Map is first to track global human influences on ocean ecosystems

"For some human activities, we have global data, like commercial fisheries catches," Micheli said. "For others, we developed models to estimate global impacts." The team consulted marine scientists and dug into years of literature describing human effects on different ecosystems, such as coral reefs, rocky reefs and deep, open waters. They developed a system to quantify how powerful each human influence is, and how fragile each ecosystem is. To map the damage, Micheli and her colleagues divided the ocean into 1-square-kilometer "cells." They determined the impact to each cell by what human activities have touched it, how forceful that touch has been and which ecosystems are there.

Their results suggest that coral reefs are in trouble; nearly half have taken a hard human punch. Other spots of concern include seagrass beds, mangrove forests in estuaries, seamounts, rocky reefs and continental shelves. Soft-bottom shallow and deep ecosystems, as well as the open ocean, fared best, though even they were not pristine in a majority of locations.

The study also shows that human influence runs deepest in the North Sea, the South and East China Seas, the Caribbean Sea, the Mediterranean Sea, the Red Sea, the Persian Gulf, the Bering Sea, along the Eastern Coast of North America and in much of the western Pacific. The oceans around the Artic and Antarctic poles have been affected very little, but the dwindling polar ice sheets will leave them vulnerable in the future, research suggests. Very limited impacts are also seen around northern Australia, in areas across the western-central Pacific and in small areas scattered along the coasts of South America and Africa. These estimates of human impact are probably optimistic, Micheli said. The study did not account for historical impacts to the oceans whose traces might still linger, and it did not include all possible impacts to marine ecosystems, only the 17 for which data were available or could be modeled.

The worldwide impact map is a scaffold, which should be filled in with on-the-ground research, Micheli said. "Globally, it's important to see what the most impacted areas are and where are the last wildernesses," she said. "Our results and approach, augmented with additional local information, can also inform management at a local and regional scale. Looking at the data globally, some information is lost."