Script for video - Ecosystems


Part 1: From Nature Study to Ecology

"We can never get enough of nature ... We need the tonic of wildness-to wade in marshes where the bittern and the meadow-hen lurk, and hear the booming of the snipe; to smell the whispering sedge where only some wilder and more solitary fowl builds her nest, and the mink crawls with its belly close to the ground."

So wrote Henry David Thoreau, writer, pencil-maker and self-appointed inspector of snowstorms. He wrote these lines in a cabin he built himself for $28.121/2 at Walden Pond near Concord, Massachusetts in 1845.

"Silver Springs is a thermostatic, chemostatic, and biostatic ecological community in seasonally pulsing steady state climax. The rate of primary production of the whole community is linearly proportional to the light intensity under natural conditions. The efficiency of primary production relative to incoming light of usable wavelengths reaching plant level is about 5.3 percent."

So wrote Howard T. Odum, professor, author and pioneer ecologist, describing a pond in Florida in 1957. He wrote these lines as a part of a scientific study published in a technical journal.

For Thoreau the most important thing was to go "to the woods to front only the essential facts of life." To "spend one day as deliberately as nature, and not be thrown off the track by every nutshell and mosquito's wing that falls on the rails ... to stand right fronting face to face to a fact, and see the sun glimmer on both its surfaces, as if it were a scimitar, and feel its sweet edge dividing you through the heart and marrow."

In other words, to live in nature and with nature and not set oneself above nature. We should, Thoreau advised, learn nature's secrets not in order to conquer her or to exploit her resources. Instead we should learn to live in harmony with nature and, indeed, to unite with nature in a kind of emotional and spiritual union.

For Odum, on the other hand, the important thing was to understand the workings of nature so that we could better predict what would happen if we changed things. For instance, what would happen if we changed the energy input; if we modified the food chains; if we changed the abiotic base; if some toxic waste entered the web? How prove the productivity of pond, farm or forest? In other words, the goal was a scientific understanding of nature so that we humans could better control nature for our own human purposes. Both of these approaches to the natural world have long histories. Only very recently have they come together to help form the modern science of ecology and to spark the environmental movements of the past few decades. The tradition Thoreau represents is sometimes called the naturalist tradition. Its roots go back to early Greek and Roman civilizations. Thoreau himself was fond of quoting Homer, Cicero, Virgil, Pliny and other classical writers as authorities for what he called a "noble, clear sighted way of life."

This was and is an approach to nature on direct experience, on minimal interference in the great cycles of nature, on wilderness and the purity of unsullied natural things. It is a tradition that has much in common with some Eastern religions like Buddhism, Hinduism and Taoism.

Though individuals often mixed them together, the historical tradition that Odum grew from was different from that of Thoreau. In earlier times it was most openly stated by the philosopher Francis Bacon in sixteenth century England. Bacon was not much interested in a humble reverence for nature. He wanted to dominate her. To understand and then to use nature for human purposes. "The enlargement of the bounds of Human Empire [note the capital H and E] to the effecting of all things possible," wrote Bacon. "The world is made for man, not man for the world."

Some scholars point out that Bacon, one of the early pioneers in scientific philosophy, took his basic approach to nature directly out of the Jewish, Christian and Moslem religious traditions of the western world. God created the heavens and the earth to be good the Bible, and he placed Adam and Eve on earth to take charge. "To have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth."

At about the same time Henry David Thoreau was building his cabin at Walden Pond, another naturalist across the ocean was strolling down a path every noon at his country home in Down, England. He was putting together ideas that would shock the scientific and the social world of his day-and of ours. His name was Charles Darwin.

Darwin, like Thoreau, was fascinated by nature. He began, as many naturalists have always begun, by observing nature. And by making collections of beetles, butterflies and other plants and animals near his home. But Darwin went a step further. He wondered. He asked himself questions. Why are there so many different kinds of plants and animals? How did each plant and animal get to be the way it is today? How is one plant or animal related to the other plants and animals living around it? And to the physical environment-the rocks, the water, the soil, the climate?

When Darwin got a chance to go on a voyage of exploration around the world as an unpaid naturalist, he snapped up the opportunity. At every stop on the five-year-long voyage of HMS Beagle, Darwin would go ashore and explore the local geology and the living communities of plants and animals he found there.

