Drying of the American West

“For most people in the region, the news hasn’t
quite sunk in. Between 2000 and 2006 the seven
states of the Colorado basin added five million
people, a 10 percent population increase.
Subdivisions continue to sprout in the desert,
farther and farther from the cities whose own
water supply is uncertain.”
National Geographic
February 2008

Drying of the West

The American West was won by water management.
What happens when there’s no water left to manage?

When provided with continuous nourishment, trees, like people, grow complacent.

Tree-ring scientists use the word to describe
trees like those on the floor of the Colorado
River Valley, whose roots tap into thick
reservoirs of moist soil. Complacent trees aren’t
much use for learning about climate history,
because they pack on wide new rings of wood even
in dry years. To find trees that feel the same
climatic pulses as the river, trees whose rings
widen and narrow from year to year with the river
itself, scientists have to climb up the steep,
rocky slopes above the valley and look for
gnarled, ugly trees, the kind that loggers
ignore. For some reason such “sensitive” trees
seem to live longer than the complacent ones.
“Maybe you can get too much of a good thing,”
says Dave Meko.

Meko, a scientist at the Laboratory of Tree-Ring
Research at the University of Arizona, has been
studying the climate history of the western
United States for decades. Tree-ring fieldwork is
hardly expensive-you need a device called an
increment borer to drill into the trees, you need
plastic straws (available in a pinch from
McDonald’s) to store the pencil-thin cores you’ve
extracted from bark to pith, and you need gas,
food, and lodging. But during the relatively wet
1980s and early ’90s, Meko found it difficult to
raise even the modest funds needed for his work.
“You don’t generate interest to study drought
unless you’re in a drought,” he says. “You really
need a catastrophe to get people’s attention,”
adds colleague Connie Woodhouse.

Then, in 2002, the third dry year in a row and
the driest on record in many parts of the
Southwest, the flow in the Colorado fell to a
quarter of its long-term average. That got
people’s attention.

The Colorado supplies 30 million people in seven
states and Mexico with water. Denver, Las Vegas,
Phoenix, Tucson, Los Angeles, and San Diego all
depend on it, and starting this year so will
Albuquerque. It irrigates four million acres of
farmland, much of which would otherwise be
desert, but which now produces billions of
dollars’ worth of crops. Gauges first installed
in the 19th century provide a measure of the flow
of the river in acre-feet, one acre-foot being a
foot of water spread over an acre, or about
326,000 gallons. Today the operation of the
pharaonic infrastructure that taps the
Colorado-the dams and reservoirs and pipelines
and aqueducts-is based entirely on data from
those gauges. In 2002 water managers all along
the river began to wonder whether that century of
data gave them a full appreciation of the river’s
eccentricities. With the lawns dying in Denver, a
water manager there asked Woodhouse: How often
has it been this dry?

Over the next few years Woodhouse, Meko, and some
colleagues hunted down and cored the oldest
drought-sensitive trees they could find growing
in the upper Colorado basin, both living and
dead. Wood takes a long time to rot in a dry
climate; in Harmon Canyon in eastern Utah, Meko
found one Douglas fir log that had laid down its
first ring as a sapling in 323 B.C. That was an
extreme case, but the scientists still collected
enough old wood to push their estimates of annual
variations in the flow of the Colorado back deep
into the Middle Ages. The results came out last
spring. They showed that the Colorado has not
always been as generous as it was throughout the
20th century.

The California Department of Water Resources,
which had funded some of the research, published
the results as an illustrated poster. Beneath a
series of stock southwestern postcard shots, the
spiky trace of tree-ring data oscillates
nervously across the page, from A.D. 762 on the
left to 2005 on the right. One photo shows the
Hoover Dam, water gushing from its outlets. When
the dam was being planned in the 1920s to deliver
river water to the farms of the Imperial Valley
and the nascent sprawl of Los Angeles, the West,
according to the tree rings, was in one of the
wettest quarter centuries of the past millennium.
Another photo shows the booming skyline of San
Diego, which doubled its population between 1970
and 2000-again, an exceptionally wet period along
the river. But toward the far left of the poster,
there is a picture of Spruce Tree House, one of
the spectacular cliff dwellings at Mesa Verde
National Park in southwestern Colorado, a pueblo
site abandoned by the Anasazi at the end of the
13th century. Underneath the photo, the graph
reveals that the Anasazi disappeared in a time of
exceptional drought and low flow in the river.

