A Citizen's Guide to Ecology
Lawrence B. Slobodkin
Oxford University Press, New York (USA), 2003 (2003)
245 pages, including appendix, references and index.

Lawrence Slobodkin starts with an introduction where he explains the idea behind the book, as well as some basic concepts. Thus, when talking about the idea of ecology, he emphasizes the importance of change:

The practical problems of ecology are all concerned with changes. Earthquakes, moving glaciers, years of drought and years of flood, volcanoes, and building projects all cause ecological changes. Sometimes new kinds of organisms burst onto the world scene and make major changes. Even in the absence of human disturbance, the world goes through changes of many kinds and on many scales. The practical concern with ecology is based on the real possibility that we are disturbing the world in dangerous ways and that our understanding and knowledge are so inadequate that we can cause irreparable damage without even noticing until it is too late.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 5)

Slobodkin, therefore, is no dogmatic conservationist. He seems to understand that there is no nature without change. Ecology is a process, and it is not always easy to figure out the ultimate consequences of a given event:

One change initiated by the US Forest Service in the early twentieth century was to fight the occurrence of wildfires. This was successful enough that undergrowth and dead wood became thick on the floor of western forests.

In 1987 a wildfire of singular intensity, with the capacity to leap over roads and firebreaks, appeared in Yellowstone Parl, scorching at least 20 percent of the park. The land looked dead. Almost immediately a book appeared proclaiming "the end of nature." [Slobodkin is referring to Bill McKibben's The End of Nature] To claim nature has "died" is silly and nonproductive, even if it sells books. Nature changes. It cannot pass away.

In 2000, another drought year, once again uncontrollable wildfires struck Yellowstone. The are of the forest that had been spared in 1987 now was burning. I was in Yellowstone Park during the fire and saw that the formerly burned-over sections were a green tree nursery of small lodgepole pines, unburned by the new fires.

Fires had happened before and will happen again, and the forests of Yellowstone Park will certainly change as a result of those fires, but the changes will not by any means be catastrophic. There will still be forests in Yellowstone Park. In fact, the cones of several of the trees of Yellowstone release their seeds only if they are baked in a fire.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, pp. 10-11)

It quickly becomes clear, then, that Slobodkin is not your usual ecologist or environmentalist. He seems to consider ecology quite important (perhaps even central) to our future, but that does not make him a raving lunatic spreading news of the end of the world. His approach is slightly different, which is quite refreshing:

Concern with ecology is necessary. It is not a fad. We can and do change the properties of nature, although the mechanisms of ecology do not change, just as the laws of chemistry and physics do not change.

Nature is neither wise nor benign nor malicious. There are no immaterial forces guiding ecological systems, although these are sometimes suggested. Solving practical problems of ecology requires using science and technology in a political, social, and even religious context.

We are, directly or indirectly, actors in nature. Its rules limit us and its dangers challenge us. If ecologists are very successful, they will help maintain the pleasant and livable properties of the world. If not, the world will change in unpleasant ways.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 11)

That approach contrasts with what we see in the majority of cases:

Ecology is in danger of becoming an uncomfortable blend of a science and a passé but still trendy mass movement. Nevertheless, the residual enthusiasts for ecology have a copious supply of study material available. We are bombarded by magazines, news reports, and enough television specials to make even the most beautiful landscape trite. Small bookstores have a section on ecology or environmental crisis just after cook-books and before the economics section. Most of the popular ecology books are designed to encourage depression or alarm. Bleak predictions of disaster provide pleasurable frissons, once supplied by such ideas as an invasion from Mars and infant damnation. Literally hundreds of books dealing with environmental and ecological problems will appear this year. A few of these will be picture books of remarkable beauty.

But beauty does not sell books fast enough. Therefore, these lovely picture books will probably include a proviso that they are accounts of endangered islands in a sea of advancing environmental degradation.

Most books about ecology are listed as nonfiction, which is not necessarily the same as being demonstrably true. There is also ecological fiction, in the same sense as detective fiction and science fiction.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 13)

As the author explains in the introduction, he is convinced that it is possible (indeed, necessary) for regular citizens to learn the basic ideas of ecology, which is why he embarked on this project. And he does so without forgetting his roots as a scientist. For example, he explains how he introduced his college students to the ecological framework of mind:

The students were then asked to insert knitting needles in the ground and see how many newly shed leaves the needles picked up. From this they could determine, if it was late in the fall and the trees above were almost bare, how many layers of leaves there were when the leaves were still on the trees. This way of measuring the number of leaf layers that were on the trees by determining the layers on the ground has obvious weaknesses related to drifting of leaves and sampling, but, except for leaves too small to pierce with a needle, is independent of leaf size.

