Introduction 引言
This report explores the hypothetical scenario wherein Earth's contemporary terrestrial landmasses undergo extreme fragmentation, resulting in a global archipelago of numerous, significantly smaller islands. This scenario, exemplified by imagining the land between the Pecos River and Rio Grande becoming an isolated island, serves as a thought experiment to probe the profound ecological consequences of large-scale habitat fragmentation applied globally. The analysis aims to provide a comprehensive, scientifically grounded assessment of the potential cascading impacts across interconnected Earth systems. It integrates principles and evidence from island biogeography, oceanography, climatology, terrestrial and marine ecology, paleontology, evolutionary biology, and biogeochemistry to evaluate the likely outcomes.
本报告探讨了一个假设场景,即地球当代陆地在极端碎片化的情况下,形成一个由众多显著较小的岛屿组成的全球群岛。这个场景通过想象佩科斯河与格兰德河之间的土地变成一个孤立的岛屿来进行思考实验,以探讨大规模栖息地碎片化在全球范围内的深远生态后果。该分析旨在提供一个全面的、科学基础的评估,评估潜在的连锁影响在相互关联的地球系统中的表现。它整合了岛屿生物地理学、海洋学、气候学、陆地和海洋生态学、古生物学、进化生物学和生物地球化学的原则和证据,以评估可能的结果。
The report is structured to systematically address key areas of impact. It begins by examining the fundamental principles of island biogeography and how they predict biodiversity outcomes in such a fragmented world. Subsequently, it investigates the potential reconfiguration of global ocean circulation patterns, including surface currents and the deep thermohaline circulation, due to the removal of large continental barriers. Following this, the analysis explores the consequent transformations in global and regional climate patterns, focusing on temperature and precipitation regimes. The report then delves into the direct consequences for terrestrial ecosystems, considering habitat loss, edge effects, barriers to movement, and the specific fate of large-bodied species. Impacts on marine and coastal ecosystems are assessed next, considering the vastly increased coastline length, altered nutrient runoff, new salinity gradients, and potential shifts in upwelling zones. To provide long-term context, the scenario is compared with past geological events involving continental fragmentation, such as the breakup of Pangea and Gondwana. The differential success of species based on key traits like dispersal ability, adaptability, and body size is then considered. Finally, the report synthesizes the potential cascading effects across trophic levels, biogeochemical cycles (particularly carbon), and the provision of ecosystem services resulting from these large-scale geographic and climatic changes.
该报告的结构旨在系统地解决关键影响领域。它首先考察岛屿生物地理学的基本原理,以及这些原理如何预测在如此碎片化的世界中生物多样性的结果。随后,它研究了由于大型大陆屏障的移除,全球海洋环流模式的潜在重构,包括表层洋流和深层热盐环流。接下来,分析探讨了全球和区域气候模式的随之变化,重点关注温度和降水模式。报告随后深入探讨了对陆地生态系统的直接影响,考虑栖息地丧失、边缘效应、运动障碍以及大型物种的特定命运。接下来评估了对海洋和沿海生态系统的影响,考虑到大幅增加的海岸线长度、改变的营养物质径流、新的盐度梯度以及潜在的上升流区变化。为了提供长期背景,该情景与涉及大陆碎片化的过去地质事件进行比较,例如盘古大陆和冈瓦纳大陆的分裂。 基于关键特征如传播能力、适应性和体型的物种成功差异被考虑在内。最后,报告综合了这些大规模地理和气候变化所导致的跨营养级、生物地球化学循环(特别是碳)以及生态系统服务提供的潜在级联效应。
While inherently theoretical, examining this extreme scenario offers valuable insights into the fundamental roles that landmass configuration plays in shaping Earth's climate, oceans, and biodiversity. It underscores the potential severity of habitat fragmentation when scaled globally and highlights the intricate interconnectedness of Earth's systems.
虽然本质上是理论性的,但考察这一极端情景提供了对陆地配置在塑造地球气候、海洋和生物多样性方面的基本作用的宝贵见解。它强调了当全球范围内规模化时栖息地碎片化的潜在严重性,并突显了地球系统之间错综复杂的相互联系。
I. Island Biogeography Principles in a Fragmented World
I. 碎片化世界中的岛屿生物地理学原则
The transformation of continents into archipelagos necessitates an analysis grounded in the principles of island biogeography, which explain patterns of species richness and distribution in isolated habitats.
大陆转变为群岛的过程需要基于岛屿生物地理学原则进行分析,这些原则解释了孤立栖息地中物种丰富度和分布的模式。
A. Foundational Theories: ETIB and NTIB
A. 基础理论:岛屿生态平衡理论(ETIB)和新岛屿生态平衡理论(NTIB)
The cornerstone of modern island biogeography is the Equilibrium Theory of Island Biogeography (ETIB), developed by Robert MacArthur and E.O. Wilson.1 ETIB posits that the number of species (species richness, S) found on an island represents a dynamic equilibrium determined by the interplay between the rate at which new species immigrate to the island and the rate at which existing species go extinct.1 As species accumulate on an island, the immigration rate of new species declines, because the pool of potential colonists not already present shrinks.2 Conversely, the extinction rate increases with rising species richness, attributed to factors like smaller population sizes per species and increased interspecific competition for limited resources.5 The equilibrium species number (Ŝ) is reached when the immigration rate equals the extinction rate (I = E), resulting in a relatively stable number of species, although the identities of those species may change over time (species turnover).3 Mathematically, the rate of change in species number can be expressed as dS/dt = I - E.4
现代岛屿生物地理学的基石是由罗伯特·麦克阿瑟和 E.O.威尔逊提出的岛屿生态平衡理论(ETIB)。ETIB 认为,岛屿上物种的数量(物种丰富度,S)代表了一种动态平衡,这种平衡由新物种移民到岛屿的速率与现有物种灭绝的速率之间的相互作用决定。随着物种在岛屿上的积累,新物种的移民速率下降,因为潜在的殖民者池(尚未存在的物种)缩小。相反,随着物种丰富度的增加,灭绝速率上升,这归因于每个物种的种群规模较小以及对有限资源的种间竞争加剧。当移民速率等于灭绝速率(I = E)时,达到平衡物种数量(Ŝ),从而导致相对稳定的物种数量,尽管这些物种的身份可能随时间变化(物种更替)。数学上,物种数量的变化速率可以表示为 dS/dt = I - E。
While ETIB provides a powerful framework, it has been refined by subsequent theories. The Niche-Based Theory of Island Biogeography (NTIB) represents a significant development, building upon ETIB by explicitly incorporating the concept of ecological niches.6 Drawing from the MacroEcological Theory on the Arrangement of Life (METAL), NTIB proposes that the number of available niches, particularly climatic niches defined by factors like temperature and precipitation, is a fundamental predictor of species richness, operating alongside island area and isolation.6 ETIB implicitly accounts for habitat heterogeneity, often correlated with area, but NTIB quantifies niche availability directly. This allows NTIB to offer a more direct ecological mechanism for observed patterns, such as the tendency for tropical islands to have higher species richness than temperate islands of similar size, a pattern linked to greater niche diversity in the tropics.6 NTIB also refines the modeling of extinction by distinguishing between higher short-term extinction rates during initial colonization (due to factors like habitat alteration) and long-term rates driven by competition, providing a more nuanced view of community assembly dynamics.6
虽然 ETIB 提供了一个强大的框架,但它已被后续理论所完善。基于生态位的岛屿生物地理理论(NTIB)代表了一个重要的发展,基于 ETIB,明确纳入了生态位的概念。NTIB 借鉴了生命排列的宏观生态理论(METAL),提出可用生态位的数量,特别是由温度和降水等因素定义的气候生态位,是物种丰富度的一个基本预测因素,与岛屿面积和孤立性共同作用。ETIB 隐含地考虑了栖息地异质性,通常与面积相关,但 NTIB 直接量化了生态位的可用性。 这使得 NTIB 能够为观察到的模式提供更直接的生态机制,例如热带岛屿的物种丰富度往往高于相似大小的温带岛屿,这一模式与热带地区更大的生态位多样性有关。NTIB 还通过区分初始定殖期间(由于栖息地改变等因素)较高的短期灭绝率和由竞争驱动的长期灭绝率,细化了灭绝建模,提供了对群落组装动态的更细致的视角。
A comparison highlights the key distinctions and complementarities:
比较突出了关键的区别和互补性:
Table 1: Comparison of Key Principles: ETIB vs. NTIB
表 1:关键原则比较:ETIB 与 NTIB
Feature 特征 | Equilibrium Theory of Island Biogeography (ETIB) | Niche-Based Theory of Island Biogeography (NTIB) |
Core Premise 核心前提 | Species richness (S) is a dynamic equilibrium between immigration (I) and extinction (E) rates.1 | Species richness (S) is determined by I, E, and explicitly by the number of available ecological (climatic) niches.6 |
Key Predictors 关键预测因子 | Island Area (A), Island Isolation (Distance, D).1 | Number of Niches (N), Island Area (A), Island Isolation (D).6 |
Area Effect 面积效应 | Larger A increases target size (↑I) and reduces extinction risk (↓E) due to larger populations/more habitats.2 | Area effect partially mediated by correlation between A and N; larger A still influences target effect and population size.6 |
Isolation Effect 孤立效应 | Greater D decreases I; may increase E (reduced rescue effect).2 | Isolation effect on I retained; successful establishment also depends on niche availability.6 |
Immigration (I) 移民 (I) | Decreases as S increases.2 | Decreases as S increases, influenced by D and N (saturation limit).6 |
Extinction (E) 灭绝(E) | Increases as S increases; decreases with larger A.2 | Increases as S increases; decreases with larger A; distinguishes short-term (initially high) and long-term rates.6 |
Niche Role 生态位角色 | Implicit via habitat diversity correlated with area.6 | Explicit: Number of climatic niches is a primary driver of S, explaining latitudinal gradients.6 |
This comparison underscores that while ETIB provides the foundation, NTIB offers a more ecologically explicit framework by incorporating niche availability. In the context of global fragmentation, this distinction is critical. The process doesn't merely reduce land area; it likely homogenizes the environment within each resulting small island fragment. Consequently, the number of available niches per island would plummet, potentially driving species richness down even more severely than predicted by area effects alone. The global impact hinges significantly on the environmental heterogeneity retained within the newly formed islands.6
这种比较强调了虽然生态系统理论的基础提供了基础,但新生态系统理论通过纳入生态位可用性提供了更具生态学明确性的框架。在全球碎片化的背景下,这一区别至关重要。这个过程不仅仅减少了土地面积;它可能还会使每个形成的小岛碎片内的环境同质化。因此,每个岛屿可用的生态位数量将急剧下降,可能导致物种丰富度的下降比仅仅通过面积效应预测的还要严重。全球影响在很大程度上取决于新形成的岛屿中保留的环境异质性。6
B. Area, Isolation, and Species Richness
B. 面积、隔离与物种丰富度
The relationship between island area and species richness (the Species-Area Relationship, SAR) is one of the most consistent patterns in ecology.9 Larger islands generally harbor more species than smaller ones.2 Several mechanisms underpin this relationship. Larger islands present a larger "target" for dispersing organisms, increasing the probability of colonization (the target area effect).3 They typically encompass a greater diversity of habitats and microclimates, providing niches for a wider array of species (the habitat diversity hypothesis).3 Furthermore, larger areas can support larger population sizes for each species, which buffers them against stochastic extinction events and reduces overall extinction rates.3 This relationship is often described by the power-law function S = cA^z, where S is species richness, A is area, and c and z are constants reflecting the intercept and slope of the relationship in logarithmic space.6 The constant z typically falls between 0.15 and 0.35, implying that a tenfold increase in area roughly doubles the number of species.9 Conversely, habitat loss (a reduction in area) leads to a predictable decline in the number of species an area can sustain; a 90% habitat loss can reduce sustainable species richness by about half.16
岛屿面积与物种丰富度之间的关系(物种-面积关系,SAR)是生态学中最一致的模式之一。较大的岛屿通常比较小的岛屿拥有更多的物种。几种机制支撑着这种关系。 较大的岛屿为分散的生物提供了更大的“目标”,增加了定殖的概率(目标区域效应)。它们通常包含更丰富的栖息地和微气候,为更广泛的物种提供了生态位(栖息地多样性假说)。此外,较大的区域可以支持每个物种更大的种群规模,这使它们能够抵御随机灭绝事件,并降低整体灭绝率。这个关系通常用幂律函数 S = cA^z 来描述,其中 S 是物种丰富度,A 是面积,c 和 z 是反映关系在对数空间中截距和斜率的常数。常数 z 通常在 0.15 和 0.35 之间,意味着面积增加十倍大致会使物种数量翻倍。相反,栖息地丧失(面积减少)会导致一个区域能够维持的物种数量可预测地下降;90% 的栖息地丧失可能会使可持续的物种丰富度减少约一半。
However, the SAR is not always straightforward. For very small islands, the relationship may break down (the "small island effect"), with species richness potentially varying independently of area due to factors like disturbance or stochastic colonization.10 Conversely, very large and old islands may exhibit a secondary increase in species richness beyond what immigration-extinction dynamics alone would predict, due to in situ speciation – the evolution of new species within the island itself.10
然而,SAR 并不总是简单明了。对于非常小的岛屿,这种关系可能会失效(“小岛效应”),物种丰富度可能会因干扰或随机定殖等因素而独立于面积变化。相反,非常大且古老的岛屿可能会表现出物种丰富度的二次增加,超出移民-灭绝动态所能预测的范围,这归因于原位物种形成——新物种在岛屿内部的进化。
Island isolation, typically measured as distance from the mainland or nearest large source pool, also profoundly affects species richness.1 Increased isolation acts as a barrier to dispersal, reducing the rate at which new species arrive and colonize.3 Consequently, more isolated islands generally support fewer species than islands of similar size located closer to a source.2 Isolation also influences extinction dynamics through the "rescue effect".3 Islands closer to a source receive more frequent immigrants, which can supplement dwindling populations and rescue them from local extinction, thereby lowering the overall extinction rate.3 Isolation can also shape the phylogenetic structure of island communities, with more isolated islands often having less phylogenetic diversity due to colonization by fewer, closely related lineages.19
岛屿孤立,通常通过与大陆或最近的大型源池的距离来衡量,也深刻影响物种丰富度。增加的孤立性作为一种扩散障碍,减少了新物种到达和定殖的速度。因此,通常更孤立的岛屿支持的物种数量少于位于更靠近源的相似大小的岛屿。孤立性还通过“救援效应”影响灭绝动态。靠近源的岛屿接收更频繁的移民,这可以补充逐渐减少的种群,并将其从地方灭绝中拯救出来,从而降低整体灭绝率。孤立性还可以塑造岛屿群落的系统发育结构,通常更孤立的岛屿由于被更少的、密切相关的谱系定殖,具有较少的系统发育多样性。
Applying these principles to the global fragmentation scenario yields stark predictions. Every fragment becomes an island, characterized by significantly reduced area compared to the original continents. Isolation varies depending on the width of the newly formed seaways, but for fragments originating from continental interiors, the effective isolation from diverse source pools could be immense. According to both ETIB and NTIB, this combination of drastically reduced area and increased effective isolation would lead to a catastrophic global decline in equilibrium species numbers.
