📚 Human Influences on the Environment | 人类对环境的影响
Human activities are transforming the planet at an unprecedented rate, leading to pollution, habitat destruction and climate change. In the IGCSE Biology specification, we study how population growth, waste production, deforestation and the burning of fossil fuels have biological consequences that threaten ecosystems and biodiversity. This article explains key concepts, processes and data required to understand and evaluate human impact on the environment.
人类活动正以前所未有的速度改变着地球，导致污染、栖息地破坏和气候变化。在 IGCSE 生物课程中，我们学习人口增长、废物产生、森林砍伐和化石燃料燃烧如何带来危及生态系统和生物多样性的生物学后果。本文将解释理解与评估人类对环境影响所需的关键概念、过程和资料。
1. Human Population Growth and Waste | 人口增长与废物
The human population has grown exponentially in the last two centuries, reaching over 8 billion. This rapid increase places huge demands on resources such as food, water and energy. As living standards rise, more waste is produced, including sewage, household rubbish, industrial chemicals and greenhouse gases. More people also mean more land is cleared for housing and agriculture, destroying natural habitats.
过去两个世纪，人类人口呈指数增长，已超过 80 亿。快速的人口增长给食物、水和能源等资源带来了巨大需求。随着生活水平的提高，产生的废物也越来越多，包括污水、生活垃圾、工业化学品和温室气体。更多的人口还意味着更多的土地被开垦用于住房和农业，破坏了自然栖息地。
Waste that is not properly managed pollutes air, water and soil. Biodegradable waste such as food scraps can be decomposed by microorganisms, but non‑biodegradable materials like plastics persist in the environment for hundreds of years. Landfill sites can leak toxic chemicals into groundwater, while incineration releases air pollutants unless carefully controlled.
未经妥善处理的废物会污染空气、水和土壤。食物残渣等可生物降解的废物能被微生物分解，但塑料等不可生物降解的材料会在环境中存留数百年。垃圾填埋场可能向地下水渗漏有毒化学物质，而焚烧除非经过严格控制否则会释放空气污染物。
2. Water Pollution by Sewage | 污水造成的水污染
Sewage contains organic matter, detergents and a large number of microorganisms, including pathogens. When untreated sewage is released into rivers or lakes, it provides a rich food source for bacteria and fungi. These decomposers respire aerobically, using up dissolved oxygen in the water. The biological oxygen demand (BOD) increases, and oxygen levels can drop so low that fish and other aerobic aquatic organisms suffocate.
污水中含有有机物、洗涤剂和大量微生物，包括病原体。未经处理的污水排入河流或湖泊时，会给细菌和真菌提供丰富的食物来源。这些分解者进行有氧呼吸，消耗水中的溶解氧。生化需氧量 (BOD) 升高，氧气水平可能降至极低，导致鱼类和其他需氧水生生物窒息死亡。
In contrast, some organisms, especially anaerobic bacteria, thrive in low‑oxygen conditions. These break down organic material and release foul‑smelling gases such as hydrogen sulfide and methane. The water becomes turbid, smelly and unsafe for drinking or recreation. Edexcel IGCSE candidates should be able to describe the biological consequences of sewage pollution and explain how increased microorganism populations deplete oxygen.
相比之下，一些生物，特别是厌氧菌，在低氧条件下大量繁殖。它们分解有机物并释放出硫化氢和甲烷等恶臭气体。水体变得浑浊、发臭，不适合饮用或娱乐。Edexcel IGCSE 学生应能描述污水污染的生物学后果，并解释微生物数量的增加如何耗尽氧气。
3. Eutrophication | 富营养化
Eutrophication occurs when excess nutrients, mainly nitrates and phosphates, enter water bodies. These nutrients come from artificial fertilizers washed off agricultural land, untreated sewage and detergents. The sudden nutrient enrichment triggers a rapid growth of algae and aquatic plants, called an algal bloom.
当过量的营养物质，主要是硝酸盐和磷酸盐，进入水体时就会发生富营养化。这些营养物质来自从农田冲刷下来的人造肥料、未经处理的污水和洗涤剂。营养物质的突然富集引发藻类和水生植物快速生长，称为水华。
As the algae cover the water surface, they block sunlight from reaching submerged plants, which eventually die because they cannot photosynthesise. The algae themselves have a short life cycle. When they die, they are decomposed by aerobic bacteria, leading to a sharp rise in BOD and a severe drop in dissolved oxygen. This oxygen depletion kills fish and invertebrates. Over time the water body can become a lifeless, smelly zone dominated by anaerobic decay.
