Impact 3.1: The status of terrestrial greenhouse gas emissions and removals are understood and quantified so that changes in relation to management strategies, land-use policies and global change can be predicted
Key performance indicator: MPI and MfE are using verified estimates of greenhouse gas (GHG) emissions and carbon storage to reduce uncertainty in national inventories.
Key issues for New Zealand’s reporting are the robustness of estimates in the annual inventory, understanding the complex processes that govern emissions and sinks, and the impact of land use. Much of this research involves refining previous estimates with more sophisticated technology, research and modelling across various scales.
2010/11 Baseline situation: Estimates of greenhouse gas emissions, and how these change with altered land use, contained many uncertainties.
|Afforestation was greater than deforestation (579,000 ha ± 2% and 75,000 ha ± 6% respectively) in New Zealand between 1990 and 2008. The difference gave MPI an estimate of carbon emissions due to forest changes.||Greater certainty in New Zealand’s national GHG inventory has been achieved through more accurate measurements of N2O from pastoral hill country, and updated emission factors; these N2O emissions are less than previously reported.||
The proposed ETS and PFSI now have more robust look-up tables for shrublands reverting to indigenous vegetation
|Modelling of growth of pine stands and kānuka/mānuka stands is providing MPI with carbon sequestration rates and how these vary regionally and temporally.||MfE has greater confidence in carbon estimates from the LUCAS plot network and understand the accuracy of carbon change that can be detected.||
N2O emissions from livestock excreta on pastoral hill country are halved if the effect of slope is taken into account, reducing New Zealand’s annual liability by over $6 million if this methodology is adopted
|The uncertainty in estimating soil carbon for perennial croplands in MfE’s Soil Carbon Monitoring System has been significantly reduced.||MfE has improved information on the impact of erosion on soil carbon stocks and the need to incorporate the effect of erosion into the Soil Carbon Monitoring System.|
Given appropriate market incentives in the proposed Emissions Trading Scheme (ETS) and the Permanent Forest Sink Initiative (PFSI), afforestation of marginal land will help improve New Zealand’s overall greenhouse gas balance. Shrublands begin to develop quite rapidly once pastoral land is abandoned, and they are likely to be the first type of indigenous vegetation ‘credits’ included in the ETS or the PFSI. Our work is contributing to improving the robustness of estimating these credits. For example, this year’s remeasurements of a national network of 104 plots (20 × 20 m) generated much-needed data on carbon sequestration rates of shrublands.
Using an additional 104 small (4 × 4 m) plots, we determined the likelihood of transition from ‘non-forest land’ (e.g. pasture, gorse, broom) to ‘forest-land’ and the rate at which this occurs.
We also contributed to improving lookup tables (a series of pre-calculated values of forest carbon stocks, by age, for a given forest type), currently available for only a few native species. Broadleaved–hardwood shrubland lookup tables are a priority because this vegetation type is common on indigenous reversion sites. At two study sites, one in North Canterbury and the other on the West Coast, we developed a refined methodology to predict carbon accumulation as a function of either shrubland volume or height, consistent with the ecological stage of the succession.
This work is part of the Measuring Greenhouse Gases & Carbon Storage Portfolio, and was supported by MPI funding.
Nitrous oxide (N2O) has a global warming potential 298 times that of CO2 so changes in the N2O estimates have a disproportionately significant impact on the national inventory. In collaborative new research with AgResearch on pastoral farming in hill country (sheep, beef and deer), we adjusted N2O emissions from livestock excreta deposition to include the effect of slope. The findings were significant – the proposed new methodology reduces estimates by 52% for the period between 1990 and 2012 relative to using current inventory emission factors. This could reduce New Zealand’s total agricultural N2O emissions by 16%. MPI is presently considering the new methodologies.
This research is part of both the Measuring Greenhouse Gases & Carbon Storage and Measuring Biodiversity Change portfolios, and was supported by MPI.
Innovative new research technology developed
We developed an automated gas chromatography technique to analyse N2O / N in order to better understand the dynamics of denitrification, particularly the leakage of N. The technique can measure extremely small quantities of N2 (50 ppm) against a large atmospheric background (800,000 ppm), while also allowing for the simultaneous detection of the other relevant gases (N2O, CH4, O2 and CO2). The system, the first in Australasia, will significantly enhance the ability of researchers in many organisations to test various strategies designed to mitigate N2O emissions from the denitrification process. The method will also be used to investigate the effectiveness of soil manipulations such as liming in further reducing N2O emissions from agriculture by increasing the activity and community structure of denitrifiers and enhancing the reduction of N2O to N2, an approach that could be of significant benefit to farmers.
This research is part of the Measuring Greenhouse Gases a& Carbon Storage Portfolio, and was supported by MBIE Core funding.