In fact, the tree rings testified that in the
centuries before Europeans settled the Southwest,
the Colorado basin repeatedly experienced
droughts more severe and protracted than any
since then. During one 13-year megadrought in the
12th century, the flow in the river averaged
around 12 million acre-feet, 80 percent of the
average flow during the 20th century and
considerably less than is taken out of it for
human use today. Such a flow today would mean
serious shortages, and serious water wars. “The
Colorado River at 12 million acre-feet would be
real ugly,” says one water manager.

Unfortunately, global warming could make things
even uglier. Last April, a month before Meko and
Woodhouse published their latest results, a
comprehensive study of climate models reported in
Science predicted the Southwest’s gradual descent
into persistent Dust Bowl conditions by
mid-century. Researchers at the National Oceanic
and Atmospheric Administration (NOAA), meanwhile,
have used some of the same models to project
Colorado streamflow. In their simulations, which
have been confirmed by others, the river never
emerges from the current drought. Before
mid-century, its flow falls to seven million
acre-feet-around half the amount consumed today.

The wet 20th century, the wettest of the past
millennium, the century when Americans built an
incredible civilization in the desert, is over.
Trees in the West are adjusting to the change,
and not just in the width of their annual rings:
In the recent drought they have been dying off
and burning in wildfires at an unprecedented
rate. For most people in the region, the news
hasn’t quite sunk in. Between 2000 and 2006 the
seven states of the Colorado basin added five
million people, a 10 percent population increase.
Subdivisions continue to sprout in the desert,
farther and farther from the cities whose own
water supply is uncertain. Water managers are
facing up to hard times ahead. “I look at the
turn of the century as the defining moment when
the New West began,” says Pat Mulroy, head of the
Southern Nevada Water Authority. “It’s like the
impact of global warming fell on us overnight.”

In July 2007 a few dozen climate specialists
gathered at Columbia University’s Lamont-Doherty
Earth Observatory to discuss the past and future
of the world’s drylands, especially the
Southwest. Between sessions they took coffee and
lunch outside, on a large sloping lawn above the
Hudson River, which gathers as much water as the
Colorado from a drainage area just over a
twentieth the size. It was overcast and
pleasantly cool for summer in New York. Phoenix
was on its way to setting a record of 32 days in
a single year with temperatures above 110°F. A
scientist who had flown in from the West Coast
reported that he had seen wildfires burning all
over Nevada from his airplane window.

On the first morning, much of the talk was about
medieval megadroughts. Scott Stine of California
State University, East Bay, presented vivid
evidence that they had extended beyond the
Colorado River basin, well into California. Stine
works in and around the Sierra Nevada, whose
snows are the largest source of water for that
heavily populated state. Some of the runoff
drains into Mono Lake on the eastern flank of the
Sierra. After Los Angeles began diverting the
streams that feed Mono Lake in the 1940s, the
lake’s water level dropped 45 vertical feet.

In the late 1970s, tramping across the newly
exposed shorelines, Stine found dozens of tree
stumps, mostly cottonwood and Jeffrey pine,
rooted in place. They were gnarled and ancient
looking and encased in tufa-a whitish gray
calcium carbonate crust that precipitates from
the briny water of the lake. Clearly the trees
had grown when a severe and long-lasting drought
had lowered the lake and exposed the land where
they had taken root; they had died when a return
to a wetter climate in the Sierra Nevada caused
the lake to drown them. Their rooted remains were
now exposed because Los Angeles had drawn the
lake down.

Stine found drowned stumps in many other places
in the Sierra Nevada. They all fell into two
distinct generations, corresponding to two
distinct droughts. The first had begun sometime
before 900 and lasted over two centuries. There
followed several extremely wet decades, not
unlike those of the early 20th century. Then the
next epic drought kicked in for 150 years, ending
around 1350. Stine estimates that the runoff into
Sierran lakes during the droughts must have been
less than 60 percent of the modern average, and
it may have been as low as 25 percent, for
decades at a time. “What we have come to consider
normal is profoundly wet,” Stine said. “We’re
kidding ourselves if we think that’s going to
continue, with or without global warming.”

No one is sure what caused the medieval
megadroughts. Today Southwestern droughts follow
the rhythm of La Niña, a periodic cooling of the
eastern equatorial Pacific. La Niña alternates
every few years with its warm twin, El Niño, and
both make weather waves around the globe. A La
Niña cooling of less than a degree Celsius was
enough to trigger the recent drought, in part
because it shifted the jet stream and the track
of the winter storms northward, out of the
Southwest. Richard Seager, of Lamont, and his
colleagues have shown that all the western
droughts in the historical record, including the
Dust Bowl, can be explained by small but
unusually persistent La Niñas. Though the
evidence is slimmer, Seager thinks the medieval
megadroughts too may have been caused by the
tropical Pacific seesaw getting stuck in
something like a perpetual La Niña.

