Canada’s boreal zone covers almost 60

Afforestation can mitigate climate change by creating new carbon sinks and increasing wood supply. However, climate change can impact the growth of trees in afforested areas and affect their characteristics, and the harvested wood products that can be manufactured from them. This study aimed to quantify to what extent the quality of the wood supply directed to primary processing is influenced by climate change and alters the carbon storage of wood products. A multi-model approach was used to estimate the carbon stocks in harvested biomass resulting from plantations of black spruce on open woodlands and hybrid poplar on abandoned farmlands in Québec (Canada) under a gradient of climate forcing projections. Results suggest that increased climate forcing negatively impacts the quality of the harvested wood product basket and influences the relative amount of lumber vs. pulpwood. However, according to our assumptions, the decay of solid wood products in landfills produced more methane emissions than paper, which may constrain their climate change mitigation potential in the absence of methane capture or flaring. The cascading use of solid wood products in bioenergy at the end of their service life significantly reduced overall emissions. This study highlights how comprehensive afforestation strategies can, in the long term, be used to maximize the carbon storage potential of harvested wood products sourced from new plantations, as long as these strategies also include better use of pulp-quality wood, improved cascading use at the end-of-life of wood products and, most importantly, the avoidance of methane emissions from landfilled wood.

Swift action to restore forests is critical for mitigating climate change and preserving biodiversity. Canada has an ambitious program to plant two billion trees to help exceed the country's emissions targets while restoring forest habitat and providing social and economic benefits. We conducted a systematic analysis of where new tree cover can maximally achieve these benefits while minimizing implementation costs. Accounting for critiques of global restoration mapping that include the overestimation of mitigation potential and inadequate biodiversity and social safeguards, we find that 19.1 Mha are available, which is much more than the approximately 1.2 Mha needed to plant two billion trees. Optimization scenarios for 1.2 Mha revealed synergies and trade-offs. Scenarios prioritizing low costs, accessibility, and high growth are concentrated in temperate and coastal areas, overlapping partly with biodiversity scenarios, but with trade-offs of higher costs. A diverse portfolio of regionally restored sites, each tailored for specific attributes, is most likely to deliver multiple benefits at the pace demanded by the current crises.

Accurate accounting of greenhouse‐gas (GHG) emissions and removals is central to tracking progress toward climate mitigation and for monitoring potential climate‐change feedbacks. GHG budgeting and reporting can follow either the Intergovernmental Panel on Climate Change methodologies for National Greenhouse Gas Inventory (NGHGI) reporting or use atmospheric‐based “top‐down” (TD) inversions or process‐based “bottom‐up” (BU) approaches. To help understand and reconcile these approaches, the Second REgional Carbon Cycle Assessment and Processes study (RECCAP2) was established to quantify GHG emissions and removals for carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O), for ten‐land and five‐ocean regions for 2010–2019. Here, we present the results for the North American land region (Canada, the United States, Mexico, Central America and the Caribbean). For 2010–2019, the NGHGI reported total net‐GHG emissions of 7,270 TgCO 2 ‐eq yr −1 compared to TD estimates of 6,132 ± 1,846 TgCO 2 ‐eq yr −1 and BU estimates of 9,060 ± 898 TgCO 2 ‐eq yr −1 . Reconciling differences between the NGHGI, TD and BU approaches depended on (a) accounting for lateral fluxes of CO 2 along the land‐ocean‐aquatic continuum (LOAC) and trade, (b) correcting land‐use CO 2 emissions for the loss‐of‐additional‐sink capacity (LASC), (c) avoiding double counting of inland water CH 4 emissions, and (d) adjusting area estimates to match the NGHGI definition of the managed‐land proxy. Uncertainties remain from inland‐water CO 2 evasion, the conversion of nitrogen fertilizers to N 2 O, and from less‐frequent NGHGI reporting from non‐Annex‐1 countries. The RECCAP2 framework plays a key role in reconciling independent GHG‐reporting methodologies to support policy commitments while providing insights into biogeochemical processes and responses to climate change.

