Conservation.

Ci-dessous un extrait traitant le sujet : Conservation.. Ce document contient 3989 mots. Pour le télécharger en entier, envoyez-nous un de vos documents grâce à notre système d’échange gratuit de ressources numériques ou achetez-le pour la modique somme d’un euro symbolique. Cette aide totalement rédigée en format pdf sera utile aux lycéens ou étudiants ayant un devoir à réaliser ou une leçon à approfondir en : Echange

---

Conservation.
I

INTRODUCTION

Conservation, sustainable use and protection of natural resources including plants, animals, mineral deposits, soils, clean water, clean air, and fossil fuels such as coal,
petroleum, and natural gas. Natural resources are grouped into two categories, renewable and nonrenewable. A renewable resource is one that may be replaced over
time by natural processes, such as fish populations or natural vegetation, or is inexhaustible, such as solar energy. The goal of renewable resource conservation is to
ensure that such resources are not consumed faster than they are replaced. Nonrenewable resources are those in limited supply that cannot be replaced or can be
replaced only over extremely long periods of time. Nonrenewable resources include fossil fuels and mineral deposits, such as iron ore and gold ore. Conservation
activities for nonrenewable resources focus on maintaining an adequate supply of these resources well into the future.
Natural resources are conserved for their biological, economic, and recreational values, as well as their natural beauty and importance to local cultures. For example,
tropical rain forests are protected for their important role in both global ecology and the economic livelihood of the local culture; a coral reef may be protected for its
recreational value for scuba divers; and a scenic river may be protected for its natural beauty.
Conservation conflicts arise when natural-resource shortages develop in the face of steadily increasing demands from a growing human population. Controversy
frequently surrounds how a resource should be used, or allocated, and for whom. For example, a river may supply water for agricultural irrigation, habitat for fish, and
water-generated electricity for a factory. Farmers, fishers, and industry leaders vie for unrestricted access to this river, but such freedom could destroy the resource,
and conservation methods are necessary to protect the river for future use.
Conflicts worsen when a natural resource crosses political boundaries. For example, the headwaters, or source, of a major river may be located in a different country
than the country through which the river flows. There is no guarantee that the river source will be protected to accommodate resource needs downstream. In addition,
the way in which one natural resource is managed has a direct effect upon other natural resources. Cutting down a forest near a river, for instance, increases erosion,
the wearing away of topsoil, and can lead to flooding. Eroded soil and silt cloud the river and adversely affect many organisms such as fish and important aquatic plants
that require clean, clear freshwater for survival.

II

METHODS OF CONSERVATION

The challenge of conservation is to understand the complex connections among natural resources and balance resource use with protection to ensure an adequate
supply for future generations. In order to accomplish this goal, a variety of conservation methods are used. These include reducing consumption of resources;
protecting them from contamination or pollution; reusing or recycling resources when possible; and fully protecting, or preserving, resources.
Consumption of natural resources rises dramatically every year as the human population increases and standards of living rise. From 1950 to 2000 the world population
more than doubled to 6 billion people, with nearly 80 percent living in developing, or poorer, nations. The large, developed nations, however, are responsible for the
greatest consumption of natural resources because of their high standards of living. For instance, the average American consumes as much energy as 27 Filipinos or
370 Ethiopians. Conservation education and the thoughtful use of resources is necessary in the developed countries to reduce natural-resource consumption. For
example, reducing the high demand for tropical hardwoods such as teak and mahogany in the United States and Japan would slow the rate of tropical forest
destruction.
To protect natural resources from pollution, individuals, industries, and governments have many obligations. These include prohibiting or limiting the use of pesticides
and other toxic chemicals, limiting wastewater and airborne pollutants, preventing the production of radioactive materials, and regulating drilling and transportation of
petroleum products. Failure to do so results in contaminated air, soil, rivers, plants, and animals. For example, if governments required that all oil tankers be fitted with
double-layered hulls, the damages to fisheries and wildlife from the many oil spills of the 20th century, such as the 1967 Torrey Canyon oil spill in the English Channel,
may have been reduced.
In many cases it is possible to reuse or recycle resources to reduce waste and resource consumption and conserve the energy needed to produce consumer products.
For example, paper, glass, freon (a refrigerant gas), aluminum, metal scrap, and motor oil can all be recycled. A preventative measure called precycling, a general term
for designing more durable, recyclable products such as reusable packaging, encourages reuse. Many states in the United States have established mandatory recycling
laws in an attempt to reduce waste and consumption.
Some resources are so unique or valuable that they are protected from activities that would destroy or degrade them. For example, national parks and wilderness areas
are protected from logging or mining in the United States because such activities would reduce the economic, recreational, and aesthetic values of the resource. Forests
and wetlands (areas with high soil moisture or surface water) may be protected from development because they enhance air and water quality and provide habitat for a
wide variety of plants and animals. Unfortunately, these areas are often threatened with development because it is difficult to measure the economic benefits of cleaner
air, cleaner water, and the many other environmental benefits of these ecosystems (the plants and animals of a natural community and their physical environment).

