Biological Diversity Ecosystem Condition and Productivity Soil and Water Role in Global Ecological Cycles Economic and Social Benefits Society's Responsibility
Indicator 2.1 Total growing stock of both merchantable and nonmerchantable tree species on forest land Indicator 2.2 Additions and deletions of forest area by cause Indicator 2.3 Area of forest disturbed by fire, insects, disease, and timber harvest Indicator 2.4 Area of forest with impaired function due to ozone and acid rain Indicator 2.5 Proportion of timber harvest area successfully regenerated
Indicator 2.1 Total growing stock of both merchantable and nonmerchantable tree species on forest land
Indicator 2.2 Additions and deletions of forest area by cause
Indicator 2.3 Area of forest disturbed by fire, insects, disease, and timber harvest
Indicator 2.4 Area of forest with impaired function due to ozone and acid rain
Indicator 2.5 Proportion of timber harvest area successfully regenerated
References

The sustainable development of our forest ecosystems depends on their ability to maintain ecological functions and processes and to perpetuate themselves over the long term. Relative freedom from stress (stability) and relative ability to recover from disturbance (resilience) within a forest ecosystem indicate ecosystem condition. Productivity refers to the ecosystem’s ability to accumulate biomass, which depends on the degree to which nutrients, water, and solar energy are absorbed and transferred within the ecosystem.

Canada’s forest ecosystems have evolved to cope with, and recover from, most natural disturbances, be they insects, diseases, or wildfires. Some of these disturbances, such as wildfires in the boreal forest, even play a key role in forest renewal. This relationship between forests and disturbances has been ongoing for eons, allowing forests to renew themselves and maintain their productivity.

Humans have brought a new variable to the equation and generated new disturbances, such as harvesting, deforestation for urban and agricultural development, and pollution. These new stressors have come at an intensity, rate, and scale that sometimes exceed the natural rate of change typically experienced by forests.

To ensure the sustainability of Canada’s forests, it is therefore important to determine whether forests have the capacity to cope with the total impact of various stressors—both old and new. If forests cannot adapt to these stressors, they will lose their ability to maintain ecological functions and processes, leading to a loss of forests over the long term.

Natural disturbances still vastly exceed harvesting in terms of the area disturbed. From 1975 to 2005, fires consumed an average of 2.3 million ha per year. The area disturbed by wildfire shows no notable trend, although there is considerable year-to-year variation. From 1975 to 2004, the average area affected by insects was almost 24 million ha per year, although there has been a substantial decline in the total area since the 1970s. If the predictions from climate change models are accurate, disturbance from fire and insects could increase significantly in the future. There is currently very little information on the volume of wood affected by natural disturbances.

The total growing stock of merchantable forests in Canada is estimated at 29 billion m3, of which about 0.6% is harvested each year. Temporary removal of forest cover through harvesting averages around 900 000 ha per year and has been relatively stable for several years. Estimates of the annual area of forest permanently converted to nonforest in Canada for reasons such as urbanization, agriculture, and forestry road construction are being improved, and range from about 55 000 to 80 000 ha per year. Research efforts are underway to clarify the real impacts of pollutants such as acid rain and ozone on forests, which slowly degrade forests over many years. Although precise estimates of the area affected are not available, it is clear that forests in southern British Columbia, the Windsor–Québec corridor, and southern Atlantic Canada require careful monitoring because of their proximity to pollution emission sources. In recent years, governments have taken steps to reduce pollution emissions.

Forest managers have adopted lower impact forestry practices over the years on the basis of the best available research data. Modified harvesting methods can be used to protect naturally regenerating trees for instance. Overall, forest regeneration has also been highly successful in Canada, especially since the 1990s when most jurisdictions passed legislation or signed agreements that require logging companies to ensure regeneration on sites they harvest. The area of nonstocked forest is slowly decreasing and forests regenerate naturally from harvesting in 85% of cases. Afforestation is low (only about 6000 to 10 000 ha per year).

It is still difficult to ascertain whether forests have the capacity to cope with the current total impact of various stressors. However, the success of regeneration efforts, combined with low-impact forestry practices, pollution controls, and afforestation, provides hope that Canada will be successful in maintaining the integrity and productivity of its forest ecosystems.