Collapse, environment, and society
Karl W. Butzer
Department of Geography and the Environment, University of Texas at Austin, Austin, TX 78712
This contribution is part of the special series of Inaugural Articles by members of the National Academy of Sciences elected in 1996.
Edited by B. L. Turner, Arizona State University, Tempe, AZ, and approved December 2, 2011 (received for review September 10, 2011)
Historical collapse of ancient states poses intriguing social-ecological questions, as well as potential applications to global change and
contemporary strategies for sustainability. Five Old World case studies are developed to identify interactive inputs, triggers, and feedbacks
in devolution. Collapse is multicausal and rarely abrupt. Political simplification undermines traditional structures of authority to favor
militarization, whereas disintegration is preconditioned or triggered by acute stress (insecurity, environmental or economic crises,
famine), with breakdown accompanied or followed by demographic decline. Undue attention to stressors risks underestimating the
intricate interplay of environmental, political, and sociocultural resilience in limiting the damages of collapse or in facilitating reconstruction.
The conceptual model emphasizes resilience, as well as the historical roles of leaders, elites, and ideology. However, a historical model
cannot simply be applied to contemporary problems of sustainability without adjustment for cumulative information and increasing
possibilities for popular participation. Between the 14th and 18th centuries, Western Europe responded to environmental crises by innovation
and intensification; such modernization was decentralized, protracted, flexible, and broadly based. Much of the current alarmist
literature that claims to draw from historical experience is poorly focused, simplistic, and unhelpful. It fails to appreciate that resilience and
readaptation depend on identified options, improved understanding, cultural solidarity, enlightened leadership, and opportunities
for participation and fresh ideas.
historical disasters | Egypt | Mesopotamia | Fayum Oasis | Ethiopia
Rise and Fall of Civilizations
T
here has been inordinate fascination
with societal collapse, an issue
outlined in the introduction to
this Special Feature (1). The concept
has intuitive appeal but ambiguous
meaning, and has been applied to states,
nations, or complex societies, in the sense
that such entities rise and flourish, but
eventually disintegrate and fail. Sociopolitical
organization, economic weakness, and
environmental or demographic trends
have received emphasis. Change takes
a long-term cyclic rhythm, at first organizing,
then expanding and integrating, before
sinking in disorder. Systemic failure in one
synergistic network may destabilize adjacent
structures. Other open questions
concern the scale of collapse, the time
frames involved, the key elements that fail,
and whether the outcome is cataclysmic or
eventually allows restructuring. Not all
breakdowns are alike.
This challenging concept and its attendant
issues were first articulated by the
Islamic historian Ibn Khaldun [after 1377
common era (CE)] (2), who identified the
periodic rise and fall of dynasties as macrostructures
in the history of sedentary
civilizations. Beginning with the Roman
Empire and continuing with its Islamic
counterparts, he attributed demise to rural
rebellions or outside invaders confronting
a ruling hierarchy that had forfeited the
solidarity of its supporters. Rather than
a global history, Khaldun’s work was an
implicit critique of Islamic society that
went beyond theological arguments. He
faulted the greed and selfishness that came
with power, at the expense of the common
good.
Khaldun’s writings were poorly disseminated,
and Western interest in collapse
was initially stimulated by Edward Gibbon
(3), who, with laborious detail, attributed
the decline and fall of the Roman Empire
to moral decay and barbarian invasions,
much like his predecessor had. Gibbon
observed that Roman collapse had
changed the sociopolitical map of Europe
and the Mediterranean world, a transformation
that continues to generate
a secondary literature. Although Gibbon
held to an ethical dimension, he recognized
that Roman collapse could not be
separated from historical processes that
shaped the dynamic context of its time,
and he was uneasy about the potential
future failure of even more enlightened
and powerful states.
When the archaeological discoveries of
the 19th century revealed a periodic failure
of kingdoms and empires across the
Near East, the collapse model became
a durable theme of social and historical
discourse. However, the message shifted:
whereas ephemeral Eastern civilizations
regularly dissolved in chaos, the comparative
durability of ancient Rome improved
the prospect that Western Europe might
endure indefinitely.
With the proliferation of biological
analogues in the mid-1800s, ontogenetic
or evolutionary qualities such as growth,
maturity, and decline were used to interpret
historical macrostructures. For social
Darwinists, material culture became an
index for the increasing achievements of
civilization, in an era when the Industrial
Revolution exuded the driving force of
“progress.” The West was seen as a new
empire, wherein technology would assure
unlimited economic growth. Problems
could and would be fixed by technological
innovation.
Oswald Spengler’s The Decline of the
West (1918–1922) (4) was written in the
wake of a world war and before the Nazi
ascendance. He redefined ontogeny in
humanistic terms that included premonitions
of the authoritarian state. His “winter”
would coincide with a demise of
abstract thought, accompanied by empowerment
of the rich, and the rise of
caesarian, demagogic leaders. Spengler
saw a society in deep crisis, and his prescient
but pessimistic ideas anticipated the
horrors of fascism and Stalinism. His insights
remain pertinent for modeling alternative
pathways of political resilience in
the wake of collapse.
By contrast, the French authors of the
Annales School chose a nonlinear track to
capture the rich detail of regional histories,
and to develop an interdisciplinary
method in which millennial demographic
waves served as a bellwether of key interactive
processes (5–7). Disjunctures
were attributed to competing economic
systems, long-distance networking, warfare,
or pandemics (8), ideas that gave
impetus to world-system history (9–11).
The annalistes eventually turned to more
humanistic studies that introduced
Author contributions: K.W.B. designed research and original
maps,performedresearch,analyzeddata,andwrotethepaper.
The author declares no conflict of interest.
This article is a PNAS Direct Submission.
1
E-mail: karl.butzer@austin.utexas.edu.
This article contains supporting information online at
www.pnas.org/lookup/suppl/doi:10.1073/pnas.1114845109/-/
DCSupplemental.