当藻类覆盖水面时，会阻挡阳光照射到沉水植物，这些植物因无法进行光合作用而最终死亡。藻类本身生命周期很短。当它们死亡时，需氧细菌对其进行分解，导致 BOD 急剧上升，溶解氧严重下降。这种氧气耗尽会导致鱼类和无脊椎动物死亡。久而久之，水体会变成无生命、发臭的区域，以厌氧腐烂为主。
4. Air Pollution: Smoke and Sulfur Dioxide | 空气污染：烟尘与二氧化硫
Burning fossil fuels, especially coal and heavy oil, releases smoke particles (soot) and sulfur dioxide (SO₂). Smoke particles can settle on leaves, reducing photosynthesis, and when inhaled they cause respiratory diseases such as bronchitis. SO₂ gas dissolves in the moisture of airways to form acid, irritating the lining of the lungs. High concentrations worsen asthma and other breathing disorders.
燃烧化石燃料，特别是煤和重油，会释放烟尘颗粒（炭黑）和二氧化硫 (SO₂)。烟尘颗粒可沉降在叶片上，减弱光合作用，吸入人体后会引发支气管炎等呼吸系统疾病。SO₂ 气体溶解在呼吸道水分中形成酸，刺激肺部内壁。高浓度还会加重哮喘和其他呼吸系统疾病。
The table below summarises common air pollutants and their biological effects:
下表总结了常见的空气污染物及其生物效应：
| Pollutant / 污染物 | Source / 来源 | Biological effect / 生物学效应 |
|---|---|---|
| Sulfur dioxide (SO₂) | Coal and oil power stations | Respiratory damage, acid rain formation |
| Nitrogen oxides (NOₓ) | Vehicle engines, factories | Irritate lungs, contribute to acid rain and smog |
| Carbon monoxide (CO) | Incomplete combustion | Binds to haemoglobin, reduces oxygen transport |
| Particulates (PM₂.₅, PM₁₀) | Vehicles, industry, wood burning | Lung damage, cardiovascular disease, reduce light for photosynthesis |
5. Acid Rain | 酸雨
Acid rain forms when sulfur dioxide and nitrogen oxides dissolve in rainwater and react to form dilute sulfuric acid and nitric acid. The pH of rain can fall below 5.0, whereas normal rainwater has a pH of about 5.6 due to dissolved carbon dioxide. Acid precipitation damages forests directly by leaching nutrients such as calcium and magnesium from the soil and by releasing toxic aluminium ions that harm tree roots.
当二氧化硫和氮氧化物溶解在雨水中并反应生成稀硫酸和稀硝酸时，即形成酸雨。雨水的 pH 可降至 5.0 以下，而正常雨水因溶解了二氧化碳，pH 约 5.6。酸沉降直接破坏森林，原因是淋洗掉土壤中的钙、镁等营养元素，并释放出有毒的铝离子，损害树木根系。
In lakes and rivers, acid rain lowers the pH so much that fish eggs cannot hatch and many aquatic insects die. The entire food web is disrupted. Limestone buildings and statues are eroded by acid rain, but the examination focuses mainly on its ecological impacts. Reducing sulfur emissions from power stations using flue‑gas desulfurisation and fitting catalytic converters in cars can lessen acid rain.
在湖泊和河流中，酸雨使 pH 大幅降低，导致鱼卵无法孵化，许多水生昆虫死亡。整个食物网受到破坏。石灰石建筑和雕像会被酸雨侵蚀，但考试主要考查其生态影响。通过电厂烟气脱硫和汽车安装催化转化器减少硫排放，可以缓解酸雨问题。
6. Greenhouse Gases and Global Warming | 温室气体与全球变暖
The greenhouse effect is a natural process in which gases such as carbon dioxide (CO₂), methane (CH₄) and water vapour trap heat in the atmosphere, keeping Earth's average surface temperature at about 15 °C. Without this effect, the planet would be too cold for most life. However, human activities have increased the concentrations of these gases dramatically, enhancing the effect and causing global warming.
温室效应是一个自然过程，二氧化碳 (CO₂)、甲烷 (CH₄) 和水蒸气等气体将热量截留在大气中，使地球平均地表温度保持在约 15 °C。没有这一效应，地球对大多数生命而言将过于寒冷。然而，人类活动大大增加了这些气体的浓度，加剧了温室效应，导致了全球变暖。
Carbon dioxide is mainly released by burning fossil fuels and deforestation. Methane comes from cattle, rice paddies and landfill sites. Higher global temperatures lead to melting of polar ice caps and glaciers, rising sea levels, more frequent extreme weather events and shifts in the distribution of species. In the exam, you may be asked to interpret data on CO₂ concentrations and temperature change or to suggest consequences for biodiversity.
