The present pattern of human activity, if continued, will lead to a major decline in the condition of nature and the quality of human life. If these concerns are corrected--if we are depleting the planet's resources, damaging its ability to sustain life, and heading toward widespread, perhaps irreversible environmental damage--then, environmentalists argue, the consequences of present activities are too great to continue. If we risk leaving an impoverished Earth for our children and grandchildren, then the benefits of current activities are transitory and unfair to the future generations that must bear the costs. There is evidence suggesting that many current trends or activities are, in fact, unsustainable. 11

Global Warming

There are many facets of environmental health that should be monitored. None, however, is more important than global warming. The results of global warming will encompass increasingly severe droughts, flooding, and storms. Sea levels will rise, and the salt seas will invade the drinking-water sources of coastal cities. Agricultural lands and coastal towns will flood. Weather will change. Warming is likely to cause severe and unpredictable droughts and heat waves. Vast crop-growing regions of the Earth will fail as rainfall declines. Grain and corn-producing regions will become semi-arid, cutting crop production.12

For several thousand years the levels of "greenhouse gases" now responsible for global warming stayed about the same. Carbon dioxide, the most abundant of the greenhouse gases, was absorbed by plants during photosynthesis and released predominantly by organisms at equivalent levels. However, during the Industrial Revolution huge quantities of carbon dioxide, methane, ozone and other gases were given off. And, since the Industrial Revolution the level of carbon dioxide and other gases have continually climbed. During this century, there has been a 10-fold increase in the use of fossil fuels. Now approximately 20 billion tons of carbon dioxide are spewed into the environment worldwide. Since the 1960s the amount of carbon dioxide has increased from 315 parts per million to 352. Carbon dioxide accounts for approximately fifty percent of the global warming. And, carbon dioxide comes largely from fossil fuel burning and deforestation.

With just the greenhouse gases now in the atmosphere, the planet's temperature will increase over 2 Fahrenheit. To maintain carbon dioxide at present levels, emissions must be lowered 60 percent. But, continued emissions are expected which should result in a temperature increase of eight degrees Fahrenheit by the year 2050.

"Ultimately, we must either switch to other energy sources such as solar energy or nuclear power or adapt on a massive scale to a warmer world. Long before all the world's oil and coal are exhausted, carbon dioxide levels will have more than quadruped. Under those conditions, virtually no one doubts that the world would warm dramatically, and with devastating consequences."13

Ozone Layer

Hovering about fifteen miles above the ground is a gas called the ozone. Ozone gas is relatively rare in the atmosphere, but is vital to all life. It is the only atmospheric gas that keeps

the sun's deadly ultraviolet rays away. The Environmental Protection Agency estimates that during the next ninety years, increased ultraviolet radiation will cause as many as 2.8 million cases of cataracts. Ultraviolet rays also cause drying of human skin and increases the incidence of skin cancers, including melanoma, which kills about a third of its victims. Additionally, there is some evidence that suggests that ultraviolet rays suppress the human body's immune responses, making people more susceptible to disease. Furthermore, Ultraviolet rays harm crops and kill ocean plankton.

There are places where there is no ozone - called "ozone holes." The first ozone hole was discovered over Antarctica, where environmental and atmospheric conditions speed ozone destruction, creating huge holes in which ozone concentrations are cut in half. One hole late in the 1980s was twice the size of the United States. Ozone holes have been discovered over the arctic, too, and ozone concentrations are quite likely declining in areas all over the globe.

The ozone layer is getting thinner each year. CFC, used in aerosol spray cans, Styrofoam, air conditioners, destroy the ozone layer. Even if everyone stopped using CFCs today, those already in the atmosphere would still be around for another hundred years. 14

Acid Rain

Acid rain is another result of the use of fossil fuels. Coal burning gives off sulfur. When gasoline is burned in automobile engines, nitrogen compounds flow into the atmosphere. The sulfur and the nitrogen compounds each combine with oxygen to form acids. These gases rise into the air and mix with water forming acids. These acids are washed from the atmosphere by rain and know, and enter lakes and streams. In Canada, New York State, New England, and the northern European nations, acid rain has damaged tens of thousands of lakes. There is increasing evidence that acid rain affect human health by increasing the intensity and frequency of asthma attacks and by working deep into our lungs to gnaw at our tissues, perhaps increasing the incidence of certain types of cancer.15

Biological Impoverishment

Tropical forests cover only 7 percent of Earth's land surface, but they contain more than half of all living species. Yet these forests are being cut and cleared at a very rapid rate-an area of about 30 million acres (about the size of the state of Washington) every year. As these unique habitats vanish, so do the species that live there.

A similar process of degradation and destruction is under way in the world's marine environments. More than half of the seas' biological productivity and nearly all of the world's catch of fish comes from the coastal zones, comprising just 10 percent of Earth's oceans. Yet these coastal zones are increasingly polluted with sediment, sewage, and industrial chemicals. Coral reefs--in many ways the equivalent of tropical forests in the diversity of life that they harbor--are dying or being carelessly destroyed at an accelerating rate.

Both deforestation and marine degradation reflect the growing loss of biological diversity.

Groundwater

About 50 percent of the population of the United States depends on underground sources of water--groundwater--for its drinking water. The U.S. geological Survey and state agencies monitor the quality of groundwater by testing wells throughout the country. The results based on testing more than 100,000 wells show that in the past twenty-five years these sources are becoming increasingly polluted by nitrate and toxic chemicals. In 1984 the U.S. Geological Survey stated: "Current trends suggest that nitrate accumulations in ground water of the United States will continue to increase in the future."16

Saving Energy on the Road

The vast majority of domestic passenger travel is in cars and light trucks--some 166 million of them--that traveled 1.6 trillion miles in 1987. This driving uses up a lot of energy. The good news is that the average car's efficiency has improved in recent years, as reflected in an increase in fuel economy form 13.3 miles per gallon (MPG) in 1973 to 20.5 mpg in 1989. The bad news is that although fuel economy has increased, so has the number of cars on the road and the number of miles the average person is traveling. From 1973 to 1989, the number of passenger cars in the United States increased 42 percent. The number of trucks increased 91 percent. The net result is that gasoline consumption has increased 9 percent since 1973, and total motor vehicle fuel consumption has increased 18 percent. Worldwide, the trend is similar.