In 2004 a group of scientists, including myself, met and discussed what needed to be done to improve the ability to forecast the possible effects of global warming on biodiversity.  The result was a paper published in BioScience, the journal of the American Institute of Biological Sciences (AIBS).

In that paper, we proposed a “Quarternary Conundrum” — we found that the fossil record gave results about climate change and biodiversity that did not agree with modern forecasts.  Here is what we wrote about that idea.  (If you are interested in more from this paper, let me know and I will post more of it, or you can obtain it from AIBS.)

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Current forecasting methods suggest that global warming will cause many extinctions, but the fossil record indicates that, in most regions, surprisingly few species went extinct during the Quaternary (from approximately 2.5 million years BCE to the present)—in North America, for example, only one tree species is known to have gone extinct (Bush and Hooghiemstra 2005). Large extinctions were reported mainly for tree species in northern Europe (68% loss of tree genera; Svenning and Skov 2004) and for large mammals (> 44 kg) in the Northern Hemisphere (MacPhee 1999).We refer to this contrast between the implications of modern forecasts and the observed fossil record as the “Quaternary conundrum.” The resolution of this conundrum is key to improving forecasts of climate-change effects on biodiversity. Among the possible explanations are that climate change during the Quaternary was greatly different from climate change forecasted for the future; that genetic and ecological mechanisms, not accounted for in formal forecasting methods, allow the persistence of many species even under rapid climate change; and that factors in addition to climate change could decrease rates of extinction.

Some recent ecological genetics research further deepens the puzzle. For example, the risk of extinction for a species in response to climate change depends on the demography and evolution of genetically differentiated populations across their geographic ranges. If populations are locally adapted, climate change will cause conditions to deteriorate across the species’ range, rather than just at the margins of the range. Modern reciprocal transplant experiments, in which spatial gradients in climate serve as proxies for temporal climate change in the future, show that these fitness losses can be large (Rehfeldt et al. 1999, Etterson 2004). For example, a reciprocal transplant experiment on lodgepole pine in Canada indicated that global warming would slow tree growth and increase mortality, resulting in a 20% loss of productivity (Rehfeldt et al. 1999). Likewise, a study of a prairie annual in the Great Plains of the United States showed a 30% reduction in seed production in climates similar to those predicted for future decades. Ecological genetic data, in each of these cases, predicted different rates of adaptive evolution in different parts of the species’ range (e.g., rear and leading edge; Hampe and Petit 2005) but generally suggested that evolutionary rates would be slower than the anticipated rate of climate change (Etterson and Shaw 2001, Rehfeldt et al. 2002).

Until recently, it was thought that past temperature changes were no more rapid than 1 degree Celsius (^oC) per millennium, but recent information from both Greenland and Antarctica, which goes back approximately 400,000 years,indicates that there have been many intervals of very rapid temperature change, as judged by shifts in oxygen isotope ratios. Some of the most dramatic changes (e.g., 7^oC to 12^oC within approximately 50 years; Macdougall 2006) are actually of greater amplitude than anything projected for the immediate future. Although these changes were probably not equally severe everywhere on the globe, a well-documented rapid warming did occur around the shores of the North Atlantic at the end of the last glaciation, when melting of the ice cover on the ocean suddenly allowed the Gulf Stream to reach the shores of northern Europe. There, temperatures rose rapidly, perhaps as rapidly as anticipated today for the next several decades (Huntley et al. 1997).

What could explain the Quaternary conundrum? One possibility is that migrations were faster than has been thought possible. A large literature examines late-Quaternary range shifts deduced from the pollen record, and recent papers consider models and seed-dispersal mechanisms that may account both for migration across geographic barriers and for rapid invasion of new territory. Sparse populations of several tree species are now known (from genetic and macrofossil evidence, supplemented by detailed analysis of mapped pollen data) to have persisted during the last glacial maximum in regions where very few, if any, pollen grains have been observed—regions that for this reason would be judged well outside the climate envelope for these species (Tomaru et al. 1998, Brubaker et al. 2005, McLachlan et al. 2005, Magri et al. 2006). These populations serve as advance colonists, allowing rapid population growth in newly available habitat.

A second explanation is that low extinction rates during Quaternary climate change may be partially attributable to ongoing adaptive evolution. Theoretical models suggest that adaptive evolution can enhance the persistence of populations in a changing environment even when migration is possible (Bürger and Lynch 1995). And rapid genetic adaptation to climate has already been documented for a few wild organisms for which long-term studies of field populations have been conducted (reviewed in Bradshaw and Holzapfel 2006). Invasive species have also evolved since their arrival in a new habitat in the 20th century, at surprisingly rapid rates of evolution (e.g., Huey et al. 2000).

A long-standing controversy regarding the role of people in Quaternary extinctions of large mammals speaks to the difficulty of quantifying impacts of multiple factors on species loss. The high extinction rate of large mammals has been widely recognized since the 19th century, and extinctions of large mammals and island birds over the past 100,000 years have been the subject of much conjecture. Paul Martin has made the now well-known case that the timing of extinctions followed human dispersal from Afro-Asia to other parts of the globe and that these extinctions resulted from human “blitzkrieg” overkill (Martin and Steadman 1999). But careful analysis of well-documented extinctions in Beringia suggests that human hunting was superimposed on a preexisting trend of diminishing animal population density (Shapiro et al. 2004, Guthrie 2006). These data suggest that the interaction of environmental change and human resource use can have a larger negative impact on biodiversity than either factor alone.

