According to new research carried out by scientists at Stanford University and the National Autonomous University of Mexico, preserving just 4 percent of the ocean could protect crucial habitat for the vast majority of marine mammal species, from sea otters to blue whales.

The findings were published in the August edition of the Proceedings of the National Academy of Sciences. Of the 129 species of marine mammals on Earth, including seals, dolphins and polar bears, approximately one-quarter are facing extinction. To pinpoint areas of the ocean where conservation could protect the maximum number of species and the ones most vulnerable to extinction, the researchers overlaid maps of where each marine mammal species is found. Their composite map revealed locations with the highest "species richness" - the highest number of different species. It's the first time that the global distribution of marine mammal richness has been compiled and presented as a map, results showed that all of the species can be represented in only 20 critical conservation locations that cover at least 10 percent of the species' geographic range.The researchers identified the 20 conservation sites based on three main criteria: how many species were present, how severe the risk of extinction was for each species and whether any of the species were unique to the area. The scientists also considered habitats of special importance to marine mammals, such as breeding grounds and migration routes.

It turned out that preserving just nine of the 20 conservation sites would protect habitat for 84 percent of all marine mammal species on Earth because those nine locations have very high species richness, providing habitat for 108 marine mammal species in all. These nine sites, which make up only 4 percent of the world's ocean, are located off the coasts of Baja California in Mexico, eastern Canada, Peru, Argentina, northwestern Africa, South Africa, Japan, Australia and New Zealand. The researchers also looked at how pollution, local climate disruption and commercial shipping overlapped with species richness in or near the nine key sites.

While nine of the conservation sites harbor numerous marine mammal species, the remaining 11 sites boast species found nowhere else. Preserving these areas is important, because species that live exclusively in one place may be at especially high risk for extinction, the authors said. For example, the critically endangered vaquita, or gulf porpoise, lives only in the upper northern Gulf of California, and only a few hundred individuals remain so this was a worthwhile study indeed.