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  • Library: Conservation of forests is needed to mitigate climate change

    Project Staff
    By Mark E. Harmon, Chad T. Hanson and Dominick A. DellaSala
    Abstract: Biomass combustion is a major biogeochemical process, but uncertain in magnitude. We examined multiple levels of organization (twigs, branches, trees, stands, and landscapes) in large, severe forest fires to see how combustion rates for live aboveground woody parts varied with tree species, size, and fire severity in Ponderosa pine (Pinus ponderosa Dougl. ex Laws.) and mixed conifer-dominated forests of the Sierra Nevada, California, USA. In high severity fire patches, most combustion loss was from branches < 2 cm diameter; in low to moderate severity patches, most was from bole charring. Combustion rates decreased as fire severity declined and with increasing tree size. Pinus species had little branch combustion, leading them to have ≈50% the combustion rate of other taxa. Combustion rates could be 100% for small branch segments and up to 57% for small tree aboveground woody biomass in high severity fire patches. However, combustion rates are very low overall at the stand (0.1%–3.2%) and landscape level (0.6%–1.8%), because large trees with low combustion rates comprise the majority of biomass, and high severity fire patches are less than half of the area burned. Our findings of low live wood combustion rates have important implications for policies related to wildfire emissions and forest management.
    (2022) Combustion of Aboveground Wood from Live Trees in Megafires, CA, USA.pdf
    Project Staff
    By Peter Wood for Sierra Club BC
    BC’s Strategic Climate Risk Assessment identifies 15 climate risks, several of which have the potential to create catastrophic impacts for BC's communities. Overall, the assessment found that the greatest climate-related risks were severe wildfire, seasonal water shortage, and heat wave events. It also found that events such as severe river flooding were of “high consequence,” though less likely to occur.
    There is a large body of scientific literature that documents the impact that industrial logging has on the severity and frequency of many of these events, yet the Assessment did not consider this information. This presents a major blind spot that could undermine the assessment’s findings and the effectiveness of the Province’s response in defending communities from worsening climate impacts.
    This report attempts to address this gap in order to understand the role that forests
    in B.C. can play in either mitigating or exacerbating those risks, depending on how we manage them. It finds that nine of these risks are substantially affected by forest management, some of which could have catastrophic consequences for the health and safety of local communities.
    (2021) Intact Forests, Safe Communities.pdf
    Project Staff
    A report by Natural Resources Defense Council, Nature Canada, Environmental Defence Canada and Nature Québec
    Protecting the world’s forests, just like a rapid transition away from fossil fuels, is essential to avoiding the worst impacts of climate change. Forests, in addition to their importance in maintaining biodiversity, play an irreplaceable role in global carbon regulation, absorbing one-third of human-caused carbon emissions from the atmosphere annually and storing this carbon long-term in their soil and vegetation. This is why forest protection and restoration are key pillars of international efforts to advance natural climate solutions (i.e., actions that preserve and enhance ecosystems’ role in absorbing and storing carbon). Preserving primary forests, which are forests that have never been impacted by significant human disturbance, is particularly critical. These forests, which are rapidly disappearing, hold unique value for the climate and biodiversity. Once gone, they are irreplaceable on any meaningful human timescale.
    (2021) How carbon loopholes for logging hinder Canada's climate leadership.pdf
    Project Staff
    A letter by 200 of the top US forest and climate scientists
    In 2020, as multiple legislative proposals attempted to shoehorn measures that would increase logging, or increase funding for logging, into COVID-19 stimulus packages, over 200 top U.S. climate and forest scientists asked Congressional leaders to avoid using the pandemic emergency as a means for stripping away forest protections and promoting logging. In a historic and unprecedented letter sent to Congress, the scientists concluded that, in order to avoid the worst impacts of the climate crisis, moving beyond fossil fuel consumption is not enough, and we must also increase forest protections and shift away from energy-intensive and greenhouse-gas polluting wood consumption.
