Frequently asked questions:

Some Questions & Answers about Carbon and Forests

THE CARBON CYCLE

How do forests cycle carbon?

Globally, forests contain more carbon in biomass (living trees and other plants), dead organic matter (deadwood, leaves) and soil than is contained in the atmosphere. About 50% of the dry weight of wood is carbon. In most Canadian forests, there is more carbon in soils and dead organic matter than in living biomass. The carbon stored in forests is removed from the atmosphere through photosynthesis (the conversion of atmospheric carbon dioxide into plant material using energy from the sun, releasing oxygen in the process). When plants die and decompose or are burned, carbon is released back into the atmosphere primarily as carbon dioxide, but some remains in the forest litter and builds up in soils over the long term.

What are forest carbon sinks and sources?

Forests are composed of many stands (areas dominated by trees of similar characteristics and age). A stand is considered a carbon sink when its uptake of carbon dioxide from the atmosphere through photosynthesis exceeds its release of carbon dioxide through processes such as decomposition and burning. It is considered a carbon source when carbon release is greater than carbon uptake. The carbon balance of a forest is the sum of the contributions of its individual stands. A forest can be a carbon sink even if some individual stands are carbon sources, and vice versa.

Whether a forest stand is a sink or source at a particular time depends on natural processes as well as management. The rate of carbon uptake due to tree growth is fastest when the trees are young and it slows as the trees become old. Very young stands growing after fire or harvesting are carbon sources because the carbon removal by regrowing trees has yet to catch up with emissions from the decomposition of dead organic matter left after the disturbance. After a decade or two, these stands become sinks when carbon uptake due to tree growth exceeds emissions from decomposition. The carbon taken up over decades or centuries can be lost in very short time periods during natural disturbances such as wildfires. Insects can also slow the growth of infested trees (reducing carbon uptake) or even kill trees, causing carbon to be released as the dead trees decompose.

What role do forests play in the global carbon balance?

Each year, billions of tonnes of carbon are exchanged between the Earth’s atmosphere, oceans, and terrestrial ecosystems, including forests. Forests store large amounts of carbon that has over time been sequestered from atmospheric carbon dioxide by growing trees. Forests have the potential to either sequester more carbon (carbon sinks), or release their stored carbon back into the atmosphere (carbon sources). Most of the carbon exchanged between forests and the atmosphere is transferred by natural processes, such as tree growth, decomposition of plant material, and disturbance (for example, fire), but human actions can also strongly influence the forest’s role in the global carbon cycle.

Before the Industrial Revolution, the carbon dioxide concentration in the atmosphere had been more or less stable for a few millennia at about 280 parts per million. Today, as a result of human activity, the concentration is about 380 parts per million, the highest level in at least 650,000 years. The Intergovernmental Panel on Climate Change (IPCC) reports that in the 1990s, fossil fuel use and various industrial processes emitted 6.4 billion tonnes of carbon per year, while permanent clearing of forests (deforestation), mostly in the tropics, resulted in emissions of about 1.6 billion tonnes of carbon per year (see the IPCC 2007 report on the physical basis of climate change). However, over half of these emissions were offset by the carbon removed from the atmosphere by oceans (about 2.2 billion tonnes per year) and by forests and other vegetation (about 2.6 billion tonnes per year). As a result of these land and ocean sinks, the net increase of carbon in the atmosphere in the 1990s was 3.2 billion tonnes per year. Thus, forests have played a major role in the global carbon balance by offsetting a large portion of the carbon dioxide emitted through human activities.

Does forest management play a role in the forest carbon balance?

Yes, forest management activities such as harvesting, tree planting, and efforts to fight forest fires and insects have an impact on the forest carbon balance. In some cases, suppression of fires and protection against insects can lead to a reduction in the area affected and help maintain the carbon stored; however, our ability to reduce fire and insect impacts on carbon in the long term or over large landscapes is uncertain. Harvesting results in large losses of carbon from the forest in the short term, but the regeneration of the trees then takes up large amounts of carbon. As well, much of the harvested carbon is stored for a long time in forest products that society needs.

CANADA’S FOREST CARBON

How big is Canada’s forest?

Canada's forests and other wooded lands span 402 million hectares and represent 10% of the world’s total forest cover. Our 310 million hectares of forest include about 30% of the world’s boreal forest and more than 25% its temperate rainforest. Only a portion of the forest is managed; here, human activities as well as natural processes have a direct impact on forest carbon. Forest management includes harvesting, tree planting, and efforts to protect values at risk from disturbances such as fire and insect infestation. For carbon accounting purposes the managed forest was defined as covering 236 million hectares in Canada's 2007 national greenhouse gas inventory report.