将这些原则应用于全球碎片化场景会产生严峻的预测。每个碎片都变成一个岛屿,其面积与原始大陆相比显著减少。隔离程度取决于新形成的海域的宽度,但对于源自大陆内部的碎片来说,与多样化源池的有效隔离可能是巨大的。根据 ETIB 和 NTIB,这种面积大幅减少和有效隔离增加的组合将导致全球平衡物种数量的灾难性下降。
C. Speciation and Extinction Dynamics
C. 物种形成与灭绝动态
The equilibrium richness predicted by island biogeography theory is maintained by the dynamic processes of extinction and immigration, and over longer timescales, speciation. Extinction rates are intrinsically linked to island size.2 Smaller islands support smaller populations, which are inherently more vulnerable to extinction from demographic stochasticity (random fluctuations in birth and death rates), environmental stochasticity (e.g., storms, droughts), genetic problems like inbreeding and drift, and catastrophic events.15 As species richness increases on an island, average population sizes may decrease, and interspecific competition intensifies, further elevating extinction risk.5 Small islands may also be more susceptible to chronic disturbances that disproportionately remove species.9 Following habitat fragmentation, there is often a time lag before all extinctions caused by the reduced area and increased isolation occur; this phenomenon is known as "extinction debt".15
岛屿生物地理学理论预测的平衡丰富度是通过灭绝和移民的动态过程维持的,随着时间的推移,物种形成也会起作用。灭绝率与岛屿大小密切相关。较小的岛屿支持较小的种群,这些种群本质上更容易受到人口随机性(出生和死亡率的随机波动)、环境随机性(例如,风暴、干旱)、近亲繁殖和漂变等遗传问题以及灾难性事件的影响。随着岛屿上物种丰富度的增加,平均种群规模可能会减少,种间竞争加剧,进一步提高灭绝风险。小岛屿也可能更容易受到慢性干扰,这些干扰不成比例地消除物种。在栖息地破碎化之后,通常会有一个时间滞后,才会发生由于面积减少和隔离增加而导致的所有灭绝现象;这一现象被称为“灭绝债务”。
While islands are often sites of elevated extinction risk, they can also be cradles of evolution, particularly through the process of adaptive radiation.22 This occurs when a single ancestral species colonizes an island environment (or archipelago) with abundant ecological opportunities—such as vacant niches resulting from the absence of mainland competitors or predators—and rapidly diversifies into multiple new species, each adapted to exploit different resources or habitats.23 Classic examples include Darwin's finches in the Galápagos, where beak shapes diversified to utilize different food sources (seeds, insects, nectar, etc.) 3, and the Hawaiian honeycreepers, which evolved an extraordinary array of bill forms adapted to various diets.22 Similar radiations are seen in Anolis lizards on Caribbean islands 19 and cichlid fishes in African lakes.24 Such in situ speciation is a key process contributing to the high levels of endemism and overall species richness observed on large, ancient, and isolated islands.10
虽然岛屿通常是灭绝风险较高的地方,但它们也可以是进化的摇篮,特别是通过适应性辐射的过程。22 当一个单一的祖先物种殖民一个生态机会丰富的岛屿环境(或群岛)时——例如,由于缺乏大陆竞争者或捕食者而产生的空缺生态位——并迅速多样化为多个新物种,每个物种都适应于利用不同的资源或栖息地时,就会发生这种情况。23 经典的例子包括加拉帕戈斯群岛的达尔文雀,它们的喙形状多样化以利用不同的食物来源(种子、昆虫、花蜜等)3,以及夏威夷的蜂雀,它们进化出适应各种饮食的非凡喙形。22 在加勒比海岛屿的安诺利蜥蜴 19 和非洲湖泊的慈鲷鱼中也可以看到类似的辐射。24 这种原位物种形成是导致大型、古老和孤立岛屿上观察到的高水平特有性和整体物种丰富度的关键过程。10
In the global fragmentation scenario, the immediate consequence would be a massive wave of extinctions driven by the drastic reduction in area and increased isolation of countless newly formed habitat patches.3 While the potential for future adaptive radiation exists on these new islands, it operates on evolutionary timescales (thousands to millions of years). This long-term process would only commence after the initial ecological collapse and would be limited to the lineages capable of surviving the fragmentation event and successfully colonizing the new island fragments. The potential for significant speciation would likely be constrained by the small size and potentially limited niche diversity of most fragments.
在全球碎片化的情景中,直接后果将是由于无数新形成的栖息地斑块面积急剧减少和孤立性增加而导致的大规模灭绝浪潮。虽然这些新岛屿上存在未来适应性辐射的潜力,但它是在进化时间尺度上运作的(数千到数百万年)。这一长期过程只有在初始生态崩溃之后才会开始,并且将限于能够在碎片化事件中生存并成功殖民新岛屿碎片的谱系。显著物种形成的潜力可能会受到大多数碎片小规模和潜在有限生态位多样性的限制。
D. Implications for Global Fragmentation
D. 全球碎片化的影响
The principles of island biogeography, particularly when refined by niche considerations, point towards several profound consequences of global landmass fragmentation. Firstly, the fragmentation process inherently reduces not only the area of habitat patches but also the environmental heterogeneity contained within them. Smaller geographic units typically encompass fewer climate zones, less topographic variation, and fewer distinct habitat types compared to large continents. According to the Niche-Based Theory of Island Biogeography 6, which posits that the number of available ecological niches is a primary determinant of species richness, this reduction in niche diversity within each fragment would impose a severe limitation on the number of species each island could support. This effect compounds the negative impact of simple area reduction predicted by classic ETIB, suggesting an even steeper decline in global biodiversity.
岛屿生物地理学的原则,特别是在考虑生态位的情况下,指向全球陆地碎片化的几个深远后果。首先,碎片化过程不仅固有地减少栖息地斑块的面积,还减少了其中所包含的环境异质性。与大洲相比,较小的地理单元通常涵盖的气候区较少,地形变化较小,独特栖息地类型也较少。根据生态位基础岛屿生物地理学理论 6,该理论认为可用生态位的数量是物种丰富度的主要决定因素,这种每个碎片内生态位多样性的减少将对每个岛屿能够支持的物种数量施加严重限制。这一效应加剧了经典 ETIB 预测的简单面积减少的负面影响,暗示全球生物多样性将出现更陡峭的下降。
Secondly, the fragmentation event would trigger a global "relaxation" process.3 Immediately after fragmentation, the newly formed islands would contain a supersaturated set of species inherited from the former larger landmasses – far more than they can sustain at equilibrium given their reduced size and increased isolation. This initiates a period of elevated extinction rates as communities "relax" towards a new, much lower equilibrium species number. Because fragmentation occurs globally and simultaneously in this scenario, this relaxation would manifest as a massive, protracted extinction crisis playing out across virtually all terrestrial landscapes over ecological and potentially evolutionary timescales. This represents a global accumulation of extinction debt 15, where the full impact of fragmentation unfolds over time rather than instantaneously.
其次,碎片化事件将触发一个全球“放松”过程。3 在碎片化之后,新形成的岛屿将包含从以前更大陆地继承的过饱和物种集合——远远超过它们在其减小的规模和增加的孤立状态下所能维持的平衡数量。这会引发一个高灭绝率的时期,因为群落“放松”到一个新的、远低于的平衡物种数量。由于在这种情况下,碎片化是全球性和同时发生的,这种放松将表现为在几乎所有陆地景观上展开的大规模、长期的灭绝危机,跨越生态和潜在的进化时间尺度。这代表了一个全球性的灭绝债务的积累 15,其中碎片化的全部影响随着时间的推移而展开,而不是瞬间发生。
Thirdly, while island biogeography emphasizes the role of isolation in limiting colonization and potentially fostering unique evolutionary trajectories 1, the pervasive influence of human activity in the modern era could significantly alter these dynamics. Studies have shown that human mediated transport can facilitate the colonization of islands by certain species, effectively overriding natural barriers and weakening the isolation effect.19 In a fragmented world where oceans form the matrix between islands, continued global shipping and travel could act as potent vectors for dispersal. Species well-adapted to human presence or capable of surviving transport (e.g., generalists, commensals, invasive species) might achieve widespread distributions, bypassing natural dispersal limitations. This could lead to a degree of biotic homogenization across the newly formed archipelagos, potentially counteracting the diversification typically expected from long-term isolation and promoting the success of a relatively small subset of adaptable species.19
第三,虽然岛屿生物地理学强调孤立在限制殖民和可能促进独特进化轨迹中的作用,但现代时代人类活动的普遍影响可能会显著改变这些动态。研究表明,人为运输可以促进某些物种对岛屿的殖民,有效地克服自然障碍并削弱孤立效应。在一个海洋形成岛屿之间矩阵的碎片化世界中,持续的全球航运和旅行可能成为强有力的传播媒介。适应人类存在或能够在运输中生存的物种(例如,广泛适应的物种、共生物种、入侵物种)可能会实现广泛分布,绕过自然传播限制。这可能导致新形成的群岛之间生物同质化的程度,可能抵消长期孤立通常预期的多样化,并促进相对少数适应性物种的成功。
II. Reconfiguration of Global Ocean Circulation
II. 全球海洋环流的重组
The hypothetical fragmentation of continents into islands would fundamentally alter the geometry of ocean basins, leading to a radical reconfiguration of ocean circulation patterns, impacting both surface currents and the deep thermohaline circulation.
大陆假设性地碎裂成岛屿将从根本上改变海洋盆地的几何形状,导致海洋环流模式的根本重组,影响表层洋流和深层热盐环流。
A. Surface Currents and Gyres: Role of Landmasses
A. 表层洋流和旋涡:陆地的作用
Ocean surface currents, the large-scale horizontal movements of water in the upper ocean, are primarily set in motion by the friction of prevailing winds blowing across the sea surface.28 However, their direction is significantly modified by the Earth's rotation through the Coriolis effect, which deflects moving water to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.28 This deflection, combined with friction between water layers, results in a net movement of water known as Ekman transport, which is roughly perpendicular to the wind direction (typically 90° integrated over depth, though closer to 45° at the immediate surface).28
海洋表层洋流是水在上层海洋中的大规模水平运动,主要是由于盛行风在海面上吹动所产生的摩擦力。然而,它们的方向受到地球自转的显著影响,通过科里奥利效应,向北半球的右侧和南半球的左侧偏转。这个偏转,加上水层之间的摩擦,导致了水的净运动,称为埃克曼输送,通常与风的方向大致垂直(在深度上约为 90°,但在表面附近更接近 45°)。
These wind-driven, Coriolis-modified currents interact with the boundaries of ocean basins, which are defined by the continents. Landmasses act as crucial barriers, deflecting currents and forcing them to turn, thereby organizing the flow into large, rotating systems known as gyres.28 The five major subtropical gyres (North Pacific, South Pacific, North Atlantic, South Atlantic, and Indian Ocean) are prominent examples, typically rotating clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.28 The shape and extent of these gyres are thus fundamentally constrained by the configuration of continents.29
这些由风驱动、受科里奥利效应影响的洋流与海洋盆地的边界相互作用,而海洋盆地的边界由大陆定义。陆地作为重要的障碍物,偏转洋流并迫使其转向,从而将流动组织成称为大洋环流的旋转系统。五大亚热带环流(北太平洋、南太平洋、北大西洋、南大西洋和印度洋)就是显著的例子,通常在北半球顺时针旋转,在南半球逆时针旋转。因此,这些环流的形状和范围在根本上受到大陆配置的限制。
Within these gyres, the interaction between the flow, the Coriolis effect, and the basin boundaries leads to distinct characteristics of the currents along the edges. Western boundary currents, found on the western sides of ocean basins (eastern coasts of continents), become intensified – they are typically narrow, deep, and fast-flowing. Examples include the Gulf Stream in the North Atlantic and the Kuroshio Current in the North Pacific.28 Conversely, eastern boundary currents, on the eastern sides of basins (western coasts of continents), are generally broader, shallower, and slower-moving, often carrying cooler water towards the equator (e.g., the California Current, Canary Current).28 This asymmetry, known as western intensification, is a direct consequence of the increasing Coriolis effect with latitude acting within the confines of the ocean basin.29
在这些大洋环流中,流动、科里奥利效应和盆地边界之间的相互作用导致了沿边缘的洋流具有明显的特征。位于海洋盆地西侧(大陆东海岸)的西边界洋流变得更加强烈——它们通常狭窄、深且流速快。例子包括北大西洋的墨西哥湾流和北太平洋的黑潮。相反,位于盆地东侧(大陆西海岸)的东边界洋流通常更宽、更浅且流速较慢,常常将较冷的水向赤道输送(例如,加利福尼亚洋流、加那利洋流)。这种不对称性被称为西部强化,是纬度增加的科里奥利效应在海洋盆地限制内作用的直接结果。
B. Thermohaline Circulation (THC/AMOC): Drivers and Sensitivity
B. 热盐环流 (THC/AMOC):驱动因素和敏感性
Beneath the surface, a slower but globally significant circulation system operates, driven by differences in water density. This is the thermohaline circulation (THC), often referred to as the Meridional Overturning Circulation (MOC) or the "global conveyor belt".30 Density is controlled by temperature (thermo) and salinity (haline) – colder water is denser than warmer water, and saltier water is denser than fresher water.32
在表面之下,一个较慢但全球重要的环流系统在运作,受水密度差异的驱动。这就是热盐环流 (THC),通常被称为经向翻转环流 (MOC) 或“全球传送带”。密度受温度(热)和盐度(盐)控制——较冷的水比较温暖的水密度大,较咸的水比较淡的水密度大。
The THC is primarily driven by the formation of dense water masses at high latitudes.48 In specific polar regions, particularly the North Atlantic (Nordic and Labrador Seas) and around Antarctica (Weddell and Ross Seas), surface waters lose heat to the cold atmosphere and/or increase in salinity due to evaporation or, more significantly, the formation of sea ice.40 When sea ice forms, salt is excluded from the ice crystals and expelled into the surrounding water (brine rejection), making it significantly saltier and denser.40 This cold, salty water becomes dense enough to sink to the deep ocean.32 The primary deep water masses formed are North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW).46
THC 主要是由高纬度地区密集水团的形成驱动的。在特定的极地地区,特别是北大西洋(北欧海和拉布拉多海)以及南极洲周围(韦德尔海和罗斯海),表层水因向寒冷大气散失热量和/或因蒸发或更显著的海冰形成而增加盐度。当海冰形成时,盐被排除在冰晶之外并排放到周围水中(盐水排斥),使其变得显著更咸和更密。这个寒冷、咸的水变得足够密以沉入深海。形成的主要深水团是北大西洋深水(NADW)和南极底水(AABW)。
These newly formed deep waters then spread equatorward, filling the deep ocean basins.47 To maintain mass balance, there must be a return flow of warmer surface waters towards the poles, such as the northward flow of the Gulf Stream system compensating for the southward flow of NADW.46 Deep water eventually returns to the surface through slow upwelling, primarily thought to occur in the Southern Ocean, aided by wind-driven divergence and mixing processes, completing the global circuit.32
这些新形成的深水随后向赤道扩散,填满深海盆地。为了维持质量平衡,必须有温暖的表层水向极地返回,例如墨西哥湾流系统向北流动以补偿南向流动的北大西洋深水。深水最终通过缓慢的上涌返回到表面,主要被认为发生在南极洋,受到风驱动的发散和混合过程的帮助,完成全球循环。
The THC is known to be sensitive to changes in the density of surface waters in the deep water formation regions.48 Significant inputs of freshwater – from melting glaciers and ice sheets, increased river runoff, or changes in precipitation patterns – can lower surface salinity, reduce density, and inhibit sinking.39 Paleoclimate records provide compelling evidence that the THC has undergone abrupt changes in the past, including slowdowns or near-shutdowns during events like the Younger Dryas cold period (~12,700 years ago) and the 8.2 ka event, often linked to massive freshwater pulses from melting ice sheets.44 These past changes in circulation were associated with significant and rapid shifts in regional and potentially global climate.49
THC 被认为对深水形成区域表层水密度的变化敏感。48 大量淡水的输入——来自融化的冰川和冰盖、增加的河流径流或降水模式的变化——可以降低表层盐度、减少密度并抑制下沉。39 古气候记录提供了有力证据,表明 THC 在过去经历了突发变化,包括在如年轻干燥期(约 12,700 年前)和 8.2 千年事件等事件期间的减缓或接近停滞,这些事件通常与融化冰盖的大量淡水脉冲有关。44 这些过去的环流变化与区域和潜在全球气候的显著和快速变化相关联。49
C. Predicted Impacts of Fragmentation on Circulation Patterns
C. 预测碎片化对环流模式的影响
Global landmass fragmentation would fundamentally alter the boundary conditions that govern ocean circulation. The removal of large continental barriers would dismantle the framework that organizes surface currents into large-scale gyres.28 It is highly probable that the major ocean gyres would collapse or break down. Surface flow might become a much more complex and less predictable tapestry of smaller eddies, jets, and inter-island currents, dictated by the intricate geometry of the new archipelagos and altered wind fields. The Antarctic Circumpolar Current (ACC), which flows largely unimpeded by land around Antarctica 34, might persist if the Antarctic continent remains intact, but its strength and interaction with other basins would inevitably change due to the altered connections and water mass properties globally.
