Human impact on marine ecosystems

I admit it. I'm a plant biologist, and I think almost entirely about terrestrial ecosystems. But most of the planet is covered by water, and most of it's salty, so it's important to know how the world's marine ecosystems are doing. That's what Benjamin Halperin and his colleagues try to tell us in today's Science (subscription required).

There's good news and bad news in the results. The bad (but unsurprising) news is that all parts of the ocean are affected by human activities and that 41% of the oceans (by area) are heavily affected. The good news is that large areas remain relatively unaffected, especially near the poles. But as the figure to the left illustrates northern Australis is also relatively free of major impacts.

The analysis also identifies a few ecosystem types that have been especially hard hit: coral reefs, seagrass beds, mangroves, rocky reefs and shelves, and seamounts. To put it another way, the marine ecosystems most greatly altered by human activities are those in coastal regions. That's no surprise, since that's where people are. What may be a surprise is that the most heavily affected areas aren't necessarily near the greatest population concentrations. Look at the big, red area in the North Sea or the red areas around Iceland, for example. The impact we're having on marine environment clearly depends on how they're being used, not merely how many people live nearby. That gives me hope. It means we may be able to find ways to reduce our impact without threatening the livelihood of those who live near the world's oceans.

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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