Cumulative Effects Assessment, Management and Monitoring

Cumulative effects are changes in the environment caused by multiple interactions among human activities and natural processes that accumulate across space and time. Stressors are actions or events that put stress on the environment and cause changes. They can be natural events such as forest fires or floods, human actions such as land clearing or pollutants and long-term effects such as climate change.

One stressor alone may have a minor effect. Together, many stressors can add up and cause cumulative effects. An important aspect of understanding cumulative effects is to identify the appropriate stressors. Cumulative effects assessment, management and monitoring are ways to do this. Understanding cumulative effects and their stressors are key to avoiding or minimizing impacts.

Assessment and Management

A cumulative effects assessment is the systematic method of identifying, analyzing, and evaluating cumulative effects. Before undertaking an assessment, it is necessary to identify valued components. Valued components are any part of the environment that are considered important by participants in the process, such as water, species at risk or human health. A cumulative effects assessment examines how stressors affect valued components. For example, a cumulative effects assessment could examine how forest fires, land clearing and climate change affect caribou. Consideration of cumulative effects is also part of the Government of Canada’s new impact assessment process.

Governments, industry and many different organizations can be involved in cumulative effects management, which identifies and implements measures to prevent, minimize, or control the adverse consequences of cumulative effects.


Environmental and cumulative effects monitoring tracks and identifies how valued components change over time. Monitoring can be part of cumulative effects assessments or management, and can be useful to:

  • provide early warning of unintended effects
  • find evidence of changes to the environment
  • help inform appropriate management options

For example, the Canada-Alberta Oil Sands Monitoring program works to provide comprehensive environmental monitoring data and information to improve understanding of the long-term cumulative effects of oil sands development.

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