The future, though, won’t be governed by that
kind of natural fluctuation alone. Thanks to our
emissions of greenhouse gases, it will be subject
as well to a global one-way trend toward higher
temperatures. In one talk at Lamont, climate
theorist Isaac Held, from NOAA’s Geophysical
Fluid Dynamics Laboratory in Princeton, gave two
reasons why global warming seems almost certain
to make the drylands drier. Both have to do with
an atmospheric circulation pattern called Hadley
cells. At the Equator, warm, moist air rises,
cools, sheds its moisture in tropical downpours,
then spreads toward both Poles. In the
subtropics, at latitudes of about 30 degrees, the
dry air descends to the surface, where it sucks
up moisture, creating the world’s deserts-the
Sahara, the deserts of Australia, and the arid
lands of the Southwest. Surface winds export the
moisture out of the dry subtropics to temperate
and tropical latitudes. Global warming will
intensify the whole process. The upshot is, the
dry regions will get drier, and the wet regions
will get wetter. “That’s it,” said Held. “There’s
nothing subtle here. Why do we need climate
models to tell us that? Well, we really don’t.”

A second, subtler effect amplifies the drying. As
the planet warms, the poleward edge of the Hadley
cells, where the deserts are, expands a couple of
degrees latitude farther toward each Pole. No one
really knows what causes this effect-but nearly
all climate models predict it, making it what
modelers call a robust result. Because the
Southwest is right on the northern edge of the
dry zone, a northward shift will plunge the
region deeper into aridity.

As the meeting neared its close, Held and Seager
stood out on the lawn, discussing Hadley cells
and related matters through mouthfuls of coffee
and doughnuts. The two men had lately become
collaborators, and a few months before had
published with colleagues the sobering Science
paper analyzing the results of 19 different
simulations done by climate modeling groups
around the world. They then averaged all these
results into an “ensemble.” The ensemble shows
precipitation in the Southwest steadily declining
over the next few decades, until by mid-century,
Dust Bowl conditions are the norm. It does not
show the Pacific locked in a perpetual La Niña.
Rather, La Niñas would continue to happen as they
do today (the present one is expected to continue
at least through the winter of 2008), but against
a background state that is more profoundly arid.
According to the ensemble model, the descent into
that state may already have started.

People are not yet suffering, but trees are.
Forests in the West are dying, most impressively
by burning. The damage done by wildfires in the
U.S., the vast majority of them in the West, has
soared since the late 1980s. In 2006 nearly ten
million acres (four million hectares) were
destroyed-an all-time record matched the very
next year. With temperatures in the region up
four degrees F over the past 30 years, spring is
coming sooner to the western mountains. The
snowpack-already diminished by drought-melts
earlier in the year, drying the land and giving
the wildfire season a jump start. As hotter
summers encroach on autumn, the fires are ending
later as well.

The fires are not only more frequent; they are
also hotter and more damaging-though not entirely
because of climate change. According to Tom
Swetnam, director of the University of Arizona
tree-ring lab, the root cause is the government’s
policy, adopted early in the 20th century, of
trying to extinguish all wildfires. By studying
sections cut from dead, thousand-year-old giant
sequoias in the Sierra Nevada and from ponderosa
pines all over Arizona and New Mexico, Swetnam
discovered that most southwestern forests have
always burned often-but at low intensity, with
flames just a few feet high that raced through
the grasses and the needles on the forest floor.
The typical tree bears the marks of many such
events, black scars where flames ate through the
bark and perhaps even took a deep wedge out of
the tree, but left it alive to heal its wound
with new growth. Suppressing those natural fires
has produced denser forests, with flammable
litter piled up on the floor, and thickets of
shrubs and young trees that act as fire ladders.
When fires start now, they don’t stay on the
ground-they shoot up those ladders to the crowns
of the trees. They blow thousand-acre holes in
the forest and send mushroom clouds into the air.

