📚 Why Biodiversity Matters | 为何生物多样性如此重要
Biodiversity — the variety of life at genetic, species, and ecosystem levels — is not merely a measure of nature’s abundance. It underpins ecosystem function, drives evolutionary processes, and provides the essential services on which humanity depends. In this article, we explore why biodiversity is so important from an A-Level Biology perspective, examining the concepts, evidence, and arguments you need for your CIE examinations.
生物多样性——即遗传、物种和生态系统层面的生命多样性——不仅仅是自然界丰饶程度的一种度量。它支撑着生态系统的功能，驱动着进化过程，并提供了人类赖以生存的基本服务。在本文中，我们从 A-Level 生物学的视角出发，探讨为何生物多样性如此重要，并梳理你在 CIE 考试中所需要的概念、证据与论证。
1. Defining Biodiversity | 生物多样性的定义
Biodiversity is a broad term encompassing three interrelated levels of biological organisation. Species diversity refers to the number and relative abundance of different species within a community. Genetic diversity describes the variety of alleles within a species or population, which forms the raw material for adaptation through natural selection. Ecosystem diversity reflects the variety of habitats, communities, and ecological processes across the Earth’s surface.
生物多样性是一个宽泛的术语，囊括了生物组织层次中三个相互关联的层面。物种多样性指一个群落内不同物种的数量及其相对丰度。遗传多样性描述一个物种或种群内等位基因的多样性，它是通过自然选择实现适应的原材料。生态系统多样性则反映了地表上栖息地、群落和生态过程的多样性。
2. The Evolutionary Foundation | 进化的基础
From an evolutionary perspective, biodiversity is both a product and a driver of natural selection. Mutations introduce new alleles into populations, generating genetic variation. When environmental conditions change, this variation enables at least some individuals to survive and reproduce, passing advantageous alleles to subsequent generations. Thus, genetic diversity directly determines a population’s evolutionary potential.
从进化的角度来看，生物多样性既是自然选择的产物，也是自然选择的驱动力。突变将新的等位基因引入种群，产生遗传变异。当环境条件发生变化时，这种变异使得至少一部分个体能够存活并繁殖，将有利的等位基因传递给后代。因此，遗传多样性直接决定了一个种群的进化潜力。
Populations with low genetic diversity, such as the cheetah (Acinonyx jubatus) in Africa, are more vulnerable to environmental changes and diseases, because they possess fewer alleles with which to respond to new selection pressures.
遗传多样性较低的种群，例如非洲的猎豹（Acinonyx jubatus），在面对环境变化和疾病时更为脆弱，因为可用于应对新选择压力的等位基因较少。
3. Measuring Biodiversity: Simpson’s Index | 测量生物多样性：辛普森指数
To quantify species diversity, ecologists use indices that combine species richness (the number of species) and species evenness (the relative abundance of individuals). Simpson’s Index of Diversity (D) is one such measure, and it is a core calculation in the CIE A-Level syllabus.
为了量化物种多样性，生态学家使用结合了物种丰富度（物种数目）和物种均匀度（个体相对丰度）的指标。辛普森多样性指数（D）就是这样一种度量方式，也是 CIE A-Level 教学大纲中的核心计算内容。
D = 1 − [ Σ n(n−1) / N(N−1) ]
In this equation, n is the total number of individuals of a particular species, and N is the total number of individuals of all species. The value of D ranges from 0 to 1, where a value close to 1 indicates high biodiversity (many species, each represented by few individuals), and a value close to 0 indicates low biodiversity (few species, often dominated by one species).
在该方程中，n 是某一特定物种的个体总数，N 是所有物种的个体总数。D 的取值范围为 0 到 1，越接近 1 表示生物多样性越高（物种多，且每个物种个体数量较少），越接近 0 则表明生物多样性越低（物种少，且常由单一物种占优势）。
| Sampling Site | Species Count (n values) | D value |
| Unpolluted river | Species A: 10, B: 12, C: 8, D: 9 | 0.92 (high) |
| Polluted river | Species A: 35, B: 2, C: 1 | 0.40 (low) |
By using indices such as Simpson’s, we can objectively compare biodiversity between different habitats or monitor changes over time — techniques that are essential for conservation decision-making.