Back home in England he settled in a quiet country home outside London to study and eventually to write a famous, revolutionary book, On the Origin of Species by Means of Natural Selection. In this book Darwin pulled together his observations with those of other naturalists and geologists. More important, he explained them with a new theory of evolution. This new theory laid basic foundations for all of biology, as well as for the yet-to-be-born science of ecology.

"Nature," said Darwin, "is a web of complex relations" in which each organism plays a role. Ecologists today call this an ecosystem with niches.

"All organic beings," wrote Darwin, "are striving to seize on each place in the economy of nature." In other words there is a "struggle for existence" in all these ecosystems.

All living things produce more offspring than can survive. There is always a variation in traits in offspring. Which will survive?

The fittest, says Darwin. "The merest trifle would often give the victory to one organic being over another." Thus nature selects who will survive. Through this process of natural selection, given enough time, whole new species will be created.

Darwin's ideas were controversial in his own day, as they are in ours. The vast majority of modern biologists, however, accept and use the framework that Darwin provided to help make sense of their own investigations into natural living systems today.

Of all the specialized sciences gathered together under the general term "biology," the science of ecology, more than any other, builds on the insights Darwin provided. It was only in our own twentieth century, however, that ecology came to be a science in its own right. And only in the last twenty-five years that it has burst upon the public scene with such dramatic impact.

Some think this vastly increased public awareness grew directly out of the first photographs taken of our planet earth from outer space. Here, at last, the idea of Darwin and others in the nineteenth century-that nature is a complex web of relationships colonizing a remarkably live planet-was obvious to everyone on earth. Get down to the details, however, and you run into hornets' nests of controversy.

Professional ecologists like Howard Odum began to learn some of the secrets of these living webs of life when they did field studies of ecosystems in the 1950s. One of the most influential was Odum's study of a pond at Silver Springs, Florida.

Unlike Thoreau, Odum and his students did more than observe with the unaided senses. They brought in all the sophisticated technology of modern science that they could find or invent. They were especially interested in quantitative studies-that is, measuring things in numbers. It wasn't enough to see the "sunlight glimmer on the silvery surface." They wanted to know exactly how much solar energy the pond received in kilocalories. They wanted to know how much of that energy was taken up by the producers, the green plants. And how much was taken by the consumers, plants and animals. They wanted to know in quantitative detail what the relationships were between each bird, snail, fish and water plant.

From their measurements they constructed detailed flow charts, not unlike factory organization charts, to trace what happened to the energy and matter in the living ecosystem. They published their findings in scientific journals, complete with charts, graphs, and footnotes.

At the same time, naturalists, poets, backpackers and wilderness lovers used some of the new scientific knowledge about natural systems to enjoy and promote nature in much the same holistic, spiritual way that Thoreau had done in the last century.

In later years some of these nature lovers went further. Natural foods, natural cures, natural balances, herbal and “new age” cures became popular. Some nature lovers went still further and began to look on science and technology as well as capitalism and “progress” as suspect activities and ideas. The very possibility of human progress led by science and reason was sharply challenged.

It was different in the 19th century. Although there were a few dissenters like Thoreau, William Burroughs and John Jacob Audubon, the general attitude of scientists as well as ordinary citizens in nineteenth century America was anti-wilderness. President Thomas Jefferson sent Lewis and Clark to explore the vast American wilderness in 1804-1806. They were directed to observe and record what they found. It was also clear that they were to be the vanguard of a nation intent on conquering the wilderness. This was the beginning of what would later be called our "manifest destiny" to create a great civilized nation from ocean to ocean.

New knowledge of nature's web of relationships served to encourage practical farmers, lumbermen, wildlife managers and engineers of all kinds to more effective efforts to manage that web. They wanted nature to produce more food, more lumber, more hunting and fishing opportunities and more energy and natural resources for a growing nation.

In order to assure the continued bounty of nature in this sense, conservation movements began. President Theodore Roosevelt, a big-game hunter himself, led the way. National parks and national forests were established. Laws governing hunting and fishing were passed and enforced. One of the most interesting and significant of the scientists who bridged the gap between the Thoreau-inspired whole-nature approach and the Darwin-grounded scientific approach was a wildlife expert named Aldo Leopold. Leopold began his career in this Theodore Roosevelt conservation tradition.