全球陆地碎片化将从根本上改变控制海洋环流的边界条件。大型大陆屏障的移除将 dismantle 组织表面洋流的大规模涡旋的框架。28 主要的海洋涡旋很可能会崩溃或瓦解。表面流动可能变成一个更加复杂且不可预测的小涡流、喷流和岛屿间洋流的拼图,这些都由新群岛的复杂几何形状和改变的风场所决定。如果南极大陆保持完整,南极环流(ACC)可能会持续存在,但由于全球连接和水团特性的改变,其强度和与其他盆地的相互作用必然会发生变化。
The impacts on the thermohaline circulation could be even more profound. Fragmentation would drastically alter the patterns of freshwater input into the oceans. Instead of large rivers draining continental interiors, runoff would occur from countless smaller islands distributed globally.46 This could significantly change surface salinity in current or potential deep water formation zones, potentially inhibiting sinking.39 Furthermore, the altered surface circulation patterns would affect how and where surface waters are cooled in high latitudes.48 The combination of modified salinity inputs and altered surface heat exchange could severely weaken, disrupt, or even lead to a complete collapse of the established THC pathways.44 The locations of deep water formation might shift, or the process might cease altogether in some regions. The pathways for deep water spreading and the routes for surface water return flow would also be fundamentally rerouted by the new island geography.
对热盐环流的影响可能会更加深远。碎片化将极大改变淡水流入海洋的模式。与其说是大河从大陆内部排水,不如说是来自全球分布的无数小岛的径流。这可能会显著改变当前或潜在深水形成区的表面盐度,可能抑制沉降。此外,改变的表面环流模式将影响高纬度地区表面水的冷却方式和位置。修改后的盐度输入和改变的表面热交换的结合可能会严重削弱、干扰,甚至导致已建立的热盐环流路径的完全崩溃。深水形成的位置可能会发生变化,或者在某些地区这一过程可能完全停止。深水扩散的路径和表面水回流的路线也将因新的岛屿地理而根本重定向。
D. Implications for Global Fragmentation
D. 全球碎片化的影响
The predicted changes in ocean circulation carry significant implications. The elimination of large continental barriers 28 means the familiar, organized basin-scale gyres that characterize today's oceans would likely cease to exist. In their place, surface circulation could become dominated by a more turbulent and less predictable regime of smaller eddies and complex flows navigating the myriad channels between islands. This represents a fundamental shift in the way the ocean surface moves, which would drastically alter the transport pathways for heat, nutrients, plankton, pollutants, and marine organisms.
预测的海洋环流变化具有重要意义。大型大陆障碍的消除意味着,今天海洋特有的熟悉的、有序的盆地规模的涡流可能会不复存在。取而代之的是,表层环流可能会被更为动荡和不可预测的小涡流和复杂流动所主导,这些流动在岛屿之间的无数通道中穿行。这代表了海洋表面运动方式的根本变化,这将极大地改变热量、养分、浮游生物、污染物和海洋生物的运输路径。
Furthermore, the stability of the thermohaline circulation appears highly vulnerable in this scenario. The THC relies on a delicate balance of temperature and salinity to drive deep water formation in specific high-latitude locations.33 Global fragmentation introduces two major disruptions: potentially widespread freshening of surface waters near formation zones due to runoff from numerous new coastlines 46, and altered surface currents that change how water is cooled.48 Both factors work against the formation of dense water required to drive the overturning circulation. Given the known sensitivity of the THC to freshwater inputs, as evidenced by paleoclimate events like the Younger Dryas 44, the scale of disruption implied by global fragmentation suggests a high probability of a significant slowdown, relocation of sinking regions, or even a complete collapse of the global conveyor belt. Such a change would dwarf past abrupt climate events in its potential impact.
此外,在这种情况下,热盐环流的稳定性似乎非常脆弱。THC 依赖于温度和盐度的微妙平衡,以驱动特定高纬度地区的深水形成。全球碎片化引入了两个主要干扰:由于众多新海岸线的径流,形成区附近的表层水可能会广泛淡化,以及改变表层洋流的变化,影响水的冷却方式。这两个因素都不利于形成驱动翻转环流所需的密集水。考虑到 THC 对淡水输入的已知敏感性,正如年轻干燥期等古气候事件所证明的那样,全球碎片化所暗示的干扰规模表明,显著减缓、沉降区域的重新定位,甚至全球传送带的完全崩溃的可能性很高。这种变化在潜在影响上将远超过去的突发气候事件。
Finally, the connections between major ocean basins – the gateways that regulate the exchange of water, heat, salt, and marine life, such as the Indonesian Throughflow 47, Drake Passage, or the Bering Strait – are defined by the current placement of continents. Fragmentation would radically reshape this global "plumbing system." Numerous new seaways would likely open between formerly contiguous land areas, while existing passages might be altered or closed depending on the specific pattern of fragmentation. This would lead to a fundamental reorganization of inter-basin exchange, rerouting major currents and changing the volume and properties of water masses transferred between the Atlantic, Pacific, Indian, and Arctic oceans, with far-reaching and potentially unpredictable consequences for the entire Earth system.
最后,主要海洋盆地之间的连接——调节水、热、盐和海洋生物(如印度尼西亚海流 47、德雷克海峡或白令海峡)交换的通道——是由大陆当前的位置决定的。碎片化将彻底重塑这个全球“管道系统”。许多新的海路可能会在以前相连的陆地区域之间开放,而现有的通道可能会根据具体的碎片化模式而被改变或关闭。这将导致海盆间交换的根本重组,重新引导主要洋流,并改变大西洋、太平洋、印度洋和北冰洋之间转移的水团的体积和性质,对整个地球系统产生深远且可能不可预测的影响。
III. Global and Regional Climate Transformation
III. 全球与区域气候转变
Changes in ocean circulation driven by landmass fragmentation would inevitably trigger profound transformations in global and regional climate patterns, altering temperature regimes, precipitation distribution, and the nature of climate extremes.
陆地碎片化引发的海洋环流变化将不可避免地引发全球和区域气候模式的深刻转变,改变温度模式、降水分布以及气候极端现象的性质。
A. Ocean's Role in Climate Regulation and Heat Transport
A. 海洋在气候调节和热量输送中的作用
The ocean plays a paramount role in regulating Earth's climate. Its immense volume and the high heat capacity of water allow it to absorb and store vast quantities of solar energy, far exceeding the capacity of the land surface or the atmosphere.43 The majority of incoming solar radiation is absorbed by the ocean, particularly in the tropical regions, effectively making the ocean a massive heat reservoir.41 This absorbed heat is not static; ocean currents act as a global distribution system, a "conveyor belt" transporting warm water from the equator towards the poles and returning colder water towards the tropics.32 This continuous redistribution of heat moderates global temperature differences, preventing extreme heat in the tropics and extreme cold at higher latitudes, thereby making much of the planet habitable.41
海洋在调节地球气候方面发挥着至关重要的作用。其巨大的体积和水的高热容使其能够吸收和储存大量的太阳能,远远超过陆地表面或大气的能力。大部分入射的太阳辐射被海洋吸收,特别是在热带地区,有效地使海洋成为一个巨大的热量储存库。这些吸收的热量并不是静态的;海洋洋流作为全球分配系统,充当“传送带”,将温暖的水从赤道运输到极地,并将较冷的水返回热带。这种热量的持续再分配调节了全球温度差异,防止了热带地区的极端高温和高纬度地区的极端寒冷,从而使地球上的大部分地区适宜居住。
The ocean is also the primary engine of the global water cycle. Constant evaporation from the ocean surface transfers moisture into the atmosphere.41 This water vapor, laden with latent heat, is transported by winds and eventually condenses to form clouds and precipitation, much of which falls over land.41 The tropics, receiving the most intense solar radiation, experience the highest rates of evaporation and consequently tend to be the rainiest regions.41
海洋也是全球水循环的主要引擎。海洋表面的持续蒸发将水分转移到大气中。这些水蒸气携带着潜热,通过风的输送,最终凝结形成云和降水,其中大部分降落在陆地上。热带地区接收最强烈的太阳辐射,经历最高的蒸发率,因此往往是降雨最多的地区。
B. Maritime vs. Continental Climates: Defining Characteristics
B. 海洋气候与大陆气候:定义特征
The influence of large water bodies versus large landmasses creates distinct climate types. Locations near oceans or large lakes experience maritime climates, while regions deep within continental interiors exhibit continental climates.57
大型水体与大型陆地的影响形成了不同的气候类型。靠近海洋或大型湖泊的地区经历海洋气候,而位于大陆内部深处的地区则表现出大陆气候。57
The defining characteristic is temperature range. Due to the high heat capacity of water, oceans warm up and cool down much more slowly than land.57 This thermal inertia moderates temperatures in coastal areas, resulting in maritime climates with relatively small daily and seasonal temperature variations – summers are typically cooler and winters milder than inland locations at the same latitude.57 A common threshold defines maritime climates as having an annual temperature range of less than 25°C.60 In contrast, continental climates, far from the ocean's moderating influence, experience much larger temperature swings between seasons and often between day and night. Summers can be very hot, and winters very cold, with annual temperature ranges often exceeding 25°C.57
决定性特征是温度范围。由于水的高热容,海洋的升温和降温速度远远慢于陆地。这种热惯性调节了沿海地区的温度,导致海洋气候具有相对较小的日间和季节温度变化——夏季通常比同纬度的内陆地区凉爽,冬季则比内陆地区温和。一个常见的阈值将海洋气候定义为年温度范围小于 25°C。相比之下,远离海洋调节影响的大陆气候,季节之间以及昼夜之间的温度波动要大得多。夏季可能非常炎热,冬季则非常寒冷,年温度范围通常超过 25°C。
Precipitation patterns also differ. Maritime climates generally receive higher amounts of precipitation (often defined as >1000 mm annually) because of the abundant moisture evaporated from the nearby water body.57 Precipitation in maritime climates is often distributed relatively evenly throughout the year or may show a winter maximum.60 Continental climates tend to be drier overall (often <1000 mm annually), as air masses moving over land lose moisture.61 Precipitation in continental regions frequently peaks during the summer months, often associated with convective storms.60 Coastal areas can receive significantly more precipitation (30-40% more) than inland areas at comparable latitudes.59
降水模式也有所不同。海洋气候通常接收较高的降水量(通常定义为每年超过 1000 毫米),因为附近水体蒸发的丰富水分。海洋气候的降水通常在全年相对均匀分布,或可能在冬季达到最大值。大陆气候总体上往往较干燥(通常每年少于 1000 毫米),因为移动在陆地上的气团失去水分。大陆地区的降水在夏季月份常常达到高峰,通常与对流风暴有关。沿海地区的降水量通常比同纬度的内陆地区显著更多(多 30-40%)。
Table 2: Maritime vs. Continental Climate Comparison
表 2:海洋气候与大陆气候比较
Feature 特征 | Maritime Climate 海洋气候 | Continental Climate 大陆气候 |
Proximity to Water 靠近水体 | High (coastal, near large lakes) 57 | Low (inland, far from large water bodies) 57 |
Annual Temperature Range 年温差 | Small (< 25°C) 60 小(< 25°C)60 | Large (≥ 25°C) 60 大于等于 25°C 60 |
Seasonal Temperature Variation | Moderate (cooler summers, milder winters) 57 | Extreme (hot summers, cold winters) 57 |
Daily Temperature Variation | Generally smaller 59 通常较小 59 | Generally larger 通常较大 |
Total Annual Precipitation | Generally High (≥ 1000 mm) 59 | Generally Lower (< 1000 mm) 60 |
Seasonal Precipitation Distribution | Often winter maximum or evenly distributed 60 | Often summer maximum 60 通常夏季最高 60 |
Humidity 湿度 | Generally Higher 59 通常更高 59 | Generally Lower 一般较低 |
C. Predicted Climate Shifts: Temperature, Precipitation, Extremes
C. 预测的气候变化:温度、降水、极端天气
Global landmass fragmentation would effectively eliminate large continental interiors, bringing nearly all land surfaces under the influence of the ocean. This implies a profound global shift away from continental climates towards predominantly maritime conditions.57
全球陆地碎片化将有效消除大型大陆内部,使几乎所有陆地表面都受到海洋的影响。这意味着全球气候将发生深刻变化,从大陆气候转向以海洋气候为主的条件。57
In terms of temperature, this suggests a significant global moderation. Areas currently experiencing extreme seasonal temperature swings (hot summers, frigid winters) would likely see these extremes greatly reduced, with warmer winters and cooler summers becoming the norm.57 However, this overall trend towards moderation could be dramatically counteracted in specific regions by changes in ocean heat transport. Areas currently kept anomalously warm by currents like the Gulf Stream/North Atlantic Drift (e.g., Northern Europe 46) could face severe cooling if the thermohaline circulation is disrupted or collapses, as discussed in Section II.46
在温度方面,这表明全球显著的温和化。目前经历极端季节温度波动(炎热的夏季,寒冷的冬季)的地区可能会看到这些极端现象大大减少,温暖的冬季和凉爽的夏季将成为常态。然而,这种整体向温和化的趋势可能会在特定地区因海洋热量输送的变化而受到显著抵消。目前因墨西哥湾流/北大西洋漂流等洋流而异常温暖的地区(例如,北欧)如果热盐环流受到干扰或崩溃,可能会面临严重的降温,如第二节所讨论的那样。
Globally, precipitation is likely to increase due to the vastly expanded ocean-atmosphere interface, leading to greater overall evaporation.41 Most land areas, now effectively coastal, would likely experience higher humidity and rainfall than their continental predecessors.56 However, the distribution of this precipitation would be radically altered by changes in atmospheric circulation patterns driven by the new land-sea configuration and ocean temperatures. While some climate models under current warming scenarios predict wetter coasts and drier interiors 56, the fragmentation scenario essentially removes the interiors, suggesting widespread increases in precipitation, albeit with highly uncertain regional patterns.
全球范围内,由于海洋-大气界面的大幅扩展,降水量可能会增加,从而导致整体蒸发量增加。大多数陆地区域,现在实际上是沿海的,可能会经历比其大陆前身更高的湿度和降雨量。然而,这种降水的分布将因新陆海配置和海洋温度驱动的气候循环模式变化而发生根本性改变。虽然一些气候模型在当前变暖情景下预测沿海地区会更潮湿而内陆地区会更干燥,但碎片化情景基本上消除了内陆,暗示降水量普遍增加,尽管区域模式高度不确定。
Regarding climate extremes, the moderation of temperatures would likely reduce the intensity and frequency of extreme heat waves and cold snaps associated with continental climates.59 However, the picture for other extremes is less clear. Altered atmospheric circulation patterns and potentially intensified evaporation could lead to changes in storm tracks and potentially increase the intensity of precipitation events in some regions.54 Warmer sea surface temperatures in some areas could fuel stronger storms 56, while altered wind patterns could impact windstorm frequency and intensity.54
关于气候极端现象,温度的适度变化可能会减少与大陆气候相关的极端热浪和寒潮的强度和频率。然而,其他极端现象的情况则不太明确。改变的大气环流模式和可能加剧的蒸发可能导致风暴路径的变化,并可能在某些地区增加降水事件的强度。某些地区的海面温度升高可能会助长更强的风暴,而改变的风模式可能会影响风暴的频率和强度。
D. Linkages to Altered Ocean Circulation
D. 与改变的海洋环流的联系
The predicted climate shifts are inextricably linked to the changes in ocean circulation outlined in Section II. The disruption or collapse of major ocean currents, particularly the THC/AMOC, would directly alter the poleward transport of heat.32 This is the primary mechanism by which fragmentation could lead to paradoxical regional cooling (e.g., in the North Atlantic region 46) amidst a potentially globally warmer or more moderated background state. The efficiency with which the ocean distributes heat across the planet would be fundamentally changed.
预测的气候变化与第二节中概述的海洋环流变化密切相关。主要海洋洋流,特别是 THC/AMOC 的中断或崩溃,将直接改变向极地的热量输送。这是碎片化可能导致悖论性区域降温(例如,在北大西洋地区)与潜在的全球变暖或更温和的背景状态之间的主要机制。海洋在全球范围内分配热量的效率将发生根本性变化。
Furthermore, ocean surface temperatures are a key driver of atmospheric circulation. They influence the formation and location of high and low-pressure systems, which in turn dictate prevailing wind patterns.31 Therefore, the radically altered sea surface temperature patterns resulting from disrupted ocean currents would lead to significant shifts in global atmospheric circulation. This could involve changes in the position and strength of jet streams, the behavior of major climate patterns like ENSO (El Niño-Southern Oscillation), and the viability of large-scale systems like monsoons, which depend on continent-ocean temperature contrasts.63
此外,海洋表面温度是大气环流的关键驱动因素。它们影响高压和低压系统的形成和位置,从而决定了主导风模式。因此,由于海洋洋流中断而导致的海表温度模式的根本改变将导致全球大气环流的显著变化。这可能涉及喷流的位置和强度的变化,主要气候模式(如 ENSO(厄尔尼诺-南方涛动))的行为,以及依赖于大陆与海洋温度对比的大规模系统(如季风)的可行性。
E. Implications for Global Fragmentation
E. 全球碎片化的影响
The climatic consequences of global fragmentation point towards a world operating under fundamentally different rules. The most immediate and pervasive impact is the near-total elimination of continental climates.57 With all landmasses effectively becoming coastal, the moderating influence of the ocean 59 would dominate temperature regimes globally. This "global maritimization" implies a reduction in extreme seasonal temperature variations across most of the planet's land surface, altering seasonality and the thermal environments experienced by terrestrial life.58
全球碎片化的气候后果指向一个在根本上运作规则不同的世界。最直接和普遍的影响是几乎完全消除了大陆气候。随着所有陆地有效地变成沿海地区,海洋的调节影响将主导全球的温度模式。这种“全球海洋化”意味着地球大部分陆地表面的极端季节温度变化将减少,改变季节性和陆生生命所经历的热环境。
However, this overall moderation masks a potentially chaotic redistribution of heat. The breakdown of established ocean current systems, particularly the heat-transporting thermohaline circulation 41, means that the delivery of heat from the tropics to higher latitudes would be drastically altered. Paleoclimate precedents show that disruptions to the AMOC can cause rapid and severe regional cooling in areas like Northern Europe, even during periods of overall warming.44 In the fragmentation scenario, such effects could occur globally but unpredictably. Some regions might cool dramatically due to the loss of warm currents, while others might warm unexpectedly, creating novel thermal landscapes largely decoupled from latitude.
