Man's voyages in space (and the television cameras they took with them) made it possible for us to stand back and take a good hard look at the planet we call earth.
We needed this view for we suddenly saw the world for what it is - an island unto itself. It draws its energy from the sun but otherwise is dependent on self-sustaining but ultimately limited resources within its own mass. We say ''limited'' because replenishing streams of these resources do not simply flow in from outer space.
The earth, it would seem, is on its own. It is this concept which must underlie global education about our land, its care, and its future.
Simply put, three principal resources - air, water, and soil - working in combination, sustain life as we know it. They are resources which, in the scheme of things, can be used and reused ad infinitum.
But, and this is the biggest ''but'' our schools have ever faced in this field, man's technolgy has arrived at the stage where our earth can be used and abused beyond its powers to fully regenerate. Even climates can be altered.
In part, this has produced abundance.
Supermarkets in many areas of the world are crammed to capacity with every conceivable foodstuff. There is little we cannot buy in the West for our table, whatever the season. Strawberries and melons are available all year long and orange juice isn't just for breakfast any more even in Iceland and Alaska.
Worldwide food production has doubled since 1950, and though a quarter of the world still goes to bed hungry at night, there is less starvation as a percentage of the world's population than at any other time in history.
There is, though, another side to this coin of abundance:
Imagine, if you will, an area near your home 10 miles long by 21/2 miles wide. Imagine, too, a fleet of bulldozers moving in one day and removing the productive topsoil from that 25 square miles, then moving on the next day to an ajacent 25 square miles and so on, day in and day out all year long.
By some estimates, if concentrated in one place, that's the amount of soil being washed and blown from North America's fertile farmlands every 24 hours. Similar soil loss plagues other parts of the world where intensive bare-soil agriculture is practiced.
It is part of the cost, if you will, of filling our supermarkets and feeding us so inexpensively.
Those weaving doomsday scenarios have air and water qualities declining well below acceptable levels by the end of this century (if you're 10 now, you'll be 29 then) and the world's topsoil disappearing below critical crop and fiber-producing levels.
Soberly reasoned analysis does not support these more extreme conclusions. But neither does it support some counterclaims that ''all's right with the world'' or, rather, that there is nothing to be overly concerned about.
This earth-world will not continue to feed its burgeoning populations simply because it has done so in the past; impressive per-acre improvements in agricultural productivity in the West will not continue in the face of environmental degradation simply because this has been the general rule in recent decades. For example, there is a limit to which additional fertilization can make up for deteriorating soil quality. Why?
Covering the earth's land surface is a thin layer of topsoil (the A horizon as soil scientists are wont to describe it) that ranges from an inch or two thick in some areas to many feet in others.
In relation to the earth's size it is tissue-thin. The skin on an apple is miles deep by contrast. Yet, this ever-so-thin layer of soil makes possible the production of the vast bulk of man's food and fiber needs.
Without this layer of topsoil, natural scientists argue, life as we know it would cease. To many city dwellers (whether schoolchildren or adults), dirt is dirt, and top soil, like ring-around-the-collar, is dirt.
But soil is very much more than what we think of as dirt. Perhaps it would help to realize that topsoil is not inert matter.
It is alive! Alive in the sense that it is home to teeming trillions of life forms. One handful of garden soil, rich in organic matter, contains more microscopic life forms than all the animals and humans living on top of the earth's soil put together.
These soil-enriching life forms play a totally indispensable role in regenerating the soil. These microorganisms work ceaselessly for the benefit of all other life forms. Through their processing, spent plant materials decay to return to the soil the very nutrients they took from that soil when they were alive.
Apart from Iceland where volcanoes still add, periodically, to that nation's real estate, the remainder of the world's land is a fixed asset. As the popular phrase has it, ''they're just not making land the way they used to any more.''
Yet, the number of people living on (and dependent upon) the world's land, continues to grow.
The world's projected population figure for the year 2,000 - a conservative 6 .2 billion - is almost meaningless by itself. So, consider this: All of the 1980 populations of Europe, Africa, North America, Latin America, and Oceania plus about half of the USSR will be added to the world total during the next 19 years.
Even so, the world has the capacity to feed this burgeoning population if - and here's the job for classroom teachers around the world - soil resources are well-managed and a more even distribution of fertilizers is realized.
