"Spaceship Earth" it has been called. When Adlai Stevenson was the U.S. ambassador to the United Nations he said:
"We travel together, passengers on a little spaceship, dependent on its vulnerable resources of air and soil; all committed for our safety to its security and peace; preserved from annihilation only by the work, the care and, I will say, the love we give our fragile craft."The first pictures the Apollo astronauts took of the Earth from space proved the Earth, at least as far as we know, is alone surrounded by lifeless space. We have no greater concern than the future of the Earth and all life on it. Exploration of space has only confirmed how very special the Earth is: the only planet with air to breathe, with liquid water, with life. To preserve it we must continue to seek greater understanding of global environmental change, and knowledge of the entire Earth system.
Human activity is now causing significant changes to the Earth on a global scale. These changes have taken place very quickly, in just the span of a few human generations. The burning of fossil fuels, for example, is putting carbon dioxide (CO2) into the atmosphere at unprecedented rates. The atmospheric concentration of CO2 has increased by approximately 25 percent since the 1800's, and by over 10 percent since 1958! Carbon dioxide allows the suns radiation to pass through it, but blocks the flow of heat radiated outward from the Earth's surface. This creates a "Greenhouse Effect" that generally warms the Earth.
Based on the present rate of increase of carbon dioxide in the atmosphere, climate models predict the Earth's surface temperature will increase by at least 2 degrees Celsius. This warming is predicted to change climate patterns, causing both drought and flooding, as well as to cause a rise in sea level. There are also continuing increases in other "greenhouse gases such as methane from industry and agriculture, chlorofluorocarbons (CFC's) from propellants and coolants, and tropospheric ozone from automobile and industrial pollution.
Add to this the fact that nearly half the world's people have daily needs for fuel and food that are reducing the Earth's vegetation and the productivity of marginal agricultural land. Because of economic and cultural forces, their very survival often depends on cutting the Earth's forests. The clearing of tropical rainforest is often done by burning, which not only destroys the world's greatest reserve of plant and animal diversity, but adds carbon dioxide to the atmosphere. In marginal agricultural areas, overcropping of the land and uncontrolled animal grazing may be turning productive soil into desert. This loss of topsoil to the wind becomes a major source of dust that in turn can affect atmospheric properties and climate.
The effects of these changes on Earth's systems are unknown. We do know that the Earth's ecosystems are delicately balanced and interconnected. The sun is the driving energy force of the biosphere. Within and among ecosystems, plants, animals, microscopic microbes, are connected in the cycling of energy and nutrients from the sun through water, air and Earth. Energy is transported through the Earth system by winds, ocean currents and climate patterns. It is also transported from the sun to plants, from plants to the small animals that eat them, to the larger animals at the top of the food pyramid. The cycle of life, from birth and growth to death and decay, links up with the cycles of soil, water and nutrient elements -- what is called biogeochemical cycling. While we do not know what effect human influences will have on the Earth, we are certain that there will be global change. For as the great naturalist John Muir once said: "When we try to pick out anything by itself, we find it hitched to everything else in the Universe."
All the human induced changes are difficult to assess and measure accurately, but it is already clear that they are playing a major role in shaping present and future global conditions. In effect, we are carrying out an uncontrolled, largely unintentional experiment. Remote sensing and climate modeling are important tools, that help us to monitor and understand these changes. By looking at images taken today, and comparing them to images taken over the last 20 - 40 years we can literally get a picture of the Earth.
As the NASA Earth System Science Committee stated:
WE, THE PEOPLES OF THE WORLD, face a new responsibility for our global future. Through our economic and technological activity, we are now contributing to significant global changes on the Earth within the span of a few human generations. We have become part of the Earth System, and on the forces of Earth change. Research holds the key to knowledge of our global future. Now, with new scientific insight and technology, we can gain deeper understanding of the Earth as a system and of the consequences of global change for humanity. By deciding to take ... steps now, we can help to ensure that the gifts of the Earth will be preserved and passed on to future generations.
The teacher should set down the end piece and pick up the ball. As you carefully rewind the yarn, each person before they let go must name one thing they (or anyone) could do to "save the Earth." (Have a copy of Fifty Simple Things... handy in case you run out of ideas.) When you are done you will have your ball of yarn back and nearly 30 ideas of how to help the planet!