据10月9日的《科学》（Science）杂志报道说，在热带地区，许多物种如果缺乏一个可以迁往的较为凉爽的地方的话，它们不久将面临因为全球气候的变暖而出现种群数的下降及灭绝的局面。这些地球上的热带地区对物种来说是一种独特的挑战，因为纬度方向的迁徙（向东或向西）并不能够给它们提供足够的救助。这些物种必须将其活动范围向高处迁移才能够躲避暑热。
Robert Colwell及其同事分析了热带的植物、昆虫和真菌等1902个物种的数据并得出结论：低地的物种种群数不久即会出现生物多元性和物种丰富程度的下降，这是因为还没有什么已经适应了较高温度的物种源可以取代那些因气温变暖而被驱往更高海拔的物种。在此期间，研究人员提出，较高海拔的物种当面临向更高海拔攀登的空间已不复存在的时候，它们将会同时面临“山顶灭绝”的处境。 此外，一项新的调查显示，在美国Yosemite国家公园内的小型哺乳动物在经过气温变暖的一个世纪之后，其活动范围发生了重大的改变。某些生活在高海拔地区的哺乳动物如高山金花鼠的活动范围已经缩小，而生活在低海拔地区的动物如巢鼠则已经将其活动范围扩大到了较高的海拔地区。
Craig Moritz及其同事说，气候变暖也搅乱了其它生活在中等海拔和高海拔地区的哺乳动物群落。为了证明这些变化，研究人员将他们的调查数据与在20世纪初由Joseph Grinnell收集的Yosemite大量的数据组进行了比较。Joseph Grinnell是一位田野生物学家，他的工作导致了“生态位”概念的问世。尽管物种的活动范围出现了显著的波动，Yosemite在过去的100年中一直维持着小型哺乳动物物种的多样性。Moritz及其同事提出，受到公园保护的广大地区可能因为允许哺乳动物随着气候的变化而迁往新的海拔高度从而保持了这些动物的多样性。在一篇Perspective中，Jens-Christian Svenning更为详细地解释了这些发现。（生物谷Bioon.com）
生物谷推荐原始出处：
Science，Vol. 322. no. 5899, pp. 258 - 261，Robert K. Colwell，John T. Longino
Global Warming, Elevational Range Shifts, and Lowland Biotic Attrition in the Wet Tropics
Robert K. Colwell,1* Gunnar Brehm,2 Catherine L. Cardelús,3 Alex C. Gilman,4 John T. Longino5
Many studies suggest that global warming is driving species ranges poleward and toward higher elevations at temperate latitudes, but evidence for range shifts is scarce for the tropics, where the shallow latitudinal temperature gradient makes upslope shifts more likely than poleward shifts. Based on new data for plants and insects on an elevational transect in Costa Rica, we assess the potential for lowland biotic attrition, range-shift gaps, and mountaintop extinctions under projected warming. We conclude that tropical lowland biotas may face a level of net lowland biotic attrition without parallel at higher latitudes (where range shifts may be compensated for by species from lower latitudes) and that a high proportion of tropical species soon faces gaps between current and projected elevational ranges.
Science，Vol. 322. no. 5899, pp. 261 - 264，Craig Moritz，Steven R. Beissinger
Impact of a Century of Climate Change on Small-Mammal Communities in Yosemite National Park, USA
Craig Moritz,1,2* James L. Patton,1,2 Chris J. Conroy,1 Juan L. Parra,1,2 Gary C. White,3 Steven R. Beissinger1,4
We provide a century-scale view of small-mammal responses to global warming, without confounding effects of land-use change, by repeating Grinnell's early–20th century survey across a 3000-meter-elevation gradient that spans Yosemite National Park, California, USA. Using occupancy modeling to control for variation in detectability, we show substantial (500 meters on average) upward changes in elevational limits for half of 28 species monitored, consistent with the observed 3°C increase in minimum temperatures. Formerly low-elevation species expanded their ranges and high-elevation species contracted theirs, leading to changed community composition at mid- and high elevations. Elevational replacement among congeners changed because species' responses were idiosyncratic. Though some high-elevation species are threatened, protection of elevation gradients allows other species to respond via migration.