然而,这种整体的温和掩盖了潜在的混乱热量重新分配。既有的洋流系统的崩溃,特别是热量输送的热盐环流 41,意味着热量从热带向高纬度的输送将会发生剧烈变化。古气候的先例表明,AMOC 的干扰可以导致像北欧这样的地区在整体变暖期间迅速而严重的区域降温。44 在碎片化情景中,这种影响可能会在全球范围内发生,但不可预测。一些地区可能因失去暖流而剧烈降温,而另一些地区可能意外升温,从而创造出在很大程度上与纬度脱钩的新型热景观。
The global hydrological cycle would also be profoundly affected. Increased evaporation from the larger effective ocean surface suggests a potential increase in total global precipitation.41 Yet, the atmospheric circulation patterns that distribute this moisture would be fundamentally changed. Large landmasses play a critical role in driving atmospheric circulation through differential heating compared to oceans, powering systems like monsoons.63 Removing these large landmasses weakens or eliminates these drivers. Consequently, while more rain might fall globally, its spatial and temporal distribution could become highly unpredictable. Strong, seasonally reliable patterns like monsoons might disappear, replaced by different, potentially more erratic rainfall regimes governed by the complex interactions between the atmosphere and the new island-studded ocean surface.
全球水文循环也将受到深刻影响。来自更大有效海洋表面的蒸发增加表明全球总降水量可能会增加。然而,分配这些水分的大气环流模式将发生根本变化。大型陆地在通过与海洋的差异加热驱动大气环流方面发挥着关键作用,推动季风等系统。移除这些大型陆地会削弱或消除这些驱动因素。因此,尽管全球可能会降更多的雨,但其空间和时间分布可能变得高度不可预测。像季风这样的强大、季节性可靠的模式可能会消失,取而代之的是由大气与新的岛屿点缀的海洋表面之间复杂相互作用所主导的不同、潜在的更不稳定的降雨模式。
IV. Consequences for Terrestrial Ecosystems
IV. 对陆地生态系统的影响
The transformation of continents into archipelagos represents the most extreme form of habitat fragmentation imaginable, leading to devastating consequences for terrestrial life through habitat loss, isolation, and pervasive edge effects.
大陆转变为群岛代表了栖息地碎片化的最极端形式,这导致了对陆地生命的毁灭性后果,包括栖息地丧失、孤立和普遍的边缘效应。
A. Habitat Loss and Fragmentation: Definitions and General Impacts
A. 栖息地丧失与碎片化:定义与一般影响
Habitat loss refers to the outright reduction in the total area available for a species or ecosystem, while habitat fragmentation describes the process by which remaining habitat is broken down into smaller, more isolated patches, separated by a matrix of altered land cover (in this scenario, the ocean).14 These two processes, often occurring concurrently 65, are widely recognized as the primary drivers of global biodiversity decline and species extinction.14
栖息地丧失是指可供某一物种或生态系统使用的总面积的直接减少,而栖息地碎片化则描述了剩余栖息地被分解成更小、更孤立的斑块的过程,这些斑块被改变的土地覆盖(在这种情况下是海洋)所隔开。这两个过程通常同时发生,被广泛认为是全球生物多样性下降和物种灭绝的主要驱动因素。
The general impacts are severe. Reduced habitat area directly lowers the carrying capacity of the environment, leading to smaller population sizes that are more vulnerable to extinction.66 Fragmentation increases isolation, hindering the movement of individuals between patches. This restricts dispersal, limits gene flow (increasing risks of inbreeding and loss of adaptive potential), and prevents recolonization of patches where local extinctions have occurred.66 Fragmentation can also alter species interactions, community structure, and ecosystem processes within the remaining patches.65 The long-standing debate in conservation biology regarding whether a single large reserve is better than several small reserves of the same total area (SLOSS) highlights the complex interplay between area and configuration 75, though the extreme nature of this scenario likely transcends the nuances of that debate.
总体影响是严重的。栖息地面积的减少直接降低了环境的承载能力,导致更小的种群规模,这些种群更容易面临灭绝的风险。66 破碎化增加了孤立,阻碍了个体在斑块之间的移动。这限制了扩散,限制了基因流动(增加了近亲繁殖和适应潜力丧失的风险),并阻止了在发生局部灭绝的斑块上重新定殖。66 破碎化还可以改变物种间的相互作用、群落结构和剩余斑块内的生态系统过程。65 关于单一大型保护区是否优于几个相同总面积的小型保护区(SLOSS)的长期辩论突显了面积和配置之间复杂的相互作用 75,尽管这一情境的极端性质可能超越了该辩论的细微差别。
B. Edge Effects: Microclimate and Biotic Changes
B. 边缘效应:微气候和生物变化
A critical consequence of fragmentation is the dramatic increase in the amount of "edge habitat" – the boundary zone where a habitat patch meets the surrounding matrix.76 As habitats are broken into smaller pieces, the ratio of edge to interior area increases significantly; in highly fragmented landscapes, edge effects can permeate the entire patch.64
碎片化的一个重要后果是“边缘栖息地”数量的急剧增加——栖息地斑块与周围基质相接的边界区域。随着栖息地被分割成更小的部分,边缘与内部区域的比例显著增加;在高度碎片化的景观中,边缘效应可以渗透到整个斑块。
Edges experience altered abiotic conditions compared to habitat interiors. Increased exposure leads to greater penetration of sunlight, higher daytime temperatures, lower nighttime temperatures (increased diurnal range), lower humidity due to increased evaporation, and increased wind speeds and turbulence.70 These microclimatic changes can extend surprisingly far into habitat fragments; studies in Amazonian forest fragments, for instance, detected edge-related microclimate alterations up to 100 meters or more from the edge.77
边缘地区的非生物条件与栖息地内部相比发生了变化。增加的暴露导致阳光的渗透增加,白天气温升高,夜间气温降低(昼夜温差增加),由于蒸发增加而湿度降低,以及风速和湍流增加。这些微气候变化可以意外地延伸到栖息地碎片的深处;例如,在亚马逊森林碎片中的研究发现,边缘相关的微气候变化可以在距离边缘 100 米或更远的地方被检测到。
These physical changes drive significant biotic shifts. Edge habitats often favor different species than interior habitats. Shade-intolerant, disturbance-tolerant, or dry-adapted plants may thrive at edges, while interior specialists decline.76 Edges can facilitate the invasion of non-native species.68 Animal communities also change, with edge-tolerant generalists often increasing in abundance, while interior specialists retreat or disappear.74 Edges can also alter predator-prey dynamics, sometimes concentrating predators (like crows, raccoons, or birds of prey using edges for hunting) or increasing nest predation rates for birds.68 In landscapes with very high densities of edges, the effects from multiple nearby edges can interact in complex ways, potentially strengthening, weakening, or creating entirely novel ecological conditions.80
这些物理变化驱动了显著的生物变化。边缘栖息地通常偏好与内部栖息地不同的物种。耐阴、耐干扰或适应干燥环境的植物可能在边缘繁茂,而内部特化物种则减少。边缘可以促进外来物种的入侵。动物群落也会发生变化,边缘耐受性广泛的通用物种通常会增加,而内部特化物种则会退缩或消失。边缘还可以改变捕食者与猎物的动态,有时会集中捕食者(如利用边缘狩猎的乌鸦、浣熊或猛禽)或增加鸟类的巢穴捕食率。在边缘密度非常高的景观中,多个相邻边缘的影响可能以复杂的方式相互作用,可能会加强、削弱或创造全新的生态条件。
C. Barriers to Movement: Migration and Dispersal
C. 运动障碍:迁徙与扩散
Fragmentation inherently creates barriers to the movement of organisms.70 In the hypothetical scenario, the newly formed seaways represent formidable, often insurmountable, barriers for most terrestrial species, replacing contiguous land corridors with a hostile oceanic matrix.
破碎化本质上会造成生物移动的障碍。在假设的情境中,新形成的海域对大多数陆生物种构成了巨大的、往往难以逾越的障碍,取代了连续的陆地走廊,形成了一个敌对的海洋环境。
This poses an existential threat to migratory species. Animals that undertake long-distance seasonal movements – including birds, mammals (like caribou or wildebeest), and insects (like monarch butterflies) – rely on connected landscapes and specific stopover habitats along their routes.70 Global fragmentation would sever these routes, making completion of migrations impossible for terrestrial migrants and severely disrupting patterns for aerial ones, likely leading to the collapse of many migratory populations.
这对迁徙物种构成了生存威胁。进行长距离季节性迁徙的动物——包括鸟类、哺乳动物(如驯鹿或角马)和昆虫(如帝王蝶)——依赖于相连的景观和沿途特定的中途栖息地。全球的破碎化将切断这些迁徙路线,使陆生迁徙者无法完成迁徙,并严重扰乱空中迁徙者的模式,可能导致许多迁徙种群的崩溃。
Beyond migration, fragmentation severely limits routine dispersal – the movement of individuals away from their birth site to reproduce elsewhere. This limitation has profound consequences for population viability. Reduced dispersal prevents gene flow between isolated populations, leading to a loss of genetic diversity through drift and increased likelihood of inbreeding depression, which reduces individual fitness and population resilience.66 Furthermore, the inability of individuals to disperse between patches prevents the "rescue effect," where immigrants from healthy populations can bolster declining ones or recolonize patches after local extinctions.3 This makes populations in isolated fragments much more vulnerable to stochastic extinction.
除了迁徙,碎片化严重限制了常规扩散——个体从出生地迁移到其他地方繁殖的运动。这一限制对种群生存能力产生深远影响。减少的扩散阻碍了孤立种群之间的基因流动,导致通过漂变失去遗传多样性,并增加了近亲繁殖抑制的可能性,这降低了个体适应性和种群韧性。此外,个体在斑块之间无法扩散,阻止了“救援效应”,即来自健康种群的移民可以增强衰退种群或在局部灭绝后重新殖民斑块。这使得孤立碎片中的种群更容易受到随机灭绝的影响。
D. Fate of Large-Bodied and Wide-Ranging Species (Megafauna)
D. 大型和广泛分布物种(巨型动物)的命运
Large-bodied animals, or megafauna (often defined as terrestrial carnivores ≥15 kg and herbivores ≥100 kg 84), are particularly susceptible to the effects of habitat loss and fragmentation.69 Their large size typically necessitates extensive home ranges to acquire sufficient food and resources.84 They often have low population densities and slow reproductive rates, making their populations less resilient to decline and slower to recover from disturbances.84
大型动物或巨型动物(通常定义为体重≥15 公斤的陆生肉食动物和体重≥100 公斤的草食动物)特别容易受到栖息地丧失和碎片化的影响。它们的体型通常需要广泛的活动范围以获取足够的食物和资源。它们通常具有低人口密度和缓慢的繁殖率,使得它们的种群对下降的适应能力较差,并且从干扰中恢复的速度较慢。
Megafauna play crucial ecological roles disproportionate to their abundance. Top predators exert top-down control on prey populations, influencing herbivore behavior and abundance, which in turn affects vegetation structure (trophic cascades).74 Large herbivores act as ecosystem engineers, modifying vegetation through grazing and browsing, dispersing seeds, cycling nutrients, and creating habitat heterogeneity through physical disturbance.69
巨型动物在生态系统中扮演着与其丰度不成比例的重要角色。顶级捕食者对猎物种群施加自上而下的控制,影响草食动物的行为和丰度,从而影响植被结构(营养级级联)。大型草食动物作为生态系统工程师,通过放牧和啃食改变植被,传播种子,循环养分,并通过物理干扰创造栖息地异质性。
Given their large area requirements and sensitivity to fragmentation, the scenario of global fragmentation into small islands spells almost certain doom for the vast majority of terrestrial megafauna.69 Iconic species requiring vast, connected landscapes – elephants, rhinoceroses, large cats (lions, tigers, jaguars), bears, wolves, large ungulate herds – would be unable to persist within the confines of small island fragments. Their extinction would represent a profound loss of biodiversity and ecological function globally. Examples like the isolation impacting Indian Rhinos and Bengal Tigers even within existing corridor systems illustrate this vulnerability.72
鉴于它们对面积的巨大需求和对碎片化的敏感性,全球碎片化成小岛屿的情景几乎注定会给绝大多数陆地巨型动物带来灭顶之灾。69 需要广阔、连通景观的标志性物种——大象、犀牛、大型猫科动物(狮子、老虎、美洲豹)、熊、狼、大型有蹄类动物群——将无法在小岛碎片的限制内生存。它们的灭绝将代表全球生物多样性和生态功能的深刻损失。像印度犀牛和孟加拉虎在现有走廊系统内受到孤立的例子就说明了这种脆弱性。72
E. Implications for Global Fragmentation
E. 全球碎片化的影响
The consequences of fragmentation for terrestrial ecosystems are severe and multifaceted. Because the scenario implies fragmentation into numerous small islands, edge effects would become the dominant environmental condition across almost all remaining land. The increased edge-to-area ratio 79, coupled with the significant penetration depth of edge influences 77, means that interior habitat conditions would effectively vanish. The global terrestrial environment would transform into one characterized by the abiotic conditions (higher light, fluctuating temperatures, lower humidity, higher wind 76) and biotic communities (dominance of generalists, invasives, edge-adapted predators 76) typical of edges. This represents a fundamental, worldwide shift in terrestrial ecosystem structure, favoring species adapted to disturbance and exposure over those adapted to stable, interior conditions.64
碎片化对陆地生态系统的影响是严重且多方面的。由于这一情景意味着碎片化为众多小岛,边缘效应将成为几乎所有剩余土地上的主导环境条件。增加的边缘与面积比, coupled with the significant penetration depth of edge influences,意味着内部栖息地条件将有效消失。全球陆地环境将转变为一种以非生物条件(更高的光照、波动的温度、较低的湿度、更强的风)和生物群落(广义物种的主导、入侵物种、适应边缘的捕食者)为特征的环境。这代表了陆地生态系统结构的根本性、全球性转变,偏向于适应干扰和暴露的物种,而非适应稳定、内部条件的物种。
The near-certain extinction of most terrestrial megafauna 69 due to the inability of small, isolated fragments to support their populations constitutes a global "trophic downgrading".84 The removal of these keystone species – top predators and large herbivores – would trigger trophic cascades 70 across virtually every island capable of supporting any remaining consumers. The absence of top predators would likely lead to irruptions of smaller predators and herbivores, while the loss of large herbivores would alter vegetation dynamics, nutrient cycling, and disturbance regimes.86 This represents a massive, uncontrolled ecological experiment, leading to widespread and unpredictable restructuring of food webs and plant communities worldwide.