Every year some 3 million acres in the US are used up by the construction of everything from highways to new housing. This is the total amount of land taken up by development. According to Emery N. Castle, president of Resources for the Future, the true loss of cropland is less than one-third of that figure - some 850,000 acres a year to be exact.
This, Mr. Emery estimates, amounts to ''less than 4 percent of the potential US cropland base of 540 million acres by the year 2,000.''
Don Parlberg, professor emeritus of
Purdue University, and considered ''level headed'' even by those most concerned with land loss, contends that the annual loss to development is ''a small fraction of 1 percent of our cropland.'' These shifts, he says, ''can be very difficult locally but they pose virtually no threat to our agricultural potential.''
Dealing with these and other land-use concerns, not just locally, regionally, or nationally, but globally, is the challenge for today.
Erosion, too, is a serious problem.
The United States Department of Agriculture (USDA) puts soil loss to water erosion at around 6 billion tons a year; wind erosion whips off nearly another billion and a half tons.
About a billion tons flows to the ocean, principally to the Gulf of Mexico, while the rest settles as sediment at the bottom of lakes, dams, and reservoirs around the US.
Worldwide, it would seem, we are storing some of our most fertile soil right where, short of dredging, it can never be used.
Robert Rodale, publisher of Organic Gardening Magazine asserts that ''In Iowa alone, so much soil is being lost to erosion that it would fill a five-ton truck every second of every day.''
And another of his startling graphics:''You would have to pile 100 feet of soil on top of the average US supermarket to show how much soil is being lost in the production of food sold in that supermarket.''
Why should this be? Simply because modern high-energy agriculture tends to look on soil as an input, just like diesel fuel and fertilizer. A farmer expects to use up so much fuel and fertilizer to produce a crop; he expects to use up many tons of soil in the process too.
The USDA says that a five-ton-a-year soil loss to the acre is acceptable because natural soil-building processes contribute an equal amount to an acre of land. Over much of the earth, it is possible to match soil loss with natural regeneration, but not in such high-yield areas as the US corn and wheat belts.
In the US, conservation practices can add between $250 and $300 an acre to the cost of farming. That demands a lot of additional working capital for the farmer with thousands of acres to work and an almost perennial glut situation depressing prices for his grain. Hence, rather than build his soil, too often he exploits it.
In effect the farmer borrows (in terms of land quality) from the future; from his son, and subsequent heirs. It frequently is his only option if he is to stay in business.
Fortunately, soil erosion can be readily controlled. In many areas of the Far East, notably China and Japan, soils have been kept productive for the past 2, 000 years by a disciplined program of returning all spent organic materials to the soil and by the construction of elaborate systems of terraces which control run off.
Jean Mayer, president of Tufts University and an acknowledged authority on world food supplies, contends that barring disastrous weather or changes in climate, the world has the technical capacity to feed itself.
''But, have we the political wisdom or determination to do so?'' he wonders. That includes having the determination to tackle soil-loss problems head-on. While food production is a vital part of feeding the world, distribution is equally critical. ''We may also one day have to choose between driving our car or feeding a child in the third world,'' he says.
The US exports ever greater quantities of the grain to the rest of the world while giving away less and less in technical aid. In terms of its GNP, the US spends about one-fourth of 1 percent in aid.
The time has arrived, Dr. Mayer says, when the US can do more to feed the world by exporting technical aid rather than grain.
And what can students in schools and colleges do to preserve rather than exploit our land?
* Become aware of the problems and the costs of not tackling them. This makes it politically acceptable to attack them.
* Insist on soil erosion programs which fundamentally attack and don't just peck at the problem.
* Nurture such soil over which you have direct control. Every good gardener knows how readily soil can be built up by feeding it (digging in) organic wastes. Compost both fertilizes and builds soil at one and the same time. Start a home compost heap, not only for its direct contribution to the nearby garden soil but for its educational value in the home.
* Encouraging towns located in the temperate zone to compost autumn leaves is similarly beneficial. Understanding how soil works and the relationship earthworms and microorganisms have to viable productive loam is a basic element in the war on soil loss.
* Grow some of your own food and help save some of the energy that now goes to process, refrigerate, and transport produce often over thousands of miles. It is now estimated that one-third of all the fresh, unprocessed vegetables consumed in the US are grown in home gardens. You can make it two-thirds.