One day last summer, Swetnam took a few visitors
up Mount Lemmon, just north of Tucson, to see
what the aftermath of such events looks like. In
May 2002 the Bullock fire roared up the northeast
slope of Mount Lemmon, consuming 30,000 acres.
Firefighters stopped it at the Catalina Highway,
protecting the village of Summerhaven. But the
very next year, the Aspen fire started on the
slope just below the village, destroying nearly
half of the 700-odd houses in Summerhaven and
burning 85,000 acres, all the way down to the
outskirts of Tucson. The entire mountainside
beyond the village remains covered with the gray
skeletons of ponderosa pines, like one big blast
zone. “Ponderosa pine is not adapted to these
crown fires,” Swetnam said, contemplating the
site from the scenic overlook above the village.
“It has heavy, wingless seeds that don’t go very
far. When you get a large hole like this, it will
take hundreds of years to fill in from the edges.”

Mount Lemmon’s forests are also experiencing a
slower, broader change. The Catalina Highway
starts out flat, at an altitude of 2,500 feet in
the Sonoran Desert, with its saguaros and strip
malls. As the road leaves the last of Tucson
behind, it climbs steeply through the whole range
of southwestern woodland ecosystems-first scrub
oak, then piñon and juniper, then ponderosa pine
and other conifers, until finally, after less
than an hour and a climb of 7,000 feet, you reach
the spruce and fir trees on the cool peak. There
is a small ski area there, the southernmost in
the United States, and its days are certainly

As Swetnam explained, the mountain is one of an
archipelago of “sky islands” spread across
southeastern Arizona, New Mexico, Texas, and into
Mexico-mountains isolated from one another by a
sea of desert or grassland. Like isles in the
ocean, these islands are populated in part by
endemics-species that live nowhere else. The
sky-island endemics are cool- and wet- loving
species that have taken refuge on the
mountaintops since the last ice age. They are
things like the corkbark fir, or the endangered
red squirrel that lives only on nearby Mount
Graham. Their future is as bleak as that of the
ski area. “They’ll be picked off the top,” said
Swetnam. “The islands are shrinking. The aridity
is advancing upslope.”

All over the Southwest, a wholesale change in the
landscape is under way. Piñons and scrubbier,
more drought-resistant junipers have long been
partners in the low woodlands that clothe much of
the region. But the piñons are dying off. From
2002 to 2004, 2.5 million acres turned to rust in
the Four Corners region alone. The immediate
cause of death was often bark beetles, which are
also devastating other conifers. The Forest
Service estimates that in 2003, beetles infested
14 million acres of piñon, ponderosa, lodgepole
pine, and Douglas fir in the American West.

Bark beetles tend to attack trees that are
already stressed or dying from drought. “They can
smell it,” says Craig Allen, a landscape
ecologist at Bandelier National Monument in the
Jemez Mountains of New Mexico. Global climate
change may be permanently teasing the piñons and
junipers apart, and replacing piñon-juniper
woodland with something new. At Bandelier, Allen
has observed that junipers, along with shrubs
such as wavyleaf oak and mountain mahogany, now
dominate the beetle-ravaged landscape: pockets of
green gradually spreading beneath a shroud of
dead piñons.

Just as there are global climate models, there
are global models that forecast how vegetation
will change as the climate warms. They predict
that on roughly half of Earth’s surface,
something different will be growing in 2100 than
is growing there now. The models are not good,
however, at projecting what scientists call
“transient dynamics”-the damage done by droughts,
fires, and beetle infestations that will actually
accomplish the transformation. Large trees cannot
simply migrate to higher latitudes and altitudes;
they are rooted to the spot. “What happens to
what’s there now?” Allen wonders. “Stuff dies
quicker than it grows.”

Over the next few decades, Allen predicts, people
in the Southwest will be seeing a lot of death in
the old landscapes while waiting for the new ones
to be born. “This is a dilemma for the Park
Service,” he says. “The projections are that
Joshua trees may not survive in Joshua Tree
National Park. Sequoias may not survive in
Sequoia National Park. What do you do? Do you
irrigate these things? Or do you let a
2,000-year-old tree die?”

While the trees die, the subdivisions
proliferate. “Our job was to entice people to
move to the West, and we did a darn good job,”
says Terry Fulp, who manages water releases at
Hoover Dam. The federal Bureau of Reclamation
built the dam in the 1930s primarily to supply
the vegetable farms of the Imperial Valley and
only secondarily to supply the residents of Los
Angeles. Farmers had first claim to the
water-they still do-but there was plenty to go
around. “At Lake Mead, we basically gave the
water away,” says Fulp. “At the time, it made
perfect sense. There was no one out here.” After
Reclamation built Hoover and the other big dams,
more people came to the desert than anyone ever
expected. Few of them are farmers anymore, and
farming, crucial as it is to human welfare, is
now a small part of the economy. But it still
uses around three-quarters of the water in the
Colorado River and elsewhere in the Southwest.

