Science, 13 December 2019, VOL 366, ISSUE 6471

《科學(xué)》2019年12月13日，第366卷，6471期

Pervasive human-driven decline of life on Earth points to the need for transformative change

人類活動導(dǎo)致地球生命普遍減少有必要進(jìn)行變革

▲ 作者：Sandra Díaz、Josef Settele、Eduardo S. Brondízio, et al.

▲ 鏈接：

https://science./content/366/6471/eaax3100

▲ 摘要：

自20世紀(jì)70年代以來，由于人口增長和人均收入增加等因素帶來的需求，人類對地球生命的影響急劇增加。

大自然目前為人類社會提供的材料比以往任何時候都多，但這是以全球生態(tài)系統(tǒng)的范圍和完整性、局部生態(tài)群落的獨特性、野生物種的豐富和數(shù)量以及當(dāng)?shù)伛Z化品種數(shù)量的空前下降為代價的。

這些變化減少了人們從大自然中獲得的利益，并威脅到子孫后代的生活質(zhì)量。經(jīng)濟擴張的好處和減少自然的代價是不平等分配的。

我們都依賴的生活結(jié)構(gòu)——大自然及其對人類的貢獻(xiàn)——正在迅速瓦解。

盡管這些威脅十分嚴(yán)重，而且迄今為止，人們在應(yīng)對這些威脅方面缺乏足夠的進(jìn)展，但通過變革性行動改變未來發(fā)展軌跡的機會仍然存在。

然而，這種行動必須立即開始，并解決自然惡化的經(jīng)濟、社會和技術(shù)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

衡量陸地生態(tài)系統(tǒng)適應(yīng)和緩解氣候變化的成功程度

▲ 作者：Michael D. Morecroft、Simon Duffield、Mike Harley, et al.

▲ 鏈接：

https://science./content/366/6471/eaaw9256

▲ 摘要：

自然生態(tài)系統(tǒng)和半自然生態(tài)系統(tǒng)必須走在減緩和適應(yīng)氣候變化努力的前列。

在當(dāng)前環(huán)境問題日益緊迫下，生態(tài)系統(tǒng)恢復(fù)代表了一系列可用的和有效的解決方案，以減少溫室氣體凈排放和適應(yīng)氣候變化。

雖然，人們可以通過監(jiān)測溫室氣體變化通量衡量緩解措施的成功與否，但適應(yīng)措施的衡量更為復(fù)雜，必須對生物多樣性和人類面臨的各種風(fēng)險的減少進(jìn)行評估。

科學(xué)家在監(jiān)測和評價適應(yīng)及減輕措施方面已經(jīng)取得了進(jìn)展，但有必要強調(diào)對提議的戰(zhàn)略的有效性進(jìn)行檢驗。

研究人員表示，人們必須綜合考慮減緩、適應(yīng)、生物多樣性和自身需求，實現(xiàn)潛在的協(xié)同效應(yīng)，避免不同目標(biāo)之間的沖突。

▲ 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.

Global circulation of Mars’ upper atmosphere

火星上層大氣的全球環(huán)流

▲ 作者：M. Benna、S. W. Bougher、Y. Lee, et al.

▲ 鏈接：

https://science./content/366/6471/1363

▲ 摘要：

就像太陽系中其他類似地球的行星一樣，火星的上層大氣（即熱層和電離層）環(huán)流是由來自上方的太陽加熱和來自下方的低層大氣的上行能量驅(qū)動的。

上層大氣中的環(huán)流在整個行星的物質(zhì)和能量的輸送和重新分配中起著重要作用。

盡管在地球大氣層中對這些過程已經(jīng)進(jìn)行了數(shù)十年的研究，但火星熱層風(fēng)的本質(zhì)仍基本未得到表征。

這里，研究人員報告了由美國宇航局的“火星大氣與揮發(fā)物演化”（MAVEN）航天器收集火星大氣新數(shù)據(jù)，這些數(shù)據(jù)令他們能在火星的熱層中測量風(fēng)速并測繪所致的大氣環(huán)流。

該環(huán)流模式比地球的要簡單并在火星的各季節(jié)中頗為穩(wěn)定，表明在火星的一年中，該行星的氣候具長期的穩(wěn)定性。

而且，研究人員表示，在某些位置的熱層風(fēng)會密切遵循遙遠(yuǎn)下方火星表面的形貌，這些發(fā)現(xiàn)提示了在火星上層大氣中探測到了地形重力波（當(dāng)風(fēng)吹過地表高度有大幅改變時所產(chǎn)生的巨形大氣波）。

▲ 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 (MAVEN) 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學(xué)循環(huán)的一個固有特性

▲ 作者：Lewis J. Alcott、Benjamin J. W. Mills、Simon W. Poulton, et al.

