Map reveals heavy human hand on oceans
The first-ever map of threatened marine areas can be used to target management efforts.
More than 40% of the world's oceans now suffer medium-high to very high impacts from human-induced threats such as global warming and ocean acidification, according to an international study published online February 14 in Science (2008, 319, 948–952). For the first time, the research maps the most threatened marine ecosystems and pinpoints the causes of the declines. The results will help in efforts to manage and conserve ocean resources.
View larger image
Led by Benjamin Halpern at the National Center for Ecological Analysis and Synthesis, the researchers compiled global databases of 17 human-driven threats, including polluted runoff and habitat destruction. They overlaid these maps with habitat data sets for 20 ocean ecosystems, including coral reefs, rocky continental shelves, and mangrove swamps.
But rather than simply mapping the footprints of human activities, the team dug deeper to calculate weights for impacts that take into account the intensity and number of the drivers at any one locale and the relative sensitivity of the ecosystem. The impact weight calculation produced scores that were divided into six levels of human influence, ranging from very low to very high impact. The results revealed that every square kilometer of the world's oceans is touched by some human-caused ecological change.
The most common threat is elevated ocean temperature, which can cause disease outbreaks and bleaching of coral reefs. "Coral reefs provide hundreds of millions of dollars in ecosystem services, such as protecting coasts from storms and sustaining fisheries," says Elizabeth Selig, a marine ecologist at the University of North Carolina (UNC) and a coauthor of the paper. Selig and her colleagues John Bruno of UNC and Kenneth Casey of the National Oceanic and Atmospheric Administration produced the first high-resolution map of ocean areas experiencing unusually high temperatures and showed that nearly half of the world's reefs are being hit by medium- to high-level impacts.
"The map allows us to determine where stressors interact so that we can set conservation priorities and design effective management interventions," Selig says. For example, decision makers can use the map to shift fishing zones or shipping lanes away from sensitive ecosystems.
