Addressing uncertainty and bias in land use, land use change, and forestry greenhouse gas inventories

National greenhouse gas inventories (NGHGIs) will play an increasingly important role in tracking country progress against United Nations (UN) Paris Agreement commitments. Yet uncertainty in land use, land use change, and forestry (LULUCF) NGHGHI estimates may undermine international confidence in emission reduction claims, particularly for countries that expect forests and agriculture to contribute large near-term GHG reductions. In this paper, we propose an analytical framework for implementing the uncertainty provisions of the UN Paris Agreement Enhanced Transparency Framework, with a view to identifying the largest sources of LULUCF NGHGI uncertainty and prioritizing methodological improvements. Using the USA as a case study, we identify and attribute uncertainty across all US NGHGI LULUCF “uncertainty elements” (inputs, parameters, models, and instances of plot-based sampling) and provide GHG flux estimates for omitted inventory categories. The largest sources of uncertainty are distributed across LULUCF inventory categories, underlining the importance of sector-wide analysis: forestry (tree biomass sampling error; tree volume and specific gravity allometric parameters; soil carbon model), cropland and grassland (DayCent model structure and inputs), and settlement (urban tree gross to net carbon sequestration ratio) elements contribute over 90% of uncertainty. Net emissions of 123 MMT CO2e could be omitted from the US NGHGI, including Alaskan grassland and wetland soil carbon stock change (90.4 MMT CO2), urban mineral soil carbon stock change (34.7 MMT CO2), and federal cropland and grassland N2O (21.8 MMT CO2e). We explain how these findings and other ongoing research can support improved LULUCF monitoring and transparency.

Substitution and carbon storage impacts of harvested wood products - Effects of increased cascading with different market responses

BackgroundThe climate impacts of wood-based products can be measured by substitution impacts and changes in product carbon stocks. Cascade use of wood aims to increase resource efficiency and minimize the impact on the environment and climate, but it may lead to changes in the product portfolios of industries. Thus, measuring the overall impact is challenging. This study analyses the impact of wood cascading on the climate under varying market responses. Cascade use here refers to discarded sawnwood product utilisation in panel and wood-based composite production. The study utilises explorative scenarios where Finnish wood-based flows are modelled in an Excel-based material flow model, and discarded sawnwood flows are shifted from energy use to material use in the end-of-life stage. The Reference case represents the situation where discarded wood-based products are only used for energy. The scenarios portray plausible market responses to cascading, with cascade production either leading to additional wood-based panel and composite production, or substituting primary sawnwood products thus leading to lower overall harvest levels. ResultsThe results show that the cascading can result in 1.6%-5.4% more avoided C emissions compared to reference when considering the substitution impacts, the carbon stock changes in wood products, and the avoided carbon loss from roundwood harvest. Besides the market response, the results vary depending on the time-period selected for the estimation of the average annual carbon stock change of wood products and the emission profile of non-wood products. ConclusionsThe results of this study indicate that cascading can contribute to climate change mitigation regardless of the market response, but it depends on the market response whether the reduction potential origins from wood-based products or indirect changes in the harvest levels. There are less avoided C emission gains in the technosystem, if cascading production substitutes primary production and therefore reduces the wood harvest. However, the opposite holds, if the average substitution impacts are significantly reduced in the future due to decarbonization of non-wood sectors. Thus, in the long-term, extending the carbon residence in the technosystem or in the ecosystem may provide a larger climate change mitigation potential than increasing the substitution impacts. Keywords: carbon stock change, cascading, forest industries, greenhouse gas emissions, harvested wood products, substitution, substitution impact

Harvested Wood Products as a Carbon Sink in China, 1900–2016

The use of harvested wood products (HWPs) influences the carbon flux. China is both the major producer and trader of HWP, so estimating the carbon stock change of China’s HWP is important to help curb climate change. Accurate reporting and accounting of carbon flows in the HWP pool is needed to meet greenhouse gas monitoring and climate change mitigation objectives under the United Nations Framework Convention on Climate Change (UNFCCC) and the Paris Agreement. This study applied production approach (PA) to estimate the carbon stock change of China’s HWP from 1900 to 2016. During the estimating period, the carbon stock of HWP in use and deposed at solid waste disposal sites (SWDS) were 649.2 Teragrams Carbon (TgC) (346.8 TgC in wood-based panels, 216.7 TgC in sawnwood and 85.7 TgC in paper & paperboard) and 72.6 TgC, respectively. The carbon amount of annual domestic harvest HWP varied between 87.6 and 118.7 TgC. However, the imported carbon inflow increased significantly after the 1990s and reached 47.6 TgC in 2016, accounting for 46% of the domestic harvest of that year. China has great mitigation potential from HWP and use of this resource should be considered in future strategies to address climate change.