Thursday, May 10, 2012

Ecosystem basics for economics

This is part two of a series adapted from remarks I made at a conference on local energy in Cooperstown, NY, May 5th. Here's Part One.

Here's my minimal ecosystem "tool kit" for applying lessons from ecosystems to economies:
  • 1st and 2nd Laws of Thermodynamics
  • Structure of ecosystems and species' roles
  • Coordination
  • Success through capture of gradients
The 1st Law of Thermodynamics says that energy can be neither created nor destroyed, but only transformed.  The standard colloquial translation is that there's no free lunch.

You can see it at work in a food chain:


The plants or phytoplankton at the bottom capture energy from the sun.  Above that, each level gets its energy from the level below.

The 2nd Law says (in one of its implications) that every time you transform energy, some of it is transformed, some of it is dissipated as waste heat that can no longer do anything useful--in the vernacular, you can't even break even.  The "trophic pyramid" (the pyramid of who eats whom) illustrates both the 1st and 2nd Laws:


Because the energy at the upper levels can only have come from the lower ones (1st Law), and because some energy is dissipated at every transformation (turning from a moth into a mouse, or a mouse into a snake), there must be less energy in the upper levels than in the lower ones. As a rule of thumb (and as illustrated above), plants end up embodying about 1% of the solar energy that strikes them, herbivores end up embodying about 10% of the energy contained in plants, the next level up has 10% of that, and so on.

As they go about their lives, obedient to these two laws, species coevolve to create structures in which they play specific functions.
The plants capture and store solar energy and create an array of chemical compounds. Some of the primary consumers help the plants propagate (bees pollinating flowers, squirels burying acrorns, birds eating berries and spreading seeds ...). Symbionts like nitrogen-fixing bacteria take a portion of the sugar a plant produces, but capture nitrogen from the air and make it available to the plant. Secondary consumers (aka carnivors) control the primary consumers. The behavior of grazing animals favors grasses over other plants. Decomposers break down the excrement, dead bodies, and dead plants, making the nutrients in them available for plants to use again.

Every one of these species (including the plants) depends on solar energy captured by the plants. Every one of them, from a buffalo to a soil bacterium, dissipates some of that energy in the course of going about its life. So the physical matter in the system mostly circulates: soil, to plants, to herbivores, to carnivores, to decomposers, and back to soil. And the circulation is driven by energy, which doesn't circulate, but passes through, getting partially dissipated at every stage of the process. Without continual infusions of new energy, the system shuts down.

We can simplify and stylize this picture, to emphasize the circulation of matter and the driving role of energy, with less of the original energy being available at each step of the cycle.

In this system, the behaviors of the various components are coordinated through genetically coded behaviors. These can be within a species, as with termite mounds that are textbooks of subtle engineering.
No single termite has any conception of the structure to which it is contributing. Each termite's genes tell it how to respond to changes in termperature, air flow, humidity, ... and the result of scads of termites individually following these cues is a structure that keeps the nest in a narrow range of desirable temperature and humidity.

Coordination can also be between species, as with the nitrogen-fixing bacteria on the roots of legumes, or the spreading of seeds by birds, or the pollinating of flowers by bees.

The flower provides nectar (energy, nutrients), and the bee helps the flower create its seeds. Not by contract, nor by charity, but by blind obedience to genetic instructions that have survived because they worked.

This is a world with a standard of "success," defined by reproduction. If you reproduce more copiously or more reliably than others, your genes will be better represented in the next generation. "Better" can mean better than other individuals in your species, or it can mean that your species tends to do a better job than other species that are trying to use the same resources as you.

To be successful, you must survive and thrive, and to do that, you have to be (relatively) good at locating, capturing, and utilizing thermodynamic gradients.

Loosely speaking, a gradient exists when two entities differ in their energy level or in the degree to which the matter in them is organized. If you have a hot cup of coffee in a cold room, there's a gradient (a difference in energy) between the coffee and the room. And this gradient will tend to get "reduced," with the coffee cooling off and the room warming up (ever so slightly), until the two things are the same temperatute--the gradient is gone.

(There's an interesting discussion of gradients from a broad perspective here, in a chapter by Dorion Sagan and Jessica Hope Whiteside.)

The first gradient that's important for most ecosystems is the one between the heat of the sun and the cool of space. The photons from the sun are carrying the sun's energy out into space, dissipating the energy being released by our star's fusion reaction.
When you put the right sort of device in the path of a gradient that's being reduced, you can get work done. A plant is just such a device, since it's able to capture photons carrying the sun's energy out into space, and use that energy to transform carbon dioxide and water into sugar, and then use the energy in that sugar to build itself and make anything from an algae mat to a tree.

The wood of the tree is now another gradient. It stores energy (as you can tell when you burn it), and it's organized in a useful way (which we take advantage of when we build with it or turn it into paper). If you don't take care of your house, the wood-eating organisms will come and make use of the gradient embodied in the wood, and when they're done, they will have turned it back into the material out of which it was made--they will have reduced the gradient.

We animals also contain gradients--the difference between us and our environments, or between us alive and us dead, on our way back to us being merely molecules. A living plant or animal is organized matter and embodied energy. When it dies, the matter will go back to being the less organized matter of the soil, and the energy will dissipate into the atmosphere, though some of each will pass for a time through other animals, and other animals, ... before the matter comes around again and the energy is finally all dispersed.

So these are the gradients that are the key to success. Plants that capture more sunlight will grow more abundantly than plants that capture less, and will have an easier time producing seeds. Herbivores that do a better job of finding and harvesting edible plants will out-compete their neighbors. Carnivores that are better at hunting will outlast the worse hunters. And animals that make effective use of the gradients they capture will outperform the "inefficient." There are different routes to success: a mammal's high metabolism makes it need more energy than a reptile, but the payoff is that it can operate under a wider variety of conditions.

In the ceaseless contest to locate, capture, and make good use of gradients, changes are constantly popping up in the genetic code that instructs organisms how to do those things. The changes that don't work get discarded, and the changes that work better get passed along, eventually displacing genes that used to be successful. They change the environment for themselves and everybody else, and eventually even newer patterns come along, and the previous successes are themselves left behind.

One change in particular stands out among the rest, and that is the "discovery" of photosynthesis, that miraculous act of standing between the sun and cold space and making the wheels of life go 'round.  There was life before photosynthesis, but it was cramped, subsisting only on chemical bonds it could find around it in the early Earth and its oceans. Photosynthesis captured some of the sun's energy and put it at the service of all other life. From there, we were off to the races.

Next: Economies and ecosystems

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