3632–3639 | PNAS | March 6, 2012 | vol. 109 | no. 10 www.pnas.org/cgi/doi/10.1073/pnas.1114845109
environmental variability as an integral
part of historical process (12, 13).
Notable is the increasing diversity of
perspectives about collapse, ranging initially
from ethical and social, to ideological
or ethnocentric, and eventually to interdisciplinary
and systemic. The underlying
ideas continue to echo. The salient
concern today is the interface between
environment and society, to require greater
attention to social science and humanities
perspectives. There has indeed been
rapid growth of theoretical sophistication
in regard to complexity and network theory,
agent-based models, resilience theory,
or tipping points. However, the challenge
for a scientific study of historical collapse
remains to develop comprehensive, integrated
or coupled models, drawing upon
the implications of qualitative narratives
that go well beyond routine social science
categories, to better incorporate the complexity
of human societies (1).
Current research in historical collapse
suggests a primary fascination with climatic
change and environmental degradation as
primary agents of change, but at the cost
of less attention to the necessary crossdisciplinary
integration. Indeed, the recent
return to environmentalism is not about
a fresh interest in the environment–society
interface, but a continuing failure to appreciate
the complexity of such interrelationships.
At issue is not whether
climatic change is relevant for sociohistorical
change, but how we can deal more
objectively with coupled systems that include
a great tapestry of variables, among
which climatically triggered environmental
change is undeniably important. The SI
Text reviews the problematic revival of
environmental determinism in regard to
the Akkadian collapse, as well as the
purported societal passivity about anthropogenic
degradation and potential future
collapse. The Old World case studies
range from early historical times to the
threshold of globalization, with additional
examples outlined in the SI Text, or presented
in the various research articles of
this Special Feature of PNAS. Examined
at different levels of detail, these cases
help single out more important, interactive
variables, to estimate time scales for
transformation, and explore the roles of
preconditioning, triggering and reconstituting
processes. The ultimate goal
would be to design complex simulation
models that incorporate sophisticated societal
components and that can be validated
(1).
This presentation attempts to transcend
simple assumptions or truisms and
monocausal explanations, by dissecting
historical examples so as to illustrate the
full palette of social-ecological variables
and why they are so important for resilience
within coupled systems. Some current
models for change pay careful attention
to biophysical variables that may
affect feedbacks, but then go on to simply
fit a group of societal factors into a few
preconceived categories, supported by
tertiary digests of no better than mixed
value, to “explain” a particular outcome by
assumed, axiomatic processes. Instead, our
five case studies (later and in the SI Text)
identify important, qualitative variables
and track their roles and interplay in systemic
outcomes. Although difficult to
simulate, societal inputs and feedbacks are
more common than environmental variables.
The case studies also offer temporal
parameters for transformation.
Anatomy of a Collapse: Old Kingdom
Egypt
The historical cycle of the Egyptian Old
Kingdom (14) closed shortly after the improbably
long reign of Pepi II [∼2278–
2184 before CE (BCE)], the last significant
ruler of the sixth Dynasty. Such long
periods of rule can lead to issues of succession,
and royal authority promptly collapsed
at the death of Pepi II, judging by
a cluster of approximately 20 powerless
kinglets, marking the seventh-eighth dynasties,
a very short time span, perhaps
from 2181 to 2160 BCE. Egypt broke apart
into several feuding provincial powers,
controlled by members of the old elite or
a novel genre of warlords, to be reunited
through force of arms after approximately
2040 BCE by a new, 11th Dynasty.
Didactic Literature. An interval of approximately
120 to 200 y (ref. 15, table S7;
ref. 16, p 464), known as the First Intermediate
Period (dynasties 9–10), represents
a radical sociopolitical transformation,
documented by written records
and archeology. Instead of burial near
Memphis, the rich or powerful began to
build rock tombs near their provincial
land-holdings. Wealth was dispersed to
new centers, with economic growth, artistic
and cultural change, and a shift to
a different style of social complexity (17).
Some of the elite were deeply disturbed by
the course of events, leading to a body of
didactic literature (labeled as instructions,
lamentations, or prophecies) that
became literary classics during the Middle
and New Kingdoms, when they were used
in the schooling of young scribes.
Few such tracts have the necessary authenticity
of historical descriptions, but
they do represent an insider perspective on
Egyptian cultural memory of a painful
transition (ref. 18, p. 109–113). The autobiography
of Ankhtifi, a southern provincial
governor [ninth Dynasty, ∼2120 (?)
BCE], was inscribed in a rock-cut tomb.
The full list of woes enumerated had not
been previously used in literary convention,
and was not a mere figure of speech.
The text elliptically reports rampant civil
war, famine, and starvation caused by Nile
failure, mass dying or aimless dislocation
of starving people, cannibalism (sic),
wanton tomb or cemetery violations, and
dispossession of the elite. Other, less authentic
admonitions of the era amplify the
themes of poverty, anarchy, and the upending
of social roles. The basic message is
a breakdown of the “cosmic order” and
social justice, perhaps in the wake of an
environmental disaster. However one
chooses to interpret such writings, there
was no central government, while justice,
order, or respect for tradition fell by the
wayside during the nadir of collapse, presumably
the seventh to eighth dynasties.
Onset of Economic Decline. During the sixth
dynasty, central authority was steadily diluted
by privileges granted to courtiers
around the throne. Mortuary temples were
already built for pharaohs of the fourth
dynasty, institutions that engaged groups of
priests, paid by the treasury in perpetuity,
whereas such foundations and their farms
were exempt from taxes, much as nonprofit
corporations are today. Gradually such
privileges were accorded to other powerful
men at court, a pattern accelerating during
sixth Dynasty times until a significant part
of the prime lands was removed from the
fiscal rolls, even as the state continued
to support the upkeep of mortuary cults
(“entitlements”).