Part of the exercise is for the students to consider what can be learned from available information. To what questions might all our numbers be an answer? Why are there almost no intact leaves and also no ribs of completely eaten leaves? Why is the number of leaf layers in our forest always around six? Why isn't it one? Why isn't it twenty? Why isn't there a deep layer of this year's and previous years' leaves lying in the ground? I could have told them the purpose of the exercises. I did not. I wanted them to learn where scientific questions come from. It worked for some of them.

Each student was then required to collect fallen leaves to identify the kinds of trees there were in the forest. With around ten leaves per student, the exercises required only nine thousand dead leaves. Anyone who has raked a backyard will realize that nine thousand leaves will not materially lessen the litter cover of a woodlot.

Is this experience equivalent to a camping trip with Thoreau? Certainly not, but it still permits firsthand understanding of some ecological processes. We had demonstrated that close observation of small things can open intellectual windows with wide views.

The fact that essentially every leaf collected had been eaten in part suggests that all of the leaves were edible to some organisms during at least part of their lives. The fact that almost none of the leaves were eaten down to the stems and veins implied that something stopped the consumption process before it was complete. This might conceivably be that the leaves had rapidly "ripened" in some sense so as to become inedible soon after the herbivores took their first bite. Another possibility is that the meals of the herbivores were interrupted by the animals being attacked by carnivores before they could finish eating.

The fact that the campus forest was green until the leaves were changed by the onset of fall therefore could be taken to imply that the herbivore population feeding on them was in fact kept low by predators.

From the fact that there was no more than three years of leaf fall on the ground, we could infer that the detritovores —the fungi, worms, wood lice, and so on— were finishing up all their potential food and were therefore not prevented by predators from growing up to their food supply.

Observations similar to these are extremely common, implying that there are discernible regularities in ecological systems in nature. More specifically, there is an inference that the food energy supply is limiting to the total nonphotosynthetic part of natural communities.

Scientific argument does not rival the charm of a coral reef, but I think it is intellectually beautiful that at least someties the complex ecological world permits itself to be understood by a suitable combination of simple observation and thought.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, pp. 28-29)

That is Slobodkin's appealing approach to the topic at hand, a mixture of scientific methodology and passion.

Before we look at any specific ecological systems it will help to understand two fundamental facts that are basic for understanding everything else. These are:

  • Water is enormously important for all life and is an extremely peculiar compound.
  • Organisms are local accumulations of energy. Energy is crucially important for all organisms.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 33)

Animals can obtain energy only by eating it. Green plants and colored bacteria perform photosynthesis, which lets them bind the energy in light into energy-rich molecules. These molecules can be taken apart by the plants themselves or by animals that eat them, releasing the energy for work and growth.

In respiration carbon dioxide is given off and oxygen is taken in. Respiration and photosynthesis are mirror images of each other. It takes exactly as much oxygen to consume a carbohydrate molecule as was produced by the photosynthetic process that produced it.

The rate at which energy is taken in by an organism is usually not equal to the rate at which it is used. A heavy meal increases our store of energy, and a session of strenuous exercise or a long fast decreases it.

For most animals there will be times when food is abundant and times when it is absent. The food, or at least the energy from the food, must be stored during the rich food season to be used when food is absent. Many animals hoard food.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 37)

The fact that tiny changes can have a major impact because their effects are multiplied by circumstances and events is one of the most intriguing and frightening aspects of ecology. Assessing the effects of prospective changes is the focus of a large proportion of ecological disputes.

Change in the concentration of atmospheric carbon dioxide seems a small problem when compared with some changes that have been brought about by organisms. One of the greatest changes organisms have brought about in the earth's atmosphere is the oxygen-rich atmosphere. Approximately 20 percent of the air is oxygen. If life had not appeared, there would be almost no atmospheric oxygen.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 43)

The fact that photosynthesis produces oxygen does not explain the 20 percent concentration of oxygen in the atmosphere. Photosynthesis is the precise mirror image of respiration. Where photosynthesis uses carbon dioxide, captures energy, and produces oxygen, respiration uses oxygen, releases energy, and produces carbon dioxide. Essentially all the photosynthetic products are respired away.

