Title: Black Gold of the Amazon
Author: Michael Tennesen
Source: DISCOVER, April 2007, p. 68
Data Base: C
BLACK GOLD OF THE AMAZON
(Fertile, charred soil created by pre-Columbian peoples sustained
surprisingly large settlements in the rain forest. Secrets of that
ancient "dark earth" could help solve the Amazons ecological
problems today.)
by Michael Tennesen
On August 13, 2005, a Saturday evening, American archaeologist James
Petersen, Brazilian archeologist Eduardo Neves, and several others
pulled up to a restaurant on a jungle road near Iranduba in the
Brazilian Amazon to have a beer. At about 6:45 p.m., two young men,
one brandishing a 38 revolver, entered the restaurant and demanded
the patrons' money. The archeologists turned over their money and
the bandits started to leave. Then, almost as an afterthought, one
of them shot Peterson in the stomach. Neves and the others raced
Petersen to the hospital, but their friend bled to death before they
could reach help.
State and municipal police reacted quickly to the news, cordoned off
roads, and brought suspects to the restaurant for identification.
Within 24 hours they had arrested the two armed bandits and their
driver and learned there were two others involved. The crime was
front-page news in Manaus, the capital of the state, a city of more
than a million, about an hour north of the study site, across the
Rio Negro. After a 21-day manhunt through the jungle, the remaining
two fugitives were captured, and when the state police brought the
criminals back, the Iranduba Chief of Police, Normando Barbosa says,
"There were hundreds of people lined up on the road that wanted to
lynch the killers."
Over the past decade, Petersen, Neves, and their band of archeologists
had become local heroes, earning the appreciation of the surrounding
community during seasonal digs conducted on the peninsula that
separated the Rio Negro and Amazon Rivers. At over 100 sites across
the peninsula, Peterson and his colleagues had unearthed evidence of
early civilizations that were far more advanced, far more broadly
connected, and far more densely occupied than the small bands of
nomadic hunter-gatherers previously hypothesized for the region.
Before the Europeans arrived, this peninsula in the heart of the Amazon
was home to communities with roads, irrigation, agriculture, soil
management, ceramics, and extended trade. These civilizations, Neves
says, were as complex as the southwest Native American cultures that
inhabited Chaco Canyon and Mesa Verde. But due to the scarcity of
stone in the Amazon, the people built with wood, and over time the
structures disintegrated, leaving little evidence of the culture.
One legacy, however, remains: their soil. "Terra preta do Indio"
-Portuguese for Indian black earth-is prized among local farmers,
and it is a direct contribution of the vanished Amazonian cultures.
While most Amazonian earth is notoriously nutrient-poor, yellowish,
sterile, and unscented, there are extensive patches of soil that are
mysteriously dark, moist, fragrant, and filled with insects, microbial
life, and organic matter. Scholars have come to realize that by
devising a way to enrich the soil, the early inhabitants of the Amazon
managed to create a foundation for agriculture-based settlements much
more populous than scholars had thought possible.
Petersen had called the soil a gift from the past, and he believed it
would reveal the region's past cultures in a new, much more complex
light. At the time of his death, he and his colleagues had been developing
a workshop for teachers in the region on the science and archaeology
surrounding terra preta. The discovery held meaning for more than
archaeologists, however. Figuring out the composition of dark earth-and
how it was formed-offers a way to improve not only soil fertility for
small farmers, but also to curb carbon emissions from the fires that
small farmers set to clear the forest. Yet after Peterson's murder
the project was shut down, and those that had gathered for both the
workshop and the August field season were sent home. Had the Amazon
proved too dangerous for such a gathering?
****
In 1542, the Spanish explorer Francisco de Orellana ventured into the
Amazon Basin and along the Rio Negro to hunt for the mythic city of El
Dorado and its rumored treasure of gold. Instead his expedition found
a network of farms, villages, and cities. "His chronicles describe
large villages, long range trade networks, paramount chiefs almost
like nobility, and they talked about the Amazon being highly
populated," says Neves.
No one ever saw those populations again.
The first scientists who studied the Amazon found little evidence to
support Orellana's claims of large populations. As productive and
lush as the rainforest appeared, the soil it stood on was dirt poor.
Betty J. Meggers, a Smithsonian archeologist who worked in the Amazon
from the mid 1900s, referred to the region as "A Counterfeit
Paradise." The apparent lushness existed only because the vegetation
was so good at sucking up every speck of nutrient released from
decaying leaves. Any nutrients remaining in the soil washed away in
the frequent rains. In short, the local soil was ill-suited for
agriculture, and without agriculture, societies would remain small.
The outcome of the slash-and-burn agriculture that is practiced today
supports that view. In this method, settlers cut down forests and burn
the cover in order to grow crops in the nitrogen and mineral-rich ash
that is left behind. But the soil in these denuded plots is productive
for only a few years before it reverts to its original nutrient-poor
state. The lack of agricultural potential helped popularize a model of
the Pre-Columbian occupation that anthropologist Michael Heckenberger
of the University of Florida, TK town, describes as "the myth of
stone-age savages frozen at the dawn of time."