Copyright © American Institute of Biological Sciences, posted with permission.

The news release from this journal’s parent organization, the American Institute of Biological Sciences, writes that “current mathematical models indicate that many species could be at risk from global warming, surprisingly few species became extinct during the past 2.5 million years, a period encompassing several ice ages. They suggest that this ‘Quaternary conundrum’ arises because the models fail to take adequate account of the mechanisms by which species persist in adverse conditions. Consequently, the researchers believe that current projections of extinction rates are overestimates.’ ”

There are 19 authors of this paper, from Australia, Denmark, France, Great Britain, Australia, and the United States; these include some of the world’s top scientists concerning ecological forecasting and the history, ecology, and genetics of extinction.

See the article at The American Institute of Biological Sciences.

One of the paper’s coauthors, Matthew J. Sobel of Case Western Reserve University, said, regarding this paper, that “The simultaneous widespread and justified alarm over global warming and changes in biodiversity has induced both outstanding scientific research and deplorable pseudoscientific work,”

According to a news release from Case Western Reserve, “Sobel raises concerns about the `blurring’ of scientific fact with public advocacy and wants public discussions to center around sound environmental facts. `Where the science has limitations that should be noted, too,’ added Sobel. His concern is that misinformation or poorly constructed forecasts may divert and reduce resources that could be better spent in other areas. Limits of scientific knowledge exist with current forecasting models, according to Sobel, and these need to be acknowledged when reporting global warming.”

Matthew Sobel is the William E. Umstattd Professor at the Weatherhead School of Management, Case Western Reserve University.

We still must be concerned about global warming and threats to the diversity of life on the Earth. There is not just one threat from human activities to the diversity of life; there are several major ones, including disruption of habitats, introduction of non-native species into new habitats, and many effects of technology. The good news is that species appear more resilient to rapid climate change than thought previously. The implication is that sound planning and policies to deal with biological diversity needs to include the multiple causes. The new article also calls for better methods of forecasting — better computer models — and better use of available data about past extinctions.

In the BioScience article, the researchers call for eight steps to better forecasting:

* Select one of the many meanings associated with the complex concept of biodiversity and target that meaning as the parameters in a specific forecast

* Evaluate and validate forecasting methods before applying them to general forecasts

* Consider the various factors that might impact biodiversity from climate change to pressures from humans on the native habitat of a species

* Obtain adequate information before making predictions about future outcomes

* Examine fossil records to aid in understanding how some plant and animal species have adapted to changes in their environments

* Improve four widely used techniques in forecasting that model individuals, groups,
integration of species and environmental factors and lastly groups or species based on theories

* Embed ecological principles in the forecasts based on air, water and animal and plant life.

* Develop better models that improve upon modeling forecasts called species-area curves that are based on specific number of species in relation to their habitat and how climate changes can modify the environment.

Jim Welter lives in Brookings, Oregon, where he has spent his life as a fisherman. I first met Jim when he was in his eighties and blind in one eye — a wiry, thin, smallish man. He came to an open public meeting I ran for fishermen and fishing guides, which was part of a study I was doing for the state of Oregon about the relative effects of forest practices on salmon. I believed that as part of a democratic process in a democracy, we scientists should hear not only from other scientific experts but from the interested public as well — whomever wanted to speak, especially those who had spent their lives dealing with Oregon’s wonderful natural resources, and thought about them and loved them.

At this meeting, Jim made one of the most remarkable, insightful suggestions about salmon that I’d heard during the entire three-year study. But the meeting he attended hadn’t started off so well. To begin with, there was considerable distrust by the fishermen and fishing guides of some scientist from California, paid by the government, who arrived in Gold Beach and was probably going to tell them what to do about their salmon. Before the meeting, the small team of scientists I had organized to do the project ate lunch with a representative of the fishermen. One of my colleagues said to him, “There seems to be some considerably hostility toward the government of Oregon.”

“Darn right,”he said, “When they came down here and told us they could manage salmon, we thought they meant that we could manage to have salmon.”

When I opened the meeting, the audience of hardworking men sat stiffly upright in their chairs with their arms folded, looking hostile, until one of them said, “Professor Botkin, do you believe that the salmon are declining?”

I replied honestly “I’ve just started this project and don’t know much of anything about salmon and don’t have any preconceived ideas. I’m just here to find out what is known.”

The audience immediately relaxed and became very helpful. By the end of the meeting, the leader of the fishing guides got up and said that the guides knew the rivers better than anybody, they spent 360 days a year on them, and they would be willing to make any measurements that would be helpful to our study.”

That was a pleasant turn around. But most remarkable of all was Jim Welter. He got up to speak and said, “I don’t know much about science, but it just makes sense that if these salmon are born and reared in freshwater streams and spend about a year there, and then go to the ocean and return when they’re three or four, that the amount of water flowing in the stream where they were born ought to make a big difference in how many survive and return.”

