Caribou and Reindeer

    Caribou and reindeer are classified by scientists as the same species, with the domesticated reindeer dispersed across parts of Europe and Asia and the wild caribou found in North America and Greenland.

    Global warming will most harm the animals adapted to the coldest environments, primarily those accustomed to life in the Arctic.

    That group includes these large mammals, which have become symbols of Christmas. Their insulated fur and lack of sweat glands allow them to survive harsh winters, but those adaptations also make longer, hotter summers very difficult to endure.

    Penguins

    The rapid melting of sea ice is a main reason that animals in the polar regions are most affected by even slight warming.

    The open-ocean species are doing okay. So the penguins in Antarctica that feed in the open ocean are doing okay; the penguin species that feed by just dropping off the ice shelves, like the Adelie and the emperor （pictured）, are declining.

    Musk oxen

    Musk oxen are large mammals that have been around since well before the last ice age. They are adapted to live in the coldest of habitats, and Graham says they may be significantly endangered as global warming shrinks their distribution ranges.

    Longer, warmer summers could have a devastating impact on their already small populations scattered across northern Canada, Greenland, and parts of Alaska.

    Seabirds

    As fish move north in search of cooler waters, animals that rely on fish for sustenance are left without many options. This group includes seabirds like the Atlantic puffin （pictured）, the tufted puffin in the North Pacific, and the rhinoceros auklet.

    Seabirds that rely on plankton are also struggling to find food. Warm surface temperatures and upwellings and downwellings cause the plankton to descend to lower depths, out of reach of surface-feeders.

    During a food shortage, many animals do not breed very well or, in some cases, at all. Disruptions in the mating patterns of several species of seabird have been reported across the globe. Some have been laying their eggs later and experiencing fewer successful hatchings.

    Possums

    Along with arctic animals, species that reside on mountaintops are also experiencing the effects of warming. Parmesan says tree possums that reside in high elevations are particularly in danger.

    There's a group that's restricted to high elevations, and the white lemuroid possum （pictured）, which is among this group, has not been seen since 2005, and it's believed to be the first mammal driven extinct by climate change.

    馴鹿與北美馴鹿

    科學家們把馴鹿與北美馴鹿歸為同一物種。馴化的馴鹿分布在亞洲和歐洲部分地區，而野生的北美馴鹿則生活在北美和格陵蘭島。

    全球變暖對已經適應最寒冷環境的動物，主要是那些習慣了北極生活的動物造成的傷害最嚴重。

    這些動物中就包括馴鹿，這種大型動物已經成為圣誕節的標志。它們有保溫的皮毛，并且缺乏汗腺，這使它們能夠在冬天的嚴寒中生存，但也使更長、更炎熱的夏天變得難以忍受。

    企鵝

    即使氣溫稍有升高，兩極地區的動物也會受到影響，這主要是由海上冰層的快速融化造成的。

    遠海帶（開闊海域）物種對這種變化還比較適應。因此，在南極洲遠海帶捕食的企鵝適應得比較好，而只靠從冰架上躍入水中捕食的阿德利企鵝和帝企鵝（如圖所示）則面臨衰落。

    麝香牛

    早在最后一次冰河時期之前，麝香牛這種大型動物就已經遍布世界各地了。它們已經適應了在最冷的地方棲息。格雷厄姆說，隨著全球變暖不斷侵蝕它們的分布范圍，麝香牛可能面臨嚴重的滅絕危機。

    更長、更炎熱的夏季可能會對分散在加拿大北部、格陵蘭島和阿拉斯加部分地區本已為數不多的麝香牛帶來毀滅性的打擊。

    海鳥

    隨著魚群為了尋找更冷的水域而向北遷移，靠捕魚維持生計的動物們也沒有更多選擇了。這些動物中就包括大西洋海雀（如圖所示）、北太平洋善知鳥和犀角海雀等海鳥。

    靠浮游生物為生的海鳥也越來越難找到食物了。升高的水面溫度、上升水流和下降水流使浮游生物下沉到更深的地方，在水面捕食的動物已無法觸及。

    在食物短缺時，很多動物的繁殖情況很差，有時甚至完全不繁殖。世界各地都出現了關于某些種類的海鳥交配模式被破壞的報道。有些海鳥產卵期推遲了，孵化率也變得更低。

    負鼠

    和北極圈的動物一樣，生活在山頂地區的物種也受到了氣候變暖的影響。帕瑪森說，生活在高海拔地區的樹負鼠境遇尤其危險。

    有些物種生活的環境僅限于高海拔地區，白狐猴負鼠（如圖所示）就是其中一種。從2005年開始，就再也沒有人發現過它們的蹤跡，人們相信這是由于氣候變化而滅絕的第一種動物。