III

CURRENT TYPES OF CONSERVATION ISSUES

There are a variety of basic conservation methods used to protect global natural resources. Although each resource has a unique set of conservation problems and
solutions, all resources are interconnected in a complex and little-understood web. Scientists have learned that damaging one thread of the web may weaken the entire
structure. It is important that this connectivity be addressed in the search for solutions to resource shortages. It would be impractical to work toward the conservation
of soil, for instance, without considering the needs and effects of nearby water and vegetation resources (see Environment).

A

Biodiversity Conservation

Biodiversity, or biological diversity, denotes the number and variety of different organisms and ecosystems in a certain area. Preserving biodiversity is essential for
ecosystems to respond flexibly to damage or change. For example, a single-species corn crop may be quickly destroyed by a certain insect or disease, but if several
different species of corn are planted in the field, some of them may resist the insect or disease and survive. The same principle applies to natural areas, which adapt to
natural environmental changes such as wildfire, drought, or disease because of the biodiversity that has evolved in the area over thousands, or even millions, of years.
For example, many forests, such as those that burned in the 1988 fires in Yellowstone National Park in Wyoming, are able to quickly regenerate because many of the
plants that thrive there have adapted to fire. Some trees, such as lodgepole pine, may even require fire to aid in reproduction. These trees produce cones that are
opened by extreme heat. The fire opens the cones and the seeds are then released into the soil.
Humans benefit greatly from the many medicines, crops, and other products that biodiversity provides. As many as 40 percent of our modern pharmaceutical medicines
are derived from plants or animals. For instance, a small plant from Madagascar, the rosy periwinkle, produces substances that are effective in fighting two deadly

cancers, Hodgkin's disease and leukemia.
Unfortunately, human activities have greatly reduced biodiversity around the world. The 20th century encompasses one of the greatest waves of extinction, or
elimination of species, to occur on the planet. The greatest threat to biodiversity is loss of habitat as humans develop land for agriculture, grazing livestock, industry,
and habitation. The most drastic damage has occurred in the tropical rain forests, which cover less than seven percent of the Earth's surface but contain well over half
of the planet's biodiversity. Only 8 percent of the rain forests in Madagascar, home of the rosy periwinkle, remain intact.
Several nations have laws protecting endangered species. An international treaty, the Convention on International Trade in Endangered Species of Wild Fauna and Flora
(CITES), went into effect in 1975 and outlawed trade of endangered animals and animal parts. In the United States, the Endangered Species Act (ESA) was enacted in
1973 to protect endangered or threatened species and their habitats. A new scientific field, conservation biology, studies ways to stop the destruction of biodiversity
and restore natural habitats.