Economic decline also resulted from
breakdown of the vital foreign trade,
mainly carried out over the entrepot of
Byblos (now Jubail, Lebanon). Cedar and
fir were imported for shipbuilding, or
luxury goods such as wine and olive oil,
for elite use. Pharaoh is likely to have profited
greatly from such transactions, but
archeology shows that, during the reign of
Pepi II, Byblos was destroyed by the
Akkadians, its Egyptian imports ending
abruptly (19) and then interrupted for
250 y. That would have cut off a critical
source of royal revenue, weakening
pharaoh’s personal power.
Environmental Trigger. Inferred from the
admonitions, Nile failures are quite plausible
in view of the limnological record of
Lake Turkana: fed to approximately 90%
by the Omo watershed in mountainous
western Ethiopia, an area with climatic
conditions similar to those of the Blue
Nile. Prominent and dated beach ridges
indicate a sporadic, early to mid-Holocene
overflow of this nonoutlet lake, through
a series of swamps to the Sobat and White
Nile rivers (20). Together with diatom assemblages,
alkalinity levels, and Omo detrital
silicates, the lake levels offer a proxy
record for Blue Nile behavior, but the
chronology is only approximate (21). A
decrease in Omo material approximately
2800 (calibrated years) BCE was followed
by an abrupt change in water chemistry, to
a closed, alkaline-saline lake, approximately
2400 BCE. This coincided with
a late fourth Dynasty shift to downcutting
(i.e., channel incision) of the Nile at Giza
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(22), implying a pattern of poor or indifferent
floods that would only inundate
parts of the flood basins. Omo influx
was minimal approximately 2100 BCE, but
sharply greater 2000 to 1800 BCE, before
declining again. Considering the partial
match of these rough dates, it is possible
but unproven that Nile failures
may have helped trigger collapse of the
old kingdom.
Civil Wars. The Egyptian record after Pepi II
not only points to dynastic instability, but
also includes direct and indirect evidence
of civil wars during the ninth to 11th dynasties.
Permanent reunification of Egypt
toward approximately 2016 BCE required
several bloody campaigns until the victory
of a Theban dynasty over the northern
center of Heracleopolis, but even then the
Delta remained to be subjugated (23, 24).
The Theban vizier later usurped the
throne, waging intermittent warfare to ascend
to the kingship as Amenemhet I
(∼1985–1956 BCE) of the 12th dynasty,
against vigorous opposition by some of the
elites (ref. 16, p. 493–495; and ref. 25).
He was later assassinated. He and his
successors had been supported by the
provincial warlords of Middle Egypt (24),
who retained considerable power until
approximately 1850 BCE, when a new king
phased out or eliminated the office of
provincial governors—potential military
contenders—and returned Egypt to
a more traditional, centralized autocracy.
Demilitarization followed, with reemergence
of a middle class (ref. 16, p. 506;
and ref. 25), ending 300 y of intermittent
warfare and civil strife. The collapse
after Pepi II had evidently unleashed unwelcome
feedbacks that repeatedly favored
destructive military unrest, variously
coupled with both elite contestation and
resilience. The didactic literature implies
that the goal of reunification remained
central to the cosmic order ascribed to
by key national power groups.
Concatenation. The details marshaled here
illustrate the immense complexity of collapse.
The economic prosperity of Egypt
had declined through the course of the
sixth Dynasty, inversely to the growing
wealth and power of now-hereditary provincial
governors. The expansion of mortuary
endowments, fiscal stagnation,
decentralization of authority, and loss of
hegemony over eastern Mediterranean
trade had served to precondition Egypt for
collapse across 160 y or more. Nile failures
probably unleashed a severe subsistence
crisis that helped trigger an economic
breakdown near the end of Pepi II’s reign,
but other factors were also involved (17,
26). Contending elite groups may originally
have used an impending crisis of
succession to undermine royal legitimacy,
in an effort to steer more power to the
provinces. However, they discovered
that social anarchy is difficult to contain
when institutional structures falter. Amid
social chaos and insecurity analogous to
that of modern Somalia, ancient Egypt
experienced political simplification as
the contestants repeatedly resorted to
armed force.
A concatenation of triggering economic,
subsistence, political, and social forces
probably drove Egypt across a threshold of
instability, setting in train a downward
spiral of cascading feedbacks. In the end,
a semblance of the cosmic order was restored,
with the support of new elites, but
with the heavy hand of military men, even
as the echoes of civil war continued to
reverberate until the authoritarian rule of
the Pyramid Age was reinstated (ref. 17;
pp. 118–119 and 130–131). The initial
breakdown took a few decades, but the
processes of collapse played out on a centennial
scale, as did reconstitution (16).
This detailed analysis, with the advantage
of a body of fragmentary but rich,
written records, helps illustrate the true
complexity of collapse. It involved more
than an impersonal network of systemic
interactions. It encompassed people, admittedly
at cross purposes and with incomplete
information, who ultimately
sought to bring their country back together,
consonant with their vision of the cosmic
order. In the persons of military leaders
and conflicted elites, one can gain a
glimpse of the ambiguous notions that
political and social resilience imply.
Autopsy of Another Collapse: New
Kingdom Egypt
A second historical example better illuminates
the socioeconomic components
and processes of national failure, with the
important benefit of specific economic
records. Under the 20th Dynasty (∼1187–
1064 BCE) (27, 28), Egypt devolved from
a powerful state to a divided nation in
which authority had been usurped by
a high priesthood that controlled the wellendowed
temples as well as military forces,
ready to engage in civil war. However, instead
of recovery, Egypt came to be ruled
by foreign dynasties.
When Did Decline Begin? The pharaoh Merenptah
shipped a great amount of grain
to alleviate famine in the wavering Hittite
empire at approximately 1210 BCE, suggesting
a major drought in Anatolia but
food abundance in the Nile Valley. Then,
in 1207, he had to fend off a determined
invasion of Libyans in alliance with several
“Sea Peoples,” perhaps mobilized by
the same environmental crisis in western
Anatolia and the Aegean world.