Persistent discrepancies between bottom‐up, terrestrial biosphere models (TBMs), and top‐down, atmospheric inversions, have made it difficult to quantify the magnitude of the North American terrestrial carbon sink. Previous studies have compared aggregated continent‐scale estimates of carbon fluxes from TBMs and inversions for all of North America, but this provides limited insights into finer‐scale mismatches that contribute to the overall discrepancies. Here we evaluate agreement between TBM and inversion carbon flux estimates at 1° × 1° resolution to provide more direct insights into where models disagree and what underlying factors drive discrepancies. We find that the additional carbon uptake estimated by inversions, in just 16% of the area of North America, is large enough to account for the discrepancy between TBMs and inversions across the whole continent. The majority of these differences occur in permafrost, peatland, and cropland regions. In these regions, we find a higher likelihood of potential biases in the weaker sink estimates from TBMs, suggesting that the stronger sink implied by inversions is more likely to be realistic. However, the current observational coverage is insufficient for fully assessing the causes of discrepancies or the magnitude of biases in either approach. Encouragingly, improved representation of agricultural processes in a TBM led to better agreement with inversions in croplands. Efforts to accurately model cropland dynamics will help improve agreement between TBMs and inversions. Overall, this work presents a clear path for reconciling the discrepancies between inversion and TBM estimates of the North American carbon sink that have persisted for two decades.

The distribution and impacts of non-native earthworms are poorly documented in Atlantic Canada meaning that we have limited knowledge about the relationship between earthworms and forest properties. To address this knowledge gap, we surveyed earthworms and sampled the soil organic layer in 41 forest stands located in New Brunswick to investigate their relationship with forest properties and impact on organic layer thickness and carbon content. We found earthworms at 39 % of the sites that we surveyed. Earthworms were more common in hardwood stands than softwood stands, at low elevations, and near current or historical human activity. Sites with earthworms had thinner organic layers and less carbon in the soil organic layer. A simple two-pool Lotka-Volterra model described the relationship between earthworm abundance and organic layer carbon well. The model predicted that earthworm invasions take about a decade to reach numbers typical of invaded sites and half a century to reach carrying capacity. Together these data suggest that, despite their long-term regional presence, much of the Acadian Forest that is not adjacent to human activity remains unimpacted and vulnerable to the effects of non-native earthworms.

The use of post-consumer wood in cascades offers several potential carbon-related benefits, including longer carbon retention, less landfilling, deferred tree harvesting, and increased substitution of emissions-intensive materials. However, the establishment of well-regulated wood cascading systems is limited in many jurisdictions. In this study, we utilized a wood products carbon dynamics model (MitigAna), and data from British Columbia (BC), Canada, to estimate the mitigation potential of cascading uses of wood.We designed three scenarios: a baseline scenario without cascading, a reuse scenario assuming an 85% recycling ratio (as the upper bound), and an achievable cascading scenario of different commodity pathways with an average 30% recycling ratio.The achievable cascading scenario resulted in a biogenic emission reduction of 1.16 MtCO2e yr-1 (2.4%) compared to the baseline. Further mitigation benefits may be achieved by reducing harvest, potentially leading to an additional 1.1 MtCO2e yr-1 reduction. However, as a major wood exporter, the circular economy policies of BC have limited influence, as many of the end-of-life events occur outside of BC and Canada's jurisdiction. If the cascading system were to be implemented exclusively in Canada, the emission reduction would only be 0.2 MtCO2e yr-1.Increasing the recycling ratio from 30% to 85% only yielded a further 2.2% biogenic emission reduction, which suggests a diminishing rate of return for the cascading uses of wood. Jurisdictions therefore may prioritize implementing a simple and cost-effective system initially.There are economic and environmental challenges associated with collection, sorting, treatment, transportation, remanufacturing and commercialization of the post-consumer wood in cascade. Continued research is necessary to address these challenges and inform the development of effective strategies in this area.

