Busy Little Engineers

This post is intended for my reference and for the awareness/benefit of anyone curious enough to read it. The following is an excerpt from author and permaculturist Toby Hemenway, called

Learning from the Ecological Engineers:
Watershed Wisdom of the Beaver

The full article can be found by clicking the link above.

Busy Little Engineers

The importance of the beaver hasn’t gone unnoticed by ecologists, and these creatures also offer both conceptual tools and affirmation to permaculturists as well. Recently, ecologists have coined a phrase to describe animals like the beaver: Ecosystem engineers. These are organisms that directly affect and regulate the availability of resources to other species, by causing physical changes in biotic and abiotic materials. In doing this they create and/or modify habitats.

I’m not wild about calling animals “engineers,” as my personal view of engineering is that it is not as creative, inspiring, or appropriate as what nature does—I’d rather call engineers “retarded beavers”—but the term is well established and will have to do here.

Ecosystem engineers fall into two camps. In the first are creatures like the beaver and earthworm, which work their magic by manipulating living and non-living materials (they are called allogenic engineers, for those who like fancy terms).

The second group are those which alter the environment by changes in their own bodies (autogenic engineers). Trees are the consummate example of autogenic engineers, and Mollison has written brilliantly of the way trees interact with and affect their environment. However, he focuses mainly on the effects of trees on the non-living world: how they affect rainfall, hydrology, soil, clouds, and wind. One could deepen his essays by describing how trees regulate the other species around them. They create habitat for many species amidst their trunks, branches, water-filled crotches, leaves, and roots. The roots provide cavities and aeration, and change soil texture and infiltration rates, which affect both underground and surface dwellers. Leaf litter changes the drainage, moisture level, and gas and moisture exchange rates in soil habitats, and creates barriers to or protection for microbes, seeds, seedlings, and animals. Trunks, branches, and leaves drop into streams, altering flow and otherwise providing new habitat. This list could go on: The ways that trees “engineer” habitat are multifold.

The principal point to grasp about ecological engineers is that they act at points of maximum leverage to change the flow, availability, and pattern of energy, nutrients, and other resources that are used by other species. They often are not part of these flows themselves, thus their interactions are on a very different level from the predator/prey relations (trophic level) upon which so many of ecology’s precepts are based.

Ecosystem engineers “design” their own habitats and those of others, and exert a great deal of control over them. This means they create stable, predictable conditions for themselves and for the ever-increasing numbers of creatures who become dependent on them, and for ecosystem processes. They damp the wild flows passing through their homes. They usually enhance biodiversity and make environments more complex.

Sound familiar? The whole idea of ecosystem engineers drops neatly into the permaculture toolbox. These species, like good designers, create and improve habitat for many species as a by-product of enhancing their own environment. They cooperate with ecosystem processes and energy and matter flows, directing them with minimal, efficient intervention, and they benefit themselves and others by doing so.

By understanding ecosystem engineers like the beaver, we can shine a bright, critical light on many of the practices and principles of permaculture. The effects of beaver on a watershed sound to me like nature’s application of P.A. Yeomans’ Keyline concepts, and support permaculture’s belief that earthworks and ponds are critical for restoring ecosystem health. In sites where beaver have returned after a century or more of absence, we have natural models that demonstrate the hugely beneficial effect of holding water on the land.

Trees, as Mollison understood, are another ecosystem engineer to learn from. Others that could be integrated into the permaculture corpus of knowledge are:

• Reef-building corals
• Earthworms and other burrowers (the whole class are called bioturbators for their churning of sediments)
• Certain key fungi and other microbes, which mobilize nutrients
• Algae, which change how light and nutrients are distributed in water
• Elephants, which uproot, trample, and eat whole forests and then deposit huge manure loads elsewhere, stimulating new growth
• Woodpeckers, which alter insect abundance and create nest sites and shelter in trees for many species
• Alligators, which dig wallows that create new habitats

      The final and most drastic ecosystem engineer is, of course, Homo sapiens. We’re not very good at it. Usually the effect of our ecosystem engineering is to reduce the possibilities for every other species, rather than to enhance them. But by looking more carefully at the many ways in which nature’s ecosystem engineers improve their own homesites while boosting the productivity and diversity of the larger environment, we can become wiser in our own manipulations.


Jones, CG, JH Lawton, M Shachak (1997). Positive and Negative Effects of Organisms as Ecosystem Engineers. Ecology 78:1946-1957.
Matthiessen, P (1959) Wildlife in America. Viking Press, New York.
Naiman, RJ (1988). Animal Influences on Ecosystem Dynamics. BioScience 38:750-752
Naiman, RJ, CA Johnston, JC Kelley (1988). Alteration of North American Streams by Beaver. BioScience 38:753-762.

Toby Hemenway is associate editor of Permaculture Activist and the author of Gaia’s Garden: A Guide to Home-Scale Permaculture (Chelsea Green, 2001). He lives in southern Oregon.




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