In 1924 he became assistant director of the U.S. Forest Products Laboratory in Madison, Wisconsin. By that time he was already beginning to question and to move away from some parts of the conservation ethic. He soon came to denounce, for instance, the ruthless extermination of predators in America. He also began to question the whole idea of human progress as a technological juggernaut that was harming nature and man.

In a cabin in the sand country along the Wisconsin River he wrote a classic book, Sand County Almanac. In this book he gave his maturing views about nature, man and science. "Conservation is getting nowhere," wrote Leopold, "because it is incompatible with our Abrahamic concept of land. We abuse land because we regard it as a commodity belonging to us. When we see land as a community to which we belong, we may begin to use it with love and respect. That land is a community is the basic concept of ecology, but that land is to be loved and respected is an extension of ethics."

In 1962 the biologist Rachel Carson, carried these ideas a step further in a famous book, Silent Spring. In this book she warned that our modern life styles led to so much toxic chemical pollution that we may end up destroying the very biosphere we depend upon for our lives.

Carson's book was read by millions of people, and more than any other single book, inspired a whole generation of environmental activists.

In the last decades of the 20th century and now in the first decade of the 21st century, some of these activists have pioneered in combining ecological science with humanistic values to help preserve natural ecosystems around the world. Tropical rain forests, arctic wildlife preserves, wetlands, old growth forests, lakes great and small, and the vast ocean ecosystems, they warn, are threatened with radical change from human activities. Most especially today by the very real possibility of global warming.

We will look at some of the facts and some of the controversies about ecosystems today in the second part of this program.

Part 2: The Web of Life

"As I sit at my window this summer afternoon, hawks are circling about my clearing; the tantivy of wild pigeons gives a voice to the air; a fish hawk dimples the glassy surface of the pond and brings up a fish; a mink steals out of the marsh before my door and seizes a frog by the shore; and for the last half-hour I have heard the rattle of railroad cars, now dying away and then reviving like the beat of a partridge, conveying travelers from Boston to the country."

So Henry David Thoreau described Walden Pond in 1847. A modern ecologist would see and hear some of the same things, but describe them in a different way. Let's take a look at the modern ecological approach to nature. First, what is ecology? The word "ecology" comes from a Greek word meaning "at home," or "place to live." Ecology is a branch of the broader field of biology. It is the branch that studies living creatures in their environment. Living creatures at home. Another way of putting it ecologists study organisms in the totality of their relationships one to another, and to the physical environment in which they live.

That's quite a mouthful. Let's take Walden Pond, for example. To the ecologist Walden Pond is an example of an ecosystem. That is, a complex web of relationships of living things and their environment that can best be described in graphic and quantitative ways.

At the most basic level we have energy. The relationships between the hawks and the pigeons, the pigeons and the pine boughs, the mink and the frogs and, not least, the human and the railroad cars can all be usefully described in terms of energy flow.

The physicist must enter here. To understand energy in ecosystems you must first understand two basic laws of energy. One is the first law of thermodynamics. This says that energy can be changed from one form to another, but energy can never be created or destroyed. This first law is sometimes called the law of conservation of energy.

The second law of thermodynamics points out that while you cannot create or destroy energy, energy is always moving "downhill" in its changes. That is, in every energy change you always lose something. And that lost something is energy as random heat, useful only for warming the universe. Another way to put this-there is no such thing as a perpetual motion machine. You never get as much work out of a machine as you put in.

As for Walden Pond, it is the sun that provides the basic high-quality energy at the bottom of the energy pyramid. Ecologists can measure with a good deal of precision exactly how many kilocalories of solar energy the pond receives in a given day, week, month or year. Ecologists have a name for organisms that can use that sunlight energy directly to power their own life activities. They are called producers. In the pond ecosystem the producers are the pondweeds, algae and other green plants that are able to use sunlight as a source of energy to produce food. The plants do this using a process is called photosynthesis.

It turns out that careful measurements have shown that, on the average, green producer plants are able to use only a small percentage of the sunlight that arrives each day. From one to five percent, depending on the particular plant and ecosystem. This means that about ninety-five percent or more of the incoming energy is sent back to the air, the water and the surrounding earth. Eventually this energy-heat energy now-is radiated back out to space. Warming the universe.

