Panarchy theory: How forest & civilizations grow & decline

Because energy is a society’s master resource, when Rome exhausted its
energy subsidies from its conquests-when it had to move, in other
words, from high energy-return-on-investment (EROI) sources of energy
to low-EROI sources-it faced a critical transition. And, at least in
the Western part of the empire, it didn’t make this transition
successfully. It couldn’t sustain the cost and complexity of its
far-flung army, ballooning civil service, hungry and restless cities,
elaborate information flows, and intricate irrigation systems. Not
that it didn’t try.

All photos in this post by Deane Rimerman

Rome’s prodigious effort to save itself by putting in place a system to aggressively manage its energy problem was simultaneously one of history’s greatest triumphs and tragedies. It was a triumph because, for a while at least, the effort reversed what seemed like the empire’s inexorable decline; but it was ultimately a tragedy because it didn’t address the empire’s underlying problem-complexity too great for a food-based energy system-and was thus bound to fail.

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Panarchy theory had its origins in Holling’s meticulous observation of
the ecology of forests. He noticed that healthy forests all have an
adaptive cycle of growth, collapse, regeneration, and again growth.
During the early part of the cycle’s growth phase, the number of
species and of individual plants and animals quickly increases, as
organisms arrive to exploit all available ecological niches. The total
biomass of these plants and animals grows, as does their accumulated
residue of decay-for instance, the forest’s trees get bigger, and as
these trees and other plants and animals die, they rot to form an
ever-thickening layer of humus in the soil. Also, the flows of energy,
materials, and genetic information between the forest’s organisms
become steadily more numerous and complex. If we think of the
ecosystem as a network, both the number of nodes in the network and
the density of links between the nodes rise.

During this early phase of growth, the forest ecosystem is steadily accumulating capital. As its total mass grows, so does its quantity of nutrients, along with the amount of information in the genes of its increasingly varied plants and animals. Its organisms are also accumulating mutations in their genes that could be beneficial at some point in the future. And all these changes represent what Holling calls greater “potential” for
novel and unexpected developments in the forest’s future. As the
forest’s growth continues, its components become more linked
together-the ecosystem’s “connectedness” goes up-and as this happens
it evolves more ways of regulating itself and maintaining its

Over time as the forest matures and passes into the late
part of its growth phase, the mechanisms of self-regulation become
highly diverse and finely tuned. Species and organisms are
progressively more specialized and efficient in using the energy and
nutrients available in their niche. Indeed, the whole forest becomes
extremely efficient-in a sense, it effectively adapts to maximize the
production of biomass from the flows of sunlight, water, and nutrients
it gets from its environment. In the process, redundancies in the
forest’s ecological network-like multiple nitrogen fixers-are pruned

New plants and animals find fewer niches to exploit, so the
steady increase in diversity of species and organisms slows and may
even decline. This growth phase can’t go on indefinitely. Holling
implies-very much as Tainter argues in his theory-that the forest’s
ever-greater connectedness and efficiency eventually produce
dim­inishing returns by reducing its capacity to cope with severe
outside shocks. Essentially, the ecosystem becomes less resilient. The
forest’s interdependent trees, worms, beetles, and the like become so
well adapted to a specific range of circumstances-and so well
organized as an efficient and productive system-that when a shock
pushes the forest far outside that range, it can’t cope. Also, the
forest’s high connectedness helps any shock travel faster across the
ecosystem. And finally, the forest’s high efficiency makes it harder
for it to realize its rising potential for novelty. For instance, the
extra nutrients that the forest ecosystem has accumulated aren’t
easily available to new species and ecosystem processes because
they’re fully expropriated and controlled by existing plants and

Overall, then, the forest ecosystem becomes rigid and
brittle. It becomes, as Holling says, “an accident waiting to happen.”
So in the late part of the growth phase of any living system like a
forest, three things are happening simultaneously: the system’s
potential for novelty is increasing, its connectedness and
self-regulation are also increasing, but its overall resilience is
falling. At this point in the life of a forest, a sudden event such as
a windstorm, wildfire, insect outbreak, or drought can trigger the
collapse of the whole ecosystem. The results, of course, can be
dramatic-large tracts of beautiful forest can be obliterated. The
ecosystem loses species and biomass and in the process much of its
connectedness and self-regulation.

But the effects on the ecosystem’s overall health may be very positive. A wildfire in a mature forest creates open spaces that allow new species to establish themselves and propagate; it destroys infestations of disease and insects; and it converts vegetation and accumulated debris into nutrients that can be used by plants and animals that reestablish themselves after the fire. The organisms that survive become much less dependent on specific,
long-established relationships with each other. Most important,
collapse also liberates the ecosystem’s enormous potential for
creativity and allows for novel and unpredictable recombination of its
elements. It’s as if somebody threw the forest’s remaining plants,
animals, nutrients, energy flows, and genetic information into a
gigantic mixing bowl and stirred.

Once-marginal species can now capture and exploit newly released nutrients, and genetic mutations that were a bane to survival can now be a boon. And because the system is suddenly far less interconnected and rigid, it’s far more resilient to sudden shock. This is a perfect setting for the forest’s plants and animals to experiment with new behaviors and relationships-a
pollinator species like a bee or wasp will try gathering nectar from a
type of flower it hadn’t previously visited, or a carnivore might try
killing and eating a different kind of prey. If such experiments fail,
the damage is less likely to cascade across the entire system. Holling thinks the world is reaching “a stage of vulnerability that could trigger a rare and major ‘pulse’ of social transformation.”

Humankind has experienced only three or four such pulses during its
entire evolution, including the transition from hunter-gatherer
communities to agricultural settlement, the industrial revolution, and
the recent global communications revolution. Today another pulse is
about to begin. “The immense destruction that a new pulse signals is
both frightening and creative,” he writes. “The only way to approach
such a period, in which uncertainty is very large and one cannot
predict what the future holds, is not to predict, but to experiment
and act inventively and exuberantly via diverse adventures in living.”

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