The study by scientists from Dundee and Portsmouth universities looked at the importance of individual species instead of the more traditional method of counting the number of species.
The report, in the journal Nature, says the most devastating effects of pollution, over-fishing and other human pressures might be seen not in the regions where most conservation efforts are carried out but in areas with fewer species, such as the seas around the UK.
Professor Terry Dawson, from the University of Dundee, said: "Conventional global conservation priority has focused on tropical sites having high biodiversity richness in terms of species.
"In contrast, our research has shown that to maintain healthy, resilient marine habitats those regions with fewer species, such as found in the seas around the UK for example, may actually be more vulnerable to catastrophic collapse from human pressures such as pollution and overfishing."
The study was carried out by an international team of researchers from Australia, Chile, Indonesia, Italy, Spain, Sweden, the US and the UK.