由于小型、孤立的碎片无法支持大多数陆地巨型动物的种群,几乎可以肯定这些物种将会灭绝,这构成了全球的“营养降级”。移除这些关键物种——顶级捕食者和大型食草动物——将引发几乎所有能够支持任何剩余消费者的岛屿上的营养级联。顶级捕食者的缺失可能导致小型捕食者和食草动物的暴发,而大型食草动物的消失将改变植被动态、营养循环和干扰机制。这代表了一场大规模、无法控制的生态实验,导致全球食物网和植物群落的广泛且不可预测的重组。
Finally, while some theoretical models suggest that habitat fragmentation per se (independent of habitat loss) might sometimes have neutral or even positive effects on species richness at a landscape scale, for instance by increasing habitat heterogeneity or reducing competition 14, these nuances are overwhelmed by the extreme nature of the proposed scenario. This scenario involves not just fragmentation but catastrophic habitat loss, turning continents into small islands surrounded by a hostile matrix (the ocean). The Species-Fragmented Area Relationship (SFAR) model explicitly incorporates the negative effects of fragmentation beyond simple area loss and predicts that standard Species-Area Relationships (SAR) significantly underestimate extinctions in landscapes with low habitat amount and high fragmentation.67 Therefore, the combined, severe negative impacts of habitat loss, extreme isolation, pervasive edge effects, and a hostile matrix make the prediction of devastating biodiversity loss far more realistic than any potential minor, theoretical benefits of fragmentation itself.
最后,虽然一些理论模型表明栖息地碎片化本身(独立于栖息地丧失)在某些情况下可能对景观尺度上的物种丰富度产生中性甚至积极的影响,例如通过增加栖息地异质性或减少竞争 14,但这些细微差别被所提议情景的极端性质所掩盖。这个情景不仅涉及碎片化,还包括灾难性的栖息地丧失,将大陆变成被敌对基质(海洋)包围的小岛。物种-碎片化区域关系(SFAR)模型明确考虑了碎片化的负面影响,超出了简单的面积损失,并预测标准的物种-面积关系(SAR)在栖息地数量少且碎片化严重的景观中显著低估了灭绝情况 67。因此,栖息地丧失、极端孤立、普遍边缘效应和敌对基质的综合严重负面影响使得预测毁灭性生物多样性丧失比碎片化本身可能带来的任何微小理论利益更为现实。
V. Impacts on Marine and Coastal Ecosystems
V. 对海洋和沿海生态系统的影响
While devastating for terrestrial life, the fragmentation of continents into islands would drastically reshape the marine realm, particularly coastal zones, creating both potential opportunities and significant challenges.
虽然对陆地生物造成了毁灭性的影响,但大陆碎片化为岛屿将极大地重塑海洋领域,特别是沿海区域,创造出潜在的机会和重大挑战。
A. Increased Coastline Length: Habitat Creation and Challenges
A. 海岸线长度增加:栖息地的创造与挑战
The most immediate physical change in the marine environment would be a dramatic increase in the total length of global coastlines. Geometrically, breaking large landmasses into smaller pieces vastly increases the perimeter-to-area ratio. This proliferation of coastline creates an enormous potential increase in the area available for shallow marine and intertidal habitats.89 These coastal ecosystems – including estuaries, coastal wetlands (salt marshes, mangroves), seagrass meadows, kelp forests, coral reefs, and sandy beaches – are among the most productive and biologically diverse on the planet.89 They serve critical ecological functions, acting as nursery grounds for commercially important fish and shellfish, providing habitat for a vast array of organisms (including marine mammals, sea turtles, and migratory birds), protecting shorelines from erosion and storm surge, filtering water, and cycling nutrients.89
海洋环境中最直接的物理变化将是全球海岸线总长度的显著增加。从几何上讲,将大型陆地块分割成较小的部分会大幅增加周长与面积的比率。这种海岸线的激增为浅海和潮间带栖息地提供了巨大的潜在面积。这些沿海生态系统——包括河口、沿海湿地(盐沼、红树林)、海草草甸、海藻森林、珊瑚礁和沙滩——是地球上最具生产力和生物多样性的生态系统之一。它们发挥着关键的生态功能,作为商业重要鱼类和贝类的育苗场,为各种生物(包括海洋哺乳动物、海龟和候鸟)提供栖息地,保护海岸线免受侵蚀和风暴潮的影响,过滤水质,并循环营养物质。
However, the realization of this potential habitat is fraught with challenges. The establishment of complex, structured habitats like coral reefs, mangrove forests, or extensive seagrass beds requires specific environmental conditions (temperature, salinity, light, substrate, wave energy) and considerable time.91 Newly formed coastlines resulting from fragmentation might initially be geologically unstable, prone to rapid erosion, and lacking the necessary conditions for these complex ecosystems to develop. Early colonization might be dominated by opportunistic or potentially invasive species better adapted to disturbance. Furthermore, human responses to newly created coastlines often involve development and the construction of artificial shoreline protection structures like seawalls, bulkheads, and revetments ("gray infrastructure").93 Studies consistently show that such shoreline hardening significantly reduces biodiversity and habitat value compared to natural shorelines or "green infrastructure" approaches like living shorelines.94 Given that coastal areas are highly desirable for human settlement 89, the immense increase in coastline could paradoxically lead to a massive increase in hardened, ecologically impoverished shorelines, offsetting the potential benefits of habitat creation. Existing pressures on coastal habitats like wetlands and seagrass beds, which are already experiencing significant losses globally 93, would likely intensify along these new, accessible coastlines.
然而,这种潜在栖息地的实现充满了挑战。建立复杂的、结构化的栖息地,如珊瑚礁、红树林或广泛的海草床,需要特定的环境条件(温度、盐度、光照、底质、波浪能量)和相当长的时间。由于碎片化而形成的新海岸线最初可能在地质上不稳定,容易遭受快速侵蚀,并缺乏这些复杂生态系统发展的必要条件。早期的定殖可能主要由适应干扰的机会主义或潜在入侵物种主导。 此外,人类对新形成海岸线的反应通常涉及开发和建设人工海岸保护结构,如海堤、挡土墙和护岸(“灰色基础设施”)。研究一致表明,与自然海岸线或“绿色基础设施”方法(如活海岸线)相比,这种海岸硬化显著降低了生物多样性和栖息地价值。考虑到沿海地区对人类定居的高度吸引力,海岸线的巨大增加可能会悖论性地导致硬化的生态贫瘠海岸线大幅增加,从而抵消栖息地创造的潜在好处。现有的对沿海栖息地(如湿地和海草床)的压力,已经在全球范围内经历了显著损失,可能会在这些新的、可接近的海岸线上加剧。
B. Altered Nutrient Runoff and Eutrophication Patterns
B. 改变的营养物质径流和富营养化模式
Nutrient pollution, primarily nitrogen and phosphorus from agricultural runoff, sewage discharge, and industrial activities, is a major driver of degradation in coastal ecosystems worldwide.89 Excess nutrients fuel excessive algal growth (eutrophication), leading to harmful algal blooms (HABs), depletion of dissolved oxygen (hypoxia or "dead zones") when the algae decompose, loss of submerged vegetation due to reduced light penetration, and alterations to food webs.89 The loss of natural landscape features like wetlands and riparian zones, which act as filters, exacerbates nutrient runoff into coastal waters.96 Currently, large rivers draining vast continental basins deliver concentrated nutrient loads to specific coastal areas, creating large, well-known dead zones like the one in the Gulf of Mexico.96
营养污染,主要是来自农业径流、污水排放和工业活动的氮和磷,是全球沿海生态系统退化的主要驱动因素。过量的营养物质促进了过度的藻类生长(富营养化),导致有害藻华(HABs)、溶解氧的耗竭(缺氧或“死区”)当藻类分解时、由于光透过率降低而导致的水下植被丧失,以及食物网的改变。自然景观特征的丧失,如湿地和河岸带,这些特征作为过滤器,加剧了营养物质向沿海水域的径流。目前,大河流经广阔的大陆流域,将浓缩的营养负荷输送到特定的沿海地区,形成了像墨西哥湾那样的大型、著名的死区。
Global fragmentation would fundamentally alter this pattern. Instead of nutrients being channeled through a few major river systems, runoff would originate from countless smaller catchments on each island, entering the ocean at numerous dispersed points along the newly formed coastlines. While the total global nutrient load from human activities might not change immediately, its delivery mechanism would shift from concentrated point sources to diffuse, widespread inputs. This could potentially reduce the size and severity of the largest existing dead zones associated with major river deltas.96 However, it would likely lead to the formation of numerous smaller, localized zones of eutrophication and hypoxia fringing islands across the globe, particularly those with significant agriculture or human populations.97 The cumulative area of coastal waters experiencing some level of nutrient-related degradation could potentially increase, impacting nearshore biodiversity and ecosystem function on a more pervasive, albeit less concentrated, scale. The susceptibility of different coastal areas would vary depending on local island characteristics (size, land use, geology) and the efficiency of nearshore water circulation in dispersing nutrient inputs.97
全球碎片化将从根本上改变这一模式。营养物质不再通过少数主要河流系统输送,而是从每个岛屿上无数较小的集水区流出,在新形成的海岸线沿线的多个分散点进入海洋。虽然人类活动造成的全球营养负荷总量可能不会立即改变,但其输送机制将从集中点源转变为弥散、广泛的输入。这可能会减少与主要河口相关的现有最大死区的规模和严重性。然而,这可能会导致在全球范围内,特别是在农业或人口密集的岛屿周围,形成许多较小的局部富营养化和缺氧区。经历某种程度的营养相关退化的沿海水域的累积面积可能会增加,从而影响近岸生物多样性和生态系统功能,尽管这种影响更为广泛,但浓度较低。 不同沿海地区的易感性会因当地岛屿特征(大小、土地利用、地质)以及近岸水循环在分散营养输入方面的效率而有所不同。97
C. New Salinity Gradients and Estuarine Dynamics
C. 新的盐度梯度和河口动力学
Estuaries, the transition zones where freshwater from rivers meets saltwater from the sea, are characterized by unique salinity gradients.100 These gradients, which fluctuate spatially and temporally with river discharge and tides, are critical ecological features.100 They structure biological communities, as different species possess different tolerances and adaptations to varying salinity levels.100 Many marine species use estuaries as vital nursery areas, benefiting from their high productivity and shelter.90 For diadromous fish (like salmon or eels) that migrate between freshwater and saltwater, estuaries provide essential acclimation zones where they can physiologically adjust to the change in salinity.100 The mixing dynamics within estuaries (e.g., stratification vs. well-mixed) also influence nutrient cycling and sediment transport.100
河口是淡水与海水交汇的过渡区,具有独特的盐度梯度。100 这些梯度随着河流排放和潮汐在空间和时间上波动,是重要的生态特征。100 它们构建了生物群落,因为不同物种对不同盐度水平具有不同的耐受性和适应性。100 许多海洋物种将河口作为重要的育幼区,受益于其高生产力和庇护。90 对于在淡水和盐水之间迁徙的洄游鱼类(如鲑鱼或鳗鱼),河口提供了必要的适应区,使它们能够在盐度变化中生理调整。100 河口内的混合动态(例如,分层与良好混合)也影响营养循环和沉积物运输。100
Global fragmentation, by definition, would create countless new interfaces between freshwater outflow (from island rivers and groundwater) and the surrounding marine environment. Former inland rivers or lakes could become new seaways or fjords. This implies the formation of numerous new estuarine-like systems around the globe.100 However, these new systems might differ significantly from existing large estuaries. Many would likely be smaller, potentially subject to more rapid and extreme fluctuations in salinity due to smaller catchment sizes and direct exposure to marine influences. Species adapted to the relatively stable or extensive gradients of large, established estuaries might struggle to cope with these new, dynamic conditions.101 Organisms attempting to move between freshwater and saltwater environments would face significant osmotic stress challenges in these potentially abrupt transition zones.100 While the total global area of brackish water habitat might increase, its ecological character and stability, and thus its suitability for existing estuarine specialist species, remain highly uncertain. The critical salinity range of 5-8 Practical Salinity Units (PSU), where major shifts in biotic processes and community composition often occur 102, would appear in numerous new locations, potentially fragmenting populations adapted to either fresher or saltier conditions. The increasing salinization already impacting delta systems due to sea-level rise and altered freshwater inputs provides a glimpse into the challenges such changes pose.103
全球碎片化,按定义,将在淡水流出(来自岛屿河流和地下水)与周围海洋环境之间创造无数新的界面。以前的内陆河流或湖泊可能会变成新的航道或峡湾。这意味着全球将形成许多新的河口状系统。然而,这些新系统可能与现有的大型河口有显著不同。许多可能会更小,可能由于集水区规模较小和直接暴露于海洋影响而面临更快速和极端的盐度波动。适应于大型、成熟河口相对稳定或广泛梯度的物种可能难以应对这些新的动态条件。试图在淡水和盐水环境之间移动的生物将在这些潜在的急剧过渡区面临显著的渗透压压力挑战。尽管全球咸淡水栖息地的总面积可能会增加,但其生态特征和稳定性,以及因此对现有河口特化物种的适宜性,仍然高度不确定。 5-8 实际盐度单位 (PSU) 的关键盐度范围,在这个范围内,生物过程和群落组成常常发生重大变化,可能会出现在许多新的地点,从而可能使适应于较淡或较咸条件的种群发生碎片化。由于海平面上升和淡水输入变化,已经影响三角洲系统的盐碱化加剧,提供了对这些变化所带来的挑战的一个窥视。
D. Potential Shifts in Coastal Upwelling Zones
D. 潜在的沿海上涌区变化
Coastal upwelling is a wind-driven process crucial for marine productivity in specific regions.35 It occurs when winds blowing parallel to a coastline, influenced by the Coriolis effect, drive surface water offshore (Ekman transport).35 This displaced surface water is replaced by colder, deeper water that "upwells" to the surface.35 This deep water is typically rich in nutrients (like nitrates and phosphates) that have accumulated from the decomposition of organic matter sinking from the surface.35 When these nutrients reach the sunlit surface layer (photic zone), they fuel massive blooms of phytoplankton, forming the base of highly productive marine food webs.35 Consequently, major coastal upwelling zones, predominantly found along the eastern boundaries of ocean basins (e.g., off the coasts of California, Peru/Chile, Northwest Africa, Southwest Africa 35), support some of the world's largest fisheries.36
沿海上涌是一个由风驱动的过程,对于特定区域的海洋生产力至关重要。35 当风沿着海岸线吹动,受到科里奥利效应的影响,推动表层水向海洋外侧流动(埃克曼输送)时,就会发生上涌。35 这种被置换的表层水被更冷、更深的水所替代,这些水“上涌”到表面。35 这种深水通常富含营养物质(如硝酸盐和磷酸盐),这些营养物质是由从表面沉降的有机物分解而积累的。35 当这些营养物质到达阳光照射的表层(光合区)时,它们会促进大量浮游植物的繁殖,形成高度生产的海洋食物网的基础。35 因此,主要的沿海上涌区,主要位于海洋盆地的东部边界(例如,加利福尼亚、秘鲁/智利、西北非洲、西南非洲的海岸外 35),支持着世界上最大的渔业之一。36
The location, intensity, and seasonality of upwelling are sensitive to the interplay between wind patterns (strength and direction), the Coriolis effect, and the orientation and topography of the coastline and continental shelf.35 Global fragmentation would radically alter at least two of these key factors: coastline configurations would be completely reshaped, and the altered atmospheric circulation (Section III) would change prevailing wind patterns.
上涌的位置、强度和季节性对风模式(强度和方向)、科里奥利效应以及海岸线和大陆架的方向和地形之间的相互作用非常敏感。全球碎片化将彻底改变至少这两个关键因素:海岸线的形态将被完全重塑,改变后的大气环流(第三节)将改变主导风模式。
Therefore, it is highly probable that the existing major coastal upwelling systems would be severely disrupted, shifted in location, significantly weakened, or eliminated altogether. While new, smaller-scale, or more transient upwelling events might occur along the coasts of some of the newly formed islands where local wind and geographic conditions align favorably, it is unlikely that these would replicate the scale, persistence, and immense productivity of the current major upwelling ecosystems.36 The complex bathymetry and dynamic currents around archipelagos might favor localized or intermittent upwelling, but the large, stable systems fueling global fisheries would likely be lost.
因此,现有的主要沿海上涌系统很可能会受到严重干扰,位置发生变化,显著减弱,或完全消失。虽然在一些新形成岛屿的沿海地区,局部风和地理条件有利的情况下,可能会发生新的、小规模或更短暂的上涌事件,但这些事件不太可能复制当前主要上涌生态系统的规模、持久性和巨大生产力。36 群岛周围复杂的水深和动态洋流可能有利于局部或间歇性的上涌,但为全球渔业提供动力的大型、稳定系统可能会消失。
E. Implications for Global Fragmentation
E. 全球碎片化的影响
The impacts on marine and coastal systems reveal a complex picture of potential gains and significant losses. While fragmentation geometrically creates an immense length of new coastline, potentially expanding the area available for coastal habitats 89, the ecological quality of these newly formed shorelines is highly questionable, particularly in the short to medium term. Initial geological instability, the time lags required for complex ecosystems like reefs or mangroves to establish, the potential dominance of opportunistic species, and the high likelihood of human modification through development and shoreline hardening 93 all suggest that this quantitative increase in coastline may not translate into a proportional increase in healthy, diverse, and functional coastal ecosystems. Quality may be sacrificed for quantity.
