📚 Threats to Biodiversity | 生物多样性的威胁
Biodiversity, the sum of all genetic, species and ecosystem variation on Earth, is vanishing at a rate far beyond natural background extinction. Human activities now drive the 'sixth mass extinction', with over one million species facing risk within decades. Understanding the threats is the first step towards effective conservation.
生物多样性是地球上所有遗传、物种和生态系统变异的总和，正以远超自然本底灭绝的速度消失。人类活动正推动着“第六次大灭绝”，未来几十年内超过一百万种物种面临风险。理解这些威胁是有效保护的第一步。
1. Biodiversity Under Threat | 生物多样性面临威胁
Biodiversity operates on three levels: genetic diversity within populations, species diversity in communities, and ecosystem diversity across landscapes. All three are being eroded simultaneously by a set of interconnected pressures, often referred to as the 'big five' threats: habitat loss, overexploitation, invasive species, pollution and climate change.
生物多样性在三个层面上运行：种群内的遗传多样性、群落中的物种多样性以及景观尺度上的生态系统多样性。所有三个层面正同时受到一系列相互关联的压力侵蚀，这些压力常被称为“五大威胁”：栖息地丧失、过度开发、入侵物种、污染和气候变化。
The current extinction rate is estimated to be 100–1000 times higher than the natural background rate, measured from the fossil record. Unlike previous mass extinctions driven by geological events, this crisis is almost entirely anthropogenic, driven by the exponential growth of human population and resource consumption since the Industrial Revolution.
据化石记录估算，当前的灭绝速率是自然本底速率的100到1000倍。与以往由地质事件驱动的大灭绝不同，这场危机几乎完全是人为造成的，根源于工业革命以来人口和资源消耗的指数级增长。
2. Habitat Loss and Fragmentation | 栖息地丧失与破碎化
Habitat destruction is the single greatest threat to terrestrial and freshwater biodiversity. Deforestation for agriculture, urban expansion, mining and reservoir construction removes entire ecosystems. In Southeast Asia, vast tracts of lowland rainforest have been replaced by oil palm plantations, directly eliminating habitats of orang-utans, tigers and countless endemic plants.
栖息地破坏是陆地和淡水生物多样性最大的单一威胁。为农业、城市扩张、采矿和水库建设而进行的森林砍伐移除了整个生态系统。在东南亚，大片低地雨林已被油棕种植园取代，直接消灭了猩猩、老虎和无数特有植物的栖息地。
Habitat fragmentation cuts remaining natural areas into small, isolated patches. Edge effects alter microclimates, favour generalist and invasive species, while reducing core habitat for specialists. Fragmented populations suffer reduced gene flow, making them vulnerable to inbreeding depression and local extinction. Metapopulation theory shows that small patches have higher extinction probabilities and lower recolonisation rates.
栖息地破碎化将剩余自然区域切割成小而孤立的斑块。边缘效应改变了小气候，有利于广布种和入侵种，同时减少了专性种的核心栖息地。破碎化的种群基因流动减少，使其易受近交衰退和局部灭绝的影响。集合种群理论表明，小斑块的灭绝概率更高，重新定殖率更低。
3. Overexploitation of Species | 物种的过度开发
Overexploitation occurs when harvesting rates exceed the reproductive capacity of a population. It has historically been the primary cause of marine defaunation. Industrial fishing fleets remove top predators such as tuna, sharks and billfish, triggering trophic cascades that restructure entire marine food webs. Bycatch of non-target species, including turtles and dolphins, further erodes biodiversity.
当捕获率超过种群繁殖能力时即发生过度开发。从历史上看，这是海洋动物减少的主要原因。工业化捕鱼船队捕走金枪鱼、鲨鱼和旗鱼等顶级捕食者，引发营养级联效应，重塑整个海洋食物网。附带捕捞海龟、海豚等非目标物种，进一步侵蚀生物多样性。
On land, illegal wildlife trade drives charismatic megafauna towards extinction. Rhino horn, elephant ivory and pangolin scales fetch high prices in black markets, fuelling poaching. Bushmeat hunting in Central and West Africa has emptied forests of large mammals, a phenomenon termed 'empty forest syndrome'. Unsustainable logging for timber, especially of rosewood and mahogany, also qualifies as overexploitation.
