Earth in Peril

Population Density, 2000

It's not difficult to see where on Earth the human footprint is having the greatest impact. The world's population today is estimated at 6.3 billion—up from two billion in 1930—with the highest population densities in India, population 1.1 billion, China, population 1.3 billion, Indonesia, population 220 million, and central Europe, population 630 million.

Population Growth Rates, 1990-95

The total number of people on the planet is growing at a lightning pace and is expected to reach nine billion by 2050. Over the next half century, 98 percent of this growth will take place in the developing world, where resources are being consumed faster than they can be renewed. This map shows recent annual rates of population growth worldwide and the alarmingly short intervals at which some populations will double in size.

City Lights of the World, 1998

Populations are becoming increasingly urbanized. Thirty years ago, only 37 percent of all people lived in cities. Experts predict that by 2030, over 60 percent of the population—five billion people—will do so. The largest share of this escalation will occur in countries where the demand for clean water, sewage systems, and electricity already outstrips supplies. Greater urbanization may have a few environmental benefits, such as reduced pressure on forests, but the costs of the trend are great. City populations consume vast amounts of energy and create air and water pollution affecting human health, local natural habitats, and the global environment.

Freshwater Resources, 2000

Water covers roughly 70 percent of Earth's surface, but only 2.5 percent of it is freshwater, which humans need for irrigation, drinking water, and other everyday uses. According to the United Nations, the scarcity of freshwater due to overuse and contamination will be the second most pressing global concern in the 21st century, after population growth. On the map above, countries with less than 5,000 cubic meters of freshwater per capita are considered short of water. Experts believe that people may be able to replenish water tables with new water-saving irrigation methods, bioengineered crops that require less water, rainwater harvesting, and public information campaigns, but it will be centuries, if ever, before freshwater is plentiful again worldwide.

Carbon Emissions, 1995

The amount of carbon dioxide polluting our atmosphere has risen 30 percent in the last 200 years as a result of increasing industrial and automobile emissions. Plants convert carbon dioxide back to oxygen, but human activities are now releasing more carbon dioxide than the world's plants can process. This map shows in magenta today's greatest polluters—the United States, Europe, China, and Japan. In the next 50 years, as industrialization increases, many of the purple areas on this map will turn to magenta and the green areas to purple unless stricter emissions standards for factories and cars are put in place.

Global Warming, 2003

Climatologists blame air pollution from carbon dioxide and other fossil fuel emissions for global warming, as the buildup of these gases in the air acts like a blanket, trapping heat close to Earth. They predict that over the next 100 years, surface temperatures will increase up to 11 degrees Fahrenheit worldwide. In arid regions, this could result in a sharp reduction in the amount of rivers and lake water. In cooler regions, intense thaws could cause severe flooding. Agricultural zones would shift radically, and hundreds of plant and animal species would face extinction. In 2003, as shown above, most places in the world were warmer than normal.

World Forests, 1997

Experts estimate that almost half of the forests that once covered Earth have disappeared, along with many indigenous plant and animal species. A large portion of this forest loss has occurred over the past 30 years through aggressive logging and agricultural clearing. On this map, frontier forests are defined as the last of the remaining original forest ecosystems that existed before human intervention began about 8,000 years ago. Modified forests, on the other hand, include areas of significant human intervention. The researchers who produced this map estimate that nearly 40 percent of the world's remaining forests are endangered.

Human Transformation of Land, late 1990s

According to the U.N. Food and Agriculture Organization, humans have altered approximately half of all the land on Earth for our own uses—around 22 percent for farming and forestry combined, 26 percent for pasture areas, and 2 to 3 percent for housing, industry, and roads. Population growth will necessitate further conversion of land, which in some regions can interfere with natural defenses against flooding, landslides, and erosion. Furthermore, experts believe that the abundance of agricultural topsoil on which our food supply depends is sharply diminishing due to overuse, urbanization, and other human-induced factors.

Coral Reef Bleaching and Ocean Hot Spots, 1997-98

The by-products of human population growth threaten animal species in nearly every habitat on Earth. In the oceans, for example, overfishing has already decimated numerous species, and rising temperatures from global warming, as indicated on the map above, threaten many more animals native to coral reefs, which are home to over 25 percent of all sea creatures. Scientists are alarmed by the recent increase in coral reef "bleaching," a sign of grave ill health, and some have predicted that more than half of the world's reefs may be gone by the year 2030. If that happens, thousands of animal species, and many islands whose shorelines are protected by reefs, will eventually disappear.