to the government on how NZ meets its obligations for the fourth reporting period of 2036 to 2040 estimates NZ’s emissions will be a full 63% lower than in 2021.
This has been boosted by higher-than-expected forestry plantings in recent years, a fall in emissions from transport, and greater use of renewables for heating and processing.
Between 2021 and 2022 NZ’s emissions fell by almost 4%. The commission estimates by 2050 NZ’s emissions will have fallen by a full 37%. Agricultural methane emissions will also fall by 13%, but this is well below the minimum target range of 24-47% set in legislation.
However, this range could itself be up for revision. Separate to the commission’s work, the government has announced an independent review of methane emissions targets in the context of “no further warming” effects.
Meantime, the CCC’s advice to get methane emissions within the existing target does not place significant faith in the multimillion-dollar investments made into new methane inhibitor and vaccination technology.
While it has assumed urease inhibitors in fertiliser, effluent treatment systems and genetics will help, it cites an uncertain future around methane mitigation tech.
It notes some inhibitors are used overseas, but that they are not suitable for NZ’s free range pastoral herds and flocks.
Overall, the commission estimates the tech is only capable of reducing agricultural emissions by 3% or 4 million tonnes of CO2 equivalent over the 2036-2040 period.
The scepticism will disappoint the red meat sector, limited in options for methane mitigation, and has the CCC falling back on more familiar approaches for the sector to enable it to make the target.
Under the EB4 (Emissions Budget) pathway modelled and based on recent land use trends, the CCC has budgeted for a 23% decline in dairying’s stocking rate and a 12% decline in sheep and beef stocking rates by 2050, compared to 2021.
That will accompany land use change, with an estimated loss of 2000 hectares of dairy land a year to horticulture, up on the past five-year average of about 1150ha a year.
While it anticipates dairy will hold the line in total output thanks to increased per cow production, meat production is expected to fall by 17% over that period, with farms being converted to native and exotic forestry. That amounts to a loss of about 500,000ha between 2021 and 2050, to about 6.5 million hectares of drystock area.
For context, between 2012 and 2022 the sheep sector experienced a loss of 3 million breeding ewes, or 1.5% a year.
The intensive forestry plantings of the past three years have seen more land go into trees than the commission anticipated, lowering the amount needed for the 2036-2040 period.
After peaking at 65,000ha of exotic plantings last year, that rate drops to 30,000ha a year to the end of the decade. It is expected to continue declining through to 2050 to only 10,000ha a year by 2050, supplied by ongoing drystock farm conversions.
However, native plantings are expected to surge, almost doubling to about 25,000ha a year by 2029 and continuing at that level through to 2050, expected to come through increased marginal and erosion prone land plantings, and reversion.
If these shifts in land use and limited tech do come into play, the commission estimates agriculture will hit a 39% reduction in methane levels by 2050. This places it well within the 24-45% target range, and compares to only a 13% reduction using current practices alone.
But how much of the fourth period budget is taken up remains dependent upon the government’s view on methane’s role in warming.
Professor Robert McLachlan of Massey University said the CCC’s work falls into a contested space, given that the government has abandoned sections of the first reduction plan from 2022-2025, has yet to release its 2026-2030 plan and has still to announce its Emissions Trading Scheme plans.