在陆地上，非法野生动植物贸易将魅力型大型动物推向灭绝。犀牛角、象牙和穿山甲鳞片在黑市上价格高昂，助长了偷猎。中非和西非的野味狩猎已使森林中大型哺乳动物消失，这一现象被称为“空林综合症”。不可持续的木材采伐，特别是红木和桃花心木，也属于过度开发。
Maximum Sustainable Yield: MSY = rN(1 - N/K)
最大可持续产量：MSY = rN(1 - N/K)，其中r为内禀增长率，K为环境容纳量。当种群降至K/2以下时，MSY无法维持。
4. Invasive Species | 入侵物种
Invasive alien species are organisms introduced outside their native range that establish, spread and cause harm to local ecosystems. They often lack natural predators or pathogens in the new environment, allowing their populations to explode. Invasive predators, competitors and pathogens can drive native species to extinction, especially on islands where endemic species have evolved without similar pressures.
外来入侵物种是指被引入其本土范围之外、定殖、扩散并对当地生态系统造成危害的生物。它们在新环境中往往缺乏自然天敌或病原体，致使其种群爆发。入侵的捕食者、竞争者和病原体可使本地物种灭绝，尤其是在岛屿上，那里的特有物种在没有类似压力下进化。
5. Pollution: Air, Water and Soil | 污染：大气、水体和土壤
Agricultural runoff rich in nitrates and phosphates causes eutrophication in freshwater and coastal marine ecosystems. Algal blooms block sunlight and, upon decomposition, create hypoxic 'dead zones' where most aquatic life cannot survive. The Gulf of Mexico dead zone, fed by the Mississippi River, regularly exceeds 15,000 km².
富含硝酸盐和磷酸盐的农业径流导致淡水和近海生态系统的富营养化。藻类大量繁殖阻挡阳光，分解时产生缺氧的“死亡区”，大多数水生生物无法生存。由密西西比河输入的墨西哥湾死亡区经常超过15,000平方公里。
Persistent organic pollutants (POPs) such as DDT and PCBs bioaccumulate in fatty tissues and biomagnify along food chains, reaching toxic concentrations in top predators. Plastic pollution entangles marine life and fragments into microplastics that enter food webs from zooplankton to humans. Light and noise pollution additionally disrupt animal navigation, reproduction and foraging behaviour.
持久性有机污染物如DDT和多氯联苯在脂肪组织中生物累积，并沿食物链生物放大，在顶级捕食者体内达到有毒浓度。塑料污染缠绕海洋生物并碎裂成微塑料，从浮游动物到人类进入食物网。光和噪声污染还会扰乱动物的导航、繁殖和觅食行为。
6. Climate Change | 气候变化
Rising global temperatures force species to shift their geographical ranges polewards or to higher altitudes. Species that cannot migrate fast enough, such as sessile organisms or those in fragmented landscapes, face extinction. Phenological mismatches occur when interdependent species respond to warming at different rates, e.g. birds hatching after peak caterpillar abundance.
全球气温升高迫使物种向极地或更高海拔迁移其地理分布区。无法足够快迁移的物种，如固着生物或处于破碎化景观中的物种，面临灭绝。当相互依赖的物种以不同速率回应变暖时，会发生物候错配，例如鸟类在毛虫丰度高峰之后孵化。
Ocean acidification, caused by absorption of rising atmospheric CO₂, decreases carbonate ion availability, impairing calcification in corals, molluscs and planktonic foraminifera. Coral bleaching, driven by marine heatwaves, has already caused severe mortality on the Great Barrier Reef. Sea-level rise inundates coastal wetlands and mangroves, critical nurseries for fisheries and buffers against storms.
