Beef + Lamb chief insight officer Jeremy Baker believes some sheep and beef farmers are probably carbon neutral given their areas of native bush and tree plantations but they are not formally recognised.
Climate Change Minister James Shaw is asking his officials how existing carbon sequestration on farms can be recognised.
“The Government wants to see a system where positive choices farmers make that are good for the climate are recognised.
“This includes questions around native bush, shelter belts, riparian planting and soil sequestration,” Shaw said.
Canterbury University has been contracted by B+LNZ to calculate the sector’s overall net carbon position, taking account of the 1.4 million hectares of native forest and 180,000ha of exotic forest on private land.
B+LNZ is also developing a system where individual farmers can calculate their carbon position and, if it is neutral, to be formally credited.
Baker says that will provide incentives for farmers to offset their carbon emissions but it will require changes to the Emissions Trading Scheme so native bush and small woodlots, regardless of age, are recognised as carbon sequestering.
Caring for existing trees and strategic new planting of trees also appeals to Environment Minister David Parker and Conservation Minister Eugenie Sage who are supportive because of benefits to water quality, erosion and biodiversity.
Because the Government has split reduction targets for methane from carbon dioxide and nitrous oxide and debate over whether methane is absorbed by trees farmers cannot offset methane emissions through sequestration.
International agreements mean the volume of carbon absorbed by 1.4m hectares of native bush on privately owned land, small woodlots, soil, pasture and animal production cannot be used to calculate a farm’s carbon footprint.
It allows only forests planted since 1990 to count as carbon sequestering and they must be at least 1ha, have crown cover of more than 30% and an average width of crown cover of at least 30 cubic metres.
Trees planted before 1990, grassland, soil, narrow shelter belts, gorse and broom are excluded.
Every 1ha of pines will sequester 28 tonnes of carbon a year until harvest, whereas native bush will continue sequestering carbon, albeit at a slower rate, for hundreds of years.
It is not just trees that absorb carbon dioxide, so do soil, grass and animal products such as wool to varying degrees.
Grazing ruminants sequester small amounts of carbon for a short time but scientists say those minor benefits are outweighed by the impact of methane generated.
NZ Wood reports trees take and store carbon from the atmosphere, which constitutes about 50% of tree dry mass, but once cut down and left to decompose, carbon is released to the atmosphere.
Carbon remains in logs harvested for use in wood products.
Pasture absorbs carbon from the atmosphere to enhance growth, livestock eat the grass, excreting some carbon and generating methane, leaving the rest in their milk or flesh which is eventually returned to the atmosphere.
Wool does contain a large amount of carbon.
The International Wool and Textile Organisation calculates 40% of the weight of clean wool is biogenic carbon, which readily breaks down into soil to start the cycle over again.
NIWA reports a well-managed pasture can sequester carbon in the foliage and soil but growing grass also produces carbon, albeit at a much lower rate than trees.
Fertile pastures absorb it at a rate 20% greater than arid areas though carbon is released by decomposing vegetation.
The Interim Climate Change Committee has rejected the notion of using soil to store carbon, saying the science is not definitive.
But research is continuing and scientists believe soil on slopes less than 20 degrees offers potential storage.
Plant and Food Research principal scientist Dr Mike Beare says soil high in both clay and mineral surface area has the highest carbon absorbing qualities.
An estimated 60% of high-producing grasslands have potential to store carbon in the topsoil but most of them are near saturation.
Research shows the greatest storage potential is in the subsoil deeper than 15cm but that requires sowing deep-rooting plants that will deposit carbon and using fill inversion tillage systems for pasture renewal.
Inversion tilling buries topsoil carbon and replaces it with low carbon subsoil brought up to the surface from a depth of 25cm to 30cm. It involves ploughing only once every 20 to 30 years.