That made a lot of sense to me, and it was refreshing to hear something constructive, especially when I had only recently learned that the Bonneville Power Administration, which built and ran the big dams on the Columbia and Snake rivers, had spent $2.5 billion on salmon research and restoration and, according to one of their top executives who spoke to me, those dollars hadn’t yielded a single sign of improvement in the salmon. How could a big agency spend that much money and have absolutely nothing to show for it? I wondered. I found out, but that’s the subject of another time, another story.

Jim Welter did more than provide us with a little verbal wisdom based on years of experience — in my career working on natural living resources, I had come across people who did provide that kind of insight, almost always interesting. But Jim took it several steps further. He went to the state of Oregon’s Department of Fish and Game and got the data for the counts of salmon crossing a dam on the Rogue and the Umpqua rivers — these were the only two rivers of the more than 20 rivers that flowed to the Pacific Ocean in Oregon south of the Columbia River, where the state actually counted salmon .

Discovering that the state didn’t know how many salmon it had on most of its rivers was pretty disconcerting to me, as I was hired to tell them what was happening to salmon and why, and this required basic information about changes in salmon numbers over time, which did not exist, I had only recently discovered, for most of the rivers.

Then Jim went to the U. S. Geological Survey and got the data for stream flow for each year on those rivers for the time that salmon had been counted. This was a remarkable step, especially because to my knowledge no agency of the state or federal government had done this comparison.

Even more remarkable was that Jim had gotten a friend who knew a little about science to help him graph the two kinds of data. He brought in a huge hand-drawn graph (this was in the days before PowerPoint, and anyway, Jim wouldn’t have used that). A nonscientist actually doing an analysis of data. Once again, no government agency had gone this far.

Sure enough, as Jim pointed out, if there was a high-water year, then four years later a lot of salmon swam upstream. If there was a low-water year, then four years later few salmon returned. Jim provided the first important insight into what might be a major factor influencing salmon abundance.

We were so impressed with Jim’s suggestion and his graph that we contracted with Ben Stout, a forester and statistician, to do a formal statistical analysis of these two data sets. And sure enough, it turned out that one could account for 80% of the variation in salmon abundance from water flow alone, and you could thereby forecast pretty well four years in advance whether or not there would be a good salmon year. Since the methods in use at the time set the catch sometimes a few months before the fishing season opened, and didn’t give the fishermen much chance to prepare, this seemed a remarkable advance.

We wrote this up as a scientific paper and proposed it to the state and to salmon fisheries scientists.

In the years since, once in a while I call Jim and ask how he’s doing. Sometimes he asks “Them government fellows ever listen to what you told them?” And I would have to admit that they hadn’t. Another time Jim said on the phone “If only we weren’t so greedy, everything would be all right.”

Although Jim wasn’t trained as a scientist, he was a natural at it. Gathering data, looking at it, thinking about it, graphing it, and coming up with insights. That was just good science. And sad to say, we had seen little like it, certainly not from the large staff of the Bonneville Power Administration. But as I said, that’s another story. If you want to hear about why BPA and other scientists did not think to plot water flow against salmon returns, write me and I’ll set that story down.

Jim Welter represents one kind of person we desperately need to help with our environmental problems: a good observer invested in natural resources without any ideological bones to pick, open to new ideas, willing to look at primary data in a fresh way, to construct graphs, and not jump to conclusions.

When I think about acting locally to help nature, I think about Jim Welter, who had more foresight with his one eye that many government employees with two.

Copyright © 2004 Daniel B. Botkin

Life comes in many sizes. The smallest creatures are bacteria. The smallest of these are about one millionth of a meter long and half that wide, and weigh less than a billionth of a billionth of a kilogram. The longest and widest creature is a surprise — not an elephant, not a whale, not a giant sequoia tree. It is a huge fungus that lives in soils in western North America, just under the ground. Some of these individuals stretch across two kilometers! If one of these giants were merely 10 cm thick, it would weight about 314,000 kilograms. These fungi live by digesting decaying vegetation in the soil, a vital role in the eternal cycling of life’s chemicals. Thank goodness, however, they have no sharp teeth or legs to walk on, or an interest in feeding on living flesh.

The heaviest organism is probably the largest of the giant Sequoia trees of California, known as the “Del Norte Titan” sequoia. It stands 94 meters high and is more than 7 meters in diameter, and weighs more than one million kilograms.

So the range of sizes of living things is huge — in terms of weight the range is from a billionth of a billionth of a kilogram to one million kilograms. This is a range that mathematicians call 12 powers of ten or 12 orders of magnitude. In terms of length the range is from a millionth of a meter to 2 kilometers, which is nine powers of ten or nine orders of magnitude.

Among mammals, our kind of creatures, the range is smaller, but it is still large. The smallest mammal is Savi’s pygmy shrew (known among scientists as Suncus etruscus). It is 3.5 centimeters long plus a 2.5_cm tail, and weighs about two grams. Though small, it has a large geographic range. This thimbleful of energy lives in the Mediterranean and is found from there to Africa and Malaysia.

The largest mammal is the blue whale, weighing in at 150,000 kilograms and 30 meters in length. On the land, the largest mammal is a male African elephant that can weigh 4,000 kilograms, so he is two million times as heavy as the smallest shrew. The range of size of mammals extends over seven powers of ten.

Out of the 12 powers of ten in weight and nine powers of ten in length, is there one that is best? The answer is: it depends — because it depends on best for what?

