Chapter 4 Land and Water Use 第四章 土地和水的利用

1 Agriculture 农业

1.1 Feeding a Growing Population 为日益增长的人口提供粮食

正常人每天需要消耗2200kcal的能量以维持健康的生活。目前越来越多的营养产品和食物在市场上销售，大米、小麦和玉米仍旧是人类最主要的营养物质和粮食产品，近年来食物的价格也在不断上涨。粮食问题是各个国家和人民都关心的问题。

1.1.1 Nutrition营养

Approximately 2,200 kcal (Calories) of food is required per day to live an active, healthy life.

缺乏蛋白质、碳水化合物、脂肪、维生素或矿物质的摄入会导致营养不良（malnutrition）和饥饿。发展中国家的人民由于贫困和不发达的经济，常常会有各种营养不足（undernutrition）的问题。而发达国家的人民又可能因为营养过剩（overnutrition）而有很多令人关注的健康问题。

●Kwashiorkor 恶性营养不良

饮食中缺乏蛋白质会导致恶性营养不良。

Young children who eat a diet is deficient in protein are vulnerable to Kwashiorkor. Symptoms: a bloated, distended belly, puffy skin.

●Marasmus 过度消瘦

饮食中缺乏胡萝卜素和蛋白质会导致过度消瘦。

Young children who eat a diet lack of calories and protein are vulnerable to marasmus. Symptoms: stunted growth and a thin, emaciated body.

●Goiter 甲状腺肿

饮食中缺碘会导致甲状腺肿。

Goiter results from a diet that is deficient in iodine. Symptoms: an enlarged thyroid gland, swollen neck.

●Anemia 贫血

饮食中缺铁会导致贫血。

Anemia results from a diet that is deficient in iron.

●Vitamin A Deficiency 维生素A缺乏症

维生素A缺乏症会导致各种传染病甚至失明。

Symptoms: increased infectious diseases and blindness.

1.1.2 Types of Agriculture 农业类型（表1—4—1）

1.1.3 Problems Associated with Agriculture农业所引起的各类问题（表1—4—2）

1.1.4 The Green Revolution 绿色革命

绿色革命指第二次世界大战之后，一些国家利用科技发展农业，扩大粮食产量的技术改革活动。印度是最早使用先进的科学技术提高粮食产量的国家，印度农业因此发生了巨大变化。

Industrial agriculture spread from developed nations to developing nations with the advent of the Green Revolution. Technologically advanced agricultural practices increased crop yields after World War Ⅱ. Advancements included the development of high-yielding monoculture crops; the use of large inputs of inorganic fertilizer; heavy use of pesticides; intensive irrigation; which dramatically increased yields and helped millions avoid starvation. But despite its successes, the Green Revolution also created new problems.

1.1.5 Genetic Engineering and Crop Production 基因工程和粮食生产

转基因食品（genetically modified organisms）的出现和普及从某种程度上解决了粮食问题。但是转基因食品对人体的影响目前还是未知的。

1.2 Controlling Pests 害虫的控制

害虫的控制对于生态系统的管理十分重要，主要途径有耕作防除、化学防治和生物防治。

The control of pests, which compete for food or cause diseases, is an important example of human management of ecosystems. Humans have a number of ways of controlling pests.

1.2.1 Cultural Control 耕作防除

It involves removing pests physically, for example by weeding with a hoe, or preventing pests establishing themselves, for example by growing a plant species that deters pests amongst a crop.

1.2.2 Chemical Control 化学防治

It uses chemicals called pesticides to limit pest populations. Pesticides are not always selective, and sometimes kill harmless animals as well as the pest species. They may be persistent and remain in the environment for long periods. Some of them affect whole food chains. Pests may develop resistance, and ever-increasing dose of pesticide will be required to have the same effect. Pesticides may be extremely expensive. Some crop species have been genetically modified to allow the crop to be protected with much less use of pesticide.

1.2.3 Biological Control 生物防治

In a biological control system, humans control the pest species using one of its natural predators. There are several techniques in biological control.

●利用生物链中的食草者来耕除杂草。Use a herbivore to control a weed species.

For example: cactoblastis larvae to control prickly pear.

●利用食肉者来消除害虫。Use a carnivore to control a herbivorous pest.

For example: hoverfly larvae to control aphids.

●利用寄生虫来消除宿主。Use a parasite to control its host.