通过使用辛普森指数这类指标，我们可以客观地比较不同栖息地之间的生物多样性，或监测其随时间的变化——这些技术对于保护决策至关重要。
4. Biodiversity and Ecosystem Stability | 生物多样性与生态系统稳定性
One of the most compelling reasons to value biodiversity is its role in maintaining ecosystem stability. Ecosystems with high species diversity tend to be more resilient to disturbances, such as droughts, fires, or pest outbreaks. This phenomenon is known as the diversity-stability hypothesis. When one species declines, others with similar ecological roles (functional redundancy) can compensate, maintaining key processes such as primary productivity and nutrient cycling.
重视生物多样性最有说服力的原因之一，是它在维持生态系统稳定性中的作用。物种多样性高的生态系统往往对干旱、火灾或病虫害爆发等扰动具有更强的抵抗力。这种现象被称为多样性-稳定性假说。当某一物种衰退时，具有相似生态功能（功能冗余）的其他物种可以加以弥补，从而维持初级生产力和养分循环等关键过程。
For example, in a diverse grassland, a dip in one grass species’ abundance due to a specific pest may have minimal impact on total biomass production, because other grass species are unaffected. In a monoculture, however, the same pest could devastate the entire crop.
例如，在多样化的草原中，某个草本植物因特定虫害而丰度下降，由于其他草本植物不受影响，总生物量的产出所受影响可能极小。然而，在单一栽培的农田中，同样的虫害却可能摧毁整个作物。
5. Genetic Diversity within Species and Its Consequences | 物种内遗传多样性及其后果
Genetic diversity, often overlooked in public discussions of biodiversity, is critical for long-term survival. A species with high genetic variation is more likely to survive changing environments, resist diseases, and adapt to new conditions. Conversely, low genetic diversity can lead to inbreeding depression — reduced fitness due to the expression of recessive deleterious alleles.
遗传多样性在公众讨论生物多样性时常被忽视，但它对于物种的长期生存至关重要。遗传变异高的物种更有可能在变化的环境中存活、抵抗疾病并适应新的条件。相反，遗传多样性低可能导致近交衰退——即因隐性有害等位基因表达而导致适合度下降。
The Northern elephant seal (Mirounga angustirostris) experienced a severe population bottleneck in the 19th century, resulting in near-zero genetic variation. Today, while the population has recovered, its uniform genotype makes it highly susceptible to disease epidemics — a reminder that population numbers alone do not guarantee conservation success.
北海象海豹（Mirounga angustirostris）在 19 世纪经历了严重的种群瓶颈，导致其遗传变异几乎为零。如今，虽然种群数量已经恢复，但其单一的基因型使其极易受到疾病流行病的影响——这提醒我们，种群数量本身并不能保证保育成功。
6. Economic and Medical Value | 经济与医学价值
Biodiversity is a vast, largely unexplored source of natural compounds used in medicine. Around 50% of the 150 most-prescribed drugs in the United States are derived from or patterned after natural products. The Pacific yew tree (Taxus brevifolia) produces paclitaxel, an important chemotherapy drug; aspirin originates from willow bark; and penicillin was discovered from the fungus Penicillium. Losing biodiversity means losing potentially life-saving chemical resources before we even know they exist.
生物多样性是一个巨大且在很大程度上尚未被探索的天然化合物库，许多化合物用于制药。美国最常开具的 150 种药物中约有一半源自天然产物或以其为模板。太平洋紫杉（Taxus brevifolia）产生紫杉醇——一种重要的化疗药物；阿司匹林源于柳树皮；青霉素则是从真菌 Penicillium（青霉菌）中发现的。失去生物多样性，意味着在可能挽救生命的化学资源尚未被我们知晓之前就将其永远丧失。
Beyond medicine, pollination by insects and bats adds approximately 10% of global agricultural production value. Birds and predatory insects control pest populations, saving billions of dollars in crop damage. These ecosystem services, often taken for granted, depend on maintaining biodiversity.
