Events & Media

Humans’ Rising Impact on the Oceans
A new global study identifies areas of promise, but also many more areas of concern

Santa Barbara, CA — Human impacts on the oceans have increased in more than two-thirds of the world during the past five years, though some areas remain lightly impacted, and still others are improving. Those and related findings are detailed in a paper co-authored by Bren School professor Ben Halpern and published today in the journal Nature Communications.

Ben Halpern

In “Spatial and temporal changes in cumulative human impacts on the world’s oceans," Halpern, lead author, and his ten co-authors, all members of a working group at the UCSB National Center for Ecological Analysis and Synthesis (NCEAS), address the widely acknowledged fact that humans are having a large and growing impact on the world’s oceans. But in this study, the researchers went after more detail, specifically trying to add what they describe as an “important spatial component to our understanding of trends in ocean condition” by identifying specific areas that are experiencing the greatest increase in impacts, and what kinds of factors are causing the change. Read the paper.

Many past studies have used the methods developed by Halpern and colleagues to identify cumulative impacts in freshwater and saltwater bodies around the world, but, the authors write, “Missing from these studies is an assessment of the location and intensity of change in cumulative impacts over time.

The researchers calculated and mapped five years of global change in cumulative impacts to marine ecosystems for 19 different types of human stressors and 20 types of global marine ecosystems. The stressors fall into four main categories: climate change (including ultraviolet radiation, ocean acidification, and sea-level rise); commercial fishing; land-based pollution; and shipping activities plus oil and gas development.

They found that nearly 66 percent of the ocean and 77 percent of the ocean within national jurisdictions shows increased human impact over the five-year study period, driven mostly by climate change pressures, leaving just 13 percent of the ocean within national boundaries experiencing unchanged or decreasing impacts. Further, approximately 5 percent of the ocean is heavily impacted and experiencing increasing pressures, while 10 percent has experienced low impact to date and is seeing decreasing pressures.

The group identified four main trends in ocean areas lying both within and beyond national jurisdictions:

  • Areas that have the highest impact and also the highest increase in impact, a condition that sounds the alarm for immediate management action.
  • Areas that have the highest impact but also the greatest decrease in impact, perhaps suggesting a management success story.
  • Areas that have the lowest impact but the highest increase in impact, indicating the need for immediate action to prevent losing a pristine area.
  • Areas of lowest impact that also have the lowest increase in impact, which may require either no action or preemptive action to maintain that favorable situation.

“The power of this approach is that it’s a flexible, multi-faceted tool that can be applied to many questions,” Halpern says. “You can identify the largest stressor in an area and which actions decrease it the most. You can start to identify which stressors should get the most attention.

“If pressure is coming from climate change,” he elaborates, “there’s much less you can do locally; you need national policy or an international agreement. But if the impact is from shipping, you can move shipping lanes. If the impacts are from fishing pressure, we have a well-developed set of tools to deal with that at a local or regional scale. We are coming back to this after five years because it’s such a powerful tool not just for answering questions about impacts but also for informing and guiding policy and management decisions at any scale, from local to global."

"Our work illustrates how greatly human impacts in the oceans may vary are across space and time,” said Elizabeth Selig of Conservation International, a partner on the project. The framework that we use and our results can help to identify where management is needed and where it has been successful. Those are critical inputs for planning better stewardship of our ocean resources."

“As the scope of global change increases, frameworks like ours that rapidly collect, visualize, and track where and how those changes are impacting ecosystems will become central to prioritizing policy and conservation actions," added co-author Kim Selkoe, who is affiliated with NCEAS and the Hawaii Institute of Marine Biology.

The project was a five-year follow-up to its high-impact forerunner, which has been cited extensively and influenced marine resource management around the world. The method has become integral to the European Union’s approach to assessing ocean resources.

Halpern said that, given the steady stream of bad news about the health of the world’s oceans, the researchers were surprised at some of the bright spots.

“Based on the news and science we read daily about global patterns of human activity, we kind of assumed everything would be getting worse,” he said. “But we found that there are places where the pressures are stable or decreasing. Also, while some climate change impacts are getting worse globally, at the regional scale, some places are seeing a reduced impact of climate change.”

The upper map shows which areas of the world have seen ocean impacts increase, decrease, or remain stable over the past five years. The lower map illustrates the level of impacts (from low to high), as well as whether those impacts are increasing, decreasing, or remaining stable.


The Bren School of Environmental Science and Management at the University of California, Santa Barbara, is home to an interdisciplinary graduate program focused on environmental problem solving through the integration of science, management, law, economics, and policy. Offering both a professional Master of Environmental Science and Management degree and a PhD track, the school’s mission is to play a leading role in researching environmental issues, training scientists and environmental management professionals, and identifying and solving environmental problems around the world. It is ranked among the top four programs of its kind in the nation and is the only such program in the western United States. For more information, go to