Science, 13December2019, VOL 366, ISSUE 6471
《科学》2019年12月13日，第366卷，6471期
生态学Ecology
Pervasive human-driven decline of life on Earth points to the need for transformative change
人类活动导致地球生命普遍减少有必要进行变革
▲作者：Sandra Díaz、Josef Settele、Eduardo S. Brondízio, et al.
▲链接：
https://science.sciencemag.org/content/366/6471/eaax3100
▲ 摘要：
自20世纪70年代以来，由于人口增长和人均收入增加等因素带来的需求，人类对地球生命的影响急剧增加。
大自然目前为人类社会提供的材料比以往任何时候都多，但这是以全球生态系统的范围和完整性、局部生态群落的独特性、野生物种的丰富和数量以及当地驯化品种数量的空前下降为代价的。
这些变化减少了人们从大自然中获得的利益，并威胁到子孙后代的生活质量。经济扩张的好处和减少自然的代价是不平等分配的。
我们都依赖的生活结构——大自然及其对人类的贡献——正在迅速瓦解。
尽管这些威胁十分严重，而且迄今为止，人们在应对这些威胁方面缺乏足够的进展，但通过变革性行动改变未来发展轨迹的机会仍然存在。
然而，这种行动必须立即开始，并解决自然恶化的经济、社会和技术根源。
▲Abstract
The human impact on life on Earth has increased sharply since the 1970s, driven by the demands of a growing population with rising average per capita income. Nature is currently supplying more materials than ever before, but this has come at the high cost of unprecedented global declines in the extent and integrity of ecosystems, distinctness of local ecological communities, abundance and number of wild species, and the number oflocal domesticated varieties. Such changes reduce vital benefits that people receive from nature and threaten the quality of life of future generations. Both the benefits of an expanding economy and the costs of reducing nature’s benefits are unequally distributed. The fabric of life on which we all depend—nature and its contributions to people—is unravelling rapidly. Despite the severity of the threats and lack of enough progress in tackling them to date, opportunities exist to change future trajectories through transformative action. Such action must begin immediately, however, and address the root economic, social, and technological causes of nature’s deterioration.
Measuring the success of climate change adaptation and mitigation in terrestrial ecosystems
衡量陆地生态系统适应和缓解气候变化的成功程度
▲作者：Michael D. Morecroft、Simon Duffield、Mike Harley, et al.
▲链接：
https://science.sciencemag.org/content/366/6471/eaaw9256
▲ 摘要：
自然生态系统和半自然生态系统必须走在减缓和适应气候变化努力的前列。
在当前环境问题日益紧迫下，生态系统恢复代表了一系列可用的和有效的解决方案，以减少温室气体净排放和适应气候变化。
虽然，人们可以通过监测温室气体变化通量衡量缓解措施的成功与否，但适应措施的衡量更为复杂，必须对生物多样性和人类面临的各种风险的减少进行评估。
科学家在监测和评价适应及减轻措施方面已经取得了进展，但有必要强调对提议的战略的有效性进行检验。
研究人员表示，人们必须综合考虑减缓、适应、生物多样性和自身需求，实现潜在的协同效应，避免不同目标之间的冲突。
▲Abstract
Natural and seminatural ecosystems must be at the forefront of efforts to mitigate and adapt to climate change. In the urgency of current circumstances, ecosystem restoration represents a range of available, efficient, and effective solutions to cut net greenhouse gas emissions and adapt to climate change. Although mitigation success can be measured by monitoring changing fluxes of greenhouse gases, adaptation is more complicated to measure, and reductions in a wide range of risks for biodiversity and people must be evaluated. Progress has been made in the monitoring and evaluation of adaptation and mitigation measures, but more emphasis on testing theeffectiveness of proposed strategies is necessary. It is essential to take an integrated view of mitigation, adaptation, biodiversity, and the needs of people, to realize potential synergies and avoid conflict between different objectives.
空间及地球科学
Space and Earth Sciences
Global circulation of Mars’ upper atmosphere
火星上层大气的全球环流
▲作者：M. Benna、S. W. Bougher、Y. Lee, et al.
▲链接：
https://science.sciencemag.org/content/366/6471/1363
▲ 摘要：
就像太阳系中其他类似地球的行星一样，火星的上层大气环流是由来自上方的太阳加热和来自下方的低层大气的上行能量驱动的。
上层大气中的环流在整个行星的物质和能量的输送和重新分配中起着重要作用。
尽管在地球大气层中对这些过程已经进行了数十年的研究，但火星热层风的本质仍基本未得到表征。
这里，研究人员报告了由美国宇航局的“火星大气与挥发物演化”航天器收集火星大气新数据，这些数据令他们能在火星的热层中测量风速并测绘所致的大气环流。
该环流模式比地球的要简单并在火星的各季节中颇为稳定，表明在火星的一年中，该行星的气候具长期的稳定性。
而且，研究人员表示，在某些位置的热层风会密切遵循遥远下方火星表面的形貌，这些发现提示了在火星上层大气中探测到了地形重力波。
▲Abstract
The thermosphere of Mars is the interface through which the planet is continuously losing its reservoir of atmospheric volatiles to space. The structure and dynamics of the thermosphere is driven by a global circulation that redistributes the incident energy from the Sun. We report mapping of the global circulation in the thermosphere of Mars with the Mars Atmosphere and Volatile Evolution spacecraft. The measured neutral winds reveal circulation patterns simpler than those of Earth that persist over changing seasons. The winds exhibit pronounced correlation with the underlying topography owing toorographic gravity waves.
Stepwise Earth oxygenation is an inherent property of global biogeochemical cycling
地球逐步充氧是全球生物地球化学循环的一个固有特性
▲作者：Lewis J. Alcott、Benjamin J. W. Mills、Simon W. Poulton, et al.