除了医学，昆虫和蝙蝠的授粉服务使全球农业总产值增加了约 10%。鸟类和捕食性昆虫控制着害虫种群数量，为人类节省了数十亿美元的作物损失。这些常常被视为理所当然的生态系统服务，都依赖于生物多样性的维持。
7. Agricultural Importance: The Gene Bank | 农业的重要性：基因库
Agriculture depends heavily on genetic diversity in crop varieties and livestock breeds. Wild relatives of cultivated crops contain alleles for disease resistance, drought tolerance, and improved nutritional content. These valuable traits can be bred into commercial varieties to enhance resilience in a changing climate.
农业在很大程度上依赖于作物品种和牲畜品系的遗传多样性。栽培作物的野生近缘种含有抗病性、耐旱性和更高营养价值等优良性状的等位基因。这些有价值的性状可以被培育到商用品种中，以增强其在不断变化的气候中的抵抗力。
The Irish Potato Famine (1845-1852) serves as a historical warning. Ireland cultivated a small number of potato varieties with identical genetic backgrounds. When the water mould Phytophthora infestans arrived, the entire crop was susceptible — approximately one million people died from starvation. Maintaining genetic diversity among crops is a matter of food security.
爱尔兰马铃薯饥荒（1845-1852）是一个历史性的警示。当时爱尔兰种植的马铃薯品种稀少，且遗传背景相同。当致病疫霉（Phytophthora infestans）到来时，所有作物都不具抗性——约一百万人死于饥饿。维持作物的遗传多样性是一个粮食安全问题。
8. Ecosystem Services: Nutrient Cycling and Climatic Regulation | 生态系统服务：养分循环与气候调节
Biodiversity drives many ecological processes that sustain life on Earth, collectively known as ecosystem services. Decomposers such as bacteria and fungi break down organic matter, releasing nitrogen, phosphorus, and other nutrients back into the soil. This process — nutrient cycling — is essential for the growth of plants and, consequently, for all organisms in the food web.
生物多样性驱动着维持地球生命的许多生态过程，统称为生态系统服务。细菌和真菌等分解者分解有机物质，将氮、磷等养分释放回土壤中。这一过程——养分循环——对于植物的生长乃至整个食物网中的一切生物都至关重要。
Forest ecosystems, mangroves, and peatlands capture and store carbon dioxide from the atmosphere. Coral reefs and coastal wetlands act as natural barriers against storms and erosion. These regulating services, which would cost trillions of dollars to replace artificially, depend on the structural and functional integrity of ecosystems — a direct product of their biodiversity.
森林生态系统、红树林和泥炭地能够从大气中捕获并储存二氧化碳。珊瑚礁和沿海湿地是抵御风暴和侵蚀的天然屏障。这些调节服务若要以人工方式进行替代，将耗资数万亿美元——它们依赖于生态系统结构和功能的完整性，而这是生物多样性的直接产物。
9. Threats to Biodiversity | 生物多样性面临的威胁
Modern rates of species extinction are estimated to be 100 to 1000 times higher than background rates in the fossil record. The principal drivers are habitat destruction, overexploitation, pollution, invasive species, and climate change — often abbreviated in examinations as the HIPPO factors. Each of these factors acts synergistically, accelerating the loss of biodiversity.
据估计，现代物种灭绝速率是化石记录中本底灭绝速率的 100 到 1000 倍。主要驱动因素包括栖息地破坏、过度开采、污染、入侵物种和气候变化——在考试中常被简称为 HIPPO 因素。这些因素往往协同作用，加速生物多样性的丧失。
Tropical rainforests, which house over 50% of terrestrial species, are cleared at an estimated rate of 10 million hectares annually. Coral reefs support 25% of marine biodiversity yet cover less than 1% of the ocean floor; global warming driven ‘bleaching’ events have already damaged large sections of these ecosystems. When you understand the scale of these threats, the urgency of conservation becomes undeniable.
