The Climate Change Commission — in its final advice to the Government on emissions budgets out to 2035 — has taken on board some of the criticism its draft view received from the farm sector, but has not materially changed its story.
It still envisages a future in which New Zealand's output of meat and milk solids flatlines at something close to current levels while the emissions intensity of that output (emissions of methane per kilogram of meat or milk solids) continues to decline.
It extrapolates forward longstanding trend improvements in productivity — defined as output of meat or milk solids per head.
Together, those two trends would allow farmers to do slightly better than the medium-term statutory target of a 10 per cent decline in biogenic methane emissions from 2017 levels by 2030, with 13 per cent fewer cattle and sheep.
Its recommended budgets would have biogenic methane emissions falling from 33.7 million tonnes of carbon dioxide equivalent (using an outdated exchange rate), or 37 per cent of gross emissions in 2019, to an annual average of 31.5 million tonnes in the first budget period (2022 to 2025), then 30 million tonnes in the second (2026-30) and 28.5 million tonnes in the third (2031-35.)
The commission's final advice, released on Wednesday, acknowledges that its previous assumptions were overly optimistic and beyond what can be achieved.
It has "significantly" lowered projected productivity improvements for the sheep and beef sector, after updating assumptions relating to future production such as lambing rates and the potential for improvements in farm practice.
"We found that ... the reduction in stock numbers we had previously assumed would likely only be achievable with reduced production." The commission also now acknowledges that the increase it advocates in the area devoted to new native forests, to act as carbon sinks offsetting emissions of long-lived greenhouse gases, would have some opportunity cost in terms of the loss of grazing land — albeit only 20 per cent of the area planted, to reflect the expectation that a lot of the new native forest would be established on steeper, erosion-prone land with relatively low grass growth.
Offsetting that, its "demonstration" pathway now assumes 3500 hectares a year can be converted from pasture to horticulture, up from 2000ha previously.
The commission's fewer-but-better cattle and sheep story rather glosses over the fact that, according to the national greenhouse gas inventory, emissions factors for both dairy cattle and sheep — that is, emissions per head — have been increasing at a compound annual growth rate of 0.8 per cent since 1990. In simple terms, heavier animals eat more and belch more.
The commission says that the Biological Emissions Research Group and the Agricultural Greenhouse Gas Research Centre have identified several changes farmers can make to reduce emissions.
But it acknowledges no one option or approach will work for all farmers — an argument strongly made by the sector lobby groups — nor should all farmers be expected to achieve the same levels of emissions reductions.
"The key requirement for any practice change to reduce total biogenic methane emissions, and not just emissions intensity, is to reduce total dry matter consumption. The challenge for farmers is to find a better balance between livestock numbers, production levels and feed inputs (supplementary feed and fertiliser) which enables them to maintain farm profitability while reducing emissions," the commission says.
"This generally means a greater proportion of dry matter consumed is used for production and less for animal 'maintenance'." Easier said than done.
Since the commission released its draft advice in February, officials have updated the national greenhouse gas inventory to reflect emissions as of 2019, two years later than the baselines the commission had then and which were used when the Zero Carbon Act set its targets.
Between 2017 and 2019, biogenic methane emissions — 90 per cent of which arise from the digestive functions of livestock, the rest from landfills — rose by 0.4 per cent.
That compares with a 4.6 per cent increase over the same period in carbon dioxide emissions from fossil fuel use and 2 per cent for nitrous oxide, which unlike methane but like CO2 is a long-lived greenhouse gas.
A higher starting point for national greenhouse gas emissions inevitably means a more stringent reduction path is needed to reach a given target end point. The longer we wait, the harder it gets.
But the difference — which is a longstanding one — between the much slower growth in methane than CO2 emissions, combined with the fact that methane has a relatively short half-life in the atmosphere, strengthens the case for the two-gases approach which goes a lot easier on enteric methane emissions than on CO2 from gas-guzzling cars and coal-fired boilers.
In the end, the commission has only shaved 1 percentage point off its 2030 target for reduction in biogenic methane emissions, to 12 per cent from 13 per cent previously. It does, however, expect more of that reduction to come from landfills, leaving 11 per cent to come from livestock.
The commission continues to hold that the 2030 target, and a further reduction to 17 per cent below 2019 levels by 2035, are achievable with the widespread adoption of current best practice.
But beyond that, the Zero Carbon Act's target range of a 24 to 47 per cent decline in methane emissions by 2050 will require either new technology like methane inhibitors or a methane vaccine or, failing that, significant land use change out of pastoral farming.
And that is before any more ambitious nationally determined contribution pledge the Government might yet make to the global climate change summit in November.
Meanwhile, farmers have to think about how to adapt to a dryer and less equable climate than they have been used to.
Late last month, Statistics New Zealand reported than over the five years to June 2020, the amount of rain and snow that fell nationwide was down 3 per cent on the previous five years, and down 11 per cent on the second half of the 1990s. And that was not so long ago. Moa did not still stalk the bush.