As the Arctic ice begins to melt, species like polar bears are starting to suffer, and they are not alone. Many other species that depend on the cold temperatures in the Arctic and Antarctic may be at risk of extinction.
Examples from the past can help us understand how the species living on Earth today might respond to global warming.
The last period of warming on the planet took place at the end of the Pleistocene ice age, over 10,000 years ago. This period coincides roughly with the extinction of the woolly mammoths, which lived in northern Europe and Asia.
It may not have been the warmer climate itself that directly killed the mammoths. However, climate change altered the vegetation in the areas where woolly mammoths lived. Grassland areas turned into forested areas, which mammoths were not well-suited to.
To survive, mammoths had to move further north but the loss of their habitat meant they eventually went extinct, some time around 4,000 years ago.
A similar process is taking place today. The Earth is warming up and this is likely to change local habitats. Species may have to move further north to find the conditions they are used to, if they are in the northern hemisphere. In the southern hemisphere, they will need to move further south to find a cooler climate.
Not every species can migrate though. Some organisms are not mobile enough to move to a new habitat. Others are cut off from nearby habitats by discontinuities in the landscape created by humans, such as roads.
Another problem is that the topography (the shape of the land) may be very different in the area to the north or south, because of hills, mountain ranges or other features. Again, this would make it difficult for populations to move closer to the poles in order to survive.
Although some populations living in tropical, sub-tropical and temperate regions may be able to migrate closer to the poles to avoid the effects of global warming, this is not an option for species that already live close to the poles. When the climate warms, it destroys their habitat and leaves them with nowhere to go.
Polar bears are one example. They survive by hunting seals on the sea ice for part of the year, before going further inland until the next hunting season begins. They need to build up enough fat on their bodies during the hunting season to survive the rest of the year. Now that the sea ice is melting, the hunting season is becoming shorter, and many polar bears can no longer catch enough food to survive. The polar bear population is now in decline.