In the wet 1920s, as the dam was being planned,
seven states drew up the Colorado River Compact
to divvy up 15 million acre-feet of its water.
California, Nevada, and Arizona-the so-called
Lower Basin states-would get half, plus any
surplus from the Upper Basin states of Wyoming,
Colorado, New Mexico, and Utah. The compact also
acknowledged Mexico’s rights to the water.
Surpluses were almost always on hand, because the
Upper Basin states have never fully used the 7.5
million acre-feet they are entitled to under the
compact. They are only entitled to use it, in
fact, if in so doing they don’t prevent the Lower
Basin states from getting their 7.5 million-the
compact is unfair that way. But in the wet 20th
century, it didn’t seem to matter.

In 1999 both Lake Mead and Lake Powell-created in
1963 upstream of Lake Mead to ensure that the
Upper Basin would have enough water even in
drought years to meet its obligation to the Lower
Basin-were nearly full, with 50 million acre-feet
between them. Two years later, representatives of
the states in the basin completed long and
difficult negotiations with the Bureau of
Reclamation on new guidelines for dividing up the
surpluses from Lake Mead. Then came the drought.
Both lakes are now only half full. “Those
guidelines are almost a joke now,” says the
Southern Nevada Water Authority’s Pat Mulroy.
“All of a sudden, seven states that had spent
years in surplus discussions had to turn on a
dime and start discussing shortages.”

Mulroy, a crisp, tanned, fiftysomething blonde
with a tailored look and a forceful personality,
has run the Las Vegas water district since 1989.
During that time she has watched the area’s
population growth consistently outstrip
demographic projection. The population is almost
two million now, having grown by 25 percent
during the drought years; Mulroy is convinced it
will go to three million. Before the drought, she
and her colleagues nevertheless thought their
water supply, 90 percent of it from Lake Mead,
was safe for 50 years. In 2002 they were
celebrating the opening of a second water intake
from Lake Mead, 50 feet lower than the old one,
which more than doubled their pumping capacity.
Now they are scrambling to insert a third “straw”
even deeper into the sinking lake. Las Vegas is
also trying to reduce its dependence on the
Colorado. The SNWA is exercising water rights and
buying up ranches in the east-central part of the
state. It plans to sink wells and tap groundwater
there and pump as much as 200,000 acre-feet of it
through a 250-mile pipeline to the city. There is
considerable local opposition, of course, and an
environmental impact statement must be
prepared-but there is “zero chance,” Mulroy says
grimly, that the pipeline won’t be built.

Other southwestern cities are also realizing
their vulnerability to drought. Phoenix, hellish
as it is in summer and bisected by the dry bed of
the Salt River, is better off than most-for the
moment. “In 2002 Phoenix was virtually the only
city in the Southwest that had no mandatory
restrictions,” says Charlie Ester, water
resources manager at the Salt River Project in
Phoenix. “We didn’t need them.” Phoenix pumps
groundwater whenever it needs to, though it is
under a state mandate to stop depleting the
aquifer. And it gets a little over a third of its
water from the Colorado River via the Central
Arizona Project, a 336-mile-long canal. But the
Salt River remains its biggest source. The
riverbed is dry in the city because the SRP has
half a dozen dams in the mountains north and east
of the city, which convert the Salt and its
tributary, the Verde, into chains of terraced

Phoenix would thus seem to possess that holy
grail of water managers: a diversified portfolio.
But Ester was still disconcerted to see his lake
levels dropping in the drought, until they were
less than half full. After he called the
tree-ring lab, Dave Meko and climatologist Katie
Hirschboeck looked into the tree-ring records for
the Salt and Verde Rivers’ watersheds.

“They found they were virtually identical,” Ester
says. “There were only three years out of 800
where the Colorado was wet and the Salt was dry
or vice versa. What that means is, if we have a
bad drought in Arizona, and the Salt dries up, we
can’t rely on the Colorado to bail us out. So
what are we going to do? Well, we’re going to
hurt. Or move.”

Since the Hoover Dam was built, there has never
been a water shortage on the Colorado, never a
day when there was simply not enough water in
Lake Mead to meet all the downstream allocations.
Drought, and a realistic understanding of the
past, have made such a day seem more imminent.
Under the pressure of the drought, the seven
Colorado basin states have agreed for the first
time on how to share prospective shortages.
Arizona will bear almost all the pain at first,
because the Central Arizona Project, which came
on line in 1993, has junior rights. Nevada will
lose only a small percentage of its allotment.

