Using forests to mitigate climate change
Mitigating climate change requires action on many fronts, in all sectors of the economy. Forests and the forest sector alone cannot do the job, but they can make a major contribution to the effort.
Both actions focused on forests and actions focused on use of forest products can contribute to mitigation.
Mitigation involving forests
Forests can be significant greenhouse gas (GHG) sources and significant carbon sinks as a result of natural processes (such as fire, insect infestations and tree growth) and of human activities (such as harvesting, afforestation and deforestation).
The idea behind using forests to help mitigate climate change globally therefore involves finding ways to manage them to reduce their potential to be sources and increase their potential to be sinks. For example:
- Limiting deforestation and reducing GHG emissions associated with forestry operations are two ways to decrease forests as sources. Strategies include minimizing disturbance during harvesting activities, reducing the width of forest roads and helping trees get re-established faster after harvest.
- Creating more forests through afforestation and enhancing growth in existing forests are two ways to increase forests as carbon sinks. Afforestation means establishing new forests on abandoned agricultural land or other non-forested areas.
Reducing harvesting would not have a large impact on carbon dioxide emissions from Canada’s forests for several reasons. As part of sustainable forest management, less than 0.5% of the managed forest is harvested in any given year in Canada. These harvested areas regenerate to forest, so that in any year there is substantial new storage of carbon occurring on the areas previously harvested. As well, much of the carbon removed from the forest is stored in durable forest products like lumber.
In addition, the amount of carbon released into the atmosphere from harvesting is small compared with the amount released due to forest fires and other natural disturbances like insect infestations. The area burned annually is, on average, 2.5 times larger than the area harvested; a big portion of the carbon goes up in smoke. Foresters recognize that fire is an important part of the life cycle of the many forests, and although governments and industry spend about half a billion dollars every year protecting forests from fires, we know that not all fires can be stopped nor should they be stopped. They help rejuvenate the forest, maintaining habitat for a wide range of wildlife as well as regulating the spread of insects and disease. However, if there were no fire protection and fires were allowed to occur naturally in all cases, a larger area would likely be burned each year than now occurs. Thus harvesting, in some areas, is simply occurring in place of natural fires that are prevented by protection efforts of governments and industry.
Finally, the impact of reduced harvesting needs to be considered. Harvested forests are used to produce everyday products like paper, lumber, panels, and doors that society needs. Reducing harvesting in Canada could have negative impacts on emissions because there will still be a demand for products to meet these needs. Wood products are traded globally, therefore reductions in harvesting in Canada would likely result in increased harvesting and emissions elsewhere, perhaps in countries where forests are not managed as sustainably as they are here. As well, there could also be increased use of more emissions-intensive products such as concrete and steel in place of wood for building houses, and metal, plastics, and resins in place of wood for products like furniture, doors, and windows.
Mitigation involving forest products
Recycled wood construction in Toronto
Additional means of reducing GHG emissions overall include: making more use of long-lived forest products such as lumber (which keep carbon out of the atmosphere and store it in buildings), developing new “green” forest products and making changes to forest product processing.
For example, wood-based construction products are generally considered to be environmentally sound alternatives to steel, aluminum, concrete and similar materials. (Researchers have developed tools such as life-cycle accounting to compare materials based on their total “life” emissions, from extraction and manufacture through to final disposal.) Another example is bioenergy, produced from wood waste or other forest sources. It provides an alternative to fossil fuel. Biofuels are renewable resources that can be replenished as new forests grow.
As well, GHG emissions can be reduced by making the best use of harvested wood through enhanced recycling and use of waste wood for bioenergy.
Wood products extend the time period during which the biomass carbon from trees is kept out of the atmosphere after harvesting. In addition, products and fuels derived from wood produced through sustainable forest management can offset fossil fuel emissions from other sectors of Canada’s economy. They can be used as alternatives to materials that require more energy to produce, such as concrete, aluminium, steel, or plastics. This would help to reduce greenhouse gas emissions from fossil fuel sources.
Challenges to using forests to mitigate climate change
The economics of afforestation to create carbon sinks has been extensively researched. One problem identified is that many of the costs of afforestation must be paid for upfront, but the carbon sink benefits develop slowly over time. This means that afforestation is not always economically attractive to the private sector.
Furthermore, it is still unclear what the trade-offs are when a land-use change such as afforestation occurs on a large scale. For example, the carbon benefits to be gained from afforestation must be weighed against the implications for the agricultural sector. Less land available for food-growing is one cost. That in turn creates another cost: namely, the need for more energy-intensive agricultural practices to meet production demand on a smaller land area—a likely outcome of which is an increase in carbon emissions.
Reducing deforestation is complicated to tackle. There are many different causes of deforestation across many sectors such as agriculture, municipal development, mining and energy. This means that policies to address deforestation must often be developed on a sector-by-sector basis. What is clear, however, is that where deforestation is reduced, the immediate outcome is reduced GHG emissions.
A tool for carbon accounting
Carbon Budget Model of the
Canadian Forest Sector
Various mitigation measures can help reduce GHG emissions resulting from forestry. One way to examine the impact of alternative measures is a carbon accounting tool that models how different forest management activities can affect the carbon balance. Called the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3), this tool can help forest managers assess the carbon implications of their actions and consider alternative approaches that may have a lower impact.
The model, developed by Canadian Forest Service researchers in cooperation with the Canadian Model Forest Network, is used widely in Canada and abroad.