▲链接：
https://science.sciencemag.org/content/366/6471/1333
▲ 摘要：
人们普遍认为，地球大气层和海洋中的渐进性充氧之路是通过3个主要步骤发生的：“大氧化事件”“新元古代氧化事件”和“古生代氧化事件”。
尽管对这些氧气的阶梯式增加已经提出了几种生物学和地质学解释，但在地质上快速但却罕见的充氧事件与已知的地壳外部构造或演化过程并不对应。
这里，研究人员用一种理论模型发现了一组涉及全球磷、碳和氧循环的内部生物地球化学反馈，这些反馈能够驱动海洋和大气中氧气浓度的快速变化。
他们表示，地球表面的充氧可能是简单的全球性生物地球化学反馈的后果。仅基于地球表面随时间推移而逐渐发生的充氧作用，该模型可产生与在地质记录中观察到的相同的三步式模式，并且不需要任何超越简单光合蓝藻细菌的生物学进展。
研究人员表示，这些发现大幅增加了宇宙中其他地方存在高氧气世界的可能性。
▲Abstract
Oxygenation of Earth’s atmosphere and oceans occurred across three major steps during the Paleoproterozoic, Neoproterozoic, and Paleozoic eras, with each increase having profound consequences for the biosphere. Biological or tectonic revolutions have been proposed to explain each of these stepwise increases in oxygen, but the principal driver of each event remains unclear. Here we show, using a theoretical model, that the observed oxygenation steps are a simple consequence of internal feedbacks in the long-term biogeochemical cycles of carbon, oxygen, and phosphorus, and that there is no requirement for a specific stepwise external forcing to explain the course of Earth surface oxygenation. We conclude that Earth’s oxygenation events are entirely consistent with gradual oxygenation of the planetary surface after the evolution of oxygenic photosynthesis.
经济学/生物学
Economics/Biology
Realizing the potential of digital development: the case of agricultural advice
实现数字发展的潜力：以农业咨询为例
▲作者：Raissa Fabregas、Michael Kremer、Frank Schilbach
▲链接：
https://science.sciencemag.org/content/366/6471/eaay3038
▲ 摘要：
移动电话的迅速普及为生活在小农家庭中的20亿人创造了可持续提高农业生产率的潜力。
许多荟萃分析表明，通过数字技术提供农业信息使农产品产量增加了4%，采用建议输入的几率增加了22%。效益可能比信息传播的成本高出一个数量级。
支持GPS的智能手机的普及可以通过定制信息增加这些好处，从而激励农民向系统贡献信息。
众所周知，信息市场限制了这类系统通过纯粹的商业手段达到社会效率规模的能力。
研究人员表示，公众对数字农业推广的支持有明确的作用，但由农业部门设计的信息往往难以让农民理解和使用。
而实现移动通信系统的潜力，也需要反馈机制进行严格的测试和持续的改进。
▲Abstract
The rapid spread of mobile phones creates potential for sustainably raising agricultural productivity for the 2 billion people living in small holder farming households. Meta-analyses suggest that providing agricultural information via digital technologies increased yields by 4% and the odds of adopting recommended inputs by 22%. Benefits likely exceed the cost of information transmission by an order of magnitude. The spread of GPS-enabled smartphones could increase these benefits by enabling customized information, thus in centivizing farmers to contribute information to the system. Well-known distortions in markets for information limit the ability of such systems to reach the socially efficient scale through purely commercial means. There is a clear role for public support for digital agricultural extension, but messages designed by agricultural ministries are often difficult for farmers to understand and use. Realizing the potential of mobile communication systems requires feedback mechanisms to enable rigorous testing and continuous improvement.
Why whales are big but not bigger: Physiological drivers and ecological limits in the age of ocean giants
为什么鲸鱼大而不是更大：生理驱动和生态限制
▲作者：J.A. Goldbogen、D. E. Cade、D. M. Wisniewska, et al.
▲链接：
https://science.sciencemag.org/content/366/6471/1367
▲ 摘要：
在陆地上，通常会以小型生物吃小型猎物而大型生物以大型猎物为食来实现这种平衡。
但是，这种范式在海洋中却瓦解了，因为在海洋中，世界上最大的捕食动物却以微小的猎物为食。对这种现象的解释尚无定论。
研究人员用微处理器技术设计的水下野生动物示踪器对有齿和滤食性鲸类进行了标记，并计算了它们的用能效率。
结果发现，这两种鲸类动物的较大体型可通过进食更多的猎物及有效地捕食猎物来增加它们的能效。
然而对各种体型的齿鲸类而言，它们在深海猎食所获能量最终受到其每次下潜时可得到猎物的有限丰度的约束。
相比之下，滤食动物则会始终显示来自食物能量的快速增加，其微小猎物的总生物量和能含量会超过最大型齿鲸的猎物的平均值。
因此，对这些无齿鲸来说，其体型大小可能受其生物学因素的限制，而不是可获得猎物量的限制。
▲Abstract
The largest animals are marine filter feeders, but the underlying mechanism of their large size remains unexplained. We measured feeding performance and preyquality to demonstrate how whale gigantism is driven by the interplay of prey abundance and harvesting mechanisms that increase prey capture rates and energy intake. The foraging efficiency of toothed whales that feed on single prey is constrained by the abundance of large prey, whereas filter-feeding baleenwhales seasonally exploit vast swarms of small prey at high efficiencies. Given temporally and spatially aggregated prey, filter feeding provides an evolutionary pathway to extremes in body size that are not available to lineages that must feed on one prey at a time. Maximum size in filter feeders is likely constrained by prey availability across space and time.