Is Canada’s managed forest a carbon sink or source?

Throughout most of the past century, Canada’s managed forest has been a strong carbon sink, adding more and more carbon to the amount already stored. This was largely because during the first half of the 20th century, there were periods of relatively few fires and insect outbreaks (compared with the 19th century) in Canada’s forests, allowing them to grow older on average and, in the process, sequester more carbon. In recent decades, the area burned each year by wildfires has doubled, annual harvest rates have increased somewhat, and rates of carbon uptake by aging forests have slowed. These factors have decreased the average annual carbon sink provided by Canada’s managed forest over the past century.

Within the managed forest, the area burnt by forest fires varies considerably from year to year. Greenhouse gas emissions from fires can exceed removals of carbon by forest growth and dwarf carbon removals from forest management activities. According to estimates prepared by Natural Resources Canada’s Canadian Forest Service and reported in Environment Canada’s annual greenhouse gas National Inventory Report, between 1990 and 2005 Canada’s managed forest was an overall sink in all but five years (1995, 1998, 2002, 2003, and 2004). It ranged from a source of 137 million tonnes CO2e (carbon dioxide equivalents) in 1995 to a sink of 174 million tonnes CO2e in 1992. (Sources and sinks are measured in carbon dioxide equivalents, which account for emissions or removals of carbon dioxide as well as, in the case of sources, emissions of methane and nitrous oxide from forest fires.) This variability makes it difficult to detect a clear trend since 1990.

Why does the forest carbon balance fluctuate so much?

The fluctuation in the sink–source carbon balance of Canada’s managed forest from 1990 to 2005 (see question above) was closely associated with the area annually burned. In extreme fire years, like 1995, direct emissions from wildfires in the managed forest have represented up to 45% of Canada’s total greenhouse gas emissions. In Canada, wildfires started by natural phenomena such as lightning are responsible for about 85% of the area burned in the total forest (managed plus unmanaged forest). As well, since 1999, the mountain pine beetle infestation in western Canada has been increasing emissions as trees are killed and begin to decay. Harvesting had a fairly steady impact on the managed forest carbon balance; throughout most of the 1990–2005 period, the area harvested each year remained fairly stable.

How are Canada’s forest carbon sinks and sources determined?

Almost 20 years ago, scientists with Natural Resources Canada’s Canadian Forest Service (CFS) began developing a sophisticated model of Canada’s forest carbon budget. The Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) is a computer simulation model that incorporates the latest scientific understanding of the factors that affect forest carbon. It contains the best available information on forests and tree growth from resource management agencies in all of Canada’s provinces and territories (except Nunavut, which has almost no forest). Each year the CFS Carbon Accounting Team improves the model and incorporates new information to provide the latest estimates for reporting by Environment Canada in its annual greenhouse gas National Inventory Report.

HARVESTING AND FOREST CARBON

What happens to the carbon in harvested timber?

When harvesting occurs, 40-60% of the tree biomass (branches, roots, leaves) remains in the forest, where it decomposes slowly over time. At the same time, the harvested areas regenerate to become forests again so that over time there is substantial new storage of carbon. The harvested logs are sent to mills to be converted into forest products such as lumber or paper. Depending on the use and disposal of these products, the carbon may be stored for a very long time, or it may be released into the atmosphere relatively quickly.

Harvesting at Vancouver Watersheds - cable yarder and rigging In Canada, around 45–50% of the carbon harvested and removed from the forest is stored in long-lasting structures like houses. This carbon is not released back into the atmosphere until many decades later when, for instance, a house has been torn down and the wood burned or sent to landfills.

Around 25–30% of the carbon goes into less-durable products such as wooden pallets or newspapers and other paper goods that are quickly disposed of. Strategies that prolong the storage of carbon in wood products and landfills can contribute to reducing carbon emissions.

The remaining carbon (about 25%) is in the bark and leftover wood pieces, which are often used to fuel pulp and paper mills, thus providing a renewable energy substitute for fossil fuels.

How do wood products contribute to the carbon balance?

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.

How much carbon is released into the atmosphere through Canada’s harvesting?

Only a fraction of the carbon in harvested wood is actually emitted into the atmosphere (as carbon dioxide) upon harvest, or shortly thereafter. From1990 to 2005, harvesting in Canada’s managed forests resulted in an average of about 43 million tonnes of biomass carbon in branches, roots, and leaves being left in the forest each year and the transfer each year of about 41 million tonnes of biomass carbon from the forest ecosystem to the forest products sector.