The producer plants use some of that manufactured food-concentrated sunlight you might call it-for their own growth and life activities. Most of the plant food, however, is eaten by the consumers. In ecosystem terminology, the consumers are living things-animals primarily-that convert the plant-produced food energy into new kinds of living structures and new kinds of living activities. Structures like eyes and ears, legs and wings, claws and brains. Activities like walking and swimming, eating and thinking. In the case of Walden Pond, the consumers are the hawks, the pigeons, the fish, the frogs, the microscopic water plants and in his day, Henry David Thoreau. Each consumer may be only one link in what is called a food chain. The producers, we pointed out, are able to use only a few percent of the incoming sunlight energy. The consumers, it turns out, can do a little better in efficiency. They can convert about ten percent of the producer food into consumer life energy.

There is one more class of organisms that live at and in Walden Pond and perform an essential function in that ecosystem. These organisms are by far the most numerous and few people even know they exist. They are what ecologists call decomposers. In the water itself, and especially on the bottom of the pond, there live billions on billions of bacteria, molds and other microscopic organisms that are able to decompose the dead plants and animals, as well as the wastes from living plants and animals. In that process they are able to use what remains of the locked-up sun energy of the producers and consumers for their own growth, reproduction and survival. After the decomposers are through, all of the originally captured sun energy has been used-and lost. Not destroyed, mind you, but lost. Unavailable anymore for any useful purpose. Sent back out to space to warm the universe.

Energy flow is only one way ecologists have for looking at a given ecosystem. You can also do a detailed study of the way matter circulates within the ecosystem. Like energy, matter too can neither be created nor destroyed. From the matter point of view, life is built of twenty to thirty essential kinds of atoms. Mostly built, as a matter of fact, of just six kinds of atoms-sulfur, phosphorus, carbon, oxygen, hydrogen and nitrogen.

Some remember these important six by the mnemonic device, S. P. COHN.

All of the life-important atoms circulate around in the ecosystem. The ecologist can trace their flow into and out of the air, water and earth. Into and out of the producer plants, the consumer animals and the decomposer microorganisms. In the air, water and soil, the atoms and the relatively simple compounds they make; things like carbon dioxide, water, inorganic acids, bases and salts-are called the abiotic level of the ecosystem.

Producer plants take up abiotic chemicals and use them as raw materials for building a bewildering variety of much more complicated chemicals. Chemicals like sugars, starches, proteins, oils, enzymes, nucleic acids and the literally billions of kinds of organic chemicals that go to make up the Leaf, the stem, the seed and the fruit.

These plant-produced chemicals are then used by the consumer animals to make still more chemicals. Chemicals just as complex and even more incredibly organized together to make the functioning hawk, mink, frog and human being. Which chemicals are then broken apart once again, recycled back into the abiotic from which they came. This recycling is the job of the decomposers in every ecosystem. These broad patterns of matter and energy cycling in the ecosystem provide a basic framework which ecologists can use in trying to understand the fascinating complexities of specific environments.

In addition, ecologists have found other new ways to study ecosystems. They investigate things like population size, structure and growth; limiting factors and succession patterns; predator-prey and parasite-host relationships; species competition; ecological indicators; homeostatic capabilities and more.

Some ecologists specialize in the study of freshwater ecosystems like Silver Springs, Florida or Walden Pond, Massachusetts. Others specialize in tropical rain forests, ocean beaches, northern hardwood forests, prairies, agricultural regions, mountain slopes, deserts, bogs and just about any place where life exists.

The field is limited only by the limits of the earth itself. And as a matter of fact, not by the earth either. Some ecologists are already beginning to plan and study a new field--space ecology.

Ecology also overlaps with almost all other human sciences and indeed with most human activities. A new field called ecological economics is an important example of this overlap. One of the questions, for instance, being asked today by ecological economists is “How can you value an ecosystem in money, in dollars and cents?”

