Picture five oil rigs in your nearby ocean. These oil rigs are different sizes and operate in different locations and at different times. Each of these rigs has an impact on marine life and water quality, but each to a different degree.

When the individual impacts of each of these rigs accumulate over time and space, it is known as “cumulative effects.” Think of this like a snowball fight. It’s easy to dodge snowballs when you’re up against one other person.  But when five people are throwing snowballs at you, it’s much harder to avoid getting hit. And the more hits you take, the more bruises you’re bound to get.

Cumulative effects recognizes that the impact of an individual action may be relatively minor on its own, but could be much more significant when considered in combination with the effects of other past, present and future actions. Effective assessment of cumulative effects is one of the most challenging issues in resource management.

As the pace and scope of industrial activity in Arctic Alaska grows, the need to predict and account for the cumulative effects of oil exploration and development and increasing vessel traffic—including infrastructure and operations—becomes more critical. To avoid or minimize environmental degradation caused by industrial activities or accidents such as oil spills, federal agencies need a reliable way to assess the cumulative effects of proposed actions on the surrounding environment.

This is not an easy task, especially when dealing with multiple decisions that affect large areas over long time periods. The rewards, however, are significant: by understanding and considering the long-range impact of multiple activities over a large spatial area, industry, government regulators, communities and stakeholders may be able to better manage oil exploration and development in Alaska’s Arctic Ocean to avoid or minimize environmental harm.

Unfortunately, the Bureau of Ocean Energy Management (BOEM), the agency that manages offshore conventional and renewable energy resources (think offshore oil rigs and wind turbines), has not done a good job of analyzing potential cumulative effects in the Arctic in past environmental reviews.

For example, when assessing the cumulative impacts from an Arctic lease sale, BOEM reasoned that because there were 11 existing offshore projects, the proposed project would contribute approximately one-tenth the cumulative effects of waste water, construction, transportation and oil spills influencing water quality. Here, BOEM divided the number of proposed offshore projects (one) by the total number of offshore projects (11) to assess cumulative impact of oil development activities to water quality (=1/11).

This is a deeply flawed approach. Under this logic, each successive project would be responsible for incrementally less impact. With 100 projects, the new proposed project would only be responsible for 1/100 of the impact—but the cumulative effect of 100 projects would likely be far greater than the impacts of 10 projects. Also, this approach doesn’t account for the scale and location of each offshore facility, which are important factors to assessing harm. Combining all of the offshore projects together into a percentage masks the damages to the surrounding environment from a single offshore facility.

One major stumbling block for BOEM is the lack of a standardized approach and methodology for conducting cumulative effects analysis. BOEM can significantly improve its analysis of cumulative effects by developing and adhering to a standardized approach and methodology to cumulative effects analysis. Development of a transparent, broadly accepted approach and methodology for cumulative effects analysis, with common language and accounting for regional factors, will allow the agency to compare results across different planning areas.

A standardized approach and methodology that considers both positive and negative tradeoffs will provide BOEM with structure and guidance in analyzing cumulative effects. Recognizing the importance of cumulative effects, a governmental working group recommended improved understanding and consideration of the cumulative impacts of human activities in the Arctic.

The future health of sensitive Arctic ecosystem depends upon the use of sound analysis to determine the true impact of industrial activities. And good policies should be grounded in good science and analysis.