The emissions of carbon dioxide from harvesting are sometimes compared with those from cars and trucks, which in Canada, from 1990 to 2005, averaged about 115 million tonnes of carbon dioxide per year. However, the timing of the biomass carbon emissions is quite different than that of the car and truck emissions, which occur immediately. The biomass left in the forest decomposes slowly, while the biomass carbon that is transferred out of the forest (equivalent to about 150 million tonnes of carbon dioxide each year) is emitted over time according to the use made of the wood. From 1990 to 2005, biomass carbon equivalent to about 65–75 million tonnes of carbon dioxide was stored in products that last for decades, such as lumber used in housing, while an amount equivalent to about 35-45 million tonnes of carbon dioxide was stored in less-durable products (including paper) and was emitted to the atmosphere in the first few years after harvest. Much of the remaining carbon was released shortly after harvest from the burning of wood waste or biofuel as a renewable source of energy.

What is the long-term impact of harvesting on forest carbon?

The long-term impact of harvesting on the amount of carbon stored in Canada’s managed forests varies depending on the region being considered and the type of forest harvested. Harvesting in old-growth forests results in “working” forests that can contain less carbon than the original old-growth forests; however, the fact that much of the harvested carbon is stored for a long time in durable forest products helps to partially offset this. In some regions, harvesting activity may to some extent replace natural fires as a major forest disturbance so that the net long-term effect on the forest carbon may be minimal. Harvesting of second-growth forest (forest that has been harvested in the past) generally will have little long-term impact on the carbon.

If the ultimate goal is to reduce the amount of carbon being emitted into the atmosphere, then the impacts of harvesting should be considered in light of carbon emissions from other sectors of the economy whose products can be used in place of forest products. Most products that are substitutes for wood products, such as aluminium, steel, and cement, require more energy to produce and consequently their production involves greater greenhouse gas emissions. As well, research is ongoing to better understand how to harvest forests and use wood products in ways that help maintain and enhance forest carbon while contributing to society’s efforts to reduce greenhouse gas emissions.

How would reduced harvesting impact forest carbon emissions?

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.

5-man crew sky lead harvesting - minimal site damage 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.

LAND-USE CHANGE AND FOREST CARBON

Does land-use change affect the forest carbon balance?

The establishment of new forests (called afforestation) on abandoned agricultural land or other non-forest areas increases the forest area and creates a carbon sink while the new forest grows. If the new forest is maintained, it becomes a long-term store of carbon. It will eventually also have more trees that can be harvested sustainably, thus increasing the amount of wood available to meet society’s needs.

In contrast, deforestation—the permanent clearing of forest for non-forest land uses—causes considerable carbon dioxide emissions. With less forest area remaining, long-term sustainable harvest levels decrease. Globally, the carbon dioxide released through deforestation, mostly in tropical forests, accounts for about 20% of human-caused greenhouse gas emissions, more than what accumulates from all modes of transportation. Reducing deforestation would therefore be one effective way to reduce human emissions of greenhouse gases.

What is the relationship between harvesting and deforestation?

Harvesting removes trees from the forest, but when sustainable forest management is practised, as in Canada, the forest is immediately encouraged to regrow. In many parts of Canada, regrowth following harvesting is actively assisted by tree planting programs. Provinces have legislated standards to ensure that forests are regrown following harvest on public lands. In contrast, deforestation is the permanent clearing of forest and conversion of the land to another land use, such as agriculture, roads, or municipal development, which does not involve forest.

How much does land-use change in Canada contribute to carbon emissions?

In Canada, the creation of new forests does not occur on a large scale—around 9,000 hectares of afforestation occurs each year. This relatively small area results in the removal from the atmosphere of around 1 million tonnes of carbon dioxide each year, and this will slowly increase over time as new trees grow.

Deforestation has a bigger impact, but this is still quite small on a global scale. The area deforested annually in Canada has fallen from 70,000 hectares in 1990 to 56,000 hectares in 2005. The emissions in 2005 were 21 million tonnes of carbon dioxide equivalents, or CO2e, down from 29 million tonnes in 1990. Conversion of forest for agricultural purposes accounted for over half of the deforested area; other major causes were urban expansion, industrial development, and resource extraction.

CLIMATE CHANGE AND FOREST CARBON

Does climate play a role in the forest carbon balance?

Yes, climate plays an important role in the forest carbon balance. The productivity of forests and the distribution of forest carbon in biomass, dead organic matter, and soils are affected by climate. Forests in warmer regions grow faster than those in colder areas and store a higher proportion of their carbon in living biomass (as opposed to dead organic matter). In colder regions, trees tend to grow more slowly, but dead organic matter decomposes even more slowly. As a result, less forest carbon is stored in living biomass in colder regions, while a larger proportion is stored in dead organic matter and soils.