We know that wetlands, for instance, are useful to cities and villages in many ways. They act as water storage areas, they act to prevent floods, to purify water by taking out toxic chemicals, to recharge underground water tables. Wetlands also provide wildlife refuges and opportunities for recreational hunting and fishing. Even though it is often difficult to do, all of these benefits to human beings and more can be and are being now measured not just in words but in numbers, in dollars and cents. These financial figures can then be entered into hard-nosed economic analyses of profit and loss, balance sheet projections and gross national product,

Some of the values that ecosystems provide are more difficult if not impossible to measure in dollars and cents. What is the monetary value, for instance, of a beautiful sunset, of the pleasure many people take in the “tonic of wildness?” And for that matter, how do you measure the value of life to a rabbit or deer or wolf quite apart from any connection to human beings?

No doubt, the most important applications of ecology today are to the critical problems of human life aboard our spaceship earth. And here come the questions that make headlines.

When you get to specific cases like acid rain, the greenhouse effect, oil spills, nuclear wastes, pesticide residues, etc. the answers are not easy. This is partly because we just don't know enough yet. And partly because the answers often depend as much on what people value as what people know.

For instance. Ecologists and naturalists can offer many reasons why a given ecosystem should be preserved as a wilderness. Why no roads should be built, and all but the most determined and hardy visitors kept out. In a democratic society, however, these reasons must be balanced against equally cogent ones that others may put forward for developing these same lands. For using the natural resources therein to create jobs, increase wealth and overcome poverty.

In some controversial cases, ecologists can be more definitive about the facts. At the very least they can present the scientific evidence linking such and such an event. And they can tell us to that degree we can have confidence in those links.

Some ecologists, for instance, are spending a great deal of time right now studying the damage that acid rain may cause in forest and fresh water ecosystems in this country and abroad. Others study the possible effects of toxic waste leakage from old landfills. Or the ecological consequences of cutting tropical rain forests in Brazil or reducing the flow of water in the Colorado River. Others study ways to control pests like the zebra mussels or lamprey eels or the possible harm from genetic modified plants or animals..

Still others try to trace the effects on ecosystems from oil spills like that at Valdez, Alaska in 1989.Or the effects on arctic wildlife from oil exploration and drilling in arctic regions. Or from nuclear power accidents like those at Three Mile Island in Pennsylvania or at Chernobyl in the Ukraine (former USSR).

Larger scale studies of the entire earth biosphere are also being made today, using very large computers. The greenhouse effect, global warming, depletion of the ozone layer, nuclear winter, toxic wastes in the ocean are just a few of the most important.

Unfortunately our knowledge of ecosystems, small or large, is still very incomplete. In addition, there are so many variables that even the largest computer cannot take them all into account. Despite these handicaps, ecologists are making progress and providing important insights into the earth's amazing life cycles.

This work of ecologists combined with the passion of environmentalists has already led to much good news in the late 20th and early 21st century. Harmful air and water pollution of rural and urban ecosystems in the developed world of Europe, America, Australia and Japan has been sharply controlled and reduced. Despite economic growth in the developed world, there is also more wilderness preservation going on today than ever before. Similar progress is also being made in large areas of the underdeveloped world in Asia and South America and Africa although many many problems in many many of these ecosystems remain severe.

The rapid growth of human populations in the 19th and 20th centuries has itself caused great change in natural ecosystems. Today, in the 21st century human populations have stopped growing in the developed world and there is even some worry about population decline. In the poor parts of the world population growth has been dramatically slowed and the prediction is that it too will reverse as the poor world gets richer.

Similar stories can be told about natural resources. Contrary to common belief, natural resources that come directly out of our ecosystems -- oil, timber, land and minerals -- are not in short supply in the 21st century nor do most scientists expect them to be in near or long-term future.

And finally, the good news is that however the approach might vary, ecologists and naturalists and all concerned and intelligent citizens can agree that a new ethic about the earth is slowly taking root. An ethic shared by a growing majority of spaceship earth's passengers and crew.

Ecology means "living at home," and we know now that our home is this blue-white spaceship we call earth. As the politician Adlai Stevenson once said, "We travel together, passengers on a little space ship, dependent on its vulnerable supplies of air and soil ... preserved from annihilation only by the care, the work, and I will say the love, we give our fragile craft."

The scientist, engineer and poet Buckminster Fuller had another way of putting it.

"Environment, to each must be,

All that is that isn't me.

Universe in turn will be

all that isn't me and me."