Nature Gallery (Global Trends)

Air Pollution
Air pollution is one of the most pervasive environmental problems because atmospheric currents can carry contaminated air to every part of the globe. Most air pollution comes from motor vehicle emissions and from power plants that burn coal and oil to produce energy for industrial and consumer use. Carbon dioxide and other harmful gases released into the air from these sources adversely affect weather patterns and the health of people, animals, and plants.
Industrialized nations produce most of the world’s air pollution. For example, although the United States is home to just 5 per cent of the world’s population, the country generates 22 per cent of human-made carbon dioxide emissions and 19 per cent of all greenhouse gases such as carbon dioxide and methane. These emissions harm the environment by causing acid rain and global warming, and by depleting the protective ozone layer that surrounds the earth.

Acid rain, a serious threat around the world, occurs when sulphur dioxide and nitrogen oxide emissions from motor vehicles and fossil-fuel burning power plants fall back to Earth as acidic precipitation. Acid rain has contaminated many lakes in Canada and the northeast United States, and has been documented even in the non-industrial state of Hawaii. In the United Kingdom, 57 per cent of all trees are moderately to severely defoliated due to corrosive fallout, and production of food crops has declined in many parts of the world. Acid rain has eroded the surfaces of great art and architectural treasures, including the ancient sculptures of Rome and the Sphinx in Egypt.

Global Warming
Global warming is another negative by-product of air pollution, and although there is debate about the sources of the problem, most scientists agree that the earth is heating up. One of the principal causes is thought to be high atmospheric concentrations of gases such as carbon dioxide and methane. These and related substances are called greenhouse gases because they trap heat in the earth’s atmosphere instead of letting it radiate into space, thereby raising air temperature.

Since 1800, atmospheric carbon dioxide levels have risen 25 per cent, largely due to the burning of fossil fuels. Based on current levels of greenhouse-gas emissions, average temperatures around the globe will increase by 1° to 3°C (1.8° to 5.4°F) by the year 2050. By comparison, temperatures dropped only 3°C (5.4°F) during the last Ice Age, which blanketed much of the earth in glacial ice. If the warming trend continues, glaciers would melt, causing sea levels to rise by as much as 65 centimetres (26 inches), a depth that would inundate most coastal cities. Low-lying island nations such as the Maldives would disappear altogether, and fertile farmland would turn to desert.

Although emission of greenhouse gases has dropped 11 per cent in recent years, this may be only a temporary lull due to the worldwide recession and industrial slowdowns. In fact, it would take a 60 per cent cut in emissions to stabilize atmospheric gases at current levels.

Another serious problem related to air pollution is the shrinking of the upper atmospheric ozone layer that blocks out dangerous ultraviolet (UV) light. First reported over Antarctica in the 1980s, ozone holes have since been detected over parts of North America and elsewhere. The holes are created when ozone molecules are destroyed by chlorofluorocarbons (CFCs), chemicals that are used in refrigerants and aerosol containers and can drift into the upper atmosphere if not properly contained.

Some scientists estimate that 60 per cent of the ozone layer may already have been lost to pollution, and that even a 10 per cent loss could add a total of 300,000 new cases of skin cancer and 1.6 million cases of eye cataracts worldwide. The high levels of UV light that cause skin cancer and eye problems may also harm plankton, the foundation of the food chain in oceans. Serious declines in plankton levels could lead to catastrophic losses of other sea life.

In December 1997, at an international summit in Kyoto, Japan, world leaders signed the Kyoto Protocol, an agreement requiring 138 industrialized countries to limit emissions of six greenhouse gases, including carbon dioxide, methane, and nitrous oxide, which would otherwise cause significant global warming.
Smog and Motor Vehicles
Finally, urban air pollution, usually in the form of smog generated by industry and motor vehicles, remains a serious health hazard for more than one billion people around the world. During the 1980s, European countries cut sulphur dioxide emissions by 27 per cent, and the volume of most pollutants dropped in the United States. Even so, cities such as Los Angeles, New York, Mexico City, and Beijing record unhealthy levels of air pollution on one day out of every three.