B

Forest Conservation

Forests provide many social, economic, and environmental benefits. In addition to timber and paper products, forests provide wildlife habitat and recreational
opportunities, prevent soil erosion and flooding, help provide clean air and water, and contain tremendous biodiversity. Forests are also an important defense against
global climate change. Through the process of photosynthesis, forests produce life-giving oxygen and consume huge amounts of carbon dioxide, the atmospheric
chemical most responsible for global warming. By decreasing the amount of carbon dioxide in the atmosphere, forests may reduce the effects of global warming.
However, huge areas of the richest forests in the world have been cleared for wood fuel, timber products, agriculture, and livestock. These forests are rapidly
disappearing. The tropical rain forests of the Brazilian Amazon River basin were cut down at an estimated rate of 14 million hectares (35 million acres) each year--an
area about the size of the state of Wisconsin--in the 1990s. The countries with the most tropical forests tend to be developing and overpopulated nations in the
southern hemisphere. Due to poor economies, people resort to clearing the forest and planting crops in order to survive. While there have been effective efforts to stop
deforestation directly through boycotts of multinational corporations responsible for exploitative logging, the most effective conservation policies in these countries have
been efforts to relieve poverty and expand access to education and health care.
In 2005 the Food and Agriculture Organization of the United Nations issued a major report, titled "Global Forest Resources Assessment 2005," on the status of the
world's forests. Based on a five-year study, the report found that forested areas throughout the world were continuing to decline at a rate of about 7.3 million hectares
(18 million acres) per year, an area equivalent in size to Panama or Sierra Leone. However, the rate of decline had slowed in comparison with the period from 1990 to
2000, when the world lost about 8.9 million hectares (22 million acres) of forested area per year. Africa and South America continued to have the largest net loss of
forests, while forest loss also continued in North and Central America and the Pacific Islands. Only Europe and Asia showed a net gain in forested areas due to forest
planting, landscape restoration, and expansion of natural forests. China, in particular, reported a large-scale afforestation effort. In 2005 the world's total forest area
was just under 4 billion hectares (10 billion acres).
In the United States and Canada, forests are threatened by extensive logging, called clear-cutting, which destroys plant and animal habitat and leaves the landscape
bare and unproductive if not properly reforested. Small pockets of ancient forests from 200 to 1,200 years old still exist but are threatened by logging interests. Until
the 1990s, the U.S. Forest Service was directed by Congress to maximize the harvest of timber in order to provide jobs. In the late 1980s and early 1990s, however,
environmentalists sued the government for violating the National Environmental Policy Act (NEPA), and heavy logging was deemed nonsustainable. As a result, the
timber harvest was reduced and foresters were directed to follow a more sustainable policy called ecosystem management. This policy required foresters to focus on
conserving natural habitats rather than maximizing tree harvest. Despite this change, many ancient forests remain unprotected.

C

Soil Conservation

Soil, a mixture of mineral, plant, and animal materials, is essential for most plant growth and is the basic resource for agricultural production. Soil-forming processes
may take thousands of years, and are slowed by natural erosion forces such as wind and rain. Humans have accelerated these erosion processes by developing the land
and clearing away the vegetation that holds water and soil in place. The rapid deforestation taking place in the tropics is especially damaging because the thin layer of
soil that remains is fragile and quickly washes away when exposed to the heavy tropical rains (see Desertification). Globally, agriculture accounts for 28 percent of the
nearly 2 billion hectares (5 billion acres) of soil that have been degraded by human activities; overgrazing is responsible for 34 percent; and deforestation is responsible
for 29 percent.
In addition to reducing deforestation and overgrazing, soil conservation involves reforming agricultural soil management methods. Some of the most effective methods
include strip-cropping, alternating strips of crop and uncultivated land to minimize erosion and water runoff; contour farming, planting crops along the contours of
sloping lands to minimize erosion and runoff; terracing, which also reduces erosion and runoff on slopes; growing legumes, such as clover or soybeans, to restore
essential nitrogen in the soil (see Nitrogen Fixation); and minimizing tillage, or plowing, to reduce erosion.

D

Water Conservation

Clean freshwater resources are essential for drinking, bathing, cooking, irrigation, industry, and for plant and animal survival. Unfortunately, the global supply of
freshwater is distributed unevenly. Chronic water shortages exist in most of Africa and drought is common over much of the globe. The sources of most freshwater
supplies--groundwater (water located below the soil surface), reservoirs, and rivers--are under severe and increasing environmental stress because of overuse, water
pollution, and ecosystem degradation. Over 95 percent of urban sewage in developing countries is discharged untreated into surface waters such as rivers and harbors.
About 65 percent of the global freshwater supply is used in agriculture and 25 percent is used in industry. Freshwater conservation therefore requires a reduction in
wasteful practices like inefficient irrigation, reforms in agriculture and industry, and strict pollution controls worldwide.
In addition, water supplies can be increased through effective management of watersheds (areas that drain into one shared waterway). By restoring natural vegetation
to forests or fields, communities can increase the storage and filtering capacity of these watersheds and minimize wasteful flooding and erosion. Restoration and
protection of wetlands is crucial to water conservation. Like giant sponges, wetlands stabilize groundwater supplies by holding rainfall and discharging the water slowly,
acting as natural flood-control reservoirs.

