Accidents and natural disasters have caused environmental damage. In 1986, a leak from a pesticide plant in India killed 3,600 people and injured 100,000. That same year, an accident at the Chernobyl nuclear power plant in the Soviet Union exposed people, crops, and animals to deadly radiation over a wide area.

In 2011, an earthquake and tsunami damaged Japan's Fukushima nuclear power plant. Radioactive materials leaked into the environment. Such accidents have prompted citizens to call on industries and governments to improve safety measures.

Changes to Deserts and Forests

As you have read, desertification is a major problem, especially in the Sahel region of Africa. Another threat—especially in Africa, Latin America, and Asia—is deforestation, or the cutting of trees without replacing them. In many developing countries, forests are resources that provide needed jobs and increased wealth. People cut trees for firewood or shelter, or to sell in markets abroad. Some burn down forests to make way for farms and cattle ranches, or for industry.

However, once forests are cleared, rains wash nutrients from the soil, destroying its fertility. Deforestation also causes erosion, or the wearing away of land, which encourages flooding.

Aerial photo of an intersection of thick forest with cleared area that has been turned into fields.

A soy plantation in the Amazon rain forest in Brazil shows how acres of forest are cleared for agricultural purposes.

Rain forests like those of the Amazon basin play a key role in absorbing poisonous carbon dioxide from the air and releasing essential oxygen. They are also home to millions of animal and plant species, many of which have become extinct because of deforestation.

Rich nations are the greatest consumers of the world's resources and produce much of the world's pollution. However, they have also led the campaign to protect the environment. They have passed laws to control pollution and ensure conservation in their own countries. In 1992, the UN sponsored the first “earth summit” at which world leaders discussed how to clean up and preserve the planet. Although governments agreed to limit damage, they disagreed over who was responsible and how to pay for any clean up.

The summit raised other hotly debated issues. Should economic development take priority over protecting the environment? Are people, especially in rich nations, willing to do with less in order to preserve the environment? How can emerging nations afford costly safeguards for the environment?

The Debate Over Climate Change

Another environmental challenge—one that is hotly debated—is climate change, often referred to as global warming. Global warming refers to the increase in Earth's average surface temperature over time. Scientists have recorded the rising temperatures over the past century and a greater rise since 1975. The warming trend is changing precipitation patterns, raising ocean temperatures and sea levels, and causing glaciers to melt.

Most scientists link today's climate change to rising levels of carbon dioxide and other gases released into the atmosphere by human activity such as burning of fossil fuels. “Greenhouse” gases like carbon dioxide trap warmth in Earth's atmosphere.

Some scientists and policymakers, however, disagree with this view. They argue that climate change is due to natural fluctuations in Earth's climate.

The debate over a treaty called the Kyoto Protocol raised a key question: Does economic development have to conflict with protecting the environment? The treaty, signed by 140 countries, with the major exceptions of the United States and Australia, went into effect in 2005. Its purpose is to lower the emissions of carbon dioxide and other “greenhouse” gases. Many developing nations refuse to sign because they say they must exploit their resources in order to develop fully. The United States did not sign because it believes the treaty could strain economic growth. Nations that have signed the treaty, however, argue that developed nations must lead the way in slowing emissions.

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Table of Contents

World History Topic 1 Origins of Civilization (Prehistory–300 B.C.) Topic 2 The Ancient Middle East and Egypt (3200 B.C.–500 B.C.) Topic 3 Ancient India and China (2600 B.C.–A.D. 550) Topic 4 The Americas (Prehistory–A.D. 1570) Topic 5 Ancient Greece (1750 B.C.–133 B.C.) Topic 6 Ancient Rome and the Origins of Christianity (509 B.C.-A.D. 476) Topic 7 Medieval Christian Europe (330–1450) Topic 8 The Muslim World and Africa (730 B.C.-A.D. 1500) Topic 9 Civilizations of Asia (500–1650) Topic 10 The Renaissance and Reformation (1300–1650) Topic 11 New Global Connections (1415–1796) Topic 12 Absolutism and Revolution Topic 13 The Industrial Revolution Topic 14 Nationalism and the Spread of Democracy (1790–1914) Topic 15 The Age of Imperialism (1800–1914) Topic 16 World War I and the Russian Revolution (1914–1924) Topic 17 The World Between the Wars (1910–1939) Topic 18 World War II (1930–1945) Topic 19 The Cold War Era (1945–1991) Topic 20 New Nations Emerge (1945–Present) Topic 21 The World Today (1980-Present) United States Constitution Primary Sources 21st Century Skills Atlas Glossary Index Acknowledgments