The uptake of carbon dioxide (CO2) by terrestrial ecosystems is critical for moderating climate change1. To provide a ground-based long-term assessment of the contribution of forests to terrestrial CO2 uptake, we synthesized in situ forest data from boreal, temperate and tropical biomes spanning three decades. We found that the carbon sink in global forests was steady, at 3.6 ± 0.4 Pg C yr-1 in the 1990s and 2000s, and 3.5 ± 0.4 Pg C yr-1 in the 2010s. Despite this global stability, our analysis revealed some major biome-level changes. Carbon sinks have increased in temperate (+30 ± 5%) and tropical regrowth (+29 ± 8%) forests owing to increases in forest area, but they decreased in boreal (-36 ± 6%) and tropical intact (-31 ± 7%) forests, as a result of intensified disturbances and losses in intact forest area, respectively. Mass-balance studies indicate that the global land carbon sink has increased2, implying an increase in the non-forest-land carbon sink. The global forest sink is equivalent to almost half of fossil-fuel emissions (7.8 ± 0.4 Pg C yr-1 in 1990-2019). However, two-thirds of the benefit from the sink has been negated by tropical deforestation (2.2 ± 0.5 Pg C yr-1 in 1990-2019). Although the global forest sink has endured undiminished for three decades, despite regional variations, it could be weakened by ageing forests, continuing deforestation and further intensification of disturbance regimes1. To protect the carbon sink, land management policies are needed to limit deforestation, promote forest restoration and improve timber-harvesting practices1,3.

This study applied the Canadian Model for Peatlands (CaMP) to 63.9 million hectares of peatlands within boreal and temperate ecozones of Canada to assess the trends in atmospheric carbon (C) emissions and removals and C sequestration over 30 years (1990–2019). The CaMP modelled net ecosystem productivity (NEP) for peatlands within the study area indicated a net C sink at an annual mean rate of 30.9 Mt C y−1 (48.4 g C m−2 y−1). Net Biome Productivity (NBP), which accounts for losses of carbon due to wildfire, reduced the C sink to 19.0 Mt C y−1 (29.8 g C m−2 y−1). On an area-weighted basis, the Hudson Plains and the Boreal Plains had the highest NBP (34.9 and 34.0 g C m−2 y−1, respectively) and the Atlantic Maritime and Boreal Shield West had the lowest (25.3 and 24.6 g C m−2 y−1 respectively), with the Boreal Shield East having intermediate NBP (27.5 g C m−2 y−1). NBP was highest in peatlands with forest cover, rising with increasing nutrient status (bog < poor fen < rich fen). These modelled values compare well with long-term carbon accumulation rates found in the literature for Canadian peatlands ranging from 6 to 70 g C m−2 y−1. While most years peatlands were a net sink of C, years with extensive fires resulted in peatlands being a small net source of C. The study highlighted that forested peatlands were important in driving the C sequestration sink but were also sensitive to climate warming due to high rates of soil CO2 emission and large wildfire C emissions. This highlights an important, yet vulnerable role these forested peatlands play in Canada's national greenhouse gas accounting. While this research is the first to produce estimates of C sequestration and greenhouse gas emission and removal rates across such a large area of Canada, further research is required across peatland types and ecozones to improve parameterization, validation, and process representations. Our results stress the importance of ecozone-specific analyses and accounting for infrequent large fire years and fire risk in land management policy and carbon accounting.

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Growth and yield models in forest management planning are used to project future forest conditions and estimate quantities such as wood volume and biomass. These models are crucial for assessing forest sustainability, however, some models currently used in Canada do not adequately account for climate and other environmental variables, which limits their effectiveness under a changing climate. Climate-sensitive growth and yield models (CSGYMs) are therefore urgently needed to support forest management decisions. The Canadian Forest Service (CFS) has developed a strategic plan to advance climate-sensitive growth and yield modeling in Canada through collaboration with provincial and territorial agencies, as well as other partners. The primary objective of this plan is to provide a national-level modelling approach to predicting and managing forest growth, mortality, and other ecosystem services. The climate sensitive growth and yield modelling initiative emphasizes collaboration, open data, and open -source code principles to ensure widespread accessibility and uptake of models, thus contributing to the sustainable management of forest resources. This technical review reports on the status of growth and yield models currently applied in each province and territory, assesses the level of climate sensitivity associated with each of these models, synthesizes the relevant modeling approaches and input data required to implement climate sensitivity into these models, and suggests possible pathways for achieving CSGYM at a national scale. Widespread collaboration will be the key to advancing the development of CSGYMs.

