The Human Impact on Marine Systems

Fig. 1 from Halpern et al. Global map (A) of cumulative human impact across 20 ocean ecosystem types. (Insets) Highly impacted regions in the Eastern Caribbean (B), the North Sea (C), and the Japanese waters (D) and one of the least impacted regions, in northern Australia and the Torres Strait (E).

ResearchBlogging.orgSome readers dialed into the news might wonder why we have not blogged on a recent paper in Science by Halpren et al. In the paper the authors set out to provide a “synthesis of spatial data on the distribution and intensity of human activities and the overlap of their impacts on marine ecosystems” to “provide flexible tools for regional and global efforts to allocate conservation resources; to implement ecosystem-based
management; and to inform marine spatial planning, education, and basic research.” Indeed this is the first attempt to assess our global footprint on the oceans. The delay results from my want to contemplate the implications of the paper and the model itself. With any model there are assumptions that can affect the model output and the conclusions we draw from it.

The study focuses on multiple impacts including: Nutrients (fertilizer); Organic pollutants (pesticides); Inorganic pollutants (impervious surfaces); Direct human (population density); Pelagic, low-bycatch fishing; Pelagic, high-bycatch fishing; Demersal, destructive fishing; Demersal, non-destructive, low-bycatch; Demersal, non-destructive, high-bycatch fishing; Artisanal fishing; Oil rigs; Invasive species; Ocean pollution; Shipping; Seasurface temperature; UV; and Ocean acidification. Overall an impressive list with substantial effort that produces the above map. Mark Spalding, a Nature Conservancy marine scientist who coauthors the study, states “I think the big surprise from all of this was seeing the complete coverage of human impacts…There’s nowhere really that escaped. It’s quite a shocking map to see.” Over 41% of the oceans are strongly impacted. Overfishing and climate change remain the two biggest threats.

Several habitats are given impact scores with a medium high score being near 4. The average across all localities for each habitat are: Coral Reefs (3.88), Seagrass (3.10), Rocky reefs (4.75), Hard Shelf (6.89), Hard Slope (2.64), Hard Deep (2.77), Pelagic Waters (2.76), Mangroves (4.30), Seamounts (3.10), Soft Shallow (1.52), Soft Shelf (4.68), Soft Slope (2.97), Soft Deep (3.79), Deep Waters (1.04). My only concern with this otherwise impressive study is the even weighting of effects across all habitat types that is applied. To clarify, as I understand, the model assumes the same fishing intensity produces the same impact irrespective of habitat. We know this not to be the case as deep-water fisheries are more sensitive due to slow growth, increased longevity, and overall lower densities. Several other examples could be drawn upon where different habitats have differential affects to the factors above (e.g. coral reefs and acidification). How are the numbers affected by this assumption? Despite this, the study provides a baseline that can be refined and points to future research priorities.

Halpern, B.S., Walbridge, S., Selkoe, K.A., Kappel, C.V., Micheli, F., D’Agrosa, C., Bruno, J.F., Casey, K.S., Ebert, C., Fox, H.E., Fujita, R., Heinemann, D., Lenihan, H.S., Madin, E.M., Perry, M.T., Selig, E.R., Spalding, M., Steneck, R., Watson, R. (2008). A Global Map of Human Impact on Marine Ecosystems. Science, 319(5865), 948-952. DOI: 10.1126/science.1149345

Dr. M (1801 Posts)

Craig McClain is the Executive Director of the Lousiana University Marine Consortium. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Additionally, Craig is obsessed with the size of things. Sometimes this translated into actually scientific research. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (, a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web.