Heckenberger's own experience had led him to question that view. In the
early '90s, while living with the Kuikuro Indigenous tribe in the upper
Xingu region-about 600 miles southeast of Manaus-he discovered a ruling
class structure more complex than needed for a group of only 300 people.
Could there have been a grander past? When he dug beyond the village
borders he found vast amounts of broken pottery, along with evidence of
a giant plaza, roads, causeways, canals, and even bridges-the remains
of an earlier, much larger civilization.
In the mid-1990s Heckenberger invited Peterson, his former teacher, to
spend time at his field site. After visiting the Kuikuro in the Xingu,
they took a short excursion, traveling up the Rio Negro from its
junction with the Amazon at Manaus. One day Heckenberger headed out by
himself on a boat that ended up on a Rio Negro beach, where a farmer
was tilling the soil and turning up mounds of broken ceramics embedded
in coal-black terra preta. Heckenberger could see that this rich soil
extended over an area two miles along the Rio Negro shore. He collected
some pottery samples and took them back to show Petersen, a ceramics
expert. The abundance of the pottery piqued Peterson's growing interest
in the mystery of Amazon settlements.
In the months to follow, the two worked to develop a project around the
site with Neves, and the Central Amazon Project was born. They wrote up
institutional agreements, permits, got seed money, and began fieldwork
in 1995. Their early finds seemed to challenge the Meggers' vision of
the pre-Columbian Amazon, so the group turned to another model proposed
by Donald Lathrap, an archeologist at University of Illinois. In the
1960s, he had hypothesized from linguistic and ceramic evidence that the
confluence of the Amazon, Rio Negro, and Madera rivers may have been the
heart of an agriculturally-based civilization that once extended from
the Caribbean to Southern Brazil.
Heckenberger left the Central Amazon Project in 1999 to concentrate on
the Kuikuro, but Petersen and Neves continued. Over the years,
excavation expanded beyond the original site, called Acutuba, to
include other spots in a 20-square mile area on the peninsula that
juts between the Amazon and Rio Negro Rivers. Gradually funding switched
from U.S. institutions to predominantly Brazilian, and Neves took more
of an oversight capacity. But Petersen continued to participate every
summer. In a 2005 interview with the Vermont Quarterly, Peterson called
his Central Amazon research "some of the richest, most exciting
archeology anywhere on the planet."
****
In August of 2006, the archeologists of the Central Amazon Project touch
down at the international airport in Manaus and travel two hours by boat
and car to Iranduba. It is the first time the members-up to 30 or 40
depending on the day-have gathered since Petersen's death. Eduardo Neves
oversees the project, coordinating the comings and goings of the
visiting archeologists like a proud parent. Eleven years after its
founding, the Project has expanded from the initial Autuba site to 10
active excavations out of more than 100 Pre-Columbian sites discovered
on this small peninsula.
Neves is eager to introduce the group's excavation sites, which he
believes represent a microcosm of what was going on in prehistoric times
along the flood plains of the Amazon River. The oldest site, Donna
Stella, contains artifacts that have been dated as far back as 7000 BC.
According to Fernando Costa, a Ph.D. student at the University of Sao
Paulo who runs this site, Donna Stella was a quarry, one of the rare
spots in the Amazon that had stone hard enough to make tools. "The
people here had projectile points, axes, scrappers, at least 10 to
15 kinds of tools in all," Costa says.
Yet traces of habitation vanish after about 1500 years "and we don't
see them until more than 5000 years later, " Neves says. He suspects
the people may have vanished due to a longterm drought. Whatever the
reason, humans do not reappear in the Central Amazon until about
300 BC. The culture of the time is known as the Autuba phase, and
"people are already farmers, playing around with a variety of domestic
plants, and making fancy, elaborate ceramics," Neves says.
In the afternoon, Neves takes me to the Hatahara site, about eight
miles from Donna StellaCK, which contains traces of a more agricultural
way of life. Here pottery shards litter the ground. At one of the
site's two excavations, the broken bits stick out from the earthen walls
of a large square pit. The layers of protruding pottery are so tight
and thick they look almost like wall coverings.
The Hatahara site showcases four separate occupations by sedentary farmers.
The people of the Autuba phase, who are thought to have come from
the Caribbean coast, may have been the first to settle the area, living
in villages up to five acresCK in size, with each supporting 100 to 200
people. Neves believes that they lived on fish, wild meats, palms,
fruits, and manioc, a root that can grow in poorer soils year round.
Although this early culture had only rudimentary agricultural practices,
Neves says, the plant and animal refuse they were leaving provided the
substrate for future terra preta soils.
Helena Lima, a PhD student at the University of Sao Paulo, is trying to
pinpoint when and how this soil was used to support greater populations
in the Amazon Basin. She sees a stark difference between the Autuba
phase, from 300 BC to 400 AD, and the later Manacapuru phase from 400
to 900 AD. "The Manacapuru were the first people who really changed the
soil," she says.