    (2020) Over 200 Top U.S. Climate and Forest Scientists Urge Congress: Protect Forests to Mitigate Climate Crisis.pdf
    Project Staff
    By Suzanne W. Simard et al
    Temperate forests provide crucial ecosystems services as living sinks for atmospheric carbon (C) and repositories of biodiversity. Applying harvesting at intensities that minimize losses offers one means for mitigating global change. However, little is known of overstory retention levels that best conserve ecosystem services in different regional climates, and likewise as climate changes. To quantify the effect of harvest intensity on C stocks and biodiversity, we compared five harvesting intensities (clearcutting, seedtree retention, 30% patch retention, 60% patch retention, and uncut controls) across a climatic aridity gradient that ranged from humid to semi-arid in the Douglas-fir (Pseudotsuga menziesii) forests of British Columbia. We found that increased harvesting intensity reduced total ecosystem, aboveground, and live tree C stocks 1 year post- harvest, and the magnitude of these losses were negatively correlated with climatic aridity. In humid forests, total ecosystem C ranged from 50% loss following clearcut harvest, to 30% loss following large patch retention harvest. In arid forests this range was 60 to 8% loss, respectively. Where lower retention harvests are sought, the small patch retention treatment protected both C stocks and biodiversity in the arid forests, whereas the seedtree method performed as well or better in the humid forests. Below-ground C stocks declined by an average of 29% after harvesting, with almost all of the loss from the forest floor and none from the mineral soil. Of the secondary pools, standing and coarse deadwood declined in all harvesting treatments regardless of cutting intensity or aridity, while C stocks in fine fuels and stumps increased. The understory plant C pool declined across all harvesting intensities in the humid forests, but increased in arid forests. Shannon’s diversity and richness of tree and bryoid species declined with harvesting intensity, where tree species losses were greatest in the humid forests and bryoid losses greatest in arid forests. Shrub and herb species were unaffected. This study showed that the highest retention level was best at reducing losses in C stocks and biodiversity, and clearcutting the poorest, and while partial retention of canopy trees can reduce losses in these ecosystem services, outcomes will vary with climatic aridity.
    (2020) Harvest Intensity Effects on Carbon Stocks and Biodiversity Are Dependent on Regional Climate in Douglas-Fir Forests of British Columbia.pdf
    Project Staff
    A report by the US Forest Service
    Forests are considered a natural solution for mitigating climate change because they absorb and store atmospheric carbon. With Alaska boasting 129 million acres of forest, this state can play a crucial role as a carbon sink for the United States. Until recently, the volume of carbon stored in Alaska’s forests was unknown, as was their future carbon sequestration capacity.
    In 2007, Congress passed the Energy Independence and Security Act that directed the Department of the Interior to assess the stock and flow of carbon in all the lands and waters of the United States. In 2012, a team composed of researchers with the U.S. Geological Survey, U.S. Forest Service, and the University of Alaska assessed how much carbon Alaska’s forests can sequester.
    The researchers concluded that ecosystems of Alaska could be a substantial carbon sink. Carbon sequestration is estimated at 22.5 to 70.0 teragrams (Tg) of carbon per year over the remainder of this century. In particular, Alaska’s dense coastal temperate forests and soils are estimated to sequester 3.4 to 7.8 Tg of carbon per year. Forest management activities were found to have long-term effects on the maximum amount of carbon a site can sequester. These findings helped inform the carbon assessment sections of Chugach and Tongass National Forests’ land management plans.