对海洋和沿海系统的影响揭示了潜在收益和重大损失的复杂图景。虽然碎片化在几何上创造了大量新的海岸线,可能扩大了沿海栖息地可用的面积,但这些新形成的海岸线的生态质量在短期到中期内是高度可疑的。初始的地质不稳定性、复杂生态系统(如珊瑚礁或红树林)建立所需的时间滞后、机会主义物种的潜在主导地位,以及通过开发和海岸加固进行人类改造的高可能性,都表明这种海岸线的定量增加可能不会转化为健康、多样和功能齐全的沿海生态系统的成比例增加。质量可能会为数量而牺牲。
The pattern of nutrient pollution is also likely to transform. Large, concentrated dead zones associated with major rivers 96 might diminish, but the problem could become more diffuse and pervasive. Runoff from countless islands could lead to widespread, chronic, low-level eutrophication and localized hypoxia in nearshore waters globally, potentially impacting a larger cumulative area and degrading coastal biodiversity more broadly, albeit less intensely in any single location.97
营养污染的模式也可能发生变化。与主要河流相关的大型集中死区可能会减少,但问题可能变得更加分散和普遍。来自无数岛屿的径流可能导致全球近海水域广泛、慢性、低水平的富营养化和局部缺氧,可能影响更大累积面积,并更广泛地破坏沿海生物多样性,尽管在任何单一地点的强度较低。
The creation of numerous new freshwater-saltwater interfaces 100 represents a systemic challenge to organisms and ecosystems adapted to specific salinity regimes. Estuaries, crucial nursery habitats, and nearshore zones influenced by freshwater plumes would experience altered, potentially more variable salinity gradients.101 This widespread disruption could cause significant physiological stress for many organisms, alter species distributions, impact larval transport, and destabilize ecosystems dependent on predictable salinity patterns across a vast portion of the new global coastline.103
大量新的淡水-盐水交界面的形成对适应特定盐度环境的生物和生态系统构成了系统性挑战。受淡水流影响的河口、关键的幼鱼栖息地和近海区域将经历改变,可能更加多变的盐度梯度。这种广泛的干扰可能会对许多生物造成显著的生理压力,改变物种分布,影响幼体运输,并破坏依赖于可预测盐度模式的生态系统,覆盖新全球海岸线的广泛区域。
Perhaps most critically from a human perspective, the likely disruption and potential collapse of major coastal upwelling zones 36 represents a catastrophic threat to global marine productivity. These zones currently support a disproportionately large share of global fisheries catch.35 Their demise, driven by altered coastlines and circulation patterns, would lead to a collapse in primary production in these regions, triggering devastating consequences for global fisheries, marine food webs, and the human communities reliant upon them.
从人类的角度来看,最关键的是,主要沿海上涌区的可能破坏和潜在崩溃代表了对全球海洋生产力的灾难性威胁。这些区域目前支持着全球渔业捕捞的一个不成比例的大份额。它们的消亡,由于海岸线和环流模式的改变,将导致这些地区初级生产的崩溃,进而对全球渔业、海洋食物网以及依赖它们的人类社区造成毁灭性的后果。
VI. Geological Analogues and Long-Term Trajectories
VI. 地质类比与长期轨迹
To understand the potential long-term ecological and evolutionary trajectories following global fragmentation, it is instructive, though potentially limited, to compare the hypothetical scenario with past geological events involving the breakup of supercontinents.
为了理解全球碎片化后潜在的长期生态和进化轨迹,比较假设情景与过去涉及超级大陆分裂的地质事件是有启发性的,尽管可能有限。
A. Continental Drift and Past Fragmentation Events (Pangea, Gondwana)
A. 大陆漂移与过去的碎片化事件(盘古大陆,冈瓦纳)
The Earth's continents are not fixed but move over geological timescales, driven by plate tectonics.107 This process has led to repeated cycles of supercontinent assembly and breakup over Earth's history.108 The most recent and well-documented supercontinent was Pangea, which formed by the Permian period (~250+ million years ago) and incorporated nearly all major landmasses.107 Pangea began to break apart during the Triassic and Jurassic periods (~200-180 Ma).107 This initially led to the separation of a northern landmass, Laurasia (North America, Eurasia), and a southern landmass, Gondwana (South America, Africa, Antarctica, Australia, India, Arabia), separated by the Tethys Seaway.107 Subsequently, Gondwana itself fragmented in stages, starting in the Jurassic/Early Cretaceous (~180-140 Ma) with the separation of Africa/South America from Antarctica/Australia/India, followed by the opening of the South Atlantic separating Africa and South America, and the northward drift of India, Australia, and eventually Antarctica's isolation.107 Earlier supercontinents, like Rodinia (~1.1 Ga - 750 Ma) and potentially others like Pannotia and Columbia, also existed and fragmented, influencing earlier Earth history and the evolution of early life.63
地球的大陆并不是固定的,而是在地质时间尺度上移动,这一过程是由板块构造驱动的。这一过程导致了地球历史上超级大陆的组装和分裂的重复周期。最近且文献记载最为详尽的超级大陆是盘古大陆,它形成于二叠纪(约 2.5 亿年前),几乎包含了所有主要陆地。盘古大陆在三叠纪和侏罗纪期间(约 2 亿-1.8 亿年前)开始分裂。这最初导致了北部陆块劳亚(北美、欧亚)和南部陆块冈瓦纳(南美、非洲、南极洲、澳大利亚、印度、阿拉伯)之间的分离,这两个陆块由特提斯海相隔。随后,冈瓦纳本身在侏罗纪/早白垩纪(约 1.8 亿-1.4 亿年前)开始分阶段碎裂,首先是非洲/南美与南极洲/澳大利亚/印度的分离,接着是南大西洋的开辟,分隔了非洲和南美,以及印度、澳大利亚向北漂移,最终导致南极洲的孤立。早期的超级大陆,如罗迪尼亚(约 11 亿年前-7.5 亿年前)以及可能存在的其他如潘诺提亚和哥伦比亚,也曾存在并碎裂,影响了 早期地球历史和早期生命的演化。63
The process of continental breakup involves rifting, where the continental crust is stretched and thinned, often accompanied by significant volcanic activity, including the formation of Large Igneous Provinces (LIPs) like the Central Atlantic Magmatic Province (CAMP) associated with Pangea's initial breakup, or the Karoo-Ferrar and Paraná-Etendeka provinces linked to Gondwana's fragmentation.108 As rifting progresses, new ocean basins form and widen through seafloor spreading.107
大陆破裂的过程涉及裂谷形成,其中大陆地壳被拉伸和变薄,通常伴随着显著的火山活动,包括形成大型火成省(LIPs),如与盘古大陆初次破裂相关的中大西洋火成省(CAMP),或与冈瓦纳大陆碎裂相关的卡鲁-费拉尔和巴拉那-埃滕德卡省。随着裂谷的进展,新的海洋盆地通过海底扩张形成并扩大。
B. Paleoceanographic and Paleoclimatic Consequences
B. 古洋洋流和古气候的后果
The changing configuration of continents throughout these cycles profoundly impacted ocean circulation and climate. The opening and closing of seaways altered the pathways for ocean currents, fundamentally changing how heat and salt were transported around the globe.63 For example, the opening of the Atlantic Ocean created new circulation patterns, while the closure of the Tethys Seaway restricted connections between oceans. The formation of passages like the Drake Passage between South America and Antarctica allowed for the development of the Antarctic Circumpolar Current, thermally isolating Antarctica and contributing to its glaciation.118 Changes in ocean circulation, particularly in deep water formation regions, likely influenced the strength and stability of the thermohaline circulation, linking tectonic shifts to long-term climate variability.49
大陆在这些周期中的变化配置深刻影响了海洋环流和气候。海峡的开闭改变了海洋洋流的路径,从根本上改变了热量和盐分在全球的运输方式。例如,大西洋的开辟创造了新的环流模式,而特提斯海峡的关闭限制了海洋之间的连接。南美洲和南极洲之间的德雷克海峡的形成使南极环流得以发展,热隔离了南极并促成了其冰川化。海洋环流的变化,特别是在深水形成区域,可能影响了热盐环流的强度和稳定性,将构造运动与长期气候变异联系起来。
Continental configuration also affects climate through other mechanisms. The assembly of large supercontinents can lead to increased continentality (more extreme inland climates), changes in global albedo (reflectivity), and potentially enhanced weathering of mountain ranges formed during collision, which draws down atmospheric CO2 and can lead to global cooling and glaciation.63 Conversely, supercontinent breakup is often associated with increased volcanic activity (releasing CO2), the formation of extensive shallow seas as continents subside and sea levels rise (reducing weathering), and altered ocean heat transport, generally leading to warmer "greenhouse" climates.108 The extreme cold of the Neoproterozoic "Snowball Earth" events has been linked to the equatorial position and subsequent breakup of Rodinia, which maximized silicate weathering and CO2 drawdown.63 The formation of Pangea itself is thought to have contributed to the severity of the end-Permian mass extinction, partly by reducing shallow marine habitats and altering ocean circulation.107
大陆构造还通过其他机制影响气候。大型超级大陆的形成可能导致大陆性增强(内陆气候更极端)、全球反照率(反射率)的变化,以及在碰撞过程中形成的山脉的风化加剧,这会降低大气中的 CO2 并可能导致全球变冷和冰川化。相反,超级大陆的分裂通常与火山活动增加(释放 CO2)、随着大陆下沉和海平面上升而形成的广泛浅海(减少风化)以及改变的海洋热传输相关,通常导致更温暖的“温室”气候。新元古代“雪球地球”事件的极端寒冷与罗迪尼亚的赤道位置及其随后的分裂有关,这最大化了硅酸盐风化和 CO2 的降低。潘吉亚的形成被认为也对二叠纪末大灭绝的严重性有所贡献,部分原因是减少了浅海栖息地并改变了海洋环流。
C. Evolutionary Consequences: Vicariance and Diversification
C. 进化后果:隔离与多样化
The rearrangement of landmasses through continental drift has been a major engine of biological evolution. Vicariance biogeography explains the distributions of many related groups of organisms now found on widely separated continents.110 When a continuous ancestral population is fragmented by a new geographic barrier, such as an ocean opening between drifting continents, the isolated populations evolve independently, potentially leading to allopatric speciation.112 This process is invoked to explain the disjunct distributions of groups like the flightless ratite birds (ostriches in Africa, rheas in South America, emus/cassowaries in Australia) 110, the southern beeches (Nothofagus) found across southern continents 110, marsupial mammals (dominant in Australia, also present in South America) 112, and certain reptile and fish lineages with Gondwanan affinities.116
大陆漂移导致的陆地重组是生物进化的主要动力。隔离生物地理学解释了现在分布在广泛分离的大陆上的许多相关生物群体的分布。当一个连续的祖先种群被新的地理障碍(例如漂移大陆之间出现的海洋)分割时,孤立的种群独立进化,可能导致异域物种形成。这个过程被用来解释像无飞鸟类(非洲的鸵鸟、南美的驼鸟、澳大利亚的鸸鹋/食火鸡)这样的群体的分布不连续,110,分布在南方大陆的南方山毛榉(Nothofagus)110,袋鼠类哺乳动物(在澳大利亚占主导地位,也出现在南美)112,以及某些与冈瓦纳有亲缘关系的爬行动物和鱼类谱系。116
Continental fragmentation, by creating isolated landmasses, fosters evolutionary divergence and provides opportunities for adaptive radiation as lineages adapt to new environments and ecological opportunities in the absence of former competitors or predators.109 The breakup of Pangea and Gondwana led to increasing provincialization of terrestrial biotas as continents drifted apart.109 Paleontological evidence suggests a correlation between periods of increased continental fragmentation and increased global marine biodiversity, possibly due to factors like increased habitat area (especially shallow marine shelves), altered nutrient fluxes, and the creation of new ecological niches.107 However, the relationship is complex; neutral theoretical models suggest that fragmentation itself might not automatically increase global diversity unless it directly drives speciation through vicariance, and the effects might be slow or limited depending on the scale and connectivity.113
大陆碎片化通过创造孤立的陆地块,促进了进化分化,并为适应辐射提供了机会,因为谱系在没有以前竞争者或捕食者的情况下适应新的环境和生态机会。109 泛古陆和冈瓦纳的分裂导致了陆地生物群落的省域化加剧,因为大陆逐渐漂移分开。109 古生物学证据表明,增加的大陆碎片化时期与全球海洋生物多样性的增加之间存在相关性,这可能是由于栖息地面积的增加(尤其是浅海架)、营养物质流动的变化以及新生态位的创造等因素。107 然而,这种关系是复杂的;中性理论模型表明,碎片化本身可能不会自动增加全球多样性,除非它通过地理隔离直接驱动物种形成,并且其影响可能会根据规模和连通性而缓慢或有限。113
D. Comparing Past Events to the Hypothetical Scenario
D. 将过去事件与假设情景进行比较
While past supercontinent cycles provide the only large-scale analogues for landmass fragmentation, there are crucial differences between these geological events and the hypothetical scenario:
虽然过去的超级大陆周期提供了陆地碎片化的唯一大规模类比,但这些地质事件与假设场景之间存在关键差异:
Despite these differences, the similarities lie in the fundamental consequences of breaking land connections: increased isolation, altered ocean basin geometry leading to changed circulation and climate, and the potential for vicariance and subsequent evolutionary divergence among isolated biotas.
尽管存在这些差异,但相似之处在于破坏陆地连接的基本后果:增加的孤立性、改变的海洋盆地几何形状导致的气候和环流变化,以及孤立生物群体之间的地理隔离和随后的进化分歧的潜力。
E. Implications for Global Fragmentation
E. 全球碎片化的影响
Comparing the scenario to past geological events highlights critical aspects of the potential outcome. The most significant difference lies in the timescale. Geological fragmentation, occurring over millions of years 109, allowed life to adapt and diversify through processes like vicariance and adaptive radiation, ultimately contributing to increased global biodiversity over the long term.111 In stark contrast, the rapid, global fragmentation posited in the scenario would trigger an immediate and catastrophic ecological collapse. The principles of island biogeography and habitat fragmentation (Sections I and IV) predict massive extinctions due to drastic area reduction and isolation, occurring on ecological timescales that far outpace the slow processes of evolutionary adaptation and speciation. Any subsequent evolutionary diversification would occur only among the small fraction of lineages surviving the initial cataclysm, playing out against a backdrop of ecological devastation – a fundamentally different dynamic from the gradual divergence seen during past continental breakups.
将该情景与过去的地质事件进行比较突显了潜在结果的关键方面。最显著的区别在于时间尺度。地质碎片化发生在数百万年间,允许生命通过隔离和适应辐射等过程进行适应和多样化,最终在长期内促进了全球生物多样性的增加。与此形成鲜明对比的是,情景中假设的快速全球碎片化将引发立即且灾难性的生态崩溃。岛屿生物地理学和栖息地碎片化的原则(第一部分和第四部分)预测,由于面积的急剧减少和孤立,将导致大规模灭绝,这一过程发生在生态时间尺度上,远远超过缓慢的进化适应和物种形成过程。任何后续的进化多样化仅会发生在幸存于初次灾难的小部分谱系中,并在生态破坏的背景下展开——这与过去大陆分裂期间观察到的渐进性分歧有着根本不同的动态。
Furthermore, the end state of a world composed solely of small islands lacks a direct analogue in Earth's history since the assembly of Pangea.107 Past configurations always included large continental masses that exerted significant influence on global climate and ocean circulation. A planet entirely covered by oceans interspersed with small islands would likely represent a novel Earth system state. The resulting ocean circulation patterns (Section II) and climate dynamics (Section III) might operate under fundamentally different principles than those governing past geological eras, making precise long-term predictions based on paleoclimate analogues challenging.
此外,完全由小岛组成的世界的最终状态在地球历史上自盘古大陆组装以来没有直接的类比。过去的构型总是包括大型大陆块,这些大陆块对全球气候和海洋环流产生了显著影响。一个完全被海洋覆盖、夹杂着小岛的星球可能代表了一种新颖的地球系统状态。由此产生的海洋环流模式(第二节)和气候动态(第三节)可能在根本上与过去地质时代的原则不同,这使得基于古气候类比进行精确的长期预测变得具有挑战性。
Finally, insights from neutral theory applied to past tectonic events 113 suggest that the physical separation of landmasses, in itself, might not be the primary driver of large-scale diversity changes, unless it directly facilitates speciation via vicariance. This reinforces the conclusion that the overwhelming impacts predicted in the hypothetical scenario stem from the ecological consequences of the fragmentation – the drastic habitat loss, extreme isolation, pervasive edge effects, hostile oceanic matrix, and associated climate shifts – rather than simply the geometric pattern of subdivision itself. The ecological disruption is the dominant factor, far outweighing the slower, more subtle influences of geographical reconfiguration alone.