For example: encarsia, a parasitic wasp, to control the greenhouse whitefly Trialeurodes vaporariorum.

●破坏害虫的繁殖周期。Disrupt the breeding cycle of a pest if it mates once only in its life.

For example: release of irradiation-sterilised males of the screw worm fly, a flesh-eating parasite of cattle.

●控制害虫的行为。Control pest behaviour.

For example: chemicals called pheromones are used to attract apple codling moths into lethal traps.

1.2.4 Pesticides 杀虫剂（表1—4—3）

1.2.5 Advantages and Disadvantages of Pesticides 杀虫剂的利弊

The Pesticide Treadmill 杀虫剂的陷阱

杀虫剂或农药的大量使用使一些害虫改变了其原有的基因，具有了一定的抗药性，因此要在使用杀虫剂的时候不断提高杀虫剂的浓度。

Survivors of pesticide application reproduce and pass their genes for pesticide resistance on to their offspring. Increasing the amount or concentration of the pesticide is necessary due to resistance. Even at increased strength, some pests survive and the cycle repeats. This positive feedback loop is called the pesticide treadmill.

Costs and Benefits of Pesticide Use杀虫剂使用的花费和优势

The price of food is determined by the economic forces of supply and demand. The cost of applying a pestcide to the crops will influence the price of food. External costs are not considered including: pesticide runoff into waterways; health effects to exposed individuals; contaminated water or soil; pesticide residues on food.

Failures with Biological Control 生物防治失效

生物防治存在很多潜在的风险，当捕食者与被捕食者之间关系不够密切时，生物防治很难起到其预想的作用。

Any potential biological control agent must be tested thoroughly before its release. Sometimes scientists are so anxious to introduce a control that insufficient research is done, and problems arise.

If the link between the predator and prey is not close enough, the control agent may become a pest in its own right! An example of failed biological controls are illustrated as followed:

House sparrows were introduced into California to control larvae on fruit trees. Sparrows are very successful at exploiting other food sources, and:

●did not successfully control the insect larvae

●reproduced very rapidly and now do enormous damage to crops

Although setting up a successful biological control system is complicated, many conservationists prefer to use biological control systems rather than chemical control.

1.2.6 Integrated Pest Management (IPM) 害虫整合管理

IPM是指利用害虫的自然天敌，利用庄稼的轮作，干扰其繁殖交配，少量应用一些窄谱或天然杀虫剂来减小害虫的可容忍度。

The goal of IPM is not to completely eradicate pests, only to reduce their numbers to economically tolerable levels. IPM makes use of the natural enemies of the pest species, crop rotation, the use of pheromones or introduction of sterile males into the population to interfere with reproduction, and limited use of carefully applied narrow spectrum or natural pesticides.

Circle of Poison：在美国是禁止使用某些农药的。For example, pesticides banned in the US are used legally in other countries. Crops are exported from those countries to the US where residents are exposed to a banned pesticide.

Rachel Carson 蕾切尔·卡森：美国人，于1962年提出反对使用DDT（双对氯苯基三氯乙烷，英文Dichloro Diphenyl Trichloroethane)，唤起了人们对环境保护的公众意识。

She is the author of the book Silent Spring(1962).She raised public awareness about the consequences of DDT use, and raised public awareness about environmental issues.

2 Forestry 林业

2.1 Several Ways of Forest Formation森林形成的几种方式

●Tree plantation树木的种植

树木的种植指在某一个固定的区域种植单一物种的树木，用于商业木材的砍伐。

Tree plantation refers to areas that are commercially maintained for timber resources. Often a monoculture of genetically identical tree species are clear-cut and replanted at regular intervals.

●Old-growth forests 老龄林

老龄林指不会被人类的活动和自然灾害所改变的森林。

Old-growth forests are forests that have not been modified by human activities or natural disasters in 200 years or more.

●Secondary-growth forests次生林

次生林指由于人类的采伐和自然灾害，植物群落从次生裸地生长，通过一系列次生演替所形成的森林。

Secondary-growth forests follow secondary succession after land clearance due to human activity or some type of natural disaster (fire, volcanic eruption, hurricane, etc.).

2.2 Deforestation采伐森林

采伐森林指从伐区中获取木材，用于能源、农业和城市建设。

Deforestation refers to removing large tracts of forested land for fuelwood, agriculture, or urban development.