Take, for example, a question that has long been of interest to people — what is the best size for a beast of burden? What we would like to get is the largest burden carried the longest distance for the least amount of food and water. Here we can take food to represent a supply of fuel or energy. So the question is the same as asking what is the most fuel efficient automobile, train engine, or airplane — what carries the biggest load for the least fuel?

If you have been on a diet to lose or gain weight, then you might think that energy use is simply a matter of total body weight. An apple contains about 100 calories; a half kilogram of human body fat about 1000 calories. If you gain a kilogram a year, diet books will tell you that you have been eating just 50 calories too many a day — half an apple’s worth. This seems to apply to everybody, whatever one’s size. And it’s a good enough approximation for people. Even though we come in a range of sizes, the smallest adults are about half the length of the largest, and this is small compared to the ranges of all living things.

But in fact the use of energy per body cell declines with body size. This is a consequence of a rule of geometry, known as the surface-volume ratio. The ratio of surface area to volume of any three-dimensional object declines with size. This is because the volume increases with the cube of the diameter, while the surface area increases with the square of the diameter. The result is a rapid change in the ratio. You can see this by blowing up a balloon. A balloon that is one centimeter in diameter has a surface area of 3.14 square centimeters, and a volume of about half of a cubic centimeter. The surface to volume ratio is six. A 10 centimeter balloon has a surface area of 314 square centimeters and a volume of 523 cubic centimeters. The surface to volume ratio drops by a power of ten, to 0.6. By the time you have blown up the balloon to one meter in diameter, it has a surface area of 31,400 square centimeters, and its volume has expanded to 523,333 cubic centimeters. The surface to volume ratios has declined 0.6 to 0.06. The bigger an object, the less surface there is for any unit of volume.

Why does this matter for a beast of burden? The answer has to do with metabolism — the chemical reactions that go on inside each cell that keep the organism alive. In a warm-blooded mammal, each cell produces heat as a byproduct of its metabolism. This heat keeps the animal warm, but it can also make it too warm. An imaginary animal that was as round as a balloon and 10 centimeters in diameter would have ten times as much surface area for each cell, compared to a 100-centimeter wide animal. If the two animals had the same metabolic rate, and if the only way that they could lose heat was directly from exchange at the surface with the environment, then the larger one would be much hotter.

A surface exchanges heat energy with its environment in four ways: by radiating heat energy as infrared light; by evaporating water (sweating for us), and through two methods that depend on the contact of the surface with the surrounding air or water: conduction and convection. Convection exchange is the transfer to the wind – to moving air – or to a current of water. Conduction exchange is the transfer simply due to the contact of the surface with still air or water. If the surface is warmer than the air or water, it warms the molecules of the fluid that touch it. These rise and are replaced by colder molecules, which in turn are warmed.

The consequence of this is that small mammals, like a Savi’s pygmy shrew, have to have a very fast metabolism to keep from freezing to death, and to keep as warm as a large animal. If you pick up a puppy or kitten, you can feel its rapid heartbeat, indicating its very high metabolism. Meanwhile, a large mammal, like an elephant, has to keep its metabolism much slower so that it doesn’t overheat. So if you live in a cold climate and you want to stay warm, there are benefits to being large. If you live in a hot climate and want to keep cool, there are benefits to being small.

If you think all this is complicated, you are in good company, because it has fooled some good scientists. In the 1960s, when psychedelic drugs were fashionable, several scientists experimented with the effects of LSD on an elephant. They published their results in the prestigious American journal, Science — the journal of the American Association for the Advancement of Science.

These scientists had calculated the dose based simply on body weight, not on the surface to volume ratio. First they found how many milligrams of LSD put a cat into a rage. Then they took that number and multiplied it by the ratio of the weight of the cat (2.6 kilograms) to the weight of the elephant. This resulted in a dose of 297 mg of LSD. By comparison, a dose of 0.2 milligrams puts a human being on a “trip.”

Unfortunately, the elephant died immediately after he received this 297 mg dose, and the authors of the scientific article concluded that elephants were especially sensitive to LSD. But they made a fundamental mistake. In his marvelous book, How Animals Work, the American scientist, Knut Schmidt-Nielsen, explained the mistake. The scientists assumed that the dose of a drug was simply a matter of body weight. In reality the proper dose of anything depends on metabolic rate, and since this decreases with body size, the elephant should have received a dose of 3 mg of LSD to get the same “trip” that a person receives from 0.2 mg. So the poor elephant was given an overdose 99 times too large!

Let us imagine the highly unlikely procession of two million shrews employed by their human owner to carry a tonne of material, and compare this with a single elephant pulling the same weight. Not only would it be pretty much impossible to organize two million shrews to work together to pull the load, but their metabolic rates are so high that they would eat much, much more than the single elephant, and they would be an extremely inefficient way to move material. Based strictly on the brawn required to move a burden, the bigger the better. One big draft horse will eat less than two smaller horses whose combined weight equals his.

But, of course, we humans find much more to life than pulling around heavy weights efficiently. And there is much more to life on Earth as well. So to try to answer the question: what is the best body size for a living organism? We have to return to the question best for what tasks?