Plants respire around a third of the energy they fix in photosynthesis for their own use. Herbivores eat a large share of living leaves. Almost all organic material that falls to the ground, as dead leaves and wood, is eaten by decomposers —bacteria and molds. Some organic material may be consumed by wildfires. In these processes essentially all of the oxygen produced by photosynthesis is recombied with carbon to produce carbon dioxide. Where did the atmospheric oxygen come from? Thinking of it in a slightly different way: If respiration and fire are the precise reverse of photosynthesis and if all organisms, plants and animals, use respiration, why was any oxygen left over to help form the atmosphere?

Part of the explanation is the important concept that things in nature never come out quite even unless there is some mechanism that forces them to. Over global space and geologic time very slight failures to come out even result in massive accumulations or eliminations.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 47)

Over billions of years rainwater and river water have drained into the oceans and ultimately evaporated to fall as rain once more —an endless cycle of water. The early oceans were much less salty. If we boil water in a teakettle, a visible crust of minerals soon forms inside the kettle. The boiling water that evaporates leaves its dissolved minerals behind, so that the salt content of the oceans has been gradually increasing for the last four and a half billion years.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 73)

Upwelling regions, along with estuaries and regions that receive drainage from the continents, are the source of more than 90 percent of the world's supply of edible fish. When the water leaves the continent and flows out into the ocean it enters a condition similar to that of summer stagnation in lakes, in which light is present but nutrients are diminishing, to be replenished from deep, dark waters in upwelling regions. The time between sinking and upwelling for any single water molecule may be thousands of years.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, pp. 79-80)

Protecting plants from parasites occasionally has unpleasant side effects. For years extremely toxic chemicals were added to the soil on eastern Long Island to protect potato plants from the golden eel worm, a little nematode that infects their roots. This poisoned local wells. The present solution is to drink bottled water and to switch from growing potatoes to growing grapes, which are afflicted with an entirely different selection of pests and parasites, requiring quite different poisons to control them.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 87)

Underemphasized in this pictures is that lakes take in a great deal of material from their watershed —leaves, pieces of wood, and a miscellany of organic garbage. This exogenous material may be eaten by bacteria, which are in turn prey for microzoo-plankton, which feed larger zooplankton, which in turn feed fish.

In fact there are two more or less distinct food webs in each lake. One is based on bacteria, whose energy supply comes largely from material washed in from the watershed. The other is based on phytoplankton grown in the lake from recycled mineral nutrients; their energy supply is the photosynthesis occurring in the lake itself.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 96)

The watershed for a pond may be a single valley, but the watershed for the ocean is all the land on earth. All the rocks of all the continents are washed in water heading for the ocean. This drainage is where nutrients come from, balancing the loss to the deep sea from the sinking of detritus.

At first glance this seems unreasonable. Why hasn't the land been exhausted of its nutrients in the last few billion years? It would have been, except for the fact that many of the rocks and mountains on land were originally formed under the sea. They are made up of the nutrient-rich sedimentary detritus that succeeded in sinking to the bottom and has accumulated over millions of years. This sounds like wild speculation, but it is much more certain than most supposed scientific facts, because we can find the fossils of deep ocean animals in the rocks of high mountains.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 98)

Let humanity do its worst! Rain will still fall, rivers will still flow, and there will still be storms and floods and droughts. There will still be photosynthetic organisms pumping out oxygen, and nonphotosynthetic organisms using it and burning the products of photosynthesis. However, there is no certainty that any particular species or landscape will survive. The problems for humans are in the details. Will our particular species survive?

Some global properties involve relatively small quantities of matter —thousands of tons rather than millions. People can affect these, and they can change rapidly over periods of tens, hundreds, and thousands of years rather than thousands of millenia. The quality of air and of river water and the chances for survival of some landscapes and of many species, including our own, are in our hands.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 99)

We may want to destroy or reduce a population that is declared a pest or a danger. In that case the attack should focus on the organisms of highest reproductive value. For example, it has long been known that the number of rats in a modern city approximates the number of humans, and if public sanitation deteriorates, the rats can outnumber the humans.

Rats are usually attacked by placing poison baits and traps in places rats pass. This procedure selectively destroys itinerant males. The animals of highest reproductive value —the nesting mothers— may not be damaged, nor is their care of the young disturbed by excess attention from males. The effect of this sort of policy is that large numbers of rats can be caught and displayed, demonstrating that the eradication company is doing its job, but the reduction per dollar in the rat population is minimal, ensuring that the eradication company and the rats both can continue.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 126)

Extinction is generally a bad thing, but that assertion requires defense. Who wants mosquitoes? There are five basic reasons to preserve species and populations from extinction. I will present them in order of what I consider descending significance. This is my personal order. Different ordering is possible.