Variations in weather from year to year also affect the carbon balance. Carbon uptake levels and decomposition rates vary with temperature and precipitation, as do rates of disturbances like wildfire and insect infestations that can cause carbon losses over large regions.

How will climate change affect the future forest carbon balance?

Mountain pine beetle Climate change is expected to have a profound impact on the carbon balance of Canada’s forests. The biggest short-term impacts will result from changes in disturbance regimes. For example, scientists at Natural Resources Canada’s Canadian Forest Service predict that the forest area annually burned in Canada is likely to double by the end of the century, resulting in large emissions of carbon. More frequent and longer lasting droughts are expected to contribute to this increase. Similarly, increases in the area and intensity of insect outbreaks are expected to cause carbon losses. Already, climate change, in the form of warmer winters, has contributed to the major infestation of the mountain pine beetle in British Columbia and its recent spread over the Rocky Mountains into Alberta. A key question is whether the insect will be able to expand its range through Canada’s boreal forests.

Some aspects of climate change, such as longer growing seasons or greater concentrations of carbon dioxide in the atmosphere, are expected to increase tree productivity (at least initially). A warmer, wetter climate may also enhance decomposition rates. Northern regions of Canada are expected to warm faster than more southerly areas, resulting in the melting of permafrost; this may release methane from frozen soils and initiate decomposition of previously frozen organic carbon.

What will be the effect of other global changes on forest carbon?

Air pollution has an impact on forests. Human activities, such as the burning of fossil fuels, release nitrogen into the air, which then falls on forests. Where natural nitrogen is in limited supply, this nitrogen deposition may cause accelerated tree growth. On the other hand, increased ozone and some other air pollutants may reduce tree productivity.

Another impact comes from global trade. With increases in the volume of trade, the broadening of trading partners, and direct point-to-point delivery of shipments, Canadian forests are more likely to come under attack from invasive alien pests.

At present, it is difficult to predict the combined impact on the forest carbon balance of the many global changes resulting from human activities. Carbon stocks will increase in some forest regions and decrease in others. How forests are managed may need to change in response to global changes; this is especially true of climate change, although strategies for adaptation may mitigate its effects somewhat. What is certain at present is that climate change and other global changes increase uncertainty about the future of Canada’s forest carbon. These issues are the subject of ongoing research at Natural Resources Canada’s Canadian Forest Service.

FORESTS, CLIMATE CHANGE MITIGATION AND THE KYOTO PROTOCOL

How are forests treated in the Kyoto Protocol?

Under the 1992 United Nations Framework Convention on Climate Change, 191 nations, including Canada, have committed to actions to stabilize “greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic [human] interference with the climate system.” In the Kyoto Protocol to the Convention, developed countries further agreed in 1997 to limit their greenhouse gas emissions in 2008–12 relative to their 1990 emissions. Under the Protocol, the 36 participating developed countries must report and account for their greenhouse gas emissions from afforestation and deforestation. They also have the option of including emissions and removals from forest management, cropland management, grazing land management, and revegetation in their annual reporting and accounting.

What was Canada’s position on forests in the Kyoto Protocol?

Fighting fires in British Columbia Canada negotiated vigorously to ensure that countries participating in the Kyoto Protocol (the “Parties”) had the option of including forest management when accounting for greenhouse gas emissions and removals. The Canadian government believed this option would be an incentive for Parties to focus on reducing carbon dioxide emissions from and increasing the carbon uptake in forests, which would ultimately support sustainable forest management. At the same time, the government believed it might also help Canada meet its commitments for emission limitations and reductions under the Protocol. However, because forests are often subject to fires and insect infestations, which release carbon dioxide, Canada’s managed forest could also be a carbon source. For that reason, Canada supported the inclusion of forest management in the Protocol as an option rather than a requirement. This allowed more time to analyze and better understand how forest management would affect Canada’s Kyoto accounting.

How did Canada decide whether to include forest management in its Kyoto accounting?

Natural Resources Canada’s Canadian Forest Service (CFS), in cooperation with resource management agencies in all provinces and territories (except Nunavut, which has almost no forest), conducted a detailed analysis to determine whether Canada’s managed forest was likely to be a sink or source from 2008 to 2012, the commitment period under the Kyoto Protocol. Such projections are difficult because it is impossible to determine today what area will be burned or subject to insect infestations in the future, yet these factors greatly affect whether the managed forest will be a sink or source. As a result, the CFS and its partners decided to use an analytical technique that assigns probabilities to the likelihood of future disturbances by wildfires and major forest insects, based in part on historical fire and insect patterns. They also factored in how forest management activities such as harvesting, planting, and salvage logging after natural disturbances would affect the forest carbon balance. The sophisticated CFS Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) was used for the analysis.