▲ 鏈接：

https://science./content/366/6471/1333

▲ 摘要：

人們普遍認(rèn)為，地球大氣層和海洋中的漸進(jìn)性充氧之路是通過3個主要步驟發(fā)生的：“大氧化事件”“新元古代氧化事件”和“古生代氧化事件”。

盡管對這些氧氣的階梯式增加已經(jīng)提出了幾種生物學(xué)和地質(zhì)學(xué)解釋，但在地質(zhì)上快速但卻罕見的充氧事件與已知的地殼外部構(gòu)造或演化過程并不對應(yīng)。

這里，研究人員用一種理論模型發(fā)現(xiàn)了一組涉及全球磷、碳和氧循環(huán)的內(nèi)部生物地球化學(xué)反饋，這些反饋能夠驅(qū)動海洋和大氣中氧氣濃度的快速變化。

他們表示，地球表面的充氧可能是簡單的全球性生物地球化學(xué)反饋的后果。僅基于地球表面隨時間推移而逐漸發(fā)生的充氧作用，該模型可產(chǎn)生與在地質(zhì)記錄中觀察到的相同的三步式模式，并且不需要任何超越簡單光合藍(lán)藻細(xì)菌的生物學(xué)進(jìn)展。

研究人員表示，這些發(fā)現(xiàn)大幅增加了宇宙中其他地方存在高氧氣世界的可能性。

▲ 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.

Realizing the potential of digital development: the case of agricultural advice

實現(xiàn)數(shù)字發(fā)展的潛力：以農(nóng)業(yè)咨詢?yōu)槔?/strong>

▲ 作者：Raissa Fabregas、Michael Kremer、Frank Schilbach

▲ 鏈接：

https://science./content/366/6471/eaay3038

▲ 摘要：

移動電話的迅速普及為生活在小農(nóng)家庭中的20億人創(chuàng)造了可持續(xù)提高農(nóng)業(yè)生產(chǎn)率的潛力。

許多薈萃分析表明，通過數(shù)字技術(shù)提供農(nóng)業(yè)信息使農(nóng)產(chǎn)品產(chǎn)量增加了4%，采用建議輸入的幾率增加了22%。效益可能比信息傳播的成本高出一個數(shù)量級。

支持GPS的智能手機的普及可以通過定制信息增加這些好處，從而激勵農(nóng)民向系統(tǒng)貢獻(xiàn)信息。

眾所周知，信息市場限制了這類系統(tǒng)通過純粹的商業(yè)手段達(dá)到社會效率規(guī)模的能力。

研究人員表示，公眾對數(shù)字農(nóng)業(yè)推廣的支持有明確的作用，但由農(nóng)業(yè)部門設(shè)計的信息往往難以讓農(nóng)民理解和使用。

而實現(xiàn)移動通信系統(tǒng)的潛力，也需要反饋機制進(jìn)行嚴(yán)格的測試和持續(xù)的改進(jìn)。

▲ 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

為什么鯨魚大而不是更大：生理驅(qū)動和生態(tài)限制

▲ 作者：J.A. Goldbogen、D. E. Cade、D. M. Wisniewska, et al.

▲ 鏈接：

https://science./content/366/6471/1367

▲ 摘要：

在陸地上，通常會以小型生物吃小型獵物而大型生物以大型獵物為食來實現(xiàn)這種平衡。

但是，這種范式在海洋中卻瓦解了，因為在海洋中，世界上最大的捕食動物卻以微小的獵物為食。對這種現(xiàn)象的解釋尚無定論。

研究人員用微處理器技術(shù)設(shè)計的水下野生動物示蹤器對有齒和濾食性鯨類進(jìn)行了標(biāo)記，并計算了它們的用能效率。

結(jié)果發(fā)現(xiàn)，這兩種鯨類動物的較大體型可通過進(jìn)食更多的獵物及有效地捕食獵物來增加它們的能效。

然而對各種體型的齒鯨類而言，它們在深海獵食所獲能量最終受到其每次下潛時可得到獵物的有限豐度的約束。

相比之下，濾食動物則會始終顯示來自食物能量的快速增加，其微小獵物的總生物量和能含量會超過最大型齒鯨的獵物的平均值。

因此，對這些無齒鯨來說，其體型大小可能受其生物學(xué)因素的限制，而不是可獲得獵物量的限制。

▲ 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.