最后,应用于过去构造事件的中性理论的见解表明,陆地块的物理分离本身可能不是大规模多样性变化的主要驱动因素,除非它直接通过地理隔离促进物种形成。这加强了这样的结论:在假设情境中预测的压倒性影响源于碎片化的生态后果——剧烈的栖息地丧失、极端的孤立、普遍的边缘效应、敌对的海洋基质以及相关的气候变化——而不仅仅是细分的几何模式本身。生态破坏是主导因素,远远超过了地理重构单独带来的缓慢而微妙的影响。
VII. Differential Species Success in a Fragmented World
VII. 破碎世界中的物种成功差异
In the dramatically altered world of fragmented continents, not all species would fare equally. Survival and colonization success would depend heavily on specific biological traits, leading to a profound filtering of the global biota.
在剧烈改变的破碎大陆世界中,并非所有物种都能同样生存。生存和殖民的成功在很大程度上取决于特定的生物特征,导致全球生物群落的深刻过滤。
A. Role of Dispersal Ability (Passive vs. Active)
A. 分散能力的作用(被动与主动)
Dispersal ability becomes a paramount trait for survival and colonization in an archipelagic world.13 The ocean matrix represents a significant barrier for most terrestrial organisms.127 Successful crossing would largely depend on the mode and range of dispersal. Species capable of long-distance passive dispersal via wind (e.g., lightweight seeds, spores, small insects) or ocean currents (e.g., floating seeds, rafting on debris) would have a significant advantage.7 Organisms tolerant of saltwater exposure during transit would also be favored. Flight (birds, bats, some insects) offers another means of crossing water gaps, although the distances involved might still be prohibitive for many volant species. Conversely, species reliant on active terrestrial locomotion (most mammals, reptiles, amphibians, flightless insects) or possessing only short-distance dispersal mechanisms would be severely isolated on their respective island fragments, unable to colonize new areas or receive immigrants.13
在群岛世界中,扩散能力成为生存和殖民的首要特征。海洋基质对大多数陆生生物构成了显著的障碍。成功穿越在很大程度上取决于扩散的方式和范围。能够通过风(例如,轻质种子、孢子、小昆虫)或海洋洋流(例如,漂浮种子、在碎片上漂流)进行远距离被动扩散的物种将具有显著优势。在运输过程中能够耐受盐水暴露的生物也会受到青睐。飞行(鸟类、蝙蝠、某些昆虫)提供了另一种跨越水域的方式,尽管涉及的距离对于许多会飞的物种来说可能仍然是一个障碍。相反,依赖主动陆地运动(大多数哺乳动物、爬行动物、两栖动物、不会飞的昆虫)或仅具备短距离扩散机制的物种将在各自的岛屿碎片上严重孤立,无法殖民新区域或接收移民。
Human activities could provide an alternative dispersal pathway. Species associated with human transport (e.g., commensal rodents, insects, weedy plants) might achieve widespread distribution, bypassing natural barriers.20
人类活动可能提供一种替代的传播途径。与人类运输相关的物种(例如,伴生啮齿动物、昆虫、杂草植物)可能实现广泛分布,绕过自然障碍。20
Over evolutionary timescales, theoretical models suggest that species with intermediate dispersal abilities might achieve the highest diversification rates across archipelagos. They are capable enough to colonize new islands occasionally, establishing isolated populations, but not so capable that constant gene flow prevents divergence and speciation.127 However, in the context of rapid fragmentation, the initial filter favors excellent passive dispersers or human-associated species for immediate colonization success.15 Arrival opportunity, influenced by factors like island proximity to sources and prevailing wind/current patterns, would remain a critical factor determining which islands receive colonists.13
在进化时间尺度上,理论模型表明,具有中等扩散能力的物种可能在群岛中实现最高的多样化率。它们足够能够偶尔殖民新岛屿,建立孤立种群,但又不至于过于强大,以至于持续的基因流动阻碍了分化和物种形成。然而,在快速碎片化的背景下,初始过滤器更倾向于优秀的被动扩散者或与人类相关的物种,以实现即时的殖民成功。到达机会受到岛屿与来源的接近程度以及主导风/洋流模式等因素的影响,将仍然是决定哪些岛屿接收殖民者的关键因素。
B. Adaptability: Generalists vs. Specialists
B. 适应性:通才与专才
Ecological specialization refers to the breadth of resources or habitats a species utilizes. Specialists have narrow requirements, often thriving in stable environments where they can efficiently exploit specific resources, while generalists utilize a wider range of resources and habitats, often exhibiting greater flexibility.81
生态专业化是指一个物种利用的资源或栖息地的广度。专业化物种的需求较窄,通常在稳定的环境中茁壮成长,能够高效利用特定资源,而广泛适应的物种则利用更广泛的资源和栖息地,通常表现出更大的灵活性。81
Habitat fragmentation and associated disturbances generally favor generalists over specialists.6 Specialists are highly vulnerable because the specific habitats or resources they depend on may be lost, reduced, or altered within fragments.81 Their lack of flexibility makes it difficult to adapt to changing conditions or utilize alternative resources found in the matrix or edge habitats.81 Generalists, by contrast, are often better equipped to survive in modified landscapes. They may be able to utilize resources in both the remaining habitat fragments and the surrounding matrix (though the ocean matrix is hostile for terrestrial life), exploit newly opened niches created by disturbance, and tolerate the altered conditions prevalent in edge habitats.6 Studies show generalists often disperse more readily into disturbed areas and can become over-represented in fragmented landscapes.81
栖息地碎片化和相关干扰通常更有利于广泛适应者而非专门适应者。专门适应者高度脆弱,因为它们依赖的特定栖息地或资源可能在碎片中丧失、减少或改变。它们缺乏灵活性,使得适应变化的条件或利用矩阵或边缘栖息地中的替代资源变得困难。相比之下,广泛适应者通常更能在改造的景观中生存。它们可能能够利用剩余栖息地碎片和周围矩阵中的资源(尽管海洋矩阵对陆生生命是敌对的),利用干扰所创造的新开放生态位,并耐受边缘栖息地中普遍存在的改变条件。研究表明,广泛适应者往往更容易扩散到受干扰的区域,并可能在碎片化的景观中过度代表。
In the globally fragmented scenario, the pervasive edge effects (Section IV.B), the likely instability of newly formed island ecosystems, and potential climate fluctuations (Section III.C) would create strong selective pressure against specialists adapted to stable, interior conditions.81 Generalist species, particularly those tolerant of disturbance and capable of utilizing a variety of food sources, are predicted to be far more successful in surviving the initial fragmentation and colonizing the new island world. Generalist predators might benefit from the concentration of prey along edges or the ability to exploit resources across different microhabitats within fragments 82, although even generalists can be limited if critical resources become scarce.82 Species already associated with human-modified environments would likely thrive.20
在全球碎片化的情境中,普遍存在的边缘效应(第 IV.B 节)、新形成岛屿生态系统的可能不稳定性以及潜在的气候波动(第 III.C 节)将对适应稳定内陆条件的专门物种施加强大的选择压力。81 预测通用物种,特别是那些耐扰动并能够利用多种食物来源的物种,在经历初始碎片化和殖民新岛屿世界时将更为成功。通用捕食者可能会从沿边缘集中出现的猎物或在碎片内不同微生境中利用资源的能力中受益 82,尽管即使是通用物种在关键资源稀缺时也可能受到限制。82 已经与人类改造环境相关的物种可能会蓬勃发展。20
C. Body Size Evolution: The Island Rule and its Modulators
C. 体型演化:岛屿法则及其调节因素
Body size is another key trait influencing species' fates on islands. The "island rule" describes an empirical pattern where, compared to their mainland relatives, small mammals tend to evolve larger body sizes (insular gigantism) on islands, while large mammals tend to evolve smaller body sizes (insular dwarfism).131
体型是影响物种在岛屿上命运的另一个关键特征。“岛屿法则”描述了一种经验模式,即与其大陆亲属相比,小型哺乳动物在岛屿上往往进化出更大的体型(岛屿巨型现象),而大型哺乳动物则往往进化出更小的体型(岛屿侏儒现象)。131
Several ecological mechanisms have been proposed to explain this pattern. For small mammals, release from mainland predators and reduced interspecific competition on islands may relax constraints on body size, allowing them to evolve larger sizes, which can confer advantages in resource acquisition, dominance, or metabolic efficiency.133 For large mammals, resource limitation on islands (limited food availability and total area) is thought to select for smaller body sizes, which require less energy and may allow for higher reproductive rates.133 Reduced predation pressure might also relax the need for large size as a defense mechanism.135
已经提出几种生态机制来解释这一模式。对于小型哺乳动物来说,摆脱大陆捕食者和岛屿上减少的种间竞争可能会放松对体型的限制,使它们能够进化出更大的体型,这可以在资源获取、主导地位或代谢效率方面带来优势。对于大型哺乳动物来说,岛屿上的资源限制(有限的食物供应和总面积)被认为会选择较小的体型,因为较小的体型需要更少的能量,并可能允许更高的繁殖率。减少的捕食压力也可能放松对大型体型作为防御机制的需求。
However, the island rule is not universally accepted and appears to be context-dependent.133 Some studies, particularly those using phylogenetically controlled methods, find weak or no general support for the rule, suggesting that patterns might be specific to certain taxonomic groups (clades) rather than a general phenomenon.133 For example, carnivores consistently tend towards dwarfism, while murid rodents often exhibit gigantism.133 The strength and direction of size evolution are modulated by factors such as island area (stronger effects on smaller islands), isolation (stronger effects on more remote islands), island climate and productivity, the presence/absence of specific predators or competitors, and the evolutionary history of the lineage.132
然而,岛屿法则并未得到普遍接受,似乎是依赖于特定的背景。133 一些研究,特别是那些使用系统发育控制方法的研究,发现对该法则的支持较弱或没有支持,这表明这些模式可能特定于某些分类群(谱系),而不是普遍现象。133 例如,食肉动物通常倾向于侏儒化,而鼠科啮齿动物则常常表现出巨型化。133 体型演化的强度和方向受到岛屿面积(对较小岛屿的影响更强)、隔离程度(对更偏远岛屿的影响更强)、岛屿气候和生产力、特定捕食者或竞争者的存在/缺失,以及谱系的进化历史等因素的调节。132
In the fragmented world scenario, assuming some mammals survive the initial fragmentation, the island rule's predictions could manifest. Any surviving large mammals (a highly unlikely prospect, see Section IV.D) would face intense pressure for dwarfism due to the severe limitations on area and resources on small islands.135 Surviving small mammals, particularly rodents, might experience ecological release from predators and competitors, potentially leading to gigantism, especially on islands lacking significant predation pressure.132 However, the overall impact of the island rule would be secondary to the initial extinction filter, acting only on the subset of species that manage to persist.
在碎片化的世界情景中,假设一些哺乳动物在初始碎片化后幸存下来,岛屿法则的预测可能会显现。任何幸存的大型哺乳动物(这是一种极不可能的前景,见第 IV.D 节)将面临由于小岛上面积和资源的严重限制而导致的侏儒化的强大压力。幸存的小型哺乳动物,特别是啮齿动物,可能会经历来自捕食者和竞争者的生态释放,这可能导致巨型化,尤其是在缺乏显著捕食压力的岛屿上。然而,岛屿法则的整体影响将是次要的,仅作用于那些能够持续存在的物种子集。
D. Implications for Global Fragmentation
D. 全球碎片化的影响
The interplay between species traits and the fragmented environment leads to several key conclusions about the resulting biosphere. Firstly, the primary filter shaping the surviving and colonizing biota would be the ability to cross oceanic barriers. This strongly favors species with excellent passive dispersal mechanisms (wind, water 7) or those inadvertently or intentionally transported by humans.20 Terrestrial species lacking these capabilities face near-certain isolation and eventual extinction on their fragments. This implies a fundamental shift in the functional composition of the global terrestrial biota, filtering out entire groups based on dispersal mode and favoring taxa often considered "weedy," cosmopolitan, or possessing specific adaptations for long-distance travel over water.
物种特征与碎片化环境之间的相互作用导致了关于结果生物圈的几个关键结论。首先,塑造幸存和殖民生物群落的主要过滤器是跨越海洋障碍的能力。这强烈有利于具有优秀被动扩散机制(风、水 7)的物种,或那些被人类无意或故意运输的物种。20 缺乏这些能力的陆生物种面临几乎肯定的孤立和最终在其碎片上灭绝。这意味着全球陆生生物群落的功能组成发生了根本性变化,基于扩散方式过滤掉整个群体,并偏向于那些通常被认为是“杂草”的、广布的,或具有特定适应能力以进行水上长途旅行的分类群。
Secondly, the environmental conditions created by fragmentation – pervasive edge effects [Insight IV.E.1], novel and potentially unstable climates [Insight III.E.2], and disrupted ecosystems – would exert strong, global selection pressure favoring ecological generalists.81 Specialist species, which constitute a large fraction of biodiversity in stable, complex ecosystems 81, would likely face widespread extinction due to the loss of their required habitats and inability to adapt to the rapidly changing, edge-dominated environments. This process would likely lead to significant biotic homogenization, reducing global biodiversity and functional diversity as a few widespread, adaptable generalists replace numerous locally adapted specialists.
其次,碎片化所创造的环境条件——普遍的边缘效应 [Insight IV.E.1]、新颖且可能不稳定的气候 [Insight III.E.2] 和破坏的生态系统——将施加强大的全球选择压力, favoring 生态通才。81 专门物种在稳定、复杂的生态系统中占据了大量的生物多样性 81,可能由于其所需栖息地的丧失和无法适应快速变化的边缘主导环境而面临广泛灭绝。这个过程可能导致显著的生物同质化,减少全球生物多样性和功能多样性,因为少数广泛分布、适应性强的通才取代了众多地方适应的专门物种。
Thirdly, while evolutionary patterns like the island rule 131 might eventually shape the body sizes of surviving populations, these effects are secondary to the initial, catastrophic filter imposed by the fragmentation event itself. The island rule would only operate on the limited subset of species – likely biased towards small-bodied, well-dispersing generalists – that manage to survive the habitat loss, isolation, and environmental changes. The potential for dwarfism in large mammals, a key component of the rule, might be largely irrelevant if few or no large mammals survive the fragmentation process, as predicted in Section IV.D. Any subsequent gigantism in small mammals would be an evolutionary response occurring long after the primary ecological catastrophe has unfolded.
