 According to a new study, ocean warming will alter the geographic ranges of most marine species and strongly modify current global marine biodiversity patterns by the year 2100. The expanding range of numerous species will cause net local increases in diversity across many regions, especially in the first half of the century. Effects are predicted to be significantly stronger with greater increases in global temperature, although changes are projected even under lower levels of warming. These findings emphasize the urgency of mitigating climate change. They also highlight some of the important conservation challenges ahead and suggest specific regions where ecosystem conservation efforts could have the greatest impact. The researchers began their investigation with modeled current-day species distribution data for nearly 13,000 species from 23 Phyla, 10 times more species than have been included in comparable previous studies. To determine how the species ranges may change, they projected these distributions using climate velocity, a measurement that combines the rate and direction of movement of ocean temperature bands over time, together with several factors constraining species dispersal, such as geographical boundaries, depth limits, and species thermal tolerances. Whereas previous models have made predictions for a limited number of well-studied species, this new approach provided much richer detail about likely global patterns of changes in the compositions of whole communities under two warming scenarios of different intensity. One trend seen in many areas was a net increase in local diversity, or species richness, due to high rates of species invasion. Though significant net biodiversity losses are expected for specific regions, particularly within the tropics, the changing climate will actually help many species expand into new areas. These invaders may thrive in the absence of their usual competitors and predators and interact with native species in unpredictable ways. As a result of these invasions, currently distinct ecological communities will become much more similar to one another by centuries end. This pattern brings unprecedented conservation challenges in managing interactions between invading and native species and in preparing for other ecological surprises that seem certain to arise. The study suggests key locations for focused conservation efforts in regions where major predicted biodiversity changes coincide with current high levels of human activities and in high latitude zones where current human pressure is low, but biodiversity change is expected to be high. These results highlight the need to promote international cooperation to address regional ecological effects that will span national boundaries. They also show that while the effects of ocean warming are severe under the current climate trajectory, these effects could be reduced if warming could be limited.