Peatlands cover approximately 12% of the Canadian landscape and play an important role in the carbon cycle through their centennial- to millennial-scale storage of carbon under waterlogged and anoxic conditions. In recognizing the potential of these ecosystems as natural climate solutions and therefore the need to include them in national greenhouse gas inventories, the Canadian Model for Peatlands module (CaMP v. 2.0) was developed by the Canadian Forest Service. Model parameterization included compiling peat profiles across Canada to calibrate peat decomposition rates from different peatland types, to define typical bulk density profiles, and to describe the hydrological (i.e., water table) response of peatlands to climatic changes. A total of 1217 sites were included in the dataset from published and unpublished sources. The CORESITES table contains site location and summary data for each profile, as well as an estimate of total carbon mass per unit area (in megagrams of C per hectare). Total carbon mass per unit area at each location was calculated using bulk density and carbon content through each profile. The PROFILES table contains data for depth (in centimeters), bulk density (in grams per cubic meter), ash and carbon content (in percentage), and material descriptions for contiguous samples through each peat profile. Data gaps for bulk density and C content were filled using interpolation, regression trees, and assigned values based on material description and/or soil classification to allow for the estimation of total carbon mass per unit area. A subset of the sites (N = 374) also have pH and pore water trace-elemental geochemistry data and are found in the WATER table. The REFERENCES table contains the full citation of each source of the data and is linked to each core location through the SOURCEDATA table. The LOOKUP table defines codes in the database that required more space that what was sufficient in the metadata tables. The data can be accessed on Open Government Canada and will be useful for future work on carbon stock mapping and ecosystem modeling. All metadata and data are provided © Her Majesty the Queen in Right of Canada, 2023 and information contained in this publication may be reproduced for personal or public noncommercial purposes with attribution, whereas commercial reproduction and distribution are prohibited except with written permission from NRCan; complete details are noted in the Supporting Information file Metadata S1 (see Class III.B.3: Copyright restrictions).

Forest aboveground biomass (AGB) is an important attribute informing on carbon storage, forest function, and habitat condition. Accurate knowledge of current AGB and its dynamics is essential for sustainable forest management and carbon monitoring. Common methods for estimating AGB, such as permanent sample plots, yield curves, or simulations, often fail to adequately capture the spatial distribution and structural complexity of forest attributes. To address these limitations, we present an integrated model-driven, data-informed approach for developing AGB yield curves exclusively from remotely sensed data, including an annual time series data of Landsat informed annual AGB values, tree species composition, and age. We applied this approach to a 76.5 million-hectare study area, encompassing diverse forest conditions, species, and ages, partitioned into 34 150 × 150-km analysis tiles to account for local variation. The 37-year AGB time series (1984–2021) were filtered to create a representative and noise-reduced sample set for developing remote sensing-derived AGB yield curves (RSYC). Using a nonlinear mixed-effects modeling framework, we generated 127 RSYC models for eight tree species across the study area. Developed yield curves offered insights into AGB dynamics across different forest types and conditions. The performance of RSYC models was evaluated using three independent datasets: permanent sample plots, existing yield curves, and an established growth and yield simulator. Assessment of the RSYC models showed the influence of geographic position and tree species representation in the reference data. In general, the RSYC models tended to underestimate AGB and AGB increments, with relative RMSE ranging between 22.66% and 70.30% for permanent sample plots. We discuss the challenges associated with model validation, data filtering processes, and the advantages of utilizing wall-to-wall AGB time series data from remote sensing. Our findings confirm the feasibility of developing AGB yield curves exclusively from remotely sensed data, covering a wide range of species and stand structural conditions representing a large spatial extent.

