During the late 1900s and early 2000s,

• The world has seen stunning achievements in technology, including journeys into space.

• From space capsules and space stations, astronauts have gazed down on planet Earth.

• It appeared vulnerable, like something that might not last forever.

From outer space, (1)

• Astronauts have been able to see some of the forces that threaten Earth: burning rain forests, polluted skies, swirling dust storms, lands stripped of plants, and sprawling megalopolises---areas where cities have grown so large they run into each other.

From outer space, (2)

• Photographs taken from space prove what the environmentalist fear: Earth faces grave challenges.

• These challenges are not challenges of the past, but for today and for the future.

Population Growth• The world population has grown greatly in recent decades.

• The rapid population growth, resulting partly from improved medical care, strains the Earth’s limited resources.

• It also strains relationships between developed countries and developing countries, which have different views of who is most responsible for the uses and abuses of Earth’s resources.

Today• Nearly 97 percent of the population growth

occurs in developing countries---countries seeking to industrialize, but still wanting to follow traditional ways.

• Developed countries, like the United States, have long been industrialized and can offer a higher standard of living---the measure of a person’s wealth and personal well-being.

To keep their economies strong,

• Developed countries consume larger amounts of natural resources.

• To feed their booming populations, developing countries clear more and more land of trees and plants.

• Developed lands often purchase the products of forests and fields, encouraging people to clear even more land.

• The result is two dangerous environmental trends: deforestation and desertification.

Deforestation• The clearing of forests,

deforestation, is one of the by-products of a growing world population.

• People have cut down forests and jungles to provide more farmland, fire-wood, and timber.

• Countless plants, animals, and insects have lost their habitats, or the special environments required for particular organisms to live.

Deforestation continued…• Ecologists especially

worry about destruction of the tropical rain forests along the Equator.

• Although tropical rain forests cover only about 6 percent of the Earth’s surface, they support 50 percent of the world’s species of plants and animals.

• The rain forests also help keep humans alive.

• Through the process of food-making known as photosynthesis, they remove carbon dioxide from the air and return oxygen.

Desertification • Elsewhere, in places with hot, dry

climates, a different environmental threat is occurring.

• People need land to graze livestock and to grow crops.

• Overgrazing grasslands and over planting fields leave the land exposed to erosion.

• The result is desertification, or the turning of fertile land into desert.

• One of the hardest hit areas is the Sahel, a Western African grassland bordering the Sahara.

• Conditions are worsened by severe droughts, or long periods without rain.

• Lack of rain has turned large stretches of land along the Sahara into vast wastelands.

Urbanization• Throughout the world, there has been a growing

trend toward urbanization, or the movement of people from rural areas to cities.

• For the most part, industrialized countries are already urbanized.

• The majority of their populations live in or near cities.

• In developing countries, however, many people still live as subsistence farmers, growing just enough food to meet their needs.

• In recent decades, however, more and more people in developing countries have moved into cities in search of work.

• They hope to escape starvation and disease, but instead, they find overcrowding, crime, and pollution.

• Many end up living in slums, the rundown, poverty stricken portions of a city.

Urbanization 2• Developing countries

have a hard time keeping up with this rapid migration, or movement of people.

• As more people move to cities, there are fewer remaining behind in rural areas to grow food for the booming urban populations.

Industrialization

• The switch from an economy based on farming to an economy based on industry is called industrialization.

• Unfortunately, industrialization has caused a wide range of environmental problems.

• Signs of pollution were noticeable as early as the Industrial Revolution in Europe.

• Other signs of problems have been identified more recently because of the increased awareness of the environment.

Industrialization 2• The following are some of

the biggest challenges caused by industrialization:– Planning the use of natural

resources– Dealing with pollution– Addressing the problem of

global warming– Finding paths to

sustainable development

Industrialization 3• Consuming Scarce Resources:

– Industries run on nonrenewable resources such as coal, petroleum, or natural gas.

– It takes millions of years to produce these fuels.

– When they run out, these resources will be gone forever.

– Yet industrial nations consume, or use them at an alarmingly fast rate.

– Scientist worry that scarce natural resources may one day disappear.

– They urge two actions:• 1. conserving resources, or using

them wisely• 2. developing alternate

renewable energy resources, such as solar power or wind power.

Industrialization 4• Pollution:

– Human behavior has polluted both the water and the air.

– For years, factories and businesses have dumped industrial wastes, sewage, and pesticides into coastal waters and landfills, where chemicals leak into groundwater.

– Fish, wildlife, coral reefs, and humankind have suffered from this practice.

– Scientists warn that polluting the oceans threatens the entire food chain, which starts with the microscopic plankton (weakly swimming animal and plant life) that float on the seas.

Gas Emissions• Gas emissions released from

factories and automobiles also harm the air we breathe.

• Chemically loaded smog---polluted fog---hovers in a huge, dirty, gray cloud above some cities.

• In many places, the sulfur gas produced by factories mixes with moisture in the air to produce acid rain.

• Poisonous downpours have killed forests in both North America and Europe.

Global Warming• Scientists who study

the climate say the planet has heated up over the past century.

• Many of them point to a single cause: the emissions of carbon dioxide and other gases from factories and gas-burning vehicles.

Greenhouse Effect• These gases, say scientists, produce a greenhouse effect.• The gases trap solar energy in the form of heat, the same way that a

nursery greenhouse does.• Some scientists warn that “greenhouse gases,” unless curbed, could create

disastrous problems.• The most serious effects include the melting of polar ice caps.• Some climate experts forecast the eventual rising of seas and flooding of

coastal areas, submerging parts of cities like New York.

Destruction of the Ozone Layer

• Emission of chlorofluorocarbons (CFCs), the gases used in aerosols, air conditioning, refrigerators, and foam packaging, has also raised concern among scientists.

• They warn that CFCs destroy the ozone layer, a thin protective layer of gas in the upper atmosphere.

Ozone Layer • Human life depends on the

ozone layer.• The ozone layer absorbs most

of the sun’s cancer-causing ultraviolet radiation.

• The depletion (weakening) of the ozone, say scientists, seems to cause a seasonal reduction of ozone over Antarctica called the ozone hole.

• This hole starts to appear each August and reaches its largest size by October.

MEAs• Multinational

environmental agreements (MEAs) reached in Montreal in 1987 and Kyoto in 1997 have focused on the reduction of CFC emissions.

• Since 1987, the ozone hole has begun to shrink.

Sustainable Development• Economic development that

does limit the ability of future generations to meet their needs is known as sustainable development.

• Nations have tried to promote this policy in various ways.

• In the 1970s, for example, people declared the so-called Green Revolution as a solution to feeding the world’s population.

The Green Revolution

• The Green Revolution provided a new strains of rice, corn, and other grains that have high yields.

• Unfortunately, production methods required greater quantities of pesticides, which damaged the environment.

The United Nations• Today, individual

countries and international organizations such as the UN promote programs that conserve natural resources and curb the dumping of toxic wastes.

• The United States, for example, encourages recycling and the development of alternative fuels for automobiles.

Water• People are also taking a

careful at water-one of the most basic necessities of life.

• The UN report has shown that one-sixth of the world lacks clean water for drinking or farming.

• More than 5 million people die every year from not having sufficient water to drink or from drinking untreated, polluted water.

• Not enough time has passed to see if the world can achieve sustainable development.

• This goal is perhaps the biggest challenge of the twenty-first century.