Due to global warming, in fact due to us, many species are threatened today. Countless ice sheets that once stood tall are melting, and still, not many are willing to accept it. Polar bears get their food by swimming from ice sheet to ice sheet, for example. As these sheets melt, they are forced to swim longer distances to collect food than they once did. Some die of exhaustion and starvation as they try to swim.
Not only polar bears but the Pacific Walrus, which depend on ice to rest, are declining also.

Pacific Walrus resting on ice
Plants, too, are being forced to move. An example, the Santa Rosa Mountains in California's species have moved on average 215 feet up. They are the Jeffrey Pine Tree and California Lilac. Below, as it gets hotter and hotter, plants desperately move toward better weather. This dramatic change is just the beginning. As the plants and animals move toward colder parts of the earth, we do, to, and we infect those. Soon there will be no place for the animals and plants to go, and they will go extinct.
Birds are also changing, and for the worse. They now are migrating earlier than before. Scientists believe that this is because the bird's winter climate is warmer. It triggers a cell in the bird's brain, causing it to leave earlier. This, however, causes problems. For example, in the spring, robins arrive in Colorado around two weeks earlier than they did in the 1970s. However, climate change has increased snowfall on the mountains. Since there is more snow, robins can not feed until it melts.
Black Guillemots in Alaska are declining because of the warming climate and less Arctic Sea ice. They can not fly from their nests on land to their fishing grounds at the edge of the ice. Since it is too far away, young birds are now starving.

Black Guillemot trying to find food
You might think that the fish and coral reefs are good, in fact prospering, but that is not the case. Because the ocean absorbs more and more carbon dioxide, the chemical processes are changing. To understand how it is bad for the sea, we must understand how coral reefs are made.
Corals are tiny animals that are grouped together. They use animals dissolved in water to build hard coverings around themselves. When they die, they leave the skeleton behind. Over time, these skeletons create coral reefs. Coral reefs provide rich and different habitats for marine animals, such as sponges, worms, crabs and fishes. Many fishes eaten by people, such as flounder, are part of coral-reef food chains. Coral reefs protect beaches against waves, and are now dying worldwide because of us.

Coral bleaching
Reef-building corals contain microorganisms called algae within their tissues. during photosynthesis, algae produce nutrients that the corals use some of. If algae dies, corals lose their color. This process is called Coral Bleaching*. Scientists are are not fully sure, but believe based on evidence that it is related to unusually warm water temperatures. However, some species such as the Bowhead whales, which feed on plankton** they filter, are thriving. So do capelin***, which also benefit from more plankton.
These are a small portion of the species global warming is killing off.
* Coral Bleaching is when a coral is bleached white, normally because all the algae in the coral dies. Since algae makes the color in a healthy coral, without it the coral would be white.
** Plankton are microscopic organisms that drift at the surface of the water. Krill, for instance, are plankton.
*** Capelin are fish that feed on plankton.