Quantifying the biophysical climate change mitigation potential of Canada's forest sector

Abstract

Abstract. The potential of forests and the forest sector to mitigate greenhouse gas (GHG) emissions is widely recognized, but challenging to quantify at a national scale. Forests and their carbon (C) sequestration potential are affected by management practices, where wood harvesting transfers C out of the forest into products, and subsequent regrowth allows further C sequestration. Here we determine the mitigation potential of the 2.3 × 106 km2 of Canada's managed forests from 2015 to 2050 using the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3), a harvested wood products (HWP) model that estimates emissions based on product half-life decay times, and an account of emission substitution benefits from the use of wood products and bioenergy. We examine several mitigation scenarios with different assumptions about forest management activity levels relative to a base case scenario, including improved growth from silvicultural activities, increased harvest and residue management for bioenergy, and reduced harvest for conservation. We combine forest management options with two mitigation scenarios for harvested wood product use involving an increase in either long-lived products or bioenergy uses. Results demonstrate large differences among alternative scenarios, and we identify potential mitigation scenarios with increasing benefits to the atmosphere for many decades into the future, as well as scenarios with no net benefit over many decades. The greatest mitigation impact was achieved through a mix of strategies that varied across the country and had cumulative mitigation of 254 Tg CO2e in 2030, and 1180 Tg CO2e in 2050. There was a trade-off between short-term and long-term goals, in that maximizing short-term emissions reduction could reduce the forest sector's ability to contribute to longer-term objectives. We conclude that (i) national-scale forest sector mitigation options need to be assessed rigorously from a systems perspective to avoid the development of policies that deliver no net benefits to the atmosphere, (ii) a mix of strategies implemented across the country achieves the greatest mitigation impact, and (iii) because of the time delays in achieving carbon benefits for many forest-based mitigation activities, future contributions of the forest sector to climate mitigation can be maximized if implemented soon.

A Participatory Approach to Evaluating Strategies for Forest Carbon Mitigation in British Columbia

“…Participants generally recognized the mitigation potential of limiting wood waste at harvest and using a portion of harvest residues for energy to replace local fossil fuel use, especially since the carbon would otherwise be emitted to the atmosphere, either progressively through decay or immediately through slash-and-burn, as discussed by Miner, et al [55] and Smyth, et al [56]. Participants insisted that bioenergy should only be used to replace emission-intensive fossil fuels such as coal and diesel, but not clean energy (for example, see [57]).…”

“…Nonetheless, some participants advocated the strategy for its potential to lower the area harvested each year (because more wood is extracted per hectares, a given harvest volume can be achieved from less area). Higher utilization scored relatively high in terms of its climate change mitigation potential, with many participants highlighting the benefits of reducing both the amount of harvesting waste left to decay or to be burned on site and the area harvested while maintaining carbon transfer into wood products (discussed in [5,56]). …”

“…This discrepancy can be explained by the concerns brought up by various participants in regards to what percent of the carbon removed through harvesting was considered to remain stored and the extent to which there would be substitution in wood products. In effect, without contesting the benefits associated with the production of wood products, some participants highlighted the uncertainties associated with factors used to calculate carbon storage and displacement effects (for instance, see [53,56,60]), expressing a concern that the current numbers may overestimate the benefit of using harvested wood products. Others also discussed the issues associated with leakage (i.e., emissions avoided in one location simply occur in another location, see [61]), pointing out that the paper products that are not produced in BC could simply be produced somewhere else if consumption does not diminish.…”

“…First, participants may support a strategy even though they do not perceive it as the best performing, especially since participants could support more than one strategy. This is particularly important in the context of forest carbon management in BC, since only an approach that combines various strategies that are adapted to geographical and economic particularities will be able to maximize climate benefit [5,56,68]. Second, as previously explained, the LLWP strategy was judged as having Long-lived wood products (LLWP), higher utilization, and rehabilitation are the strategies that received the greatest support in both regions, which somewhat differs from the results of the group evaluation where old growth conservation ranked the highest.…”

Cradle-to-Gate Environmental Life Cycle Assessment of the Portfolio of an Innovative Forest Products Manufacturing Unit

“…To estimate the effects of the substitutions, LCA results of competitors' products are used (Smyth et al 2014). To be fair; the impact on climate changes of HWP should be subtracted even if it affects just a bit of the end result.…”