PNAS：气候变暖可能为热带生物带来巨大灾难
随着全球气候变暖，相比其它物种而言，人们更多地是担忧北极熊和企鹅的生存状况。然而一份最新的研究表明，全球变暖有可能对数量占到全球物种一半以上的热带物种造成更大的灾难。相关论文5月5日在线发表于美国《国家科学院院刊》（PNAS）上。
气候变化模型认为，极地附近温度的上升幅度要比赤道附近的大。由于这个原因，科学家之前猜测热带物种遭受气候变化的影响要小一些。
最新的研究表明，这个猜测是完全错误的。研究领导者、美国加州大学洛杉矶分校的海洋学家Curtis Deutsch表示，由于热带一年之内的温度要比高维度地区更稳定一些，所以热带生物，特别是昆虫等冷血动物，能够应付的温度范围很窄。这样一来，即使是较小的升温，它们对温度变化的强烈敏感性也会将它们置于危险的境地。
Deutsch和同事查阅了以前的相关文献，找到了38种昆虫的实验室数据，包括蝴蝶、甲虫等，这些昆虫分布范围从北纬50度至南纬40度。研究人员根据气候变化模型，预测了这些昆虫收集地2100年的温度。他们将预测的未来温度加入到这些昆虫的种群生长曲线上，结果发现，距今约100年后，热带昆虫的繁殖率比今天减慢了大约20%。在另一方面，高维度昆虫的繁殖率却增加了。而降低的繁殖率有可能导致多种热带昆虫的灭绝，除非它们进行适应或迁移。Deutsch说，最终的结果将依赖于生态变化的层叠效应，“结果如何很难预测。”
美国杜克大学的保护生物学家Stuart Pimm认为，这一研究很有思想性。不过他主张，一个物种的存活与否最终更多地要依赖于它迁离开高温度区域的能力，而不是忍受的能力。
英国约克大学的保护生物学家认为这一研究是一种号召，以呼吁更多的人进行热带研究。他说，“如果即将出现大灭绝危机的话，我们应该开始提出证明”，只有牢靠的灭绝证据，而不是预测，才能刺激气候变化政策的转变。（科学网 梅进/编译）
生物谷推荐原始出处：
（PNAS），doi：10.1073/pnas.0709472105，Curtis A. Deutsch，Paul R. Martin
Impacts of climate warming on terrestrial ectotherms across latitude
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*Program on Climate Change and Department of Oceanography and Department of Biology, University of Washington, Seattle, WA 98195; and ¶Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523
Edited by David B. Wake, University of California, Berkeley, CA, and approved March 3, 2008 (received for review October 4, 2007)
Abstract
The impact of anthropogenic climate change on terrestrial organisms is often predicted to increase with latitude, in parallel with the rate of warming. Yet the biological impact of rising temperatures also depends on the physiological sensitivity of organisms to temperature change. We integrate empirical fitness curves describing the thermal tolerance of terrestrial insects from around the world with the projected geographic distribution of climate change for the next century to estimate the direct impact of warming on insect fitness across latitude. The results show that warming in the tropics, although relatively small in magnitude, is likely to have the most deleterious consequences because tropical insects are relatively sensitive to temperature change and are currently living very close to their optimal temperature. In contrast, species at higher latitudes have broader thermal tolerance and are living in climates that are currently cooler than their physiological optima, so that warming may even enhance their fitness. Available thermal tolerance data for several vertebrate taxa exhibit similar patterns, suggesting that these results are general for terrestrial ectotherms. Our analyses imply that, in the absence of ameliorating factors such as migration and adaptation, the greatest extinction risks from global warming may be in the tropics, where biological diversity is also greatest.
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