第三,虽然像岛屿法则 131 这样的进化模式可能最终会影响幸存种群的体型,但这些影响相对于由碎片化事件本身施加的初始灾难性过滤作用是次要的。岛屿法则只会作用于那些能够在栖息地丧失、孤立和环境变化中幸存下来的有限物种子集——这些物种可能偏向于小型、分散能力强的广泛适应者。如果在碎片化过程中幸存下来的大型哺乳动物很少或没有,那么大型哺乳动物的侏儒化潜力(这一法则的关键组成部分)可能就大大无关紧要,如第四节 D 所预测的那样。任何后续的小型哺乳动物的巨型化将是一个在主要生态灾难发生很久之后才出现的进化反应。
Table 3: Predicted Success Factors for Species Traits in a Fragmented World
表 3:在碎片化世界中物种特征的预测成功因素
Trait Category 特征类别 | Specific Trait 具体特征 | Predicted Influence on Survival/Colonization Success | Rationale / Supporting Snippets |
Dispersal Mode 分散模式 | Passive (Wind/Water) 被动(风/水) | Strongly Positive 强烈积极 | Essential for crossing ocean barriers naturally.7 |
Active Flight (Long-distance) | Positive 积极 | Can cross moderate water gaps, but range limited.15 | |
Active Terrestrial 活跃陆地 | Strongly Negative 强烈负面 | Unable to cross ocean barriers.13 | |
Human-Associated 人类相关 | Positive (for some species) | Can bypass natural barriers via human transport.20 | |
Dispersal Distance 分散距离 | Long-Distance Capability 长距离能力 | Strongly Positive 强烈积极 | Increases probability of reaching isolated islands.15 |
Intermediate Distance 中间距离 | Potentially Positive (Long-term diversification) | May allow colonization but maintain isolation for speciation.127 | |
Short-Distance Capability | Strongly Negative 强烈负面影响 | Insufficient to cross ocean gaps.13 | |
Niche Breadth 生态位宽度 | Generalist 广泛适应者 | Strongly Positive 强烈积极 | Tolerates edge effects, disturbed/novel habitats, variable resources.6 |
Specialist 专家 | Strongly Negative 强烈负面 | Requires specific, stable (likely interior) conditions lost due to fragmentation/edge effects.6 | |
Body Size (Terrestrial) 体型(陆生) | Small 小 | Generally Positive (Survival/Dispersal) | Easier passive dispersal, lower resource needs, potential for gigantism post-colonization.131 |
Large (Megafauna) 大型(巨型动物) | Strongly Negative (Survival) | High area/resource needs, vulnerable to fragmentation, unlikely to survive initial event.69 Potential for dwarfism if survive.135 | |
Reproductive Strategy 生殖策略 | Self-Compatibility / Asexual Reproduction | Positive (especially for plants) | Overcomes mate limitation after long-distance dispersal by single propagule (Baker's Law).128 |
Obligate Outcrossing 强制异交 | Negative 负面 | Requires establishment of viable population for reproduction.128 | |
Lifespan (Plants) 寿命(植物) | Longer Lifespan 更长的寿命 | Potentially Positive 潜在的积极影响 | Increases window for reproductive opportunities post-colonization.128 |
VIII. Synthesis: Cascading Effects on Ecosystem Function
VIII. 综合:对生态系统功能的级联影响
The profound changes in geography, climate, ocean circulation, and biodiversity resulting from global fragmentation would inevitably cascade through ecosystems, altering fundamental processes like trophic interactions, biogeochemical cycles, and the provision of ecosystem services essential for planetary health and human well-being.
全球碎片化所导致的地理、气候、海洋循环和生物多样性的深刻变化,必然会在生态系统中产生连锁反应,改变基本过程,如营养相互作用、生物地球化学循环,以及对地球健康和人类福祉至关重要的生态系统服务的提供。
A. Trophic Cascades from Top Predator/Herbivore Loss
A. 顶级捕食者/草食动物丧失引发的营养级级联效应
Trophic cascades describe the propagation of impacts through a food web, typically initiated by changes in the abundance of organisms at high trophic levels.85 The removal or addition of top predators, for example, can cause reciprocal changes in the populations of their prey (herbivores or smaller predators) and, indirectly, the organisms those prey consume (e.g., plants).74 These cascades can be "top-down," driven by changes in predators, or "bottom-up," driven by changes in resource availability (e.g., nutrients for primary producers).88
营养级级联效应描述了影响在食物网中的传播,通常是由高营养级生物丰度的变化引发的。例如,顶级捕食者的移除或增加可以导致其猎物(草食动物或较小捕食者)种群的相应变化,并间接影响这些猎物所消费的生物(例如植物)。这些级联效应可以是“自上而下”的,由捕食者的变化驱动,或“自下而上”的,由资源可用性(例如,初级生产者的营养)变化驱动。
Habitat fragmentation and loss are known to disproportionately impact species at higher trophic levels, particularly large-bodied top predators and herbivores, due to their extensive area requirements and sensitivity to isolation.70 As established in Section IV.D, global fragmentation would likely lead to the extinction of most terrestrial apex consumers and large herbivores [Insight IV.E.2]. This massive, worldwide loss of top trophic levels would inevitably trigger top-down trophic cascades on an unprecedented scale.74
栖息地的破碎和丧失已知对高营养级物种产生不成比例的影响,特别是大型顶级捕食者和草食动物,因为它们对栖息地的广泛面积需求和对孤立的敏感性。如第四节 D 部分所述,全球的破碎可能导致大多数陆地顶级消费者和大型草食动物的灭绝[Insight IV.E.2]。这种大规模的全球顶级营养级丧失将不可避免地在前所未有的规模上引发自上而下的营养级级联效应。
On islands large enough to support surviving populations of mid-sized consumers (mesopredators) and herbivores, the absence of top predators would likely lead to population irruptions of these intermediate trophic levels.70 Increased herbivore populations could lead to overgrazing or overbrowsing, dramatically altering plant community structure, reducing vegetation cover, and potentially impacting soil stability and nutrient cycling.70 Similarly, released mesopredator populations could exert intense pressure on smaller prey species, potentially driving further local extinctions. The strength and specific outcome of these cascades can vary depending on factors like food web complexity (cascades often stronger in simpler systems), ecosystem type, and the specific species involved.88 Furthermore, the potential introduction of novel predators, perhaps associated with human activity, could establish entirely new trophic interactions and cascade dynamics within the fragmented island ecosystems.87 The overall result would be a global-scale restructuring of terrestrial food webs, driven by the initial loss of apex species due to fragmentation.
在足够大的岛屿上,能够支持中型消费者(中型捕食者)和草食动物的生存种群,顶级捕食者的缺失可能会导致这些中间营养级的种群暴发。增加的草食动物种群可能导致过度放牧或过度啃食,显著改变植物群落结构,减少植被覆盖,并可能影响土壤稳定性和养分循环。同样,释放的中型捕食者种群可能对较小的猎物种类施加强大压力,可能导致进一步的地方性灭绝。这些级联效应的强度和具体结果可能因食物网复杂性(在较简单的系统中,级联效应通常更强)、生态系统类型和涉及的特定物种等因素而异。此外,可能与人类活动相关的新捕食者的潜在引入,可能在破碎的岛屿生态系统中建立全新的营养相互作用和级联动态。总体结果将是由于破碎化导致的顶级物种的初始损失,全球范围内的陆地食物网重组。
B. Biogeochemical Cycle Disruptions (Focus on Carbon Cycle)
B. 生物地球化学循环干扰(关注碳循环)
Biogeochemical cycles involve the movement and transformation of essential chemical elements (like carbon, nitrogen, phosphorus, oxygen) through the Earth's systems – atmosphere, oceans, land, and living organisms.136 These cycles are fundamental to regulating climate, supporting life, and maintaining ecosystem function.136 They are intricately linked, and human activities, particularly the burning of fossil fuels and land-use change, have already significantly altered the global carbon and nitrogen cycles, driving climate change and other environmental problems like eutrophication.136
生物地球化学循环涉及地球系统(大气、海洋、陆地和生物体)中基本化学元素(如碳、氮、磷、氧)的运动和转化。这些循环对调节气候、支持生命和维持生态系统功能至关重要。它们彼此密切相关,人类活动,特别是化石燃料的燃烧和土地利用变化,已经显著改变了全球碳和氮循环,推动了气候变化和其他环境问题,如富营养化。
The global carbon cycle involves vast reservoirs of carbon stored in rocks and sediments, the ocean, the atmosphere, and the terrestrial biosphere (plants and soils).138 Carbon moves between these reservoirs through various fluxes, including photosynthesis (atmosphere to biosphere), respiration and decomposition (biosphere to atmosphere), ocean-atmosphere gas exchange, and slow geological processes like weathering, sedimentation, and volcanic activity.138
全球碳循环涉及储存在岩石和沉积物、海洋、大气和陆地生物圈(植物和土壤)中的大量碳库。碳通过各种通量在这些库之间移动,包括光合作用(从大气到生物圈)、呼吸和分解(从生物圈到大气)、海洋-大气气体交换,以及天气化、沉积和火山活动等缓慢的地质过程。
Global fragmentation would profoundly disrupt the carbon cycle through multiple pathways:
全球碎片化将通过多种途径深刻扰乱碳循环:
Beyond carbon, the altered runoff patterns resulting from fragmentation would drastically change the delivery pathways and potentially the processing of nitrogen and phosphorus from land to sea. This would have widespread consequences for coastal eutrophication 96 and marine productivity, further intertwining the impacts on different biogeochemical cycles.136
除了碳之外,碎片化导致的改变的径流模式将极大地改变氮和磷从陆地到海洋的输送路径和潜在的处理。这将对沿海富营养化和海洋生产力产生广泛的影响,进一步交织不同生物地球化学循环的影响。
C. Impacts on Ecosystem Services
C. 生态系统服务的影响
Ecosystems provide a wide range of benefits essential for human survival and well-being, known as ecosystem services.145 These include provisioning services (food, fresh water, timber, fiber, medicines), regulating services (climate regulation, water purification, flood control, pollination, disease regulation), supporting services (nutrient cycling, soil formation, primary production), and cultural services (recreation, aesthetics, spiritual value).91
生态系统提供了一系列对人类生存和福祉至关重要的益处,称为生态系统服务。这些服务包括供给服务(食物、淡水、木材、纤维、药物)、调节服务(气候调节、水净化、洪水控制、授粉、疾病调节)、支持服务(养分循环、土壤形成、初级生产)和文化服务(休闲、美学、精神价值)。
Global fragmentation, through its impacts on biodiversity, climate, ocean circulation, and biogeochemical cycles, would severely degrade or eliminate many crucial ecosystem services on a global scale:
全球碎片化通过对生物多样性、气候、海洋环流和生物地球化学循环的影响,将严重降低或消除许多关键生态系统服务。
The loss of connectivity itself undermines ecosystem resilience and the ability of species and ecosystems to adapt to change, including climate change.72 The overall picture is one of a planet severely compromised in its ability to support complex life, including human societies, due to the cascading failures of interconnected ecological processes and services triggered by extreme fragmentation.145
连接性的丧失本身削弱了生态系统的韧性以及物种和生态系统适应变化的能力,包括气候变化。72 整体情况是,地球在支持复杂生命(包括人类社会)的能力上严重受损,原因是极端碎片化引发的相互关联的生态过程和服务的级联失败。145
Conclusion 结论
The hypothetical scenario of global landmass fragmentation into numerous small islands presents a stark illustration of the profound influence that continental configuration exerts on Earth's interconnected systems. While an extreme thought experiment, the analysis reveals the potential for catastrophic and cascading ecological consequences far exceeding those typically considered in studies of localized habitat fragmentation.
全球陆地碎片化为众多小岛屿的假设场景生动地展示了大陆配置对地球相互关联系统的深远影响。虽然这是一个极端的思想实验,但分析揭示了潜在的灾难性和级联生态后果,远远超过了通常在局部栖息地碎片化研究中考虑的后果。
Island biogeography principles predict a massive global extinction event driven by the drastic reduction in habitat area and the increased isolation of the resulting fragments.2 The equilibrium number of species sustainable on these small islands would be vastly lower than on the original continents, leading to a protracted period of species loss known as extinction debt.15 Niche theory further suggests that the likely homogenization of environments within small fragments would exacerbate biodiversity loss by reducing niche diversity.6
岛屿生物地理学原理预测,由于栖息地面积的急剧减少和由此产生的碎片的隔离加剧,将导致一次大规模的全球灭绝事件。这些小岛上可持续的物种平衡数量将远低于原始大陆,导致一个被称为灭绝债务的物种损失的漫长时期。生态位理论进一步表明,小碎片内环境的可能同质化将通过减少生态位多样性来加剧生物多样性的丧失。
The removal of large continental barriers would fundamentally reconfigure global ocean circulation. Surface gyres, constrained by continents, would likely collapse into a more chaotic system of eddies and inter-island flows.28 The thermohaline circulation, sensitive to changes in high-latitude water density, faces a high risk of disruption or collapse due to altered freshwater runoff patterns and surface cooling mechanisms.46 This would cripple the ocean's ability to transport heat, leading to unpredictable and potentially extreme regional climate shifts.41
大型大陆障碍的移除将从根本上重构全球海洋环流。受大陆限制的表面涡旋可能会崩溃成一个更加混乱的涡流和岛屿间流动系统。热盐环流对高纬度水密度变化敏感,面临由于淡水径流模式和表面冷却机制变化而导致的高风险干扰或崩溃。这将削弱海洋传输热量的能力,导致不可预测且可能极端的区域气候变化。
Consequently, global climate patterns would transform. The elimination of continental interiors would lead to a "global maritimization," characterized by moderated temperature ranges across most land surfaces.57 However, this overall moderation would mask chaotic regional temperature changes driven by disrupted ocean heat transport.46 The hydrological cycle would likely intensify, leading to higher global precipitation, but its distribution would become unpredictable as major atmospheric circulation drivers weaken.56
因此,全球气候模式将发生变化。大陆内部的消失将导致“全球海洋化”,其特征是大多数陆地表面的温度范围得到调节。然而,这种总体的调节将掩盖由于海洋热传输中断而引发的混乱区域温度变化。水文循环可能会加剧,导致全球降水量增加,但由于主要大气环流驱动因素减弱,其分布将变得不可预测。
Terrestrial ecosystems would face near-total transformation. Pervasive edge effects would dominate the small island fragments, favoring generalist and invasive species over interior specialists.64 Most terrestrial megafauna, requiring large, connected habitats, would face extinction, triggering global trophic cascades and fundamentally rewiring food webs.69 Barriers to movement would halt migrations and severely limit dispersal, leading to genetic isolation and increased extinction vulnerability.71
陆地生态系统将面临几乎完全的转变。普遍的边缘效应将主导小岛碎片,偏向于广泛适应的物种和入侵物种,而非内部专家物种。大多数陆地巨型动物需要大而连通的栖息地,将面临灭绝,触发全球营养级级联,并从根本上重塑食物网。迁徙障碍将阻止迁徙并严重限制扩散,导致遗传隔离和灭绝脆弱性的增加。
Marine and coastal ecosystems would experience paradoxical effects. While the vast increase in coastline length creates potential new habitat area 89, the quality and ecological function of these new coasts are uncertain due to instability and likely human pressures.93 Nutrient pollution patterns would shift from concentrated river plumes to diffuse runoff, potentially leading to more widespread, albeit less intense, eutrophication.96 The creation of countless new salinity gradients would destabilize estuarine and nearshore ecosystems.100 Critically, the likely disruption of major coastal upwelling zones threatens a collapse of global marine productivity and fisheries.35
海洋和沿海生态系统将经历矛盾的影响。虽然海岸线长度的巨大增加创造了潜在的新栖息地面积,但由于不稳定性和可能的人类压力,这些新海岸的质量和生态功能尚不确定。营养污染模式将从集中于河流的水流转变为弥散的径流,可能导致更广泛但强度较低的富营养化。无数新的盐度梯度的形成将破坏河口和近海生态系统。关键是,主要沿海上升流区的可能破坏威胁到全球海洋生产力和渔业的崩溃。
Comparison with past geological fragmentation events highlights the critical difference in timescale. While slow continental drift drove diversification over millions of years 111, the rapid fragmentation envisioned here would cause immediate ecological collapse, overwhelming evolutionary responses [Insight VI.E.1]. The resulting island-only world represents a novel Earth system state with no clear historical analogue [Insight VI.E.2].
与过去地质碎片化事件的比较突显了时间尺度的关键差异。虽然缓慢的大陆漂移在数百万年中推动了多样化,但这里设想的快速碎片化将导致立即的生态崩溃,压倒性的进化反应。结果,只有岛屿的世界代表了一种新的地球系统状态,没有明确的历史类比。
Survival in this fragmented world would strongly favor species with excellent passive dispersal capabilities and high ecological generalization.20 Specialists, poor dispersers, and large-bodied terrestrial animals face grim prospects. The resulting global biota would likely be impoverished, homogenized, and dominated by opportunistic species [Insights VII.D.1, VII.D.2].
在这个破碎的世界中,生存将极大地有利于具有出色被动传播能力和高生态广泛性的物种。专家、传播能力差的物种和大型陆生动物面临严峻的前景。由此产生的全球生物群落可能会贫乏、同质化,并被机会主义物种主导。
Ultimately, these cascading changes would severely disrupt fundamental ecosystem functions, including trophic structures and biogeochemical cycles, particularly the carbon cycle, through massive terrestrial carbon release and altered ocean uptake.70 This would lead to a profound degradation of the ecosystem services upon which planetary health and human civilization depend.72 This theoretical exploration underscores the critical importance of large, connected landmasses in maintaining Earth's climate stability, biodiversity, and ecological functions, and highlights the extreme potential consequences of habitat fragmentation when considered at a global scale.
最终,这些级联变化将严重扰乱基本生态系统功能,包括营养结构和生物地球化学循环,特别是碳循环,通过大规模的陆地碳释放和改变的海洋吸收。这将导致生态系统服务的深刻退化,而这些服务是地球健康和人类文明所依赖的。这一理论探索强调了大规模、相连的陆地在维持地球气候稳定性、生物多样性和生态功能方面的关键重要性,并突显了在全球范围内考虑栖息地破碎化时的极端潜在后果。