Energy Flow
The Flow of Fuel that Animates All Life
The majority of organisms receive their energy from the sun, whether directly as do plants and algae, or by consuming plants, or by consuming other animals or their remains. Energy flow is a one-way avenue, from the Sun to the earth. Therefore, the management of any ecosystem must take into account the amount of energy captured by plants and the affect this has on all the other ecosystem processes.
Every civilization depends on the capture of solar energy by plants through photosynthesis. That’s because only plants can convert that energy into edible forms. While there are other energy producers, photovoltaic, hydroelectric, geothermal, fossil fuels, etc., none of them can produce an edible form. Most of humanity has forgotten this prime connection between plants and their way of life. Without plants to convert the energy of the Sun into something we can eat, our societies, cultures, and ourselves crumble and fade away.
The Energy Pyramid
The simplest representation of how energy flows from the sun through any ecosystem is the energy pyramid (Figure 15-1, Savory & Butterfield, pg 150). From the total amount of solar energy striking the earth, part is immediately reflected back to space, a portion is absorbed by the soil or water as heat, which radiates back to space later. A very tiny portion is captured by green plants and converted into food for themselves and other organisms in the food chain. In the pyramid, plants are shown as level 1.
On the land, plants and algae at or above the soil surface capture and convert the solar energy into food. On the water, plants in the shallows that are above the water surface and those plants in open water but shallow enough to receive sunlight provide the same service. Otherwise the concept of the energy pyramid covers all environments.
Level 2 symbolizes the energy captured and stored by animals that feed directly on plants. Although it is represented as small steps from one level to the next, in actuality, the amount of energy lost to heat when moving from one level to the next is approximately 90 per cent.
Level 3 represents the predators that consume those animals at Level 2, while Level 4 is predators that consume some of the predators at Level 3.
It should be noted that humans are found in Levels 2, 3, and 4. Again at each of these Levels, 90% of the energy in the previous Level is lost to the living processes of the animals.
Humans drop out at Level 5, where the scavengers and decay organisms further reduce the energy until at Layer 6 the final decay organisms use and convert the last remaining energy to heat. It should be remembered as well that at each stage some energy moves directly to the decay levels in the forms of urine and feces and through microorganisms that feed on the plants themselves. Therefore, in real life, the levels represented here are not as clear-cut and exact. And while none of the energy is actually destroyed or used up but merely converted to heat that cannot be used as food.
An example of humans’ place in the pyramid is a fish chowder with potatoes from Level 1, salt pork from Level 2, and cod from Level 3. In less developed countries, humans may generally feed off Level 1 organisms with only occasional Level 2 or 3 consumption. In higher developed countries, the pyramid can get confusing as animals at Level 2 may be fed offal from that or higher levels to increase the protein portion of their rations.
The energy pyramid also extends below the surface so that energy flow has direct bearing on the functioning of the other 3 ecosystem processes, water cycle, mineral cycle, and community dynamics. All three need a biologically active soil to function properly and that of course requires solar energy, which is conveyed underground by plant roots or surface-feeding organisms such as worms, termites, ants, and dung beetles. (Figure 15-2, ibid., pg 152)
The Energy Tetrahedron
The two dimensional energy pyramid serves to easily inform people about how energy flows but does not provide sufficient information for management methods, especially in regard to the four key insights we’ve learned about earlier. We do know that the wider the base of the triangle, the larger the whole and a greater amount of energy is available at every level. We have used irrigation, more acreage, higher yielding crops, double cropping, etc. on cropland to widen the base. We have cleared brush, reseeded, and other methods to do the same on rangeland. In forests, we have used fire and machinery in the attempt to increase the amount of energy available. In the water we have basically ignored the energy base by constructing fish hatcheries and farms. In many cases the results have been a marked increase, but at a heavy cost in non-renewable resources and chemicals and fertilizers that destroy life and pollute the air and water.
Even if we ignore the damage these technologies do to the natural water cycle, mineral cycle, and community dynamics, so that only increasing amounts of outside energy, i.e. fossil fueled, can compensate, the technologies quickly reach the point of creating an energy debt, that is the energy inputted is greater than the energy returned. Until fossil fuels become scarce and more expensive, the industrialized countries paid little attention to the problem. Poor countries, however, have been dealing with a life and death situation for a long time. Now that fossil fuel prices are increasing, the industrialized countries are frantically searching for alternative energy sources. But until humanity realizes that energy that we can use as food can only come from plants and that managing that in relation to the water cycle, mineral cycle, and biological communities will the problem be put in the proper perspective.
