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Mapping Human Impacts on the Ocean

Impacts on the rise...

Ocean acidification, climate change, habitat destruction, over-fishing, pollution….  with a whirlwind of headlines and reports over the last few decades, it is no secret that human pressures on the ocean have led to a serious decline in ocean health globally. As our human population continues to grow and develop in coastal regions (by 2020, it is projected that about 6 billion people will live in coastal areas—60 percent of the world’s population--) increasing demand for ocean resources and consequent pressures from human activities.

While our overall impact on oceans is clear, which pressures cause the most change and what areas are experiencing the highest impact has not been as evident, until recently.


a. Representsthe difference between current (as of 2013) and earlier (as of 2008) cumulative impact scores based on anthropogenic stressors that can be compared across time. Red represents the highest impact level and blue the lowest impact level. Red areas have experienced greatest increases in cumulative impacts.

b. Represents combinations of cumulative impact and trend that includes areas with combinations of highest and lowest levels of impact already experienced with increasing and decreasing levels of impact.  Dark red areas have both high cumulative impacts and increasing rate of impacts.

A paper published in Nature Communications, “Spatial and temporal changes in cumulative human impacts on the world’s ocean” by Ocean Health Index’s lead scientist, Ben Halpern and 10 co-authors, including six from the Ocean Health Index team at the University of California, Santa Barbara and two from the team at Conservation International has calculated and mapped changes in 20 marine ecosystem types over five years caused by 19 anthropogenic stressors including climate change, fishing, and ocean and land based stressors. 

Identifying the degree to which different regions and ecosystems are affected, where impacts overlap with biodiversity hotspots  and which human-caused pressures are most harmful will help managers and policy makers make more strategic decisions for management objectives and overall conservation efforts.

Top findings

  • Almost 66 percent of the ocean showed increases of cumulative impact, mostly in tropical, subtropical and coastal regions. The French Territorial holdings in the Indian Ocean, Tanzania and Seychelles showed the most dramatic average increases.
  • National waters currently experiencing highest levels of impacts are Singapore, Jordan, Slovenia and Bosnia.  Most impacted coastal eco-regions include the Faroe Islands, Eastern Caribbean, Cape Verde and Azore Islands.
  • 13 percent  of the ocean experienced decreased impacts, mostly in the Northeast and Central Pacific and Eastern Atlantic. EEZ’s of several South Pacific Islands, the Alaskan coast, and several European countries (Slovenia, Albania, Denmark and Netherlands) showed the greatest average decreases.

Cumulative Impact scores for 2013, shown above, are based on all 19 anthropogenic stressors. Areas of permanent sea ice are shaded white and the area within maximum sea ice extent is masked to indicate where scores are less certain because change in sea ice extent could not be included.

  • Increases in climate change stressors (sea surface temperature anomalies, ultraviolet radiation, ocean acidification) caused  the highest increases in cumulative impact.

  • Impacts from 4 of 5 types of commercial fishing showed decreases of 70-80%.

  • All land-based stressors increased globally but were mostly concentrated in coastal areas of only 27 – 52 percent of all EEZ’s.

 The above findings confirm that “no part of the global ocean is without human influence” and that almost the entire ocean experiences multiple pressures.

However, mapping cumulative changes provides an opportunity for improved guidance to prioritize management efforts, show where mitigation is needed most, and also highlight what current management practices are creating positive change.

--See full article

Halpern, B. S., M. Frazier, J. Potapenko, K.S. Casey, K. Koenig, C. Longo, J. S. Lowndes, R. C. Rockwood, E.R. Selig, K. A. Selkoe and S. Walbridge. 2015. Spatial and temporal changes in cumulative human impacts on the world’s ocean.  Nature Communications, 6, 7615. http://doi.org/10.1038/ncomms8615

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