因吸收大气中不断升高的CO₂而导致的海洋酸化降低了碳酸根离子可用性，损害珊瑚、软体动物和浮游有孔虫的钙化作用。由海洋热浪驱动的珊瑚白化已在大堡礁造成严重死亡。海平面上升淹没了为渔业提供关键育苗场并缓冲风暴的沿海湿地和红树林。
7. Emerging Infectious Diseases | 新发传染病
Emerging infectious diseases are an increasingly recognised threat to biodiversity. Global trade and travel accelerate the spread of pathogens into naïve host populations. The chytrid fungus Batrachochytrium dendrobatidis has caused catastrophic declines in amphibian populations worldwide, driving over 90 species to extinction. The disease disrupts cutaneous respiration and osmoregulation in frogs.
新发传染病正成为日益受到关注的生物多样性威胁。全球贸易和旅行加速了病原体向无免疫宿主种群的传播。壶菌 Batrachochytrium dendrobatidis 已导致全球两栖动物种群灾难性下降，致使超过90种物种灭绝。该病破坏了蛙类的皮肤呼吸和渗透调节。
White-nose syndrome, caused by the fungus Pseudogymnoascus destructans, has killed millions of hibernating bats in North America by depleting fat reserves. Avian malaria, introduced to Hawaii by mosquitoes, has driven several endemic honeycreeper species to extinction. Climate change often expands the range of vectors, exposing new populations to diseases.
由真菌 Pseudogymnoascus destructans 引起的白鼻综合征通过耗尽脂肪储备已杀死了北美数百万只冬眠蝙蝠。由蚊子引入夏威夷的禽疟疾已导致多种当地特有管舌鸟灭绝。气候变化常常扩大病媒的分布范围，使新的种群暴露于疾病。
8. Genetic and Demographic Threats | 遗传与种群统计威胁
Small populations lose genetic diversity through genetic drift and inbreeding. Reduced heterozygosity lowers adaptive potential and fertility, while increasing the expression of deleterious recessive alleles. The extinction vortex describes the positive feedback loop where small size leads to inbreeding and demographic stochasticity, further reducing population size until extinction becomes inevitable.
小种群通过遗传漂变和近交丧失遗传多样性。杂合度降低会削弱适应潜力和繁殖力，同时增加有害隐性等位基因的表达。灭绝漩涡描述了小规模导致近交和种群统计随机性的正反馈循环，进一步缩小种群规模，直至灭绝不可避免。
The concept of minimum viable population (MVP) defines the smallest size required for a population to persist with a given probability over a set time. For many vertebrates, MVPs are estimated to be in the thousands. Habitat fragmentation often reduces populations below this threshold, even if patches appear occupied. Genetic rescue may be necessary to restore variation.
最小可存活种群的概念界定了种群在设定时间内以给定概率持续存在所需的最小规模。对许多脊椎动物而言，MVP估计在数千个个体。栖息地破碎化经常使种群降至这一阈值以下，即使斑块看似仍有物种占据。基因拯救可能是恢复变异的必要手段。
9. Synergistic Effects and Tipping Points | 协同效应与临界点
Threats rarely act in isolation; their interactions are often synergistic. For example, habitat fragmentation reduces population size, making species more susceptible to stochastic events such as disease outbreaks or extreme weather. Climate change can facilitate the spread of invasive species, while pollution weakens organisms, lowering their resilience to pathogens.
威胁很少孤立作用；它们的相互作用常常是协同的。例如，栖息地破碎化缩小了种群规模，使物种更易受疾病爆发或极端天气等随机事件的影响。气候变化可促进入侵物种的扩散，而污染削弱生物体，降低它们对病原体的抵抗力。
Ecosystems can exhibit tipping points where cumulative stress triggers a sudden, often irreversible shift to an alternative stable state. The Amazon rainforest, once a carbon sink, may switch to a savanna-like state if deforestation, fire and drought exceed critical thresholds. Coral reefs may shift from coral-dominated to macroalgae-dominated systems after bleaching and nutrient loading.
生态系统可表现出临界点，累积压力触发向替代稳定状态的突然且往往不可逆的转变。亚马逊雨林曾是碳汇，如果砍伐、火灾和干旱超过临界阈值，可能转变为类似稀树草原的状态。珊瑚礁在白化和营养负荷后可能从珊瑚主导转变为大型藻类主导的系统。
10. Case Study: Coral Reefs and Tropical Rainforests | 案例研究：珊瑚礁与热带雨林
Coral reefs, occupying less than 0.1% of the ocean floor, support roughly 25% of marine species. They face a combination of climate-induced bleaching, ocean acidification, overfishing, pollution and physical damage from tourism and coastal development. These multiple stressors compress the reef's resilience, leading to widespread phase shifts and biodiversity loss.