Why did Canada not include forest management in its Kyoto accounting?

The results of the analysis (see previous question) indicated that there was a greater than nine in ten chance that Canada’s managed forest would be a source of greenhouse gases in the period 2008–12. Although these forests have usually been a sink in the past, predictions for the near future indicate diminishing strength as a sink due to the impacts of wildfire, insect outbreaks (such as mountain pine beetle in western Canada and anticipated outbreaks of spruce budworm in eastern Canada), and increased salvage logging as a result of these disturbances. As well, Canada’s managed forest is fairly old and its uptake of carbon is therefore less than that of a younger forest. Many of these factors are beyond the direct control of forest managers—for example, it is impossible to try to fight all forest fires in the managed forest; some fires and some insect infestations cannot be kept in check no matter what resources are directed toward fighting them. Thus, the projected high risk of the managed forest being a source in the 2008–12 period is not the result of poor management, but rather reflects the fact that natural disturbances (past and future) will often dominate the outcome of whether Canada’s forests are a net sink or source.

Based on the analysis, the federal government, in consultation with provincial and territorial governments, decided not to include forest management in Canada’s Kyoto Protocol accounting. This does not mean that Canada can ignore the potential of forests and forest products in its efforts to limit greenhouse gas emissions. Forest management activities and the storage of carbon in harvested wood products can help reduce emissions and increase removals.

Will the international rules for forest carbon accounting change in the future?

Yes, they likely will change. The Kyoto Protocol rules and targets apply to the 2008–12 period and the international community will need to agree on rules for the post-2012 period. From Canada’s perspective, the current treatment of managed forest carbon has two problems. One is that the Kyoto rules do not focus just on the impacts of human management activities on forests. Instead, the rules require countries to define the area of forest that is subject to management (including parks, for example) and to then account for greenhouse gas emissions and removals in those forests, regardless of the causes for the emissions. Large natural fires and insect infestations take place in Canada’s forests and the rules require that all the resulting emissions must be included in the accounting. Although management activities can reduce emissions (such as through fighting fires) or increase carbon removals (such as by increasing tree growth rates), in many years the natural effects can far outweigh the effects of management.

Fletcher Paper Mill - making yellow directory paper A second problem is the treatment of carbon in harvested wood products. Under the Kyoto rules, it is assumed that each year the additional carbon stored in new products is balanced by the emissions from the disposal and decay or burning of old products. In fact, this is not accurate because each year there is a net increase in the amount of carbon stored in harvested wood products. This means that the rules overestimate the emissions produced by harvesting. The rules also assign these emissions to the country in which the wood is harvested, not to the country in which the emissions actually occur or will occur. Both aspects of the rules for the treatment of harvested wood products are problems of particular importance for a country like Canada, which is one of the world’s major producers and exporters of products like lumber, panels, and paper.

Canada and other countries will seek to improve the rules for how forest carbon is counted in the post-2012 period, so that the rules result in positive incentives for sustainable forest management, but do not punish or reward countries for emissions and removals that are out of their control.

Can the forest sector help mitigate climate change?

Yes, forest management activities and the use of forest products can contribute to reductions in greenhouse gas emissions. As a result, developing a portfolio of mitigation options is the subject of ongoing research at Natural Resources Canada’s Canadian Forest Service. In the short term, it is most effective to seek emission reductions, for example, through decreases in deforestation, protection against fire and insects, and the use of site preparation methods that conserve carbon, such as avoiding the burning of logging slash. In the long term, increasing the forest area through afforestation and reforestation and implementing management decisions that increase forest carbon stocks, such as lengthening rotations and ensuring prompt regeneration after harvest and disturbances, can also contribute to increased forest carbon stocks. Appropriately designed carbon management strategies are consistent with the principles of sustainable forest management.

The design of the most effective mitigation portfolio must also consider the contribution of harvested biomass. Wood products provide services to society with considerably lower carbon emissions during production than other, more energy-intensive products such as concrete, steel, aluminium, and plastics. Energy derived from wood fuels and wood residues, including black liquor from the production of pulp and paper, is used as a substitute for energy from fossil sources. The evaluation of mitigation options that involve increased storage of carbon in forest ecosystems and the use of harvested biomass is ongoing. In the long run, the greatest mitigation benefits can be achieved by finding the right balance between maintaining and increasing forest carbon stocks while producing an annual yield of timber, fibre, and energy from forests.