Meanwhile California would give up nothing, at
least until Lake Mead falls below 1,025 feet,
nearly 200 feet below “full pool.” At that point,
negotiations would resume. According to Bureau of
Reclamation calculations, a return of the
12th-century drought would force Lake Mead well
below that level, perhaps even to “dead pool” at
895 feet-the level at which water no longer flows
out of the lake without pumping. Reclamation
officials consider this extremely unlikely. But
their calculations do not take into account the
impact of global warming.

Every utility in the Southwest now preaches
conservation and sustainability, sometimes very
forcefully. Las Vegas has prohibited new front
lawns, limited the size of back ones, and offers
people two dollars a square foot to tear existing
ones up and replace them with desert plants.
Between 2002 and 2006, the Vegas metro area
actually managed to reduce its total consumption
of water by around 20 percent, even though its
population had increased substantially.
Albuquerque too has cut its water use. But every
water manager also knows that, as one puts it,
“at some point, growth is going to catch up to

Looking for new long-term sources of supply, many
water managers turn their lonely eyes to the
Pacific, or to deep, briny aquifers that had
always seemed unusable. Last August, El Paso
inaugurated a new desalination plant that will
allow the city to tap one such aquifer. The same
month, the Bureau of Reclamation opened a new
research center devoted to desalination in
Alamogordo, New Mexico. The cost of desalination
has dropped dramatically-it’s now around four
dollars per thousand gallons, or as little as
$1,200 per acre-foot-but that is still
considerably more than the 50 cents per acre-foot
that the Bureau of Reclamation charges municipal
utilities for water from Lake Mead, or the zero
dollars it charges irrigation districts. The
environmental impacts of desalination are also
uncertain-there is always a concentrated brine to
be disposed of. Nevertheless, a large
desalination plant is being planned in San Diego
County. In Las Vegas, Mulroy envisions one day
paying for such a plant on the coast of
California or Mexico, in exchange for a portion
of either’s share of the water in Lake Mead. “The
problem is, if there’s nothing in Lake Mead,
there’s nothing to exchange,” she says.

A more obvious solution for cities facing
shortages is to buy irrigation water from
farmers. In 2003 the Imperial Irrigation District
was pressured into selling 200,000 of its three
million acre-feet of Colorado water to San Diego,
as part of an overall deal to get California to
stop exceeding its allotment. San Diego paid
nearly $300 per acre-foot for water that the
farmers in the Imperial Valley get virtually for
free. The government favors such market
mechanisms, says the Bureau of Reclamation’s
Terry Fulp, “so people who really want the water
get it.” At that price, the irrigation water in
the Imperial Valley is worth nearly as much as
its entire agricultural revenue, which is around
a billion dollars a year. But not everyone favors
drying up farms so that more water will be
available for subdivisions. The valley is one of
the poorest regions in California, yet the
richest farmers stand to benefit most from the
sale. Many more people fear the loss of jobs and,
ultimately, of a whole way of life.

The West was built by dreamers. The men who
conceived Hoover Dam were, in the words beneath a
flagpole on the Nevada side, “inspired by a
vision of lonely lands made fruitful.” As the
climate that underpinned that expansive vision
vanishes, the vision needed to replace it has not
yet emerged. In a drying climate, the human
ecosystems established in a wetter one will have
to change-die and be replaced by new ones. The
people in the Southwest face the same uncertain
future, the same question, as their forests: What
happens to the stuff that’s there now?

In the second half of the 13th century, as a
drying trend set in, people who had lived for
centuries at Mesa Verde moved down off the mesa
into the canyons. They built villages around
water sources, under overhangs high up in the
walls of the cliffs, and climbed back up the
cliffs to farm; their handholds in the rock are
still visible. Some of the villages were
fortified, because apparently their position on a
cliff face was not defense enough. Those cliff
dwellings, abandoned now for seven centuries but
still intact and eerily beautiful, are what
attract so many visitors today. But they are
certainly not the product of an expansive,
outward-looking civilization. They are the
product of a civilization in a crouch, waiting to
get hit again. In that period, the inhabitants of
the Mesa Verde region began carving petroglyphs
suggesting violent conflict between men armed
with shields, bows and arrows, and clubs. And
then, in the last two or three decades of the
century, right when the tree rings record one of
the most severe droughts in the region, the people left.
They never came back.

– END –

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