Three further foreign onslaughts confronted
Ramesses III (1185–1153 BCE) of
the 20th dynasty. He managed to defeat
the fleet of Sea Peoples amid the Delta
marshes in 1174. However, these powerful
raiders had already destroyed all other
states of the eastern Mediterranean, including
Egyptian hegemony in the Levant,
to terminate traditional commercial relationships,
with implications for widespread
economic depression (26). Although
Ramesses III still carried out a major
building program and sent an expedition
to Punt, he made an unusual offering to
the Nile in 1179, to propitiate the river and
seek good floods (29). High-level malfeasance
and corruption surfaced in 1157,
and the king was victim to a harem conspiracy
at the time of his death.
The severity of gathering economic
problems can be gauged by unprecedented
strikes and rioting, because of insufficient
food and unpaid wages for the royal artisans
(in 1156). The vizier could turn up
only half the wheat needed, because the
temple storage facilities were empty. The
food supply had failed, the king’s authority
was brazenly challenged, and Egypt was
patently in decline.
Process of Devolution. On the accession of
the king’s son (Ramesses IV) (30), the
royal workmen were paid off with food
and silver, not by the king’s treasury but by
representatives of the High Priest (ref. 28,
p. 607). Conflict between institutions is
implied. Rolling food shortfalls continued,
with runaway inflation. Grain prices, with
respect to nonfood products, had begun to
increase in 1170, eventually increasing to
eight times and occasionally 24 times the
standard price. Inflation peaked at approximately
1130, stabilizing at approximately
1110, with food prices falling
rapidly at approximately 1100 to 1070
(31). This was the first subsistence crisis
actually recorded in accounting books
(∼1170–1110 BCE). Hardship was exacerbated
by insecurity caused by Libyan
marauders (1117–1101), favoring rural
flight and declining productivity.
Royal power and prestige were fading.
Rock for monumental construction was no
longer quarried after 1151, and an 1135
expedition to the turquoise mines of Sinai
was the last. A new High Priest had himself
represented the same size as the king
(∼1113), suggesting a more direct appropriation
of power. Looting of the royal and
private tombs at Thebes was underway
with high-level complicity, and became
scandalous under Ramesses XI (1099–
1069 BCE), who did not use his completed
tomb in the Valley of the Kings, and apparently
chose to be buried in northern
Egypt. This last monarch attempted to
avoid the inevitable, calling in the Egyptian
viceroy from Nubia, who battled the
High Priest’s army and, interestingly, assumed
the notable title Overseer of the
Royal Granaries (1086 BCE), while controlling
southern Egypt for a decade.
Thereafter, a new High Priest disenfranchised
the pharaoh as the provider of
life and safeguard of the cosmic order,
declaring him a simple agent of the
3634 | www.pnas.org/cgi/doi/10.1073/pnas.1114845109 Butzer
supreme god Amun (32). By 1075, Ramesses
XI was a mere figurehead, residing
in the Delta, with Upper Egypt ruled by
the High Priest in the name of Amun,
while Nubia became independent. Usurpation
had been completed and Egypt
was divided.
Evaluation. The subsistence crises from
1170 to 1110 were preconditioned by
(i) debilitating wars to repel invaders,
(ii) the loss of Mediterranean commerce,
(iii) official corruption, and (iv) a lack of
support from the priesthood controlling
the temple granaries. However, the repeated
waves of wild inflation strongly
suggest that famines were triggered by
Nile failures (33). At Memphis, floods had
declined by approximately 6 m from approximately
1300 to 1100 BCE, a trend
that was paralleled in Nubia, where sand
dunes swept the floodplain and agriculture
had to be abandoned (22).
However, decline of the redistributive
economy continued even after the famines
were overcome, while Egypt was divided as
a state and fragmented as a country. Unlike
the admonitions literature of the First Intermediate
Period, which espoused a
return to traditional cosmic values, during
the 20th Dynasty, there was no persuasive
exhortation toward a moral high ground
(18). Instead there is the “Tale of Woe,”
which laments arbitrary rule, violence,
excessive tax demands, falsified units of
measure, hunger, and the breakdown
of the social contract (ref. 34 and ref. 18.
pp. 291–293). Egypt was impoverished and
demoralized, and at the end of the new
kingdom, swelling disaster did not provoke
political or social resilience. Instead the
ascendant military–priestly caste exhibited
little vision. The once integrative national
bureaucracy had failed amid pervasive
corruption, giving way to a chaotic and
superstition-driven theocracy that paraded
as a “rebirth.” Nubian and Libyan dynasties
followed in control.
There was, in fact, no reconstitution
or significant restoration until the indigenous
Saite revival, which began under
a vigorous king in 664 BCE, almost a half
millennium after initial disintegration.
The end of new kingdom Egypt was a quite
different experience than old kingdom
collapse, with breaching of multiple
thresholds that apparently created virtually
irreversible changes.
Insights from Islamic Mesopotamia
Lower Mesopotamia has qualified as an
irrigation society for approximately 6000 y.
Much of the central alluvial plain was archaeologically
surveyed by Robert Adams
(35–39) before field research in Iraq came
to a halt. Such survey data are dependent
on pottery dating and are not an ideal
proxy for population trends, but cautious
inferences are possible. Premodern settlement
density peaked during Sasanid
(i.e., new Persian empire) times (226–637
CE), after which the population eventually
collapsed by as much as 95%, toward
the time of the destruction of Baghdad by
a Mongol-led coalition in 1258 CE. That
span of approximately 700 y is hardly
“abrupt” by any reckoning, but it does not
take into account that there were in fact
two distinct collapses.
During the 630s CE, the Arab Conquest
destroyed the Sasanid Empire militarily,
replacing its administrative institutions,
bringing with it a new elite and many settlers
from Arabia. Islam replaced Zoroastrianism
and Christianity as the leading
religion. Indigenous speakers of Aramaic,
Persian, and Arabic gradually amalgamated
with immigrant Arabs to forge a new,
Arabic-speaking ethnicity (40). Sociopolitical
collapse was complete by approximately
642 CE, but with some evidence of
earlier decline in response to population
loss from the Justinian plague (541 CE),
exacerbated by many decades of inconclusive
warfare between the Sasanids
and Byzantium until shortly before the
Arab onslaught.