    (2020) Forestry as a Natural Climate Solution- The Positive Outcomes of Negative Carbon Emissions.pdf
    Project Staff
    By William R. Moomaw et al
    Climate change and loss of biodiversity are widely recognized as the foremost environmental challenges of our time. Forests annually sequester large quantities of atmospheric carbon dioxide (CO2), and store carbon above and below ground for long periods of time. Intact forests—largely free from human intervention except primarily for trails and hazard removals—are the most carbon-dense and biodiverse terrestrial ecosystems, with additional benefits to society and the economy. Internationally, focus has been on preventing loss of tropical forests, yet U.S. temperate and boreal forests remove sufficient atmospheric CO2 to reduce national annual net emissions by 11%. U.S. forests have the potential for much more rapid atmospheric CO2 removal rates and biological carbon sequestration by intact and/or older forests. The recent 1.5 Degree Warming Report by the Intergovernmental Panel on Climate Change identifies reforestation and afforestation as important strategies to increase negative emissions, but they face significant challenges: afforestation requires an enormous amount of additional land, and neither strategy can remove sufficient carbon by growing young trees during the critical next decade(s). In contrast, growing existing forests intact to their ecological potential—termed proforestation—is a more effective, immediate, and low-cost approach that could be mobilized across suitable forests of all types. Proforestation serves the greatest public good by maximizing co-benefits such as nature-based biological carbon sequestration and unparalleled ecosystem services such as biodiversity enhancement, water and air quality, flood and erosion control, public health benefits, low impact recreation, and scenic beauty.
    (2019) Intact Forests in the United States- Proforestation Mitigates Climate Change and Serves the Greatest Good.pdf
    Project Staff
    By Beverly E. Law et al
    Strategies to mitigate carbon dioxide emissions through forestry activities have been proposed, but ecosystem process-based integration of climate change, enhanced CO2, disturbance from fire, and management actions at regional scales are extremely limited. Here, we examine the relative merits of afforestation, reforestation, management changes, and harvest residue bioenergy use in the Pacific Northwest. This region represents some of the highest carbon density forests in the world, which can store carbon in trees for 800 y or more. Oregon’s net ecosystem carbon balance (NECB) was equivalent to 72% of total emissions in 2011–2015. By 2100, simulations show increased net carbon uptake with little change in wildfires. Reforestation, afforestation, lengthened har- vest cycles on private lands, and restricting harvest on public lands increase NECB 56% by 2100, with the latter two actions contributing the most. Resultant co-benefits included water availability and biodiversity, primarily from increased forest area, age, and species diversity. Converting 127,000 ha of irrigated grass crops to native forests could decrease irrigation demand by 233 billion cubic metres per year. Utilizing harvest residues for bioenergy production instead of leaving them in forests to decompose increased emissions in the short- term (50 y), reducing mitigation effectiveness. Increasing forest carbon on public lands reduced emissions compared with storage in wood products because the residence time is more than twice that of wood products. Hence, temperate forests with high carbon densities and lower vulnerability to mortality have substantial potential for reducing forest sector emissions. Our analysis framework provides a template for assessments in other temperate regions.
    (2018) Land use strategies to mitigate climate change in carbon dense temperate forests.pdf
    Project Staff
    By Don Heppner, Alex Woods, Jennifer Burleigh, Harry Kope and Lorraine Maclauchlan
    The current, historically unprecedented outbreaks of mountain pine beetle and Dothistroma needle blight in British Columbia are strong indicators that relationships between pests, hosts and climate are being altered as climate changes. Numerous recent pest epidemics elsewhere in North America provide further strong evidence of the impact of changing climate on forest ecosystems.
    The interactions between pests, hosts and climate are complex, have co-evolved over centuries, and in many instances, are not well understood. This, together with the uncertainty associated with how regional climates will change, makes it difficult to predict the responses of specific pests to climate change. However, as climate changes, the environmental parameters under which present forests were established will change. When these changes result in increasingly sub-optimal conditions, trees will become physiologically stressed. Stressed trees are generally more attractive, more nutritious, and less resistant to many forest pests. Changes in thermal and moisture environments, combined with changes to host plant conditions, will interact synergistically facilitating the development of insect and pathogen outbreaks. The incidence of forest decline syndromes is also likely to increase as a result of general reductions in forest health.