With knowledge gained from the four key insights, we now see the energy pyramid as multidimensional, above and below the surface as two tetrahedrons joined at their bases. (Figure 15-3) Using this concept allows us the opportunity to increase energy flow at the soil surface, that is Level 1. The three sides of this pyramid can be named Time, Density, and Area. We can use this viewpoint to better manage, that is increase energy flow at all levels. That is, on land, the correct management can increase energy volume at Level 1, not only by increasing the density of standing vegetation on an acre, but also the time which that vegetation is growing and the rate at which it grows, and by increasing the leaf area of each plant to capture more energy.
By extending any of the three sides of the base, the volume of energy humans can harvest and use from Levels 2, 3, and 4 is larger. On the other hand, shortening any of them, decreases the available energy in those levels and all others.
Mr. Savory uses the example of a client who was experiencing a severe drought, much like the one Texas and Oklahoma experienced in 2010-11. As he tried to explain to the rancher that his problem was the energy flow, he noticed that the rancher was distracted and was looking for a quick fix. They decided to go look around the ranch. Mr. Savory broke the capped surface with his boot and pushed some of the dead, oxidizing grass into the opening. He asked the rancher if he thought that an extra ounce of grass would be produced there if it received an inch of rain, and he thought it would. They then calculated how much additional grass would be produced if he used his livestock to prepare the ground for him: 1 ounce x 1 square yard. Below are the results of those figures for typical sized properties:
640 acres 193,600 pounds 96.8 tons
320 acres 96,800 48.4
160 acres 48,400 24.2
80 acres 24,200 12.1
40 acres 12,100 6.05
10 acres 3,025 1.5
And that is figuring only one grass seed-head per square yard. It is probable that in most pastures, many more than one seed-head will be “planted” by grouping the animals into one herd so that the concentration effectively breaks the soils capping and tramples the old grass down. This also reduces the amount of time the animals stay in any one area, giving the plants there more time to grow. The greater knowledge that the land manager has about the results of increased energy flow, the more management tools are at his/her disposal.
Time (Duration and Rate of Growth)
While plants are green and growing, they convert energy that supports all life, above and below ground, all year. Therefore the longer plants are growing, the more energy is converted. This can be done either by extending the growing season or increasing the growth rate of plants in a given time.
By producing a better mineral cycle, water cycle, and greater biological complexity, one can accomplish both goals. Additionally, by not taking the plants too far down, the growing time is more efficient, as the plants grow back faster due to more leaf area.
An effective water cycle is especially important for growing season extension in drought-prone regions as the soil moisture remains available after fewer hours of sunlight and falling temperatures end the growing season. As we learned in the section on the water cycle, the availability of moisture allows the plants to begin growing immediately when temperatures rise and days begin lengthening. It also allows plants to grow much longer during any dry spell that may occur during the growing season.
The opposite problem ,too much water, due to over irrigation or poor drainage and aeration, also occurs, which cuts time off the growing season as well. Every hour lost when the temperature is adequate, but plants can’t grow to their potential due to poor aeration is that much energy lost.
Species complexity within the community also affects growing time as well. The best example is pasture that contains both cool season and warm season grasses. A healthy pasture will have enough of both to ensure that there is some part of the community is growing for as long as any growth is possible. The over-reliance on any one season of growth reduces overall energy flow. A good selection of heat- and cold-tolerant forages or crops and planting dates can also extend the growing seasons.
Density (of Plants)
Density denotes the number of plants growing on each square yard of land. Three plants convert more energy than 1, 10 more than three, 20 more than 10 and so on. Farmers, recognizing this increase in production, have long strove to plant at the density that produces the highest yields.
In environments that tend toward the nonbrittle, plant density is naturally high and there is only so much management can do to improve production. In more brittle environments, the more the disturbance, or lack thereof, by large animals affects plant density. Correctly applied, over time the use of fire, animals, or machines that mimic animal disturbance can indeed increase plant density. Incorrectly applied, any of them, but especially fire used alone, can actually decrease density and increase bare spaces. Planned disturbances by animals has a positive correlation with increasing plant densities, especially where animal impact is the highest.
While people have traditionally equated varying plant density to soil and climatic differences, in the more brittle tending environments, the management of animal impact can make a significant difference in plant density that is affordable and sustainable.
In aquatic environments, too high a density of plants resulting from the additional nutrients of detergents and other chemicals, including fertilizer run-off from cropland, can actually deplete the amount of oxygen in the water to the point that other life forms can suffocate.
Area (of Leaf)
Think of the leaf of a plant as a solar panel. The more area this panel has, the more energy it can collect from the sun. Therefore, even if you have a very dense stand of Bermuda grass, it probably won’t capture the same amount of energy as a moderate stand of Eastern Gama grass because of the difference in leaf area. So in order to capture more energy, you need to increase the number of broad leaf plants in your pastures or fields.