Repeated innovations in irrigation
strategy can be traced in Mesopotamia,
beginning with the Sasanids, who developed
a novel system that opened up
large areas for cultivation with a lattice of
intersecting canals to enclose polygons of
variable size, with waters distributed
from the Euphrates and Tigris (ref. 35, pp.
200–241). Although favoring salinization
in the long run, such basins could be
flooded annually, to optimize the use of
available water. A great canal, the Nahrawan,
was led from the Tigris near Samarra
to irrigate the eastern side of the
river. However, the Sasanid network had
begun to deteriorate in the wake of catastrophic
floods after 628 CE that destroyed
or silted up transverse canals, as
the Tigris shifted and caused the growth of
a vast swamp, accompanied by a high water
table favoring salinization of the lowermost
alluvial plain. After the Conquest,
the Sasanid system was abandoned and
new master canals were cut along different,
more traditional trajectories, but watering
less than half of its previous area.
This catastrophic disjuncture suggests
fundamental social disruption in the wake
of the Arab Conquest, as the administrative
superstructure was replaced by a
new elite, probably unfamiliar with Sasanid
methods (ref. 35, p. 218).
However, Mesopotamia promptly recovered
and, after 750 CE, became the
heartland of the powerful Abbasid Empire,
based on a modest recovery of the irrigation
system and the tribute from far-flung
provinces. It reached its apogee under
the legendary Harun al-Rashid (786–809
CE) but then began to decline as a result
of wasteful expenditures and rapacious
tax farming (40). Late Abbasid misgovernment
and weakening imperial hegemony
were punctuated by serious
rebellions and the wanton Seljuk destruction
of Khuzistan at approximately
1015 CE (41), until the economy was in
full decline and the Nahrawan canal
ceased to function (35). Islamic historians
and poets have eulogized the size, wealth,
and scholarship of Baghdad at the moment
of its demise and depopulation in
1258, but such descriptions actually harked
back 300 y, to the heyday of Abbasid civilization
(42). Instead the archaeological
evidence shows that the irrigation system
had collapsed well before any Mongol
destruction (35), and was not reconstructed
until the 20th century. Unfortunate
is that the early Islamic archives of
Iraq had only been partially studied before
their destruction by fire in 2003.
There were then two Islamic collapses in
Mesopotamia, the first in the wake of the
Arab Conquest at approximately 640
CE, the second beginning in the 10th
century and concluding with Mongol
plundering of what was left of Baghdad in
1258 CE. The first collapse spanned approximately
a century, the second as long as
300 y, and the responsible processes
were very different. However, consistent
themes were war, land use change, and
irrigation, or fiscal mismanagement.
The collapse of new kingdom Egypt and
of Islamic Mesopotamia involved the
persons and sources of indigenous power,
both worldly and divine, and the external
forces of chaos may have weighed heavily
on sociocultural consciousness. The outcomes
probably were traumatic, but in the
end, Egypt, as a society and an environment,
was more resilient than Mesopotamia
and continued to function with a
modicum of success. The failure of the irrigation
society of Mesopotamia was an
ecological tragedy, leading to the wasteland
reported by 19th century travelers (43).
Integration: A Didactic Model for
Historical Collapse
Discourse on historical collapse has tended
to be macroscopic and generalizing, based
on limited comparative research. Little
attention was given to the politicoeconomic
markers of state devolution, or the
strategic solutions that may have been attempted
but failed. Rarely considered
were the attributes of cultural identity that
might have been rejected or transformed.
The preceding analyses emphasize the wide
range of variables involved, the complicated
time frames, and the roles of textual
or insider information.
Interpreted with the aid of a simplified,
heuristic model (Fig. 1), the case studies
examined here and in the SI Text suggest
that the complexity of the social–ecological
interface is as much about interrelationships
as it is about the identification
of stressors. Related questions are
comprehensively discussed later, but, being
grounded in historical examples, a
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SPECIALFEATUREINAUGURALARTICLE
word of caution is due that the insights of
the model are not applicable to current
issues without modification.
Inputs, Triggers, and interactive Variables.
The process of breakdown typically
begins with economic or fiscal decline
caused by external and internal inputs,
some of which are long-term and precondition
a system to suboptimal performance
or weakened social-ecological
response. Others are short-term but intense,
serving as triggers (or, in combination,
as concatenations) for a deep
economic crisis provoking rapid change.
Such inputs may activate cascading (positive)
feedbacks that sustain or enhance
negative trends, to create instability in the
early stages of breakdown. If instead
there is a resilient response, leading to
beneficial readaptations, devolution may
be slowed or stabilized. In the longer term,
such pathways may allow reconstitution
and reconstruction or, alternatively, continuing
breakdown and eventual collapse.
Degradation of soils or other biotic
resources (deforestation, ground-cover
removal, soil erosion, or groundwater depletion
and salinization) represents incremental
damage that lowers thresholds
for more rapid down-the-line change,
particularly in conjunction with incompetent
administration, destructive land
use, or rural flight. Declining resource
productivity increases pressure on the environment
and may precondition an environmental
subsystem for failure.
Effective climatic inputs are most likely
to be high-recurrence perturbations, such
as excessive rains or floods, and more
persistent, decadal anomalies (such as severe
droughts) that serve as triggering
mechanisms, impacting a stressed or degraded
environment to unleash more catastrophic
forms of hydrological behavior or
slope failure (44–46). Climatic variables
can also precondition the environment by
accelerating degradation, or disastrous
floods may provoke outbreaks of epidemic
disease. Population decline or the disintegration
of economic networks may reinforce
environmental feedbacks, compromising
food production as well as
access to external information, food supplies,
markets, and raw materials.
