The distributions of different species on Earth are closely linked to the distinct climatic zones between the equator and the poles. Plants and animals found in the wet and warm tropics differ from those in the hot, dry deserts, which in turn differ from those in the cold polar zones. We know from the fossil record that these life zones have shifted in the past as climates have changed. For example, trees fossils are found where there are now no forests, and fossils of equatorial animals are found where climates are cold today. As increasing greenhouse gases rapidly warm the Earth, regional climates will change, and some species will have to adapt or migrate to avoid extinction. During climatic transitions, long lived species or those that cannot migrate quickly may suffer growth declines, altered reproduction, and changes in the way they interact with other species and their physical environment. For example, where global warming increases water stress, grasses, shrubs, and trees may grow more slowly and be attacked more severely by insect pests, leading to reduced food availability for dependent animals and less transpiration of water back to the atmosphere. 

In other cases, changes in local conditions will affect species in more subtle ways. For example as temperatures increase and sea level rises, beaches currently used by sea turtles may become submerged leaving them without a place to nest. Because for some sea turtle species the sex of hatchlings is determined by temperature – more females compared to males at warmer temperatures – rising temperatures may also lead to an overabundance of female hatchlings, and this could cause populations to decline. In this example, warming not only alters the species physical environment but its reproductive biology. These examples illustrate the diverse effects that climatic change can have on Earth’s species and ecosystems.

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