E

Energy Conservation

All human cultures require the production and use of energy--that is, resources with the capacity to produce work or power. Energy is used for transportation, heating,
cooling, cooking, lighting, and industrial production. The world energy supply depends on many different resources including traditional fuels such as firewood and
animal waste, which are significant energy sources in many developing countries. Fossil fuels account for more than 90 percent of global energy production but are
considered problematic resources. They are nonrenewable--that is, they can be depleted, and their use causes air pollution. In particular, coal plants have been one of

the worst industrial polluters since the beginning of the Industrial Revolution of the 19th century. Moreover, mining or drilling for fossil fuels has caused extensive
environmental damage.
There is a global need to increase energy conservation and the use of renewable energy resources. Renewable alternatives such as waterpower (using the energy of
moving water, such as rivers), solar energy (using the energy from the sun), wind energy (using the energy of the wind or air currents), and geothermal energy (using
energy contained in hot-water deposits within the Earth's crust) are efficient and practical but largely underutilized because of the ready availability of inexpensive,
nonrenewable fossil fuels in industrial countries.
While some countries, such as France and Japan, depend heavily on nuclear energy (energy produced by atomic fission, or splitting of the atom), it is still not a major
energy source. Excessive production costs, serious safety concerns, and problems with the handling of the dangerous radioactive wastes have virtually eliminated it as a
viable energy source in the United States.
In addition to using alternative energy resources such as solar and wind power, energy conservation measures include improving energy efficiency. For instance,
transportation accounts for most of the oil consumption in the United States. Encouraging the expansion and use of public transportation systems and carpooling
dramatically increases energy efficiency. In the household, energy can be conserved by turning down thermostats, switching off unnecessary lights, insulating homes,
and using less hot water.