Forests play a crucial role in South Korea’s carbon neutrality goal and require sustainable management strategies to overcome age-class imbalances. The Generic Carbon Budget Model (GCBM) offers a spatially explicit approach to simulate carbon dynamics at a regional scale. In this study, we utilized the GCBM to analyze the carbon budget of forests in South Korea and produce spatiotemporal maps for distribution of the forest biomass. The growth parameters of five representative tree species (Pinus densiflora Siebold & Zucc., Larix kaempferi Carr., Pinus koraiensis Siebold & Zucc., Quercus mongolica Fisch. ex Ledeb., Quercus variabilis Blume), which are the main species in South Korea, were used to operate the model. In addition, spatial data for harvest and thinning management activities were used to analyze the effects of anthropogenic activities. In 2020, the aboveground and belowground biomass were 112.98 and 22.84 tC ha−1, and the net primary productivity was 8.30 tC ha−1 year−1. These results were verified using comparison with statistics, a literature review, and MODIS NPP. In particular, broadleaf is higher than conifer forest in net primary production. The Canadian GCBM with Korean forest inventory data and yield curves successfully estimated the aboveground and belowground biomass of forests in South Korea. Our study demonstrates that these estimates can be mapped in detail, thereby supporting decision-makers and stakeholders in analyzing the carbon budget of the forests in South Korea and developing novel schemes that can serve regional and national aims related to forest management, wood utilization, and ecological preservation. Further studies are needed to improve the initialization of dead organic matter pools, given the large-scale afforestation efforts in recent decades that have established South Korea’s forests on predominantly non-forest sites.

We examine the supply chains of post-fire salvage harvest to 28 mills or 10 communities in British Columbia, Canada, and assess the net change in GHG emissions for community bioenergy and biofuels, relative to a 'do-nothing' baseline with fossil fuel use.Lowest-cost supply chains for post-fire salvage had largest hauled biomass for mills in the southern interior the province, with mills in close proximity to each other having small fibresheds and low haul costs. Supply chains were also quantified for salvage biomass hauled to communities by using a lowest GHG optimization routine that selected between liquid transportation fuels or community bioenergy (heat and/or electricity). For the first few decades, avoided GHG emissions were larger when biomass was used for bioenergy (heat and/or electricity), mainly in larger communities, to avoid fossil fuel burning. As energy systems decarbonized, biomass was used for biofuels, and production was more evenly distributed amongst the communities.Adding these results to an integrated framework with previously published ecosystem emissions and removals assessed the net change in GHG emissions for a post-fire rehabilitation and bioenergy scenario relative to a 'do-nothing' baseline with continued fossil fuel use. We found that there was an initial increase in net GHG emissions even though biogenic emissions from bioenergy were partially offset by avoided fossil fuel emissions. Over time, an enhanced sink from rehabilitation activities combined with avoided fossil fuel emissions resulted in a cu-mulative (2020-2070) GHG reduction at median levels of-6 TgCO2e with a range from reduced emissions-39 TgCO2e to increased emissions 37 TgCO2e. Cumulative avoided fossil emissions were-62 TgCO2e with range from-49 TgCO2e to-86 TgCO2e.

State and local governments are increasingly interested in understanding the role forests and harvested wood products play in regional carbon sinks and storage, their potential contributions to state-level greenhouse gas (GHG) reductions, and the interactions between GHG reduction goals and potential economic opportunities. We used empirically driven process-based forest carbon dynamics and harvested wood product models in a systems-based approach to project the carbon impacts of various forest management and wood utilization activities in Maryland and Pennsylvania from 2007 to 2100. To quantify state-wide forest carbon dynamics, we integrated forest inventory data, harvest and management activity data, and remotely-sensed metrics of land-use change and natural forest disturbances within a participatory modeling approach. We accounted for net GHG emissions across (1) forest ecosystems (2) harvested wood products, (3) substitution benefits from wood product utilization, and (4) leakage associated with reduced in-state harvesting activities. Based on state agency partner input, a total of 15 management scenarios were modeled for Maryland and 13 for Pennsylvania, along with two climate change impact scenarios and two bioenergy scenarios for each state. Our findings show that both strategic forest management and wood utilization can provide substantial climate change mitigation potential relative to business-as-usual practices, increasing the forest C sink by 29% in Maryland and 38% in Pennsylvania by 2030 without disrupting timber supplies. Key climate-smart forest management activities include maintaining and increasing forest extent, fostering forest resiliency and natural regeneration, encouraging sustainable harvest practices, balancing timber supply and wood utilization with tree growth, and preparing for future climate impacts. This study adds to a growing body of work that quantifies the relationships between forest growth, forest disturbance, and harvested wood product utilization, along with their collective influence on carbon stocks and fluxes, to identify pathways to enhance forest carbon sinks in support of state-level net-zero emission targets.