Suppose we consider a more fundamental concern: what is it that living creatures do that is necessary to maintain life on Earth? The fossil record provides a clue. Life has existed on the Earth for three and a half billion years. But for the first two billion years the only forms of life were bacteria and their ancient relatives. All the time since — 1.5 billion years — the time of animals, plants and fungi, the time of the dinosaurs, and the time of human beings, is shorter. This tells us that very small creatures can persist quite well, for a very long time, without the help of the rest of us. There must be something to being very very small – a billionth of a billionth of a meter or slightly bigger. Is small then the best size, except for carrying burdens?

For life to persist, living things require an input of energy (mostly from sunlight, converted by plants, algae, and certain bacteria, through photosynthesis to sugars and then to other organic compounds), and a supply of 22 chemical elements that are nutritionally necessities. In that first two billion years of a bacterial world, bacteria did all the necessary chemical reactions. Some captured sunlight and carried out photosynthesis. Others converted chemical elements from inorganic forms unuseable directly by life into forms that living cells can use.

For example, all proteins contain nitrogen, and all life requires protein. But nitrogen exists in our atmosphere in its simply molecular form, as N2, that is, as a molecule of two nitrogen atoms. But the chemistry inside cells cannot use nitrogen in this pure form. It must be converted either to nitrate or ammonia. Before people came along and discovered modern chemistry, only bacteria did this – except for a small amount of nitrogen oxides produced by lightning. Bacteria take pure nitrogen and convert it to nitrate and to ammonia.

Chemical elements have to cycle, and so not only is it necessary for pure nitrogen to be converted to nitrate or ammonia, but also eventually nitrogen has to return to the atmosphere in its pure form, so that it is available to be used again. Only bacteria carry out the final decomposition of nitrogen, converting nitrate and ammonia back to molecular nitrogen. Bacteria still do most of the important chemical reactions necessary to maintain life on the Earth.

Since bacteria lack teeth, mouths, claws, and other weapons, they exchange chemical elements with their environment by simple diffusion through their cell surfaces. This brings us back to the all important surface to volume ratio. If your primary goal is to take up chemical elements, convert them into organic chemicals, and then release them again, it is efficient to have a rapid rate of exchange, and therefore to have a high surface area relative to the volume of living tissue. It is best to be very small.

Not only is there an advantage, as a chemical processing form of life, to being small, but early life could not be very big. That was because the early Earth had no free oxygen in the atmosphere. Free oxygen allows rapid combustion. The early Earth had little free oxygen in its atmosphere, but the atmosphere is now about 20 percent oxygen. Before the Earth’s atmosphere became high in oxygen, complete “burning” of food as fuel was not possible. Bacteria living in an oxygenless atmosphere obtain energy by such reactions as fermentation – the same reactions that yeast use to give us bread and wine. The product, alcohol, is a very good fuel, as automobile race car drivers know. If the end product of the attempt to use energy is still a good fuel, this means that the end product contains a lot of energy, and that fermentation is not the most efficient way to get energy from organic compounds.

With only non-oxygen means of energy use, bacteria could not get very big. They could not form three-dimensional bodies of many cells, because the interior cells could not get enough raw materials fast enough to maintain their metabolism. Life was restricted to single cells, or to strips of cells one cell thick. It was life restricted to a plane, to two dimensions. The existence of animals and plants, with their large and complex bodies, had to wait for an atmosphere high in oxygen.

How did our atmosphere change from having no oxygen to being rich in oxygen? The photosynthetic bacteria did it. The process of photosynthesis releases oxygen. For early life, evolved and adapted to an oxygenless environment, that free oxygen was toxic. As a toxic waste, it was simply dumped into the environment by the bacteria. There were no pollution control laws to prevent this dumping – there were no sentient creatures with the ability to conceive of society, laws, and writing.

Over a very long time, free oxygen dumped by bacteria as a waste increased in the atmosphere. Once it reached approximately its modern level, then animals, plants, and fungi, with complex and large bodies, could evolve, and they did. It is necessary to have bacteria for all life to be sustained, and they are most efficient as small creatures.

So far, we have arrived at two answers to the question: what is the best size for an organism? To carry a burden, be big. To be a chemical factory that creates and then decomposes the necessary chemicals for life, be small. But what about us, and our consciousness, spirituality, poetry, art, music, literature and technology? Is there a best size for these qualities?

The short answer to this question is that we are not sure whether there is a single perfect size for a sentient being. But we can put some constraints on the range of sizes. To have a brain with which to think, we must have a complex body, in three dimensions, with many cells. So we cannot be very small.

But could we be as small as a shrew or as large as an elephant and still have our human qualities? We know that our brain is very large, and that many of the largest creatures that have lived on the Earth have had tiny brains by comparison. It seems unlikely that sentient creatures could be as small as shrews or mice. This is once again a consequence of the surface to volume ratio. As a general rule, longevity is proportional to metabolic rate. The faster the metabolic rate, the shorter the lifetime. Shrews, mice, and small birds live a short time. The average lifetime for many songbirds is less than one year, and the lifetime of a songbird that lives to reproduce can be as short as a few years. Pet owners know that dogs and cats live much shorter lives than we do. It is unlikely that creatures that live such short times could have time to gain the knowledge and skills to create civilization, technology, and to learn the arts. So we can begin to put some lower bounds on the “best” size for intelligent, sentient, thinking beings. It would seem necessary to be able to live a number of decades, and therefore to be as large as say the larger, longest-lived dogs.