●Clear-cutting 皆伐

皆伐指在采伐季节内，将所有的林木全部伐除。

Clear-cutting refers to removing all of the trees in one area at one time.

●Selective cutting 选择砍伐

选择砍伐指选择性砍伐成熟和已届中年的树木。

In selective cutting, either mature or intermediate-age trees are selectively removed from forested areas that have an uneven-age tree community.

●Strip cutting带伐

在某一个伐区进行带伐后，树木可以迅速重生。

Strip cutting involves removing an entire strip of trees along the contour of the land in a narrow corridor that allows for quick regeneration of the trees. Once the strip begins to grow back the loggers will clear-cut another strip of trees next to the first.

2.3 Forest Fires 森林火灾

●Surface fires 地表火

地表火指仅仅燃烧林地表面的灌木、草层的一种森林火灾。地表火可以刺激一些树木的萌发和矿物质的累积。清除林地表面的物质可以避免这类火灾。

Surface fires burn leaf litter on the forest floor, can be beneficial to forests by stimulating germination in some trees and freeing up vital mineral nutrients. They help prevent more serious fires by removing flammable ground material. If surface fires do not occur for several decades, the forest is at risk for a crown fire.

●Crown fires 树冠火

树冠火能烧毁树叶，烧焦树枝树干。一般来说树冠火很难控制。

Crown fires burn tops of trees and spread from one treetop to the next. They are difficult to control, and they kill not only trees, but wildlife.

2.4 Insects and Climate Change 昆虫和气候变化

昆虫种类和气候变化都能影响森林生态系统。

Forest ecosystems have fallen victim to invasive insect species and diseases. Rising temperatures due to climate change make it easier for invasive insect species and diseases devastate forest ecosystems.

2.5 The Protection of Forest Resources 森林资源的保护

人类对于森林的砍伐是森林资源流失的主要原因。越来越多的国家已经意识到植树造林的重要性，合理利用森林资源对于整个生态系统意义重大。

There are a number of reasons for planting trees:

as a cash crop, providing timber for building or for fuel

to reverse soil erosion, particularly valuable in areas that have become deserts

to provide valuable wildlife habitats—for example, Scots pine plantations are important habitats for red squirrels

as recreational areas, providing leisure activities such as camping and mountain biking

2.6 Deforestation采伐森林的弊端（图1—4—1）

下面为大家总结一下采伐森林的弊端。

The removal of trees destroys habitat for plants and animals that live in the understory of the trees, reduces cover, which dries out soil, increases soil erosion by eliminating the root infrastructure that held the soil in place, and eliminates a carbon reservoir, which increases atmospheric carbon.

2.6.1 Reduction in Soil Fertility降低土壤肥力

a. Deciduous trees may contain 90% of the nutrients in a forest ecosystem. These nutrients are removed if the trees are cut down and taken away.

b. Soil erosion may be rapid in the absence of trees because wind and direct rain may remove the soil. And soil structure is no longer stabilized by tree root systems.

c. The soil below coniferous forests is often of poor quality for agriculture because the shed pine needles contain toxic compounds that inhibit germination and growth.

2.6.2 Flooding and Landslips 洪水和塌方

Normally in a woodland, 25% of rainfall is absorbed by foliage or evaporates and 50% is absorbed by root systems. After deforestation water may accumulate rapidly in river valleys, often causing landslips from steep hillside.

2.6.3 Changes in Recycling of Materials物质循环的变化

a. Atmospheric carbon dioxide concentration may rise as less carbon dioxide is removed for photosynthesis.

b. Atmospheric oxygen vital for aerobic respiration is diminished as less is produced by photosynthesis.

c. The atmosphere may become drier and the soil wetter as evaporation is slower than transpiration from trees.

2.6.4 Climatic Changes气候变化

a. Reduced transpiration rates and drier atmosphere affect the water cycle and reduce rainfall.

b. Rapid heat absorption by bare soil raises the temperature of the lower atmosphere in some areas, causing thermal gradients which results in more frequent and intense winds.

2.6.5 Species Extinction—Many Species are Dependent on Forest Conditions物种的灭绝

a. Mountain gorillas depend on cloud forest of central Africa.

b. Golden lion tamarins depend on coastal rainforest of Brazil.

c. Ospreys depend on mature pine forests in north Europe.

d. Many plant species may have medicinal properties, e.g. as tranquillisers, reproductive hormones, anticoagulants, pain-killers and antibiotics.