Meeting climate change mitigation targets by 2050, as outlined in international pledges, involves determining optimal strategies for forest management, wood supply, the substitution of greenhouse gas-intensive materials and energy sources, and wood product disposal. Our study quantified the cumulative mitigation potential by 2050 of the forest sector in the province of Quebec, Canada, using several alternative strategies and assessed under what circumstances the sector could contribute to the targets. We used the Carbon Budget Model of the Canadian Forest Sector to project ecosystems emissions and sequestration of seven alternative and one baseline (business-as-usual [BaU]) forest management scenarios over the 2018-2050 period. Three baskets of wood products were used in a Harvested Wood Products model to predict wood product emissions. The mitigation potential was determined by comparing the cumulative CO(2)e budget of each alternative scenario to the BaU. The proportion of methane emissions from landfills (RCH4%) and the required displacement factor (RDF) to achieve mitigation benefits were assessed both independently and jointly. The fastest and most efficient way to improve mitigation outcomes of the forest sector of Quebec is to reduce end-of-life methane emissions from wood products. By reducing methane emissions, the RDF for achieving mitigation benefits through intensification strategies can be reduced from 1.2-2.3 to 0-0.9 tC/tC, thus reaching the current provincial mean DF threshold (0.9). Both a reduction and an increase in the harvested volume have the potential to provide mitigation benefits with adequate RCH4% and RDF. Increased carbon sequestration in ecosystems, innovations in long-lived wood products, and optimal substitution in markets offer potential avenues for the forest sector to contribute to mitigation benefits but are subject to significant uncertainties. Methane emission reduction at the end of wood product service life is emerging as a valuable approach to enhance mitigation benefits of the forest sector.

Globally, efforts to increase land sector contributions to net-zero emissions are pursued. Harvested wood products may retain carbon, and substitute emission-intensive products. The emission reductions achieved through substitution, or substitution benefits, can inform the design of climate-effective wood-use strategies. Mitigation analyses of a wood-based bioeconomy therefore need to include substitution to evaluate the mitigation outcomes across sectors. Substitution benefits can be estimated using displacement factors, which quantify the emissions avoided per unit of wood use. Here, we calculated the displacement factors of timber constructions and wood-derived biofuels to be around 1.03 and 0.45 tCO 2 e/tCO 2 e, respectively. Assuming substitution was achieved when changes in human behavior increased the share of wood use relative to the reference market share, we added the substitution benefits to a previous analysis that focused on biogenic emissions in British Columbia, Canada. At projected declining harvest rates, the theoretical maximum reduction that forest products can contribute over the period 2016 to 2050 is 66 MtCO 2 e·year −1 with an uncertainty range of 45–79 MtCO 2 e·year −1 , relative to the baseline, by focusing on long-lived, high-displacement construction applications. However, because construction uses of wood in foreign markets are not guaranteed, and constrained by market access, the practical strategy that combines construction and biofuel uses can achieve 17.4 MtCO 2 e·year −1 , equivalent to 30% of British Columbia’s 2050 target. Although a transformation of the bioeconomy may help achieve both climate and socio-economic benefits, potential conflict exists between maximizing regional and global benefits. How and where wood will be used can influence the desired mitigation outcomes.

Increased forest fires in the future will create opportunities to undertake salvage logging and replanting activities with the potential to reduce greenhouse gas (GHG) emissions relative to a 'do nothing' scenario that relies on natural regeneration. Salvage logging of fire-killed wood will generate additional useful products for society while replanting will provide opportunities to establish seedlings with genetic gain and increased climate resilience. In British Columbia, Canada, our study showed that cumulative net GHG benefit from these rehabilitation activities on about 14 % of the area burned ranges from -32 to-79 MtCO2e in 2070, but cumulative net GHG reduction benefits are not realized for 23 to 31 years due to the emissions debt that is incurred from harvest wood product emissions and residue management. Scenarios were modelled using the Generic Carbon Budget Model (GCBM) that tracked carbon in the forest and a harvested wood products model that tracked the fate of C and the substitution benefits achieved through wood use, both developed by the Canadian Forest Service. Results were evaluated across 100 simulations of future fire, developed using a log-normal model fit to historic fire events and an assumption of linearly increased area annually burned by 2070 to double the average of the period 1950 to 2018. Our results suggest that mitigation efforts might be better directed at reducing wildfire risks and emissions in the first place, rather than rehabilitating post-fire outcomes.