珊瑚礁只占不到0.1%的海底面积，却支持着大约25%的海洋物种。它们面临气候引发的白化、海洋酸化、过度捕捞、污染以及旅游和沿海开发带来的物理损害等多重压力。这些多重压力压缩了珊瑚礁的恢复力，导致广泛的相移和生物多样性丧失。
Tropical rainforests are threatened by agricultural expansion, particularly for beef, soy and palm oil. Selective logging degrades forest structure and increases susceptibility to fire. The synergistic effects of deforestation, fragmentation and climate change reduce carbon storage, alter rainfall patterns and eliminate the specialised niches required by countless epiphytes, insects and canopy vertebrates.
热带雨林受到农业扩张的威胁，特别是牛肉、大豆和棕榈油生产。择伐破坏了森林结构，增加了火灾易发性。砍伐森林、破碎化和气候变化的协同效应降低了碳储存，改变了降雨模式，并消除了无数附生植物、昆虫和冠层脊椎动物所需的特化生态位。
11. Consequences of Biodiversity Loss | 生物多样性丧失的后果
The erosion of biodiversity undermines ecosystem services on which humanity depends. Pollination, provided primarily by insects, is essential for 75% of global food crops. The decline of pollinators due to habitat loss, pesticides and disease threatens agricultural yields and food security. Water purification by wetlands and flood regulation by forests are similarly compromised.
生物多样性的侵蚀破坏了人类赖以生存的生态系统服务。主要由昆虫提供的传粉对全球75%的粮食作物至关重要。由于栖息地丧失、杀虫剂和疾病导致的传粉者减少威胁着农业产量和粮食安全。湿地的净水和森林的洪水调节功能同样受到损害。
Loss of genetic resources also reduces opportunities for drug discovery and crop improvement. Many pharmaceuticals originate from natural compounds; with each species extinction, potential medical breakthroughs are lost forever. Furthermore, cultural and aesthetic values tied to iconic species and landscapes suffer, diminishing human well-being and ecotourism economies.
遗传资源的丧失也减少了药物发现和作物改良的机会。许多药物源自天然化合物；每种物种灭绝，潜在的医学突破就永远消逝。此外，与标志性物种和景观相关的文化和审美价值受损，削弱了人类福祉和生态旅游经济。
12. Addressing the Threats – Conservation Strategies | 应对威胁——保护策略
Protected areas remain the cornerstone of in-situ conservation, but they must be large, well-connected and effectively managed. Expanding the global network of marine and terrestrial reserves, combined with restoration of degraded habitats, can reverse some losses. The Aichi Biodiversity Targets and the post-2020 Global Biodiversity Framework set ambitious goals for area-based conservation.
自然保护区仍是就地保护的基石，但它们必须面积大、连通性好且管理有效。扩大全球海洋和陆地保护区网络，再加上退化栖息地的恢复，可以扭转部分损失。爱知生物多样性目标和2020年后全球生物多样性框架为基于区域的保护设定了雄心勃勃的目标。
Ex-situ conservation, including seed banks, captive breeding and reintroduction programmes, provides insurance against extinction. Legal frameworks such as CITES regulate international wildlife trade. Community-based conservation engages local people as stewards, aligning economic incentives with biodiversity protection. Ultimately, only systemic changes in consumption, agriculture and energy systems can address the root drivers of biodiversity loss.
包括种子库、圈养繁殖和重引入计划的迁地保护为预防灭绝提供了保障。像濒危野生动植物种国际贸易公约（CITES）这样的法律框架管制国际野生动植物贸易。以社区为基础的保育让当地人民成为管理者，将经济激励与生物多样性保护结合起来。归根结底，只有消费、农业和能源体系发生系统性变革，才能解决生物多样性丧失的根本驱动因素。
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