    Large scale, pest-caused forest decline and mortality will have long-term ecological, social and economic consequences. Timber supplies, water resources as well as other forest resources will be impacted. We anticipate increasing levels of mortality in the standing inventory in many Timber Supply Areas in the province as a result of forest pest activity. Much of the immature growing stock will also be affected by increasing levels of pest-caused mortality, growth losses and regeneration delays. Although the mountain pine beetle epidemic represents a current extreme, in many Timber Supply Areas it is possible that the combined impacts of multiple pests under the influence of climate change could approach a similar magnitude of impact on the remaining timber resource.
    Although there is still much uncertainty regarding the severity and extent of climate change, there are strategies, which could be implemented to mitigate the impacts on forest health. We provide concise recommendations that would better track changing forest health conditions, increase our ability to forecast pest related impacts of climate change, increase the effectiveness of forest planning by proactively incorporating forest health issues and improve our abilities to prevent, mitigate and adapt to changing forest pest conditions. The unprecedented and concurrent outbreaks of insects and diseases in BC emphasize the need to expedite an action plan on the following nine recommendations of equal importance:
    1. Mandate expanded forest health monitoring for forest health agents at the landscape, watershed and stand level, as a component of ministry responsibility;
    2. Build a forest health research section;
    3. Implement modelling projects to predict future forest health impacts;
    4. Maintain forest health strategies and develop climate change risk assessments for each Timber Supply Area;
    5. Review and revise legislation and policy to identify forest health risks and strategies within forest stewardship plans;
    6. Institute landscape-level planning for forest health, as well as for other values;
    7. Develop and implement hazard- and risk-rating systems for forest insects and diseases;
    8. Implement changes to tree species selection and stocking standards to enable facilitated migration;
    9. Enable the research and development of products and tactics for the treatment of forest insects and diseases.
    The management of forest lands has clearly become more challenging as a result of climate change. We believe that our current forest management paradigm, which assumes stable climates and stable forest conditions, could be improved to better cope with highly uncertain future forest conditions. Forest management needs to respond and adapt to accommodate the diverse and innovative practices we will require to manage our forests into the future.
    (2009) The Implications of Climate Change to Forest Health in British Columbia-A Report to the Chief Forester.pdf
    Project Staff
    A report from the IVEY Foundation and the Canadian Boreal Initiative
    Canada is a country of forests. We have the world’s largest intact forest area in our northern boreal and our temperate and mountain forests contain biodiversity, climate control and economic values that are globally significant.
    Climate change will, and is, having a profound impact on these forest ecosystems. Many impacts, such as increases in average temperature and seasonal shifts, are happening in a more compressed timeframe than originally projected by climate scientists. Insect outbreaks, such as the mountain pine beetle, are occurring at a scale that was unimagined ten years ago and some scientists are beginning to warn that many ecosystems may have a “tipping point” beyond which their resilience will be overcome and completely new ecosystems will replace them. Clearly climate strategies in Canada must include those that address the role of this massive and globally significant forest asset.
    In parallel to these changes in the natural world, society is rapidly accelerating its discussions concerning how to mitigate against rising carbon emissions and climate change impacts. As a result governments, business and civil society are accelerating discussions concerning how to develop an effective mechanism to reduce carbon emissions. Strategies under development include an abundance of voluntary, and a few regulatory, frameworks. While none are identical, many of them contain carbon trading measures that would enable transfers of money from emitters to entities that could sequester or reduce the net rate of carbon emissions. Most of these systems include forests.
    In Canada there is a need to grapple with this emerging market and determine how it can be influenced and directed in a manner that supports the carbon storage and sequestration capacity of forests and conserves forest biodiversity, while helping to reduces our total country-wide carbon emissions (not just those of forests). How to do this involves a strategic discussion among leading advocates for policy reform. It is only in this way that we can arrive at a consensus on the key elements of a carbon reduction strategy that includes forests and a plan to secure the outcomes we seek.
    (2007) Forest Carbon sequestration and avoided emissions.pdf
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