IV

HISTORY OF CONSERVATION

Until the advent and spread of Christianity and Islam in the 4th and 5th centuries, there were many religions based on animism, the belief that all objects have a
spiritual being. This belief led to careful stewardship, or protection, of natural resources out of fear or respect for these spiritual beings. Moreover, early agricultural
lifestyles, dependent on nature to provide good crops and growing conditions, also encouraged sound land-use practices. Ancient Phoenicians, Greeks, and Romans
developed irrigation, crop rotation, and terraced hillsides as early methods of water, nutrient, and soil conservation.
In Europe, the relationship between humanity and nature became strained with the beginning of the Industrial Revolution in the 19th and early 20th centuries.
Industrialization stifled traditional agricultural lifestyles and encouraged urbanization and the marriage of science and technology to control nature and extract
resources. The Industrial Revolution led to environmental damage on a grand scale as European technology spread around the globe. Coal-burning and iron-smelting
produced waste that contaminated air and water, the concentrated populations in urban areas produced huge amounts of unconfined raw sewage that contaminated
drinking water, and vast forests and plains were cleared for agriculture.
The modern conservation movement of the United States began in the mid-19th century when resource depletion and pollution were first becoming serious problems.
Westward expansion was encouraged by the government--the Homestead Act of 1862 provided free land to settlers willing to clear it. Because land ownership required
land-clearing, the rapid migration often resulted in barren landscapes. The extensive land-clearing and the rapid depletion of wildlife resources such as buffalo and
beaver heralded a public outcry. This concern was reflected in the writings of public figures such as American essayist Ralph Waldo Emerson and naturalist author Henry
David Thoreau.
As conservation ideas gained support, a wave of conservation activity swept the country. The world's first national park, Yellowstone National Park, was established in
Wyoming in 1872 to protect an area of incredible natural beauty. In 1873, the American Association for the Advancement of Science petitioned Congress to halt unwise
use of natural resources, the Forest Reserve Act of 1891 authorized what would become known as National Forests, and the Lacey Act of 1900 established the first
wildlife protection measures by restricting commercial hunting and the trade of illegally killed animals.
The administration of President Theodore Roosevelt (1901-1909) was noted for its conservation achievements. Roosevelt set aside a total of almost 94 million hectares
(235 million acres) of public lands to protect them from exploitation by private interests. He installed forestry expert Gifford Pinchot as the head of the new U.S. Forest
Service in 1905 and adopted Pinchot's principle of multiple use, the nation's first formal natural-resource policy. The multiple-use policy advocated scientific
management of public lands for a variety of uses, including commercial development.
This conservation policy was not popular among many Americans who backed full preservation of natural areas. Naturalist and author John Muir believed that any
commercial development of natural areas was inappropriate. A powerful rift soon developed between multiple-use advocates and preservationists. This rift came to a
climax during the 12-year battle over a plan to dam the Tuolumne River in Hetch Hetchy Valley in California, and the controversy still exists today.
A renewed surge of public conservation activity occurred during the Great Depression of the 1930s. In an attempt to encourage conservation and stimulate the
economy, President Franklin D. Roosevelt established the Civilian Conservation Corp in 1933, which provided two million jobs planting trees, building dams and irrigation
systems, and establishing soil conservation and wildlife protection programs.
The conservation movement rose into the spotlight again in the 1960s as publications such as Silent Spring (1962) by American biologist Rachel Carson raised public
concerns about the health and environmental hazards of pesticides and other toxic chemicals used by industry. Several catastrophic events in 1969, including the toxic
waste fires on the Cuyahoga River in Cleveland, Ohio and a coastal oil spill in Santa Barbara, California focused media attention on the need for environmental
conservation. The estimated 20 million people across the United States who attended the first national Earth Day, a day for recognizing environmental concerns, on April
22, 1970, demonstrated massive public support for conservation issues. Conservation legislation passed in the 1970s included the Endangered Species Act, the Marine
Mammal Protection Act, the Clean Air Act, the Clean Water Act, and the Toxic Substance Control Act.
The 1980s experienced a slowdown of the conservation momentum of the 1970s. Resource conservation concerns remained in the public mind, however, due to
continued scientific discoveries concerning global warming, acid rain (a harmful mix of precipitation and damaging pollutants), and depletion of the ozone layer (a
gaseous layer in the atmosphere that protects Earth from the sun's harmful ultraviolet rays). Ecological disasters such as the nuclear reactor explosion near the
Ukrainian town of Chernobyl' in 1986 (see Chernobyl' Accident) and the tanker Exxon Valdez oil spill in Prince William Sound, Alaska in 1989, served as catastrophic
reminders of the effects of human carelessness.
The European conservation movement began to grow as the effects of industrialization worsened in the mid-20th century. Clean air legislation was enacted in the United
Kingdom in 1956 in reaction to London's industrial smog, which killed more than 2,000 people in early December 1952. Political parties with environmental or
conservation agendas sprang up in New Zealand, Australia, and Europe by the 1970s, and became known as Green Parties in the 1980s. In the 1970s and 1980s,
courageous grassroots organizations such as the Chipko movement in India (a coalition of villagers, mostly women) and the Brazilian rubber tappers (workers who
extract chicle, the tree sap used to make rubber) fought for preservation of the forests that provided their livelihood.
In 1972 the United Nations Environment Program was formed to encourage international cooperation in conservation and development strategies. Collaboration on
environmental conservation issues included the 1987 Montreal Protocol to protect the ozone layer, the 1992 United Nations Conference on Environment and
Development (UNCED) in Rio de Janeiro, Brazil, and the 1994 United Nations Conference on Population and Development in Cairo, Egypt. The participation of the United
States in this international movement was weak, while Canadian and European support and participation were strong.

The 1992 UNCED Conference, commonly referred to as the Earth Summit, was the largest international meeting ever held with 178 nations participating. Its
proceedings noted the economic and environmental gulf between the northern and southern hemispheres and emphasized a sustainable growth, utilitarian approach to
conservation. In the same year an appeal entitled World Scientists' Warning to Humanity was released. This paper was signed by 1,700 of the world's leading scientists
(including 104 Nobel laureate scientists), 19 national academies of science, and the director general of the United Nations Educational, Scientific, and Cultural
Organization (UNESCO). It stated that at the current rate of consumption, the Earth's resources may soon be reduced to the point at which the living world would be
"unable to sustain life in the manner that we know." In several publications, ecologists and economists agree that despite the immediate benefits of economic growth,
infinite growth in material and energy consumption is not compatible with the finite resources of the Earth and will undermine the well-being of both economic and
ecological systems. For these reasons, natural resource conservation has become one of the most important challenges to face the human race.

Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.