First, I see each kind of organism as a masterpiece left to us from the past. Every species on earth has literally billions of years history behind it. Its ancestors lived through one crisis after another, day by day, year by year, and millenium by millenium. They have effectively taken advantage of all the good times and somehow survived the bad. They have changed in response to some pressures, hidden from others. I believe that it is horrible that the history of any species should be brought to an end by shortsighted or careless human activity or inactivity in my lifetime. This is my personal belief. I hope others agree with me.

The second reason is a more practical one. There is much to be learned by careful study of any species, and so few species have been carefully studied that the extinction of a species, particularly an unstudied species, is intellectually equivalent to burning a book before it has ever been read. There is no guarantee as to what would be learned by the study, but the world would be a poorer place if the species were not there to be studied.

The third reason is that wild organisms of many kinds produce saleable commodities. On a very practical level species extinction is generally bad for medicine and for other business. The spectrum of herbal medicines in the health food shop of your local mall will demonstrate how many and how curious are the virtues attributed to relatively rare plants. Sometimes these are used without proper clinical testing, but their role in folk medicine is of sufficiently long standing that proper testing ought to be done and the plants ought to be around for that purpose if no other.


A fourth argument is that different people use a broad diversity of species, some of which are relatively rare and not subject to cultivation. The field of ethnobotany is now cataloguing these organisms and their uses. Survival of these species may aid the cultural survival of the people that use them.

The fifth reason that has been proposed in favor of species preservation and biodiversity I find ingenious and fascinating but transparently specious and therefore dangerous both to the future of ecology and the future of the natural world, which we have accepted as our object of study. This is the "rivet in the airplane" argument. It is a story that begins with elementary fact, then blossoms into a full-fledged parable and emerges with a reification, a creation of a mythical reality.

First facts: It is a fact that natural communities have ten to ten thousand species in them. (That is, there are from ten to ten thousand species that can be retrieved from exhaustive sampling of a reasonably small area.) If a particular species is found in a community, it obviously has some role in the community. Should that species be eliminated, whatever the role of that species had been, it is no longer precisely filled, although various competitors can and do take over parts of the role.

Now the parable. Consider an ecological community as an airplane. An airplane has many interacting parts. Imagine a passenger who finds that one screw in the cabin is loose and removes it. It will probably make no difference. But now someone else comes by, finds another loose screw, and pockets it. While a fair numberof screws can be removed without evident harm, if a sufficient number of screws have been removed, the removal of one more screw will result in the plane crashing.

In the same way, states the parable, removal of one species from a forest may do no visible harm, but if enough species have been removed, the loss of one more population results in collapse of the forest community.

This is a beautiful and vivid image. The parable asserts that loss or addition of critical species will send reverberating waves of change through a community. Sometimes this appears to be valid. Is it universally true? In what sense is there really an airplane?

What usually happens when a species is eliminated from some region? Its parasites will also be eliminated. Its predators will be hungrier. Its prey will perhaps become more abundant, and in some cases there may be other effects. Grass may grow taller, sheltering more mice, or some tree may be unable to germinate its seed.


We do know that losing a particular species from an ecosystem or adding a new species may have consequences for other species. For example, loss of elephants or alligators would be expected to seriously alter the world for other plants and animals —elephants rip up or knock down trees, warthogs feed among the newly exposed roots, and baboons lift the loose rocks in the exposed soil for scorpions and other tidbits. Alligators in the Florida Everglades dig holes that retain water even when rain is sparse, and tufts of willow trees and other vegetation come to surround these alligator holes. Similarly, beaver dams transform streams into marshes and thereby provide habitats for water-loving organisms.

To eliminate elephants or alligators or beavers would radically alter the ecosystems. But such large effects are perhaps less interesting than more subtle and specific effects that are harder to see. Termites in East Africa build mounds up to six meters high that are islands on the flat plains. This permits some plants to escape the annual fires that sweep the low grasslands.


Don't these examples simply confirm the rivet analogy? Not really. Each example relates to a few specific species. The rivet analogy makes two assumptions: first, that there is no way of telling which rivets are important, and second, that there is an airplane. But there is no airplane! There may be a pile of parts, each one closely connected to a few others, and each pile only loosely connected to several other piles, but general collapse does not occur. I am not even certain what general collapse would look like.