However, the case studies (SI Text) indicate
that environmental inputs mainly
played supporting roles in a train of events
set in motion by institutional incompetence
or corruption, civil strife and insecurity,
invasion, or pandemics. Here government
failure is likely to precondition
the system, with external war as another
potential trigger. Protracted conflict may
well be destructive for infrastructure, food
production, manufacturing, market access,
and demographic success. It can also bring
sociopolitical domination of one group
by another, enslavement, rural insecurity,
and socioeconomic or ethnic conflict,
stimulating everyday violence and rural
abandonment.
Finally, it bears emphasizing that decline
or collapse can be either consequence or
cause of sociopolitical devolution. It may
undermine traditional customs, law, and
institutions, particularly in the case of
conflict between different elite groups, so
as to reduce sociocultural resilience. Outcomes
are difficult to predict because of the
interplay of multiple, cascading, or buffering
feedbacks (Fig. 1).
Time Frames. Duration of the processes
favoring decline or recovery helps to
identify the processes of devolution as well
as the elasticity of resilience. Drawing from
the experience of the historical case
studies, Fig. 1 suggests that a preconditioning
economic decline typically
spans decades or centuries. Contrary to
frequent claims of “abrupt” collapse, the
triggers that bring economic crisis are
more likely to operate at a multidecadal
scale. The first stage of stabilization or
instability may also be fairly rapid, whereas
a more complex reconstitution or complete
breakdown is likely to span a century
or more. Time frames would also be affected
by the absence of rapid or sustained
means of communication in earlier historical
eras.
Environmental Resilience. “Resilience”
of human ecosystems can be usefully
subdivided into a triad of intersecting
environmental, political, and cultural
components. Negative feedbacks resist,
dampen, or reverse change. Preconditioning
factors may also impose a degree of
stability. Perhaps little appreciated is
that some environmental systems are more
resilient than others in regard to anthropogenic
or climatic change and their cascading
feedbacks.
Politicoeconomic structures in Europe
have been less vulnerable to collapse than
those of arid lands in the Near East. Great
irrigation networks that supported large
populations in Mesopotamia were fragile
because they are artificial, i.e., relatively
homogeneous, managed, and hierarchical
systems that require much capital or labor
to maintain, and exponentially more to
reconstruct. The desert may return after
abandonment, not because of damage to
the environment but because of human
disengagement. Critical here are land
tenure, the mobilization of labor, and the
Fig. 1. A conceptual model for historical collapse, situating the variables and processes of stress and interaction discussed in the text. Timescales range from
multidecadal to centennial. Alternate pathways point to important qualities of resilience. Red superscripts identify stages that are elaborated by blue subscripts.
Environmental components (red within boxes) are secondary to sociopolitical factors.
3636 | www.pnas.org/cgi/doi/10.1073/pnas.1114845109 Butzer
complexity of large irrigation systems. When
rent, tax, or work demands become impossible,
Near Eastern peasants have historically
abandoned their villages to enter
the broad spectrum of semipastoral pursuits
that fill the gap between cultivation and fully
mobile nomadic herding. Beyond the reach
of the tax collector, such semipastoralists
reverted to simpler lifeways in what was
a fiscal wasteland, but not a deserted
landscape. This was the condition of lower
Mesopotamia until the late 19th century
(43). That is the true meaning of socioecological
collapse in irrigable, Near Eastern
desert environments. Multiple domains
and scales of institutional displacement
imply fairly resilient “final” regimes (47),
i.e., reconstitution will be very difficult.
In southern Europe, by contrast, mixed
farming is less specialized but also less
productive. Temporary abandonment plays
out at intermediate scales in compartmentalized
but selected biohabitats. It does
not turn the land over to desert, and
renewed settlement requires more modest
community coordination or start-up investment.
In Greece, with great spatial
complexity, there were periodic waves of soil
erosion caused by climate or land use (48,
49), but urban life and agriculture soon
resumed, with the necessary investment to
mitigate much past damage. In other
words, Mediterranean and many Western
agrosystems are relatively stable and less
liable to “catastrophic” simplification. Environmental
resilience—not impairment—
is the basic difference between southern
Europe and the Near East in the longue
durée of demography and agrarian production.
It is not a matter of Eastern decadence
or Western cultural fortitude.
What may be true at a large, global scale
is more complicated at the regional or local
level. Deforestation or land clearance
can put diversity at risk, but the often
higher inherent diversity of secondary
vegetation, with its many commensal
plants, may actually impart greater resilience
to stressed biotic communities. In
northern Greece, the prehistoric pollen
record shows that plant diversity was
greater in areas of degraded vegetation
(50), whereas in Spain, Mediterranean
scrub (i.e., monte bajo) offers more nutritious
graze, especially after burns, through
increased legume dispersal (51). It also
opens opportunities for subsequent conversion
to olive groves or vineyards.
Mediterranean people regard monte bajo
not as “waste” but as land in reserve,
which is used for local pastoralism and
wood gathering, but can be converted to
more productive orchards when markets
improve (46). Early forestry experts from
higher latitudes were disturbed by the
open nature of Mediterranean woodlands,
even though they were looking at oldgrowth
formations (44, 45). Deforestation
is therefore not a simple process that can
be equated with human degradation,
and reforestation with invasive or ornamental
trees does not qualify as recovery.
Similar misunderstandings can arise about
tropical savanna woodlands (52), as to
the role of fire, or about the age and origin
of grassy mosaics in woodland (53).
Facile generalizations are equally inappropriate
in arid lands. The conjoined
Tigris/Euphrates floodplain with its radial
canal systems is vulnerable to violent floods
that destroy riverbank cities (36–38), explode
in crevasses, shift courses, overwhelm
canals with silt, or raise the water
table of desert plains liable to salinization.
By contrast, artificial irrigation in Egypt
was superimposed on the natural rhythm
of existing flood basins, to enhance the
height and duration of the inundation
while flushing soluble salts downstream.