3 Rangelands牧场

Around 30% of the total land area is managed by the US government in the US. An area of 259 million acres of those federal lands are classified as rangelands, which permit private livestock grazing. The Bureau of Land Management (BLM) in the Department of the Interior manages 164 million acres and the Forest Service in the Department of Agriculture manages 95 million acres of the federal lands classified as rangelands. The majority of these lands are in the Western US.

3.1 The Role of Rangelands in the Ecosystem牧场的生态意义

牧场的存在具有各种生态意义。Rangelands has several functional roles in the ecosystem:

a．植物栖息地a habitat for a diverse and wide array of native plant species

b．动物栖息地a habitat for a wide array of game and nongame animal species

c．提供水、空气等资源a source of high-quality water, clean air and open spaces

d．娱乐场所a setting for recreational hiking, camping, fishing, hunting and nature experiences

e．放牧场所the foundation for low-input, fully renewable food production systems for the cattle industry

3.2 Desertification and Overgrazing沙漠化和过度放牧

●Desertification沙漠化

It occurs when marginal lands on the outskirts of deserts are overgrazed by livestock or farmed. The removal of native vegetation causes the soil to dry out and the area is slowly incorporated into the expanding desert.

●Overgrazing 过度放牧

It occurs when a plant regrazed before the roots recover. Overgrazing may lead to pastures becoming less productive, soils having less organic matter and a decrease in soil porosity. In addition, overgrazing causes biodiversity to decrease by reducing native vegetation. Also overgrazing increases the incidence of disease in native plant species.

3.3 Rangeland Management 牧场管理

在美国，牧场的管理包括以下几个措施：

a．控制家畜的数量及分布，以限制承载能力 controlling the number and distribution of livestock to limit the carrying capacity

b．恢复已经退化的牧场 restoring degraded rangelands

c．将家畜由一个地方移到另一个地方，以恢复牧场 to recover the rangeland, moving livestock from one place to another

d．隔开河岸地区，以减轻对这些敏感区域的伤害fencing off riparian areas to reduce damage to these sensitive areas

e．抑制有害植物生长 suppressing the growth of invasive plant species

f．用当地草种重新耕种牧场，减轻水土流失 replanting barren rangeland with native grass seed to reduce soil erosion

g．在选定的地点提供充足的饲料providing supplemental feed at selected sites

h．在不会造成环境退化的战略据点安置水池、水槽、盐砖locating water holes, water tanks and salt blocks at strategic points that do not degrade the environment

4 Other Land Use 其他土地应用

4.1 Urban Land Development 城市土地规划

●Urban Sprawl 城市的蔓延

Urban sprawl is the growth of low-density development on the edges of cities and towns. It replaces agricultural and undisturbed lands with tract housing, shopping malls, and parking lots connected by highways and freeways.

●Urbanization 城市化

快速的人口增长是城市化的主要原因。

Urbanization is the growth of urban areas into surrounding undeveloped lands due to rapid population growth. Between 1850 and 2009, the percentage of people living in urban areas increased from 2% to 50%. Every week, more than 1 million people are added to the world's urban areas. In China and India, more than 25 million people move to cities each year.

城市化带来好处的同时也有其弊端（表1—4—4）。

4.2 Transportation Infrastructure 交通基础设施

4.2.1 Federal Highway System联邦高速公路系统

联邦高速公路对于国家的经济、人口密度、可移动性都具有重要意义。在美国，高速公路仍在不断发展，公路的建设通常是由所在州来独立设计、建设和经营的。美国联邦高速公路有效地建立了州与州、城市与城市的良好运输，同时也对环境带来以下影响：

a. less pollutants without frequent braking and acceleration, vehicles will produce less carbon monoxide, nitrogen oxides, and smog-forming volatile organic compounds

b. reduce greenhouse gases, atmospheric carbon dioxide will be decreased by improving traffic flow and reducing congestion

c. improve fuel economy and reduce foreign oil dependence

d. improve the economy

e. improve the quality of life

4.2.2 Channelization of Rivers 河流渠道化

河流渠道化是控制河水流动的有效措施。

It eliminates riparian habitats and encourages the development of floodplains. Channelization also increases the flow rate of the river and increases the risk of flooding downstream. In years of historic water levels, channels may be overwhelmed and social and economic devastation can result from the subsequent flooding.