栖息着超过 50% 陆地物种的热带雨林，以每年约 1000 万公顷的速度被砍伐。珊瑚礁支持着 25% 的海洋生物多样性，却仅占不到 1% 的海底面积；全球变暖引发的”白化”事件已经破坏了这些生态系统的大片区域。当理解了这些威胁的规模之后，保护物种的紧迫性便无可辩驳。
10. Why Conservation of Biodiversity Matters | 为什么保护生物多样性至关重要
Conservation biology is the science of protecting biodiversity for the benefit of both nature and humanity. Two complementary strategies are used: in-situ conservation, which protects species in their natural habitats (e.g., national parks, biosphere reserves), and ex-situ conservation, which protects species outside their natural habitats (e.g., seed banks, zoos, botanical gardens).
保护生物学是为了自然与人类的共同利益而保护生物多样性的科学。保护策略通常分为两种互补的方式：就地保护，即在自然栖息地中保护物种（如国家公园、生物圈保护区），以及迁地保护，即在自然栖息地之外保护物种（如种子库、动物园、植物园）。
Each approach has advantages. In-situ conservation maintains ecological interactions — species evolving within their communities — while ex-situ strategies provide an insurance policy for critically endangered species. An effective global conservation policy utilises both approaches, supported by legislation, international agreements such as the Convention on Biological Diversity, and public education.
每种方法都有其优势。就地保护维持了生态相互作用——物种在其群落内持续进化——而迁地策略则为极度濒危物种提供了保险方案。有效的全球保护政策应当综合利用两种方法，并以立法、《生物多样性公约》等国际协定和公众教育为支撑。
11. The Ethical and Aesthetic Dimension | 伦理与美学维度
Many conservationists argue that biodiversity has intrinsic value — that every species has a right to exist, independent of its usefulness to humans. This ethical position, akin to that of Aldo Leopold’s land ethic, broadens the scope of moral consideration to include all living entities. Furthermore, the aesthetic value of nature — millions of people travel to see coral reefs, whales, and rainforests — generates significant economic revenue and human wellbeing that cannot be captured by a simple ecological equation.
许多自然保护主义者认为，生物多样性具有内在价值——每个物种都有独立于对人类是否有用而存在的权利。这种伦理立场，类似奥尔多·利奥波德的土地伦理，将道德关怀的范围拓展至所有生命。此外，自然的美学价值——每年数百万人前往观赏珊瑚礁、鲸鱼和雨林——带来了巨大的经济收益和人类福祉，这是单个生态学公式无法涵盖的。
For A-Level students, understanding the ethical dimension strengthens your ability to evaluate conservation decisions in exam questions. Such questions often ask you to discuss whether economic development should be sacrificed to protect an endangered species, and a balanced answer will consider ethical, aesthetic, and scientific factors.
对于 A-Level 学生来说，理解伦理维度有助于你们在考试题目中更全面地评估保护决策。这类题目往往要求讨论是否应当为了一个濒危物种而牺牲经济发展，而一个均衡的答案应当考虑伦理、美学以及科学因素。
12. Conclusion: A Shared Responsibility | 结论：共同的责任
Biodiversity is not a luxury of planetary nature that we can choose to ignore. It is the living fabric of the biosphere — a foundation of ecosystem services, food security, medicine, and evolutionary resilience. The loss of biodiversity undermines the very systems that support human civilisations, and once a species or an ecosystem is lost, its genetic information is gone forever. As future biologists, understanding why biodiversity matters is not merely an examination objective; it is a prerequisite for making informed decisions in a rapidly changing world.
生物多样性不是一种我们可以选择无视的星球自然奢侈品。它是生物圈的生命织锦——是生态系统服务、粮食安全、医学和进化韧性的基石。生物多样性的丧失，动摇了支撑人类文明的根本体系；一旦一个物种或生态系统消失，其遗传信息便永不复存在。作为未来的生物学家，理解生物多样性为何重要不仅仅是一项考试目标；它是在迅速变化的世界中做出明智决策的先决条件。
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