Egypt could support permanent settlement
even with little artificial irrigation,
although at a much lower carrying capacity.
That was not the case in Mesopotamia,
where breakdown of complex canal networks
would force wholesale abandonment
of agriculture. Such differences underscore
the distinct environmental and land use
histories of Egypt and Mesopotamia. Environmentally
triggered collapse in Egypt
would be comparatively short-term and
have modest demographic impact, but in
Mesopotamia it could be catastrophic.
In specific ecological contexts and at
different spatial scales, environmental
inputs mobilize certain processes, define
thresholds, follow time-paths, and favor
outcomes that may be distinctive. Beyond
the exotic rivers of the Near East, precipitation
anomalies vary spatially and
temporally. However, environmentally
grounded crises are culturally screened and
perceived, so as to affect vulnerability,
resilience, and response, as well as the
timescales at which underlying processes
can be addressed. Environmental elasticity
may be critical in the mitigating of collapse,
or in the ability of a society to carry on.
Political Resilience. In conjunction with the
case studies, analogues from anthropology
and political ecology suggest that ruling
families and elites tend to support the state,
if only in self-interest. The trauma of
collapse in ancient kingdoms can be reversed
by new dynastic cycles, during which
rulers rebuilt their societies with the support
of new elite groupings, but not
necessarily with the same identity or political
center. Whatever the complex
rationales of statehood or power, elites can
come together to support a new ruler in
rebuilding similar or modified administrative
and ideological structures. In this
way, ruling dynasties were periodically able
to reassert the authority of kingship in
Egypt and Mesopotamia.
Repeated simplification and cyclic
change in Assyria in approximately 1800 to
1600 BCE is documented and interpreted
by Yoffee (54) as a net shift to greater
centralization. First, the power-sharing
councils of traditional nobility disappeared.
Eventually, the generals of the
huge army assumed that role, while the
traditional kin and landholders were displaced
from lower management roles by
civil servants, with a work force increasingly
formed of non-Assyrian deportees, to
favor non-Assyrian cultures and belief
systems. In this late Assyrian case, political
transformation was not catastrophic but
part of a strategic progression that manipulated
institutional roles.
States may collapse because of incompetent
rulers, but surviving members of
the old elites, together with new allies of
diverging persuasion, will eventually help
pick a new candidate to support. In other
words, even in the wake of substantial
change, the political class represents a key
force of resilience and potential stabilization,
in tandem with the religious establishment.
Important is the rallying of elite
groups and institutional bureaucracies,
perhaps with a shift of ideology. The
convergence of such fundamental interests
may not be able to halt a downward cycle
of collapse, but they are basic to subsequent
regeneration through the revival of
dynastic ambition, the imposition of law
and order, and a redefined symbolic cohesion
of national interests.
The darker side of revival is that it may
not involve a reassessment or reaffirmation
of old ideals embedded in cultural
memory. Many or most decisions would be
made under stress, with the goal of securing
or consolidating power. Disagreements
may have been contested by populist
demands but are more likely to be settled
by military force. Traditional values may
fall into oblivion in the course of destructive
violence, as the old order falters.
In the end, the new elites probably cast
their lot with a new military leader, as
Spengler foresaw (4), more adept at neutralizing
internal or external enemies than
championing the higher ideals of governance.
Interlinear clues from Egypt and
Mesopotamia imply that the emerging social
contract is more likely to have been
authoritarian than enlightened, with older
rules of class distinction and land tenure
rigidly enforced. In general, the chances are
that an exploitative political economy will
not favor conservationist land use (46).
Cultural Resilience. Sociopolitical structures
appear to be the most fragile components
in collapse of archaic states or traditional
societies, in which there was no
role for the equivalent of contemporary,
community-based structures. The case
studies suggest that hierarchical orders
were “simplified,” probably with a transfer
of authority. Formal institutions, dynasties,
national symbols, and states come and
go, but was this accompanied by a loss
of religious or linguistic identity? Either
or both have frequently changed in the
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SPECIALFEATUREINAUGURALARTICLE
course of human history, without engendering
collapse. However, both are critical
facets of self-identification and cultural or
social memory, and their loss can mark
ethnic transformation.
Was cultural integrity involved, in the
sense of community values, rituals of solidarity,
age-cohort and sex relationships,
strategies for subsistence, stewardship of
multigenerational resources, and general
lifeways? Such traits circumscribe a tighter
radius of “who we are,” “what we do,”
and “how we make a living,” that presumably
underlie a dominant social rationale
and are quite resistant to change.
However, the fact that cultures develop
unique situational constraints is critical in
understanding the processes of resilience.
For example, the cultural integrity of Egypt
or Mesopotamia—similar at some levels
but not at others—has remained intact
across many millennia, despite changes of
language, religion, and ethnic identity.
Collapse commonly involves demographic
change. A population may be decimated
by warfare, disease, famine, foreign
colonization, migration, expulsion, or
total elimination. Large-scale expulsion
and deportation are verified for the late
Assyrian and Neo-Babylonian empires,
symptomatic of an unstable balance between
human resources and imperial
ambitions. An inability of civilian authorities
or religious ritual to redress the ravages
of epidemic disease can spur social
unrest, and high losses leave land uncultivated
to cause subsequent famine.
Strong demographic declines may not lead
to collapse, but they can put institutional
structures under severe stress, or favor
ecologically harmful land use strategies
of short-term survival.
Since the 15th century CE, major Mediterranean
cities were dependent on Polish
wheat imported by sea (55). Such continental
economic networks are a stabilizing
force, and their breakdown can have global
demographic repercussions. Parallel cycles
of urban growth or decline throughout
Eurasia have been evident during the past
2500 y (9, 11), and have been linked to
climatic perturbations (56) or, more likely,
manpower shortages in the wake of pandemics.
However, as the disastrous modern
famines of Ireland (1840s) and India
(1940s)—each with a mortality of 1 million
or more lives—bear out, millennial or
centennial demographic waves cannot be
explained by single factors.