4.2.3 The Impact of Road Building道路建设的影响

Building roads through natural areas results in the fragmentation of habitat, and perilous road crossings by wildlife, which result in numerous deaths.

New road building in previously roadless areas provides access to heavy equipment for large-scale resource extraction.

4.3 Public and Federal Lands 公共和联邦土地

4.3.1 美国联邦机构主要负责自然资源的保护、重建和发展

Four US Federal Agencies: They administer most of the approximately 672 acres of federal lands in the US. Most of these lands are in the West, including Alaska. The lands administered by the four agencies are managed for a variety of purposes, primarily related to preservation, recreation, and development of natural resources. Each agency has different responsibilities for the lands and resources it manages.

4.3.2 土地管理局主要负责土地的可持续发展和地下矿产资源的管理

The Bureau of Land Management (BLM): In the Department of the Interior, the BLM manages land for multiple-use and sustained yields of various products and services including energy development, timber harvesting, recreation, grazing, wild horses and burros, cultural resources, and conservation. The BLM is also responsible for 700 million acres of subsurface mineral resources.

●The Forest Service 森林服务

In the Department of Agriculture, the BLM manages land for multiple uses and sustained yields of various products and services including timber harvesting, recreation, grazing, watershed protection, and fish and wildlife habitats.

●The Fish and Wildlife Service 鱼类和野生动物服务

In the Department of the Interior, the BLM manages land primarily to conserve and protect animals and plants. The National Wildlife Refuge System include refuges, waterfowl production areas, and areas protected as migratory bird habitat.

●The National Park Service (NPS) 国家公园服务

In the Department of the Interior, the BLM manages land to conserve it for public use. Activities that harvest or remove resources generally are prohibited. The National Park System includes historical structures, as well as important cultural and natural areas.

美国十分重视国家公园的建设，但同时国家公园也带来了各种挑战。

National parks in U.S. are threatened by high demand of large numbers of visitors, which leads to congestion, eroded trails, noise that disrupts wildlife and pollution from autos and visitors. Other challenging things are off-road vehicles, introduction of nonnative species that impact biodiversity and commercial activities.

为了解决国家公园的各种问题，可以采取以下措施：

a．减少私人土地的数量 reducing the amount of private land within national parks through incentives to current owners

b．提供公众教育 providing education programs to the public

c．控制出入数量 setting quotas on attendance through advanced reservation systems

d．采用收费系统 adopting a fee system that covers external costs

e．禁止驶入越野车 banning off-road vehicles

f．使用摆渡车 banning autos and instead provide shuttle buses to control traffic

g．税务刺激 providing tax incentives for property owner near national parks to use land grants

h．记录动植物明细 conducting periodic and detailed wildlife and plant inventories

4.4 Land Conservation Options 土地保护选择

土地保护选择包括维护、补救、缓解、恢复、可持续土地使用战略。

Land conservation options include preservation, remediation, mitigation, restoration and sustainable land use strategies.

表1—4—5列出了一些我们使用土地时的基本原则。

4.5 Sustainable Land-use Strategies 土地可持续利用战略

为满足不断增长的人口和不断提高的生活水平，土地资源的合理利用、可循环永续利用引起了各国政府与土地专家的重视。

4.5.1 Mitigation 减缓政策

To compensate for the environmental impact of a development project in critical wetland habitat, a developer is required to restore a wetland of equal area in another location.

4.5.2 Sustainable Use of Public Lands 公共土地的可持续利用

a. use public lands primarily for protecting biodiversity, wildlife habitats, and ecosystems

b. eliminate all government subsidies and tax breaks for using or extracting resources on public lands

c. ensure fair compensation to all citizens for the use of their property

d. hold all users of public lands responsible for all environmental damage caused by their actions

5 Mining 矿业

5.1 矿产资源的分布

5.1.1 Mineral Deposits 矿床

矿床指因地质作用所形成的，在一定条件下可以开采和利用的矿物聚集地。矿床种类较多，可分为液体矿床和气体矿床。按矿的作用方式可以分为内生矿床（内力地质作用生成）、外生矿床（外力地质作用生成）和变质矿床（变质作用生成）。

The movement of tectonic plates can concentrate minerals.