But could we be much larger? Could there be an elephant civilization, as in the children’s storybooks about Barbar the elephant? We can’t say for sure. But there are pressures of evolution and ecology that would tend to work against being both very large and very smart. The game of biological evolution is to win by having more offspring than one’s competitors, and this forces species to focus their resources. Given the million and a half named species, and probably many more yet unnamed, if you are going to put a lot of your energy and material resources into a brain, it is better to not expend your energy and chemical resources in other ways. On the other hand, If you don’t want to be eaten, it’s not a bad idea to be big and powerful. But perhaps the fact that people were not the largest, nor the fastest, nor had the biggest teeth or sharpest claws, helped force the evolution of our brains.

At this stage in our understanding of life, we can’t say for sure what the absolute “best” size is for a thinking creature that can create civilization, technology, and arts, and can appreciate beauty and philosophy. Most likely there is a range – small perhaps – that would work well. We can say that it would have to be a creature that could live a relatively long time and put its resources into brains rather than brawn. That suggests that it is not an accident of evolutionary history that people are between one and two meters in length. But it leaves unanswered the question: how much bigger might intelligent life on another planet be, or how much smaller? The range would most likely be from one meter and larger, but we cannot at this time answer this question with completeness.

And so we can make a few generalizations about being the best size for being alive. We can say that to do the chemistry required for life, it is best to be very small; while to carry burdens it is best to be very big; to think it is necessary to be not too small, but just how small or how large is a question that will have to wait much scientific research about cognition, a science only in its early stages. Meanwhile, be happy that those ancient and tiny bacteria created an oxygen atmosphere for us three-dimensional, complex creatures and that they, along with algae and green plants, still do so. And be thankful that our size makes us use our wits, not simply our brawn, so that the universe is not empty of music, art, literature, philosophy, architecture, or of beings that can ask the question: are they the best size?

Copyright © 2000 Daniel B. Botkin
written for Le Temps Strategique

The idea that nature can be restored – and will restore itself – to a single, best, perfect state is ancient. It forms the basis of the great myth of the Balance of Nature – stated and believed by the ancient Greeks and part of Western civilization ever since. According to this belief, nature exists in a perfect balance that will persist forever, and, if disturbed by human action but then released from that disturbance, will return to that single perfect state.

The idea that nature can be restored to a single best condition is also part of a modern nature-myth, the belief in nature as a machine. According to this belief, developed in the nineteenth century, nature was like a watch or steam engine. It could be operated to run steadily. Not only was nature in a balance like a well-crafted watch, but it could be operated to provide a constant output or any constant, desired condition – maximum number of trees, for example.

So by analogy with a painting – and following the ideas of the Balance of Nature and the machine-nature myth – if we restore nature, we bring it back to its original single natural state. Right? Wrong. What environmental scientists have learned in the past 30 years is that nature has no single “natural” state. Instead, we have learned that nature is truly dynamic, it is always changing, and that species have evolved and adapted to those changes. If we actually succeeded in restoring nature in the same way that we restore the Sistine Chapel, many species would go extinct – they depend on, require change.

Case in point: the Kirtland’s warbler, a pretty warbler that nests in Michigan on coarse sandy soils and only in jack pine trees. The species has long been of interest and concern among conservationists, ornithologists, and people who just enjoy the outdoors. In 1951 a survey was made of the Kirtland’s warbler, making it the first songbird in the United States to have a complete census. About 400 nesting males were found. In 1971 only 201 nesting males were found.1 The numbers were falling abruptly. What was happening? Would this warbler go extinct? The answer lay in the then current ideas about conserving, restoring, and sustaining nature. The warbler and its habitat were managed by people who believed in the Balance of Nature and the nature-machine myth, and as a result believed that any disturbance to nature was bad. In 1926 one expert on the warbler wrote in Audubon magazine that “fire might be the worst enemy of the bird.”2 Their solution: suppress forest fires so that nature could keep itself in its perfect balance – restore it like a painting back to its single best state. In this case, the perfect state was an old-growth forest – maples and other hardwoods along with some huge white pines.

This ideas of restoration and sustainability were wrong for the warbler because the jack pine woodlands it nests in occur only after fire. Kirtland’s warblers nest only in jack pine woodlands that are 6 to 21 years old, ages when the trees are 5 to 20 feet tall. Since the jack pine is a “fire species,” sustaining itself only where there are periodic forest fires, the Kirtland’s warbler thus requires change at a rather short interval – forest fires approximately every 20 to 30 years, which was about the frequency of fires in jack pine woods in presettlement times.

So two ancient myths not only failed to save the warbler, they were doing him in. Another ancient myth provided an possible answer – the myth of mother nature that the Greeks and Romans also wrote about. This is the idea that nature – the Earth and the entire system that contains and supports life – is like or is a fellow creature. And like all creatures, it has had a birth, a youth, and a maturity, and is destined to have an old age. Mother Nature was once like a young woman, beautiful, perfect in form and symmetry, and fertile. Our unfortunate fate was to be born when nature had become old and, like an aged creature, was wrinkled (Earth’s mountains), covered with warts (Earth’s volcanoes), and had lost her fertility.

Could the Mother Nature myth help? Probably not. Believing that, one would shrug and say, well, too bad for the warblers alive today, they were just born too late. Their habitat is no longer fertile; Mother Nature is just plain old.

