There is a current trend in ecology to downplay the “balance of nature”. This has created a certain dissonance within me. I like to think of myself as part of the vanguard of ecology to which the main body of science (with a growing interest in “ecological service”) is beginning to catch up with. But “balance” is so fundamental to my way of thinking that I wonder if I am not actually a member of the discredited old school mumbling against heliocentrism, evolution, and plate tectonics. Last week I realized that the dissonance lies in two distinct images of “balance” which I had not teased apart.
My favorite image for “the balance of nature” (in the classic sense) is balancing a yard stick (or meter stick) on the tip of my finger. The tip of the stick never stands still. There is always a slight circulating dance. And the tip of my finger never stands still, either. Always it, too, is doing a compensating dance to bring the stick back to plumb.
The relationship between stick tip and fingertip is a classic example of a stabilizing feedback loop (also called a negative feedback loop but I am beginning to drop this confusing albeit formally correct terminology). There is always movement, yes, but there is also a dynamic stability, a compensation to every perturbation, a preservation of a certain arrangement. There is a point of balance which the system as a whole tries maintaining.
If I understand the current trend in ecology correctly, ecologists are saying that yes, there are these stabilizing patterns in nature, and they express a delightful and important dynamic in the workings of nature but there is nothing inherently “sacred” in any particular arrangement currently maintained through stabilizing feedback loops. There is nothing fundamental that the system as a whole is trying to maintain in any of these feedback loops. If certain occasional forces become strong enough, they can knock the entire system into a completely new configuration with new balancing points.
This certainly is the case when one contemplates the geological history of long-term changes such as vast Ice Age lakes in the west drying to flat playas. And though I delight in every discovered example of a stabilizing feedback, the heart of my awe lies in another kind of “relative balance”, the kind underlying the phrase “turning the prow of our entropyship back upstream”.
Perhaps the best image I have to contrast this kind of balance with the kind expressed by the balanced meter stick is a turkey vulture spiraling within a thermal. The turkey vulture is always gliding “downhill” through the air. But if the air rises faster than the vulture descends through it, then the vulture rises relative to the ground. Unlike the meter stick, there is no point of balance trying to be maintained. Instead, there is a relative balance between gliding down and rising up. If the vulture glides down faster than the air rises, the vulture will lose altitude. If the air rises faster than the vulture descends, the vulture will rise–and from that higher altitude have more possibilities, more options, more freedom of where to then go.
Life evolves within a universe shaped by the Second Law of Thermodynamics (the downward gliding of the vulture) and upon a planet orbiting within a solar flow of energy that makes possible the thermal and ten billion other similar “upward” expressions. The tension between these two realities can lead the surface of the earth to evolve along a variety of paths. What I find so sacred is the way life collectively has evolved structures that shift this relative balance so that more of the sun’s energy is diverted into life, so that flows of nutrients are slowed and recycled, so that forces that previously blasted life are moderated.
In other words, the two balances are created by two different kinds of feedback. “Balance of nature” uses stabilizing feedback loops to keep things oscillating within a narrow range. The “relative balance” does not remain within a small range. Instead, snowballing feedback loops slowly strive to move the biosphere into new ranges of possibilities.
If I look at Sand Canyon, the eroding canyon I describe in Shifting, in terms of stabilizing feedback loops, I can see several that help stabilize eroding streams. As the erosion cuts deeper, the streambed draws closer to the water table, allowing the plants that can reverse the spiral to grow more luxuriantly. The nascent jungle of willows and cottonwoods that springs upward each spring traps stream-transported soil and helps build up the streambed until it becomes again almost level with the terraces.
But it didn’t happen in Sand Canyon because there were too many cattle and sheep in that streambed for too long each growing season. Every seedling got eaten. Again there could have been a balancing feedback loop to this cause of erosion. Such a concentration of walking meat should have attracted and nourished enough predators that the herbivores never reached such numbers. But the people have hunted out all the wolves and cougars.
In terms of “balance of nature”, some might say Sand Canyon is out of balance and others could say, “No, the forces acting upon the system have changed and so the canyon system as a whole has evolved to a new position of stability.” And that is true. But looking at it this way misses what the people are doing to the canyon in terms of snowballing feedback loops. Each year the canyon loses more of its life-supporting potential.
We are the inheritors of a multi-billion year upward spiral. The evolution of our intelligence is like the expanded view a vulture has near the top of the thermal. One could, perhaps, argue that there is nothing sacred about whether the ecosystem as a whole builds towards lesser entropy or slides towards greater entropy. But the discussion would be irrelevant to our present situation in which this shift in relative balance is due to our species that has yet to comprehend the cause and effect relationships between its efforts to decrease entropy for the human subsystem and the consequent increase in entropy this causes in the encompassing system of the biosphere. We have yet to collectively comprehend the long-term implications that running down the greater system will have on the human sub-system.
Came upon a tragically fascinating quote in a soil textbook. “The cost of dredging the several billion tons of sediment from rivers and harbors each year is about 15 times more than the cost of holding the soil on the land from where it eroded.” Soils: An Introduction to Soils and Plant Growth p. 448
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