Constructions of the nature of collapse,
like contemporary opinions of “failing
states,” must be sensitive that some criteria
are inherently Eurocentric, not crosscultural.
Peoples with different historical
experience do not necessarily share
Western perceptions of stress, chaos, or
disaster. This might indirectly affect the
political economy of traditional social
contexts. Given structural constraints and
elite demands, there may well have been
little room for community decision-making
if a top-down leadership screens the
compatibility of new ideas, adaptive
strategies, and behavioral feedbacks. Although
cultural resilience may have been
mainly passive in a longer historical frame,
there are counter-examples such as indigenous
rebellions in Ptolemaic Egypt
(57) or bloody slave and peasant revolts in
Abbasid Mesopotamia (40). Whether uprisings
achieved their desired results is
dubious because they often appear to have
provoked tighter repression. Cultural resilience
is a tricky quality. It may help
resist change, but only up to a certain
threshold, beyond which cascading feedbacks
can trigger unanticipated social or
political transformation.
From Past to Present. Several generalizations
can now be drawn from the case studies and
discussion of historical collapse:
i) The most common input attribute at an
early stage of every breakdown (except
possibly Axum) was institutional
failure, viz. incompetence, loss of economic
networks, corruption, or dynastic
crises.
ii) Civil war or invasion was as critical as
any form of climatic forcing.
iii) Environmental degradation such as soil
erosion is only documented for Axum
and the Black Death (see SI Text), in
contrast to climatic perturbations that
helped trigger breakdowns in Old and
New Kingdom Egypt, the Fayum, or
Mesopotamia on the eve of the Islamic
conquest.
iv) Demographic retraction was prevalent
during or after collapse, commonly
linked with pestilence. The
Black Death is the classic example
of a pathogen-driven, catastrophic
depopulation.
v) Ideological shifts accompanied collapse
in New Kingdom Egypt, the
Fayum, Mesopotamia, and Axum, in
part overlapping with foreign intrusion
or ethnic change.
In other words, poor leadership, administrative
dysfunction, and ideological ambivalence
appear to be endemic to the
processes of collapse. War or climatic perturbations
possibly served as triggering
mechanisms,but environmental degradation
does not appear as a universal variable.
Demographic decline was either a coagency
or a delayed result of change, except for the
Black Death. Collapse was a consequence of
multiple factors, reinforced by various
feedbacks and partly balanced by resilience,
with unpredictable outcomes. The comparative
importance of societal versus environmental
inputs seems to favor the social side.
If the number of case studies is expanded
to include others from this Special Feature,
it adds only two examples of collapse
[Greenland, the Maya (58, 59)], but four
instances in which resilience allowed fundamental
change without simplification or
breakdown (the prehistoric Levant, Iceland,
Cyprus, Colonial Mexico (44, 60–62)].
Reviewing subsistence crises in western
Europe after approximately 1200 CE
identifies food riots, peasant revolts, and
wars of religion, but no radical sociopolitical
transformations until the French Revolution.
This more recent historical
experience also suggests that environmental
or economic disasters do not necessarily
lead to social breakdown or collapse.
However, the late Medieval to early
Modern period in western Europe did see
a continuing and fundamental shift of food
producing and distribution strategies, to
a good degree in response to a series of
wrenching environmental crises. After the
Medieval Warm Period (∼850–1280 CE),
and until the Little Ice Age (∼1570–1860
CE), there were three centuries marked
by extreme climatic perturbations (63,
64) analogous to the seemingly unprecedented
disturbed weather of the past 25 y.
These environmental changes and their
context are encapsulated in the SI Text
because they suggest a transition of focal
length, organization, and available information,
in approaching the intersection
of diachronic and synchronic
perspectives.
The modernization of western European
food production during the past millennium,
as painful as it was for the many, was
decentralized and protracted. It reveals
unexpected resilience and the ability of
people under extreme stress to try new
solutions. It appears that, after overcoming
initial, ideological dissonance, people can
indeed come together to support change.
The key differences with our historical
case studies are structural. Ancient Egypt
and Mesopotamia were authoritarian, with
no feasible bottom-up options, whereas
western European societies were, to a surprising
degree, corporate and participatory
(65), with a high tolerance of individualistic
behavior (66). Change is difficult to
implement in dictatorships that cow their
citizens by force, silence dissent, and
stifle initiative. Megacrises can best be
confronted by flexibility and the cohesion
of most social classes or components
within a particular polity or region.
Historical monitoring across long timescales
is vital to situate the present or apply
to contemporary or future problems of
sustainability (67–69). However, it does not
provide simple prescriptive insights about
the risks of global change, counter-ecological
behavior, pandemics, or sustainability.
What it does do is suggest that all too much
of the alarmist literature that claims to
draw from historical experience is poorly
focused, simplistic, and unhelpful. Our
diachronic investigation implies that the
specter of historical collapse has become
3638 | www.pnas.org/cgi/doi/10.1073/pnas.1114845109 Butzer
a red herring. The pundits should instead
turn their attention to information diffusion
and socioeconomic integration, across class
lines and different spatial scales.
Modern states, even when marginally
dysfunctional, have significant advantages
over their archaic counterparts in terms of
administrative experience, information,
and an increasingly educated and engaged
citizenry. Given the increasing frequency
and scale of disastrous climatic events,
today there is an urgent need for competing
societal elites to downplay ideological
difference and face the realities of global
climate change, anticipating its momentous
socioeconomic implications. These diachronic
insights highlight the importance
of information: better understanding, enlightened
leadership, and opportunities for
broad participation and fresh ideas.
ACKNOWLEDGMENTS. Sheryl Luzzadder Beach,
Georgina Endfield, David Helgren, Andrew
Dugmore, Paul Hudson, Elisabeth Butzer, and Paul
Butzer contributed critical suggestions and feedback.
Cartographic rendering was done by John
Oswald, and Anwar Sounny-Slitine contributed to
the library search.
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