Today scientists draw attention to some of the potential consequences of global warming on wildlife. They point out that each species reacts to changes in temperature differently. Some species will undoubtedly become extinct, particularly those with narrow temperature requirements, those confined to small reserves or parks, and those living in fragile ecosystems, whereas other species may survive in greatly reduced numbers and ranges. Ecosystems considered most vulnerable to species loss in the short term are polar seas, coral reefs, mountains, coastal wetlands, tundra, taiga, and temperate forests. On the other hand, some species may be able to migrate to new environments or adapt themselves to the changing conditions in their present habitats. Also, some species may be unaffected by global warming, whereas others may emerge from it as winners, with greatly expanded numbers and ranges. Those considered most likely to prosper include weeds, pests, and disease-carrying organisms that are already common in many different environments.