So how do we restore the warbler’s habitat and sustain it? Modern environmental sciences provide the answer: by aiding or creating change. This was done on 38,000 acres set aside in Michigan for the birds. Prescribed burning was introduced, based on planning done by the Audubon Society, the U. S. Fish and Wildlife Service, and the State of Michigan Department of Natural Resources. Success! The warbler is thriving again, in its periodically changing environment.

There is more to the story – the warblers also suffered from cowbirds who lay their eggs in other birds’ nests. The unsuspecting nesters raise cowbird chicks along with their own chicks. When cowbird parasitism is common, birds like the Kirtland’s warbler suffer. Many of their own chicks die. Controlling cowbirds was also part of the solution. But without a changing environment, allowing jack pine stands to regrow, the warbler would have gone extinct, cowbirds or not.

Many species require change, and the required changes can occur at many scales of time and space. Think about restoring the salmon of the Pacific Northwest, for which billions of dollars have been spent. Salmon are fish of cold waters not far south of high-latitude glaciers. Over the time scale of glacial ages, salmon have to move among streams. The old belief that salmon always return to their natal stream except when they make a “mistake” fits in with the belief that restoring their habitat is like restoring a painting. But that “mistake” has been essential for their survival. If they could not shift among streams, by occasionally going up the “wrong” stream, they would have gone extinct when water became too cold or warm, or when other factors altered their habitats – landslides filling streams with debris; water erosion removing gravel required for the eggs. Salmon are sustainable and restorable only if changes at many time scales occur – from seasonal changes in water flow to variations in ocean El Nino events and periodic forest fires that allow alders to grow along the salmon’s stream, to the glacial-age changes already mentioned.
How then do we restore and sustain species in an ever-changing environment, to which the species are adapted?

• Allow changes to occur at natural rates and of natural kinds. This means we have to study species and their habitats from a new perspective – what kinds of changes do species need?
• Therefore, promote the scientific understanding of the kinds and rates of change required by species. The idea that change is natural is gradually altering ecological sciences, but the acceptance needs to proceed faster, before the species that depend on change go extinct.
• Avoid novel changes – like the introduction of artificial chemicals never encountered before by any life form. Just because some kinds of changes and rates of change are natural does not mean that any kind of change is acceptable. Let nature and its dynamics be our guide.
• Rethink management policies, so that the harvest of living resources is done within the world view of natural change. The world’s fisheries have been traditionally managed in the twentieth century with the goal of maintaining a single maximum sustainable yield, the same yield every year, year after year. But when fish habitats changes, and a fish species’s prey and predator also change, abundance of that fish species has to vary as well.
• Therefore, rather than seeking a constant yield from a living resource, harvest within a range determined by natural variations. The scientific way to do this has been developed and is on the shelf waiting to be applied. Push for that application.
• Change the way you think about restoring and sustaining nature. Instead of likening restoration of nature to restoring a Van Gogh or a ‘57 Chevy, think about restoring the wild and always changing Missouri River, with its frequent and sometimes abrupt changes in flow, direction, location of backwaters, meanders, and everything else.

Written for the Nature Conservancy
Copyright © 2002 Daniel B. Botkin
Originally published in TNC magazine

“A bittersweet event,” Augusta’s mayor said as the proceedings started about 8:30 am. And so it was: a willing and willful removal of one of the triumphs of the machine age, a piece of Yankee ingenuity that had provided power, jobs, and prosperity for Augusta, but did so no more.

As the time for the breaching approached, a cormorant also flew down river, black wings flapping low just above the water. Three herring gulls stood in the shallows, watching to see if anything worth eating might turn up.

As we stood by the river, I thought about my own experiences with New England water power. My friend and father-in-law, Heman Chase, had owned a small water-powered mill in East Alstead, a southwestern New Hampshire village. At the turn of the nineteenth century, seven mills lined a short stretch of a stream flowing out of Warren’s Pond. As it tumbled down a steep slope, the stream turned mill wheels to cut wood, grind grain, make cloth.

By the turn of the twentieth century, electrical transmission lines had replaced the old mechanical mills, which were soon abandoned. Heman had restored his mill with the same care and love of technology that leads the Smithsonian to restore antique airplanes, bicycle enthusiasts to restore antique bikes, and car buffs to restore Model T Fords. He installed a turbine wheel inside the mill building at the end of a long flume, instead of a big water wheel outside. The turbine had been the latest technology in the second part of the nineteenth century, invented just before mills made the transition from mechanical to electrical power generation.

Each century and each generation had had its own approach to water power and rivers. Dams were built across the United States to provide power for many kinds of industries, from textile mills to aluminum refineries; to store water for irrigation; to control water to aid ship navigation so that grain and other goods could be transported downriver; for flood control; and for recreation. But dams greatly altered stream habitat. As Thoreau observed on the Merrimack, migrating fish like shad and salmon, once common there, were rare in his time because they could not pass over the dams already in place by the 1840s. Reservoirs behind dams created habitats that favored lake fish over river and stream fish, like trout, that require fast running water and complex stream shapes, with pools alternating with white water. Those who want to keep dams support the economic benefits; suggest that the expense of removal does not justify environmental benefits; that a greatly altered floodplain will be left behind, full of mud and sand from which recovery will take a long time; that hydropower remains one of the cleanest forms of energy and, once oil prices rise, will become a vital resource once again; that recreational benefits of large reservoirs outweigh those of free-running streams; and that it is too late to save species threatened by dams anyway. Those who want to remove dams believe that ecological health of streams is essential to a sound environment; that we must do what we can to save threatened and endangered species such as salmon; that free running rivers provide a better quality of life for people, both in terms of recreation and scenic beauty.