●At divergent plate boundaries 在离散板块边界

When new crustal material emerges, minerals may be transported by heated water that dissolves metals as they emerge from the earth's crust and deposits them nearby upon cooling. In addition, as molten rock cools, heavier minerals may solidify early and sink to the bottom of the liquid, where they become more concentrated.

●At convergent plate boundaries 在聚合板块边界

Intense heat and pressure that occur when plates collide can melt metallic minerals that then flow and accumulate in cooler areas of the crust.

●Along transform faults 沿着转换断层

Increased weathering and erosion, along with transport by water, wind, and gravity separates minerals based on size and density, thereby producing varied mineral deposits.

5.2 Types of Mining 采矿的类型

●Overburden覆盖层

Overburden refers to the material that must be removed to reach the mineral.

●Surface mining 表层采矿（又叫海底采矿）

表层采矿指主要开采海底的矿产资源。

It is used to remove deposits that lie in horizontal beds close to the earth's surface.

●Mountaintop removal 山顶搬迁

山顶搬迁指使用铲土机移除山顶以获得煤矿资源。

Removing the top of a mountain may expose coal seams. The overburden is dumped into adjacent valleys. The coal is then removed with power shovels or bulldozers.

●Open-pit mining 露天采矿

露天采矿指使用一定开采工艺，移走矿体上的覆盖物，采出矿石的方法。

A huge hole is dug using explosives and heavy equipment, and the deposit is removed.

●Subsurface mining 地下采矿

地下采矿指当矿石埋藏较深时，使用地下巷道工程把矿石开采出来的方法。

Deep vertical mine shafts with horizontal tunnels branching off are blasted into the earth to remove deposits that are too far underground to reach by surface mining.

●Drilling 钻井技术

钻井技术指为获取天然气或者石油等矿物，利用机械设备将地层钻成具有一定深度的柱状圆孔。

Deep shafts are drilled into the earth to reach the geologic formation containing the desired material to remove liquids and gases (oil, natural gas and steam). Pressure in the formation forces the liquid or gas to the surface. When natural pressure is not sufficient, water, steam, or other fluids are injected to force the material out.

●Acid mine drainage 排泄酸性矿水

酸性矿水指在金属矿物和煤矿开采过程中所形成的硫酸溶液。

Acid mine drainage occurs when sulfur compounds in mine waste are exposed to air, oxidize, and dissolve in rainwater to form a sulfuric acid solution.

●Smelting 熔炼

熔炼指通过加热矿石提取矿石中的金属，可能造成空气污染和酸雨等生态问题。

The heating of ores to remove metals produces air pollution that includes heavy metals, particulate matter, and sulfur dioxide, which is a precursor to acid rain.

●Cyanide solution mining or heap-leach extraction 氰化物溶液采矿

氰化物溶液采矿指在岩石中注入氰化物，溶解岩石以提取金属。

It refers to the practice of spraying cyanide solutions on piles of crushed ore to dissolve and extract gold and create holding ponds of cyanide-laced water.

5.3 American Mining Laws美国采矿法

●The General Mining Law of 1872

It was enacted to encourage the exploration and mining of mineral resources. Currently, it enables corporations to acquire large tracts of public lands at far below market prices. Critics claim it allows corporations to remove valuable minerals from public lands without paying adequate royalties or requiring sufficient cleanup of mining sites.

●The Surface Mining Control and Reclamation Act of 1977

It requires that mined land be restored to its pre-mining state.

5.4 Environmental Problems 采矿所引起的环境问题

采矿将引起很多环境问题。

Mining leads to huge damage to the environment. The habitats above the deposit are destroyed by clear-cutting forests and removing native vegetation. In addition, mining produces lots of solid hazardous waste.

6 Fishing 渔业

6.1 Type of Fishing 捕鱼的方式和类型

●Long-line fishing延绳钓

延绳钓是一种商业捕鱼模式，目前是一种比较有争议的捕鱼模式，因为以这种方式捕鱼将会捕获大量幼鱼和稀有鱼种，从而引起各种生态问题。

It is prone to the incidental catching. Up to 80 miles of fishing line is strung out in the water with thousands of baited hooks attached to it, then hauled in to catch swordfish, tuna, and shark.