Many of us have different types of growing conditions in our properties, and plants adapt to those conditions. Wet-environment, or Hydrophytic, plants grow best in soggy, poorly aerated soils. Mesophytic plants grow best in soils with a balanced proportion of air and water. Xerophytic plants are adapted to dry environments, where the soil may be well aerated, but there is a lack of water.
Wet- and dry-type plants tend to resemble each other more than they do the middle-type plants. Both have fairly impervious skins covering their leaves, and various adaptations that function to prevent them from taking in or transpiring much water through their breathing pores. Many of both have narrow leafs or leaf stems, that can convert energy, which limits the amount of sunlight and transpiration. Some dry-type plants have broad leaves but they are likely rolled to limit transpiration as well.
Wet-type plants such as cattails and sedges usually grow in sites with either high rainfall or poor aeration. However they can also be found in sites that are severely capped, causing poor aeration. Dry-type plants, such as cactus and some grasses, are usually found where moisture is scant. Occasionally they are found in high rainfall but with capped soil leading to quick run-off or evaporation. Some of the dry-type perennial grasses are very noticeable during the dormant season as they turn white or very pale. Both types tend to grow slowly and so store only a limited amount of solar energy.
Middle-type plants are very different in that they generally have open, flat, broad leaves which curl only when stressed by lack of moisture. They lack the thick protective skins and limiting breathing pore adaptations of the other two types. They grow rapidly when moisture and temperature are balanced. Rather than drying to a pale color during the dormant season, they generally dry to a red or gold color, which indicates that they have stored more nutrition than the dry-type grasses. The difference can often be seen in arid parts of the US where grasses along the roadside, due to periodic mowing and protection from overgrazing, dry off to a reddish or golden color in the dormant season, while across the fence, overgrazed and soil that has had little disturbance, the grasses are a ghostly white. The fence-line comparison is striking and can be seen for miles.
It should be clear that in order to increase the area side of the energy triangle, more broad-leaved middle-type plants are needed. While occasionally a layer of clay or rock below the surface may prevent middle-type plant establishment, but generally severely sealed or capped soil land poorly functioning water cycle, leading to a poor water-to-air ratio, is to blame for the difficulty in establishing middle-type plants. That situation can be addressed by management. In the less brittle environments, the problem is not soil capping but poor drainage, which can also be addressed by managed animal impact and grazing. It should be noted that in both environments, that animal impact and severe grazing, but not overgrazing, produces denser stands but also prods many species into producing more leaf and less fiber. This increases the amount of energy that can be used by animals and humans.
Using Technology to Increase Energy Flow
While it is true that we can increase energy flow by using technologies, such as machinery, irrigation, fertilizers, field tiling, among others, we must be extremely careful when we do so. As we know by now, we can make changes to one ecosystem process without affecting the other three. If and when we do use technology, we must do so in ways that simultaneously improve the water cycle, mineral cycle, and biological communities. American agriculture with its dependence on fossil fuels to increase energy flow has damaged the other three ecosystem processes to the tune of millions of dollars per year. Increasing numbers of severe floods, soil, water, and food pollution, increasing numbers of birth disorders, tons of soil washed or blown away into the rivers, lakes, and oceans creating dead zones, funds for flood control, insect control, and the abandonment of thousands of farms and ranches leading to the demise of many rural businesses and towns.
Conclusion
Whether writing a holisticgoal about your community or as a land manager, describe it how it would look if energy flow was high – vegetation covered soil, plants grow fast and longer, and there would be a large variety of them. Wildlife would be abundant because of the increased plant life. Water cycles, mineral cycles, and biological communities are all effective as well.
Land managers should be somewhat more detailed in their descriptions – of course, they would still have effective water and mineral cycles, large and diverse biological communities, all of which increase energy flow. But they would also need to describe how they would attain them. Management would include increasing the time plants are growing by having good daily growth rates and extending the growing season by using polycultures or at least having two crops per year. Any planting we do will be closely spaced to ensure a high density, and we will make sure to have more leaf area by a good mixture of broad-leaved plants, good drainage, crumb structure, and plentiful organic matter in the soil, which has a good soil cover year-round. In the more brittle environments we will incorporate the use of animals into any cropland we may have.
On pastures and rangelands we will increase energy flow by using the tools of grazing and animal impact, with both livestock and wildlife, to create and keep a long and productive growing period with increased plant density and leaf area. The amount of purchased energy, not provided by our own land, would be a measurement of our success or failure.