The old mill, a seeming symbol of constancy, was just one stage in a rapid change in society and technology. For Heman, his mill was a symbol of Yankee independence and the ideal of self-sufficiency in a democratic society. Early in his career as a civil engineer, he had helped build a hydroelectric dam at Bellows Falls, Vermont, a depression-era project. He restored his little mill to run a planer, power saw, and drill press, and used the mill to teach neighborhood children carpentry and to instill in them beliefs and attitudes about America, society, and democracy.

One winter, soon after the environment had become a major social issue, I helped him install a new flume, and we spent many hours in the mill, fixing up the building. “Best way to teach physics is to see the mill running,” Heman used to say. Water power was viewed as “clean energy” in the 1970s and 1980s, not polluting the air or water. It seemed an improvement over other forms of energy generation because of these “brown” environmental issues. But today, the emphasis is shifting to the “green” issues: fish in the rivers, trees along the shores, endangered species, and the quality of human life.

Heman admired water power, but he also appreciated landscapes of New England. Making his living as a country surveyor, he spent most of his days mapping old farms that had grown back to woods and were becoming vacation retreats. Sometimes I helped, and we crossed many a stream, bog, and dense woodland, often talking along the way about nature, the conditions of forests, about individual trees or wildlife we saw, and discussing what was best for humanity in terms of politics, economics, and nature.

For 30 years, surveyor Chase had heated his home with firewood cut from his own land, carefully stewarding the forest to provide a continual supply before the terms “sustainability” and even “ecology” were familiar. He died in the 1980s, after a productive and much-admired life, a well know local personality, the country philosopher who could weld steel for his millworks and discuss economics and political history at the same time. And here I was standing before the removal of just the kind of structure my old friend had long admired. What would he think of this day, I mused.
Just after 9:00 am, a bell, tolling along the shore, was answered by a big bell in the Augusta church, announcing the time to breach the dam. The diesel shovel dug deeper and deeper into the temporary earth dam until a shout went up from the crowd and water began to spill through. The thin trickle breached the dam and eroded rapidly downward, moving ever faster. A frothy-brown mud-laden torrent began to run down the far side of the Kennebec, tumbling against an old mill building and spreading its color into the main channel. The river began to clean itself of a century and a half deposits behind the old dam.

Some would say that the removal of the dam was righting an old wrong. Others would say it was a mistake, wronging an old right. But I believe that my friend and father-in-law would have approved of the breaching of Edwards Dam. It was not a matter of absolute right or wrong, but a matter of a change in our society’s needs and desires, a continuation of change and progress, of new ideas, that has characterized American society. The dam and its mills no longer provided prosperity for Augusta, but threatened migrating fish like shad, which are in trouble along the coast. The majority of people wanted the river back. We could, one hopes, depend on other sources for energy. The river could return as a renewable resource for living things, just as Heman Chase’s woodlot had produced energy to heat his home for many years.

Although I loved the old mill in East Alstead and the nineteenth century progress it represented, I was pleased to see the Kennebec returning to its old form. The key to life, especially within a democracy, is flexibility and change. Removing this old technology was not a condemnation of anything, just a change in what we wanted and what we understood nature in Maine needed for the next century.

Unique now, Edwards is likely to be merely the first of many dams that will be removed. Edwards Dam was a relatively easy decision, because it had ceased to be of much use to Augusta and it was clear that the river had been important for migrating fish, and Maine is now a major tourist state rather than an industrial state. But other dams to follow are likely to cause much more conflict. There is already much talk about removal of bigger dams, including several major ones on the Snake River in Idaho which make ship transportation possible to Lewiston, Idaho.

The danger is that the conflicts will begin with accusations of who is right and what was wrong, rather than discuss them in terms of appropriate progress. It is likely to that conflicts will be posed as pitting needs of nature against needs of people. But as Heman Chase knew, these needs are deeply intertwined. Thoreau understood this when he canoed Maine’s river. When he wrote his famous phrase “In Wildness is the preservation of the World” he followed it with the explanation that this was because from wilderness comes “the tonics and barks that brace mankind,” a poetic way of saying that nature provides what human beings need. It was the contact between nature and human society that so interested Thoreau, and interested my watermill-owning father-in-law. When we recognize this contact and our deep interdependency with nature, we will be able to see the adjustment in where we have dams and what we dam as not a matter of true and false, right and wrong, but as a matter of landscape design that best meets many needs and desires in a world that is always changing. With the removal of Edwards Dam, the heron and the cormorant will fly again along the waters, and we will begin to enjoy nature within a changed society and changed environment. The tolling of the bell was an announcement of progress, not death or decline. We will benefit from this next stage in progress, development that helps nature, ourselves, and our relationship with nature. It is true to the American way, to the ideals of rationality and progress that have made our nation great.

Copyright © Daniel B. Botkin 1999
All Rights Reserved