二氧化碳主要来自化石燃料的燃烧和森林砍伐。甲烷来自牛群、稻田和垃圾填埋场。全球气温升高导致极地冰盖和冰川融化、海平面上升、极端天气事件更频繁以及物种分布的变化。在考试中，你可能会被要求解读关于 CO₂ 浓度与温度变化的数据，或提出对生物多样性的影响。
7. Deforestation | 森林砍伐
Deforestation is the large‑scale removal of forests, usually to provide land for agriculture, cattle ranching, timber or urban expansion. It has several severe biological consequences. Removing trees reduces the uptake of CO₂ for photosynthesis, so less carbon dioxide is removed from the atmosphere, worsening the greenhouse effect. Burning forests further releases stored carbon as CO₂.
森林砍伐是指大规模清除森林，通常是为了提供农业、放牧、木材或城市扩展的土地。这会产生若干严重的生物学后果。树木被砍伐后，通过光合作用吸收的 CO₂ 减少，因此从大气中清除的二氧化碳变少，加剧了温室效应。燃烧森林还会将储存的碳以 CO₂ 形式进一步释放。
Tree roots normally bind soil particles. Without this anchoring, soil erosion increases, and heavy rain can wash away fertile topsoil. Leaching of minerals occurs more rapidly. Forest removal also disrupts the water cycle: transpiration from leaves is reduced, so less water vapour returns to the atmosphere, which can decrease rainfall locally and affect climates. The loss of habitat causes a catastrophic decline in biodiversity. Many species become endangered or extinct. Sustainable forestry and replanting programmes can mitigate some effects.
树木的根系通常固定土壤颗粒。没有了这种固定作用，土壤侵蚀加剧，大雨会冲走肥沃的表土。矿物质的淋溶也会更快发生。清除森林还会扰乱水循环：叶片蒸腾作用减少，返回大气的水蒸气因此减少，这可能导致当地降雨量下降并影响气候。栖息地的丧失导致生物多样性灾难性地下降，许多物种濒危或灭绝。可持续林业和再植计划可以减轻某些影响。
8. Pollution from Agriculture and Non‑biodegradable Pesticides | 农业污染与不可生物降解的杀虫剂
Intensive farming uses large amounts of fertilisers and pesticides. Excess fertilisers can leach into waterways and cause eutrophication (see Section 3). Pesticides and herbicides can be washed into rivers and lakes, harming non‑target organisms. Persistent organic pollutants such as DDT are not easily broken down in the environment. They accumulate in the fatty tissues of organisms and become more concentrated at each trophic level, a process called bioaccumulation and biomagnification.
集约化农业使用大量肥料和杀虫剂。过剩的肥料会渗入水道并引发富营养化（见第 3 节）。杀虫剂和除草剂可被冲刷进入河流湖泊，危害非目标生物。持久性有机污染物如 DDT 在环境中不易被分解。它们积聚在生物体的脂肪组织中，并随营养级逐级富集，这一过程称为生物积累与生物放大。
Top predators such as birds of prey can accumulate lethal doses of these chemicals, causing thinning of eggshells and reproductive failure. The Edexcel course expects you to link pesticide use to food chains and explain the biological consequences for apex consumers.
猛禽等顶级掠食者可累积致死剂量的这些化学物质，导致蛋壳变薄和繁殖失败。Edexcel 课程要求你将杀虫剂的使用与食物链联系起来，并解释对顶端消费者的生物学后果。
9. Managing Human Impact: Sustainability and Conservation | 管理人类影响：可持续性与保护
Reducing our environmental footprint requires a combination of legislation, technology and individual action. Strategies include encouraging renewable energy sources (solar, wind, hydroelectric) to cut greenhouse gas emissions, improving sewage treatment before discharge, and promoting recycling to reduce landfill waste. Governments can impose fishing quotas and create protected areas such as national parks and marine reserves to conserve biodiversity.
减少我们的环境足迹需要法规、技术和个人行动的结合。策略包括鼓励使用可再生能源（太阳能、风能、水电）以减少温室气体排放，在排放前改进污水处理，以及推广回收利用以减少填埋废物。政府可以实行捕鱼配额并建立国家公园和海洋保护区等保护地以保护生物多样性。
At a personal level, reducing meat consumption, choosing locally produced food, using public transport and minimising single‑use plastics all contribute. In the exam, you might be asked to evaluate different methods of pollution control or to design an investigation measuring the effect of a pollutant on seed germination. Always link your answers to biological knowledge: how organisms are affected, and how ecosystems change.
在个人层面，减少肉类消费，选择当地生产的食物，使用公共交通，尽量减少一次性塑料制品都有所贡献。在考试中，你可能会被要求评估不同的污染控制方法，或设计一项测量污染物对种子萌发影响的探究。始终将答案与生物学知识联系起来：生物体如何受到影响，生态系统如何变化。
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