Although the elimination of one species may not always result in a wave of other disappearances, some species are certainly more critical than others. Also, although I oppose unfortunate metaphors, which I believe are damaging to science itself, I believe most strongly that the actual global extinction of any species is a real and irremediable lessening of the richness of the world. Our avoiding species extinction is tantamount to passing masterpieces on to coming generations.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, pp. 139-144)

Recently it has been shown that some species that meet the definition of invasive have settled into their new home and now have a broad range of ecological connections, such as might be expected of a long-term resident. Attempts to extirpate them may prove more dangerous to other resident species than leaving them alone.

It is difficult to close borders against exotic fruits, vegetables, and insects, no matter how dedicated the border guards. I believe that ultimately the fight against invasive species, despite enormous effort and flood of scientific papers, will end in defeat. How much will it matter?

There will be changes —cases of native populations being extinguished, plant cover changing over large areas, diseases breaking out in new places. Some agricultural practices will change, but the likelihood of large-scale disaster is low, and in any case not much can be done to prevent the invasions.


There is a nightmare image of the world filling completely with dandelions, kudzu, and rabbits. It isn't realistic, and it will not happen. Rosenzweig suggests: "The breakdown of isolating barriers between biogeographical provinces will not have much effect on species diversity. In the short term, it will reduce global diversity but increase local diversity... The considerable damnage [some] exotic species have been known to do comes primarily from direct effects of particular introductions."

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, pp. 151-152)

Simplistic proposals have been made to grow more forests and thereby remove carbon from the air. Aside from issues of where these forests are to be grown and who is to do the work, this scheme will not work for elementary biological reasons.

When a tree is growing it is in fact taking carbon out of the air, but once the tree reaches its full size its respiration returns as much carbon to the air as its photosynthetic activity removes. When it dies and the wood rots or is burned, all the sequestered carbon is returned to the air. The net change in atmospheric carbon dioxide produced by any tree in a forest from its birth to its disappearance is zero. Planting a forest of young trees will temporarily remove some carbon dioxide from the air, but only until the forest becomes mature and stops increasing in total wood content.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 163)

"Naturalness" also may carry the connotation of freedom from additives of all kinds. The use of additives in food is another place where ecological and medical considerations interact. Preservatives are useful precisely because they are poisonous to molds and bacteria. While we are biochemically different from molds and bacteria, all organisms are similar enough so that something that kills a bacterium is probably not the best thing for me, unless the bacterium itself is an even greater immediate danger.

Most foods may taste best when fresh, but some preservatives may enhance the flavor of foods while they ensure long shelf life. Salt meats and sausages, herrings, anchovies, sauerkrauts, and pickles owe much of their flavor to the salt that probably was first added as a preservative.

What are less defensible are some of the multisyllabic small-type dyes and other additives that are listed on the wrappings of ready-to-eat cereals, candy bars, breads, and other foods that are usually given to children. On the other hand, complete absence of these mystery additives may perhaps increase the average price of food and perhaps lower its quality.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 191)

There is great concern that these genetically engineered seeds may have dangerous ecological properties that we cannot anticipate and that these consequences may set up problems more difficult and more expensive to solve than the initial problems of insect damage.

For example, what if a gene for immunity to insects is transmitted to pest plants? While we do not expect genes in corn to make their way into other species very often, examples of this type of genetic tranmission are known. What if desirable species of insects are severely damaged by consuming engineered plants? How would this affect pollination of crops such as clover or of wildflowers?

The primary novelty of genetic engineering is that it can produce more rapid and more curious genetic modifications than could be produced by selecting genetic variants. Genes with specific properties can, in a sense, be injected directly into a genotype. I don't believe that the possible dangers of this process have yet been completely analyzed.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 194)

How we argue about ecology is often as important as the substance of our arguments. There is a temptation to focus on winning the argument. The issues of ecology are too important for that. If you happen to win an important argument by using what you know to be bad science, in the long run you will have damaged the future of science itself. You will have destroyed the authority of good science, and on some future occasion opponents may use equally specious science to destroy your position. There is a danger that using bad science to effectively win arguments will cost us one of our only sources of clear truths.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 209)

To assign moral purpose to natural events is not helpful for management. The moral implications of management procedures are our problem, not nature's. We must guard and even construct the properties of our own world to meet our needs, desires, and moral concerns. We are the only organisms capable of this in any serious way.

(Lawrence B. Slobodkin: A Citizen's Guide to Ecology, p. 211)

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