●Purse-seine fishing围网捕鱼（图1—4—2）

围网捕鱼大多通过围网渔船实现捕鱼作业，有单船围网和双船围网两种。

A net is used to surround a large school of fish such as tuna, herring or mackerel. The net is then closed at the surface like a purse and hauled aboard the ship. By-catch includes any fish that is in the area, but commonly includes dolphins that were feeding on the school of fish that was caught.

●Trawler fishing 拖网捕鱼（图1—4—3）

Large metal chain baskets holding nets are dragged across the ocean floor scouring the bottom for shrimps, scallops, and flounders. They scrape up just about everything on the ocean floor.

●Drift-net fishing流网捕鱼（图1—4—4）

渔网通常在水下50英尺，拖网捕鱼可以捕到大量非目标鱼种。

A net is set to hang in the water from the surface to as far as 50 feet below the surface and extend for up to 40 miles. Drift nets catch large numbers of individuals from non-target species including sea turtles, and dolphins that often suffocate while entangled underwater in the net.

6.2 Others About Fishing渔业的其他现象

●Bycatch混获

混获的最大特点是没有目的性地捕获了一些海洋生物。

The feature of bycatch is to catch and kill sea life (e.g., sea turtles, dolphins, sea birds).

●Whaling捕鲸

It it practiced by several countries including Iceland, Japan, Norway and Russia. Whales are large and surface to breathe every few minutes, making them easy to spot and kill.

●Aquaculture水产业

It is the practice of farming aquatic organisms. In freshwater, examples of farmed species of fish include carp, tilapia, catfish, and trout. In saltwater, examples of farmed species include seaweed, mollusks (such as oysters, clams, and mussels), crustaceans (such as shrimps) and fish (such as salmons and yellowtails). Environmental concerns about aquaculture include nutrient pollution due to excess food and biological wastes, excessive antibiotic use, changes to genetic diversity as a result of farmed escapees cross-breeding with native species, and degradation of aquatic ecosystems.

●Overfishing过度捕捞

Overfishing has depleted many of the world's most abundant fisheries. Limits or bans on fishing have been implemented in most fisheries to prevent further depletion.

渔业通过对环境的不断索取来获得其利益，因此对环境带来了一些影响（表1—4—6）。

Fishing maximizes profit by minimizing environmental resistance.

6.3 Marine Mammal Protection Act海洋哺乳动物保护法

US law prohibits the taking of marine mammals in territorial waters and by US citizens on the high seas, as well as the import of products made from marine mammals into the US.

对于捕鱼种类的基本要求：Species—the “farmed” species must:

a. grow well under captive conditions

b. accept prepared (non-living) food

c. have a high conversion ratio i.e. convert food → flesh efficiently

d. ideally be able to breed under captive conditions

e. not be particularly susceptible to diseases

It is usually expensive to farm fish so the product should command a high price. For this reason the main farmed species in UK are members of the salmon family.

7 Global Economics全球经济

7.1 Globalization全球化

It refers to improvements in technology and the integration of global economies that have led to greater connections between the people of all countries.

7.2 The World Bank 世界银行

It is not a bank in the traditional sense. Owned by 187 member countries it assists developing countries in the fight against poverty by providing financial and technical resources.

7.3 Tragedy of the Commons 公地悲剧

A resource that is free and available to everyone in a population is considered a common. Commons are vulnerable to depletion or degradation by individuals if they acquire or use more than their share; this occurs when each individual reasons that if he or she doesn't use the resource someone else will, and that that small exploitation is insignificant in comparison to the size of the commons, which results in the ultimate degradation of the resource.

7.3.1 Examples of Commons 公地的例子

Commons include publicly owned forests, rangelands, fisheries, open ocean（公海）, air, rivers, and aquifers（蓄水层）.

7.3.2 Exploiting Commons is a Rational Behavior 开发公地的合理性能

It is not necessary for individuals to behave immorally or irrationally to degrade a common. Rather, individuals are behaving rationally, and in their own personal best interest when they exploit a common.

7.3.3 Strategies to Avoid a Tragedy of the Commons 如何避免公地的悲剧

Regulations or restrictions placed on the use of the resource can be effective measures for protection. A quota system, as derived for example through fishing licenses or pollution credits, also can be effective when strictly enforced. Another strategy is to privatize a common, by dividing it up among the population. The rationale is that it is unlikely that individuals will deplete or degrade a resource that they own since they would then bear the entire cost of its overuse.