What is the land pyramid?

Aldo Leopold, answered from the texts and cited to the page.

Aldo Leopold answers

The grocer's scale is the wrong image. When a layman hears balance of nature, he pictures something like that familiar weighing device — two pans, a point of equilibrium, a static rest — and he imports to the living land properties that exist only on the grocer's counter.1 The ecologist accepts the phrase only with reservations, and for good reason: it concedes too much to the idea that there is one fixed point at which balance occurs, and that balance, when achieved, simply sits there.2

The biotic pyramid is a truer image, and it is the one I have used in my own thinking about what land actually is.3 Land, to begin with, is not merely soil. It is a fountain of energy flowing through a circuit of soils, plants, and animals.4 Plants absorb energy from the sun; that energy then moves upward through a layered structure. The bottom layer is the soil.

A plant layer rests on the soil, an insect layer on the plants, a bird and rodent layer on the insects, and so on up through various animal groups to the apex, which consists of the larger carnivores.5 Man shares an intermediate layer with the bears, raccoons, and squirrels — the omnivores, the eaters of both meat and vegetables.6 The species of any given layer are alike not in where they came from, nor in what they look like, but in what they eat.7

Each successive layer depends on those below it for food and often for other services; each in turn furnishes food and services to those above. Proceeding upward, each layer decreases in numerical abundance — for every carnivore there are hundreds of his prey, thousands of their prey, millions of insects, uncountable plants. The pyramidal form of the system reflects this progression from apex to base.8

The lines of dependency running through the pyramid are called food chains. The chain soil-oak-deer-Indian has in many places been converted to soil-corn-cow-farmer, but the structural logic is the same.9 Each species, including ourselves, is a link in many chains simultaneously — the bobwhite quail eats a thousand kinds of plants and animals, making him a link in a thousand chains at once.10

The pyramid is therefore a tangle of chains so complex as to seem disorderly; yet the stability of the system proves it to be a highly organized structure, one whose functioning depends on the cooperation and competition of all its diverse links.11 In the beginning, the pyramid was low and squat, the food chains short and simple. Evolution has added layer after layer, link after link.

The trend of evolution is to elaborate the biota — to increase the height and complexity of the pyramid, not to simplify it.12 This matters enormously for how we think about land use, because the upward flow of energy depends on the complex structure of the plant and animal community, much as the upward flow of sap in a tree depends on its complex cellular organization.

Without that complexity, normal circulation does not occur.13 The ethical implication follows directly from the ecological picture. A land-use system that strips away the uneconomic parts of the biotic community — the species that have no immediate commercial value — assumes, falsely, that the economic parts of the biotic clock will function without the uneconomic parts.14

The pyramid tells us otherwise. The function of species within it is largely inscrutable, and may remain so; the only sure conclusion is that the biota as a whole is useful, and that biota includes not only plants and animals but soils and waters as well.15 We cannot audit which links are dispensable, because we do not yet understand the tangle well enough to know what holds it together.

An ethic to supplement and guide the economic relation to land presupposes exactly this mental image — land as a biotic mechanism, a circuit of energy whose integrity we can see, feel, understand, and ultimately have faith in.16 The pyramid is not a sentimental figure. It is the image that makes the land ethic possible.

Sources

  1. To the lay mind, balance of nature probably conveys an actual image of the familiar weighing scale. There may even be danger that the layman imputes to the biota properties which exist only on the grocer's counter.
    RILEY GAME COOPERATIVE RILEY, WISCONSIN, pp. 284–285
  2. Its defects are that there is only one point at which balance occurs, and that balance is normally static.
    RILEY GAME COOPERATIVE RILEY, WISCONSIN, pp. 284–285
  3. If we must use a mental image for land instead of thinking about it directly, why not employ the image commonly used in ecology, namely the biotic pyramid? With certain additions hereinafter developed it presents a truer picture of the biota.
    RILEY GAME COOPERATIVE RILEY, WISCONSIN, pp. 284–285
  4. Land, then, is not merely soil; it is a fountain of energy flowing through a circuit of soils, plants, and animals.
    RILEY GAME COOPERATIVE RILEY, WISCONSIN, pp. 285–286
  5. The bottom layer is the soil. A plant layer rests on the soil, an insect layer on the plants, a bird and rodent layer on the insects, and so on up through various animal groups to the apex layer, which consists of the larger carnivores.
    A Sand County Almanac, and Sketches Here and There, pp. 247–249
  6. Man shares an intermediate layer with the bears, raccoons, and squirrels which eat both meat and vegetables.
    A Sand County Almanac, and Sketches Here and There, pp. 247–249
  7. The species of a layer are alike not in where they came from, nor in what they look like, but rather in what they eat.
    RILEY GAME COOPERATIVE RILEY, WISCONSIN, pp. 285–286
  8. Each successive layer decreases in abundance; for every predator there are hundreds of his prey, thousands of their prey, millions of insects, uncountable plants.
    RILEY GAME COOPERATIVE RILEY, WISCONSIN, pp. 285–286
  9. Thus soil-oak-deer-Indian is a chain that has now been largely converted to soil-corn-cow-farmer.
    A Sand County Almanac, and Sketches Here and There, pp. 247–249
  10. Thus the bobwhite quail eats a thousand kinds of plants and animals, i.e., he is a link in a thousand chains.
    Other Writings on Ecology and Conservation, pp. 576–578
  11. The pyramid is a tangle of chains so complex as to seem disorderly, but when carefully examined the tangle is seen to be a highly organized structure. Its functioning depends on the cooperation and competition of all its diverse links.
    RILEY GAME COOPERATIVE RILEY, WISCONSIN, pp. 285–286
  12. In the beginning, the pyramid of life was low and squat; the food chains short and simple. Evolution has added layer after layer, link after link. Man is one of thousands of accretions to the height and complexity of the pyramid. Science has given us many doubts, but it has given us at least one certainty; the trend of evolution is to elaborate the biota.
    RILEY GAME COOPERATIVE RILEY, WISCONSIN, pp. 285–286
  13. The upward flow of energy depends on the complex structure of the plant and animal community, much as the upward flow of sap in a tree depends on its complex cellular organization. Without this complexity normal circulation would not occur.
    RILEY GAME COOPERATIVE RILEY, WISCONSIN, pp. 285–286
  14. It assumes, falsely, I think, that the economic parts of the biotic clock will function without the uneconomic parts.
    A Sand County Almanac, and Sketches Here and There, pp. 247–249
  15. The only sure conclusion is that the biota as a whole is useful, and biota includes not only plants and animals, but soils and waters as well.
    RILEY GAME COOPERATIVE RILEY, WISCONSIN, pp. 284–285
  16. An ethic to supplement and guide the economic relation to land presupposes the existence of some mental image of land as a biotic mechanism. We can be ethical only in relation to something we can see, feel, understand, love, or otherwise have faith in.
    A Sand County Almanac, and Sketches Here and There, pp. 247–249