The terra preta soils at Hatahara and the other sites are made from a
mixture of plant refuse and animal and fish bones, along with large
quantities of charcoal deposited when settlers, lacking tools stronger
than stone, used stone axes and slow-burning fires to clear forest.
Such smoldering fires produced more charcoal than ash. The charcoal,
soot, and other carbon remains (collectively called bio-char) in turn
retained more nutrients, particularly potassium and phosphorous,
which are limited in tropical soils. The resulting improvement in soil
fertility may have supported a larger, more stable crop-based population,
although studies of fossilized pollen have not yet revealed the plants
cultivated.
The next phase, the Paredo, occurred from about 700 to 1200 AD, and
Neves suspects the Paredao were outsiders from the south. The
occupation is peaceful, though, and the Paredo and the Manacapuru
live and trade with each other.
The Paredo exploited terra preta soils even more than their
predecessors. While the initial settlers in this area may have built
the dark soils by accident, William Woods, director of environmental
studies at the University of Kansas, says, "at some point they recognize
their importance and start to promote them." Over time, the villages of
the Paredo become larger, denser, and surrounded by agricultural fields.
Populations grow into the thousands in sites ranging from five to 40
acres, and the lack of fortification strongly suggests that the people
lived in peace.
But around 1200 , the Guarita people from the east start to threaten,
and the Paredo begin building defensive structures. This phase lasts
into the European occupation. Over the same period, the Paredo vanish.
The Guarita apparently moved in from areas near the mouth of the Amazon,
which have even more terra preta soils than the Paredo, and bring with
them wilder, multicolored styles of pottery.
"They are like the Barbarians attacking the Romans," Neves speculates.
He suspects that the newcomers may also have had a valuable
possession-corn. This new, more nutritious staple requires better
soils, and it is not unreasonable to suspect that Guarita drove the
Paredo out to take over their terra preta.
The condition of the interred remains suggests that the inhabitants of
all four occupations were robust-a wellbeing that extended even after
death. In their catalog of the site's human remains, Anne Rapp and her
husband Claide Moraes, both students at the University of Sao Paulo,
find evidence that hints at ceremonial procedures, priests, and
perhaps a cottage industry of funerary artisans as well.
Although the Central Amazon may not have been the center of the empire
that Lathrop envisioned, the evidence from these culturesCK doesn't
match up at all to Meggers' idea of a stunted, counterfeit paradise.
****
As thrilling as this evidence is for archaeologists, it excites even
staid soil scientists like Johannes Lehman of Cornell University. His
interest in dark-earth studies is not based on inferences from the
archaeological record, but upon laboratory analysis and recreation of
the mysterious terra preta itself. In it, he sees the potential for
creating sustainable farming practices-and even combating global
warming.
Lehmann explains that nutrients from plant and animal remains-like
nitrogen, phosphate, and potassium-bind to the charcoal or bio-char,
preventing them from being washed away by the constant rains or
evaporating into the air. As the charcoal ages, it breaks down in the
soil. Micropores in the charcoal provide more surfaces for nutrients
to adhere to, which in turn encourages microorganisms to colonize the
soil. Somehow this process results in soil with up to 10 times as much
carbon as unaltered soils nearby. Although the complete transformation
of soil ingredients to true terra pretra may take more than four years,
soil scientists believe that the mixture can have immediate effects
when added to nutrient-poor soils. Experiments outside of Manaus have
shown that plots treated with charcoal and fertilizer (which contains
plant nutrients)-a mix akin to terra preta- yielded as much as 880
percent more than plots with fertilizer alone.
In 2001 Petersen published a paper reporting one example of a farmer
who had cultivated on terra preta soils near Autuba for 40 years
without ever adding any fertilizer. "That's incredible," Woods says.
"We don't get that in Iowa." A few years of Amazonian rains will
wash away the nutrient-laden ash from slash-and-burn techniques, but
the charcoal in the terra preta soils persists. The charcoal in
terra preta soils at Central Amazon project goes back in some places
as much as 2500 years.
Cultivating terra preta today and increasing its distribution would
have several advantages, Lehmann says. First, because the enriched
soil encourages intensive growth in smaller, more permanent areas,
it would discourage farmers from moving on and burning more Amazonian
forest. Second, terra preta could reduce carbon emissions. The late
Wim Sombroek-a legendary soil scientist whose interest in terra preta
reached back to the 1960s, earning him the name "the Godfather of
Dark Earth"- showed in 2002CK that 50 percent of the original carbon
in plants and trees used to make bio-char remains in the terra preta
soils after the conversion. Brazil is the world's eighth-largest
emitter of greenhouse gases, and most emissions come not from industry
and cars but from loggers, ranchers, and farmers burning the forest.
By improving their soil with bio-char, Amazonian farmers could work
in accord with the Kyoto treaty. Just substituting slash-and-char
for slash-and-burn could reduce human-produced carbon emissions in
the Amazon by 12 percent.
Even better, burning agricultural wastes in a controlled process
called pyrolization can convert wood and other organic waste into
volatile gases and bio oil that can be used as an energy source. The
process is win-win: burning the biomass not only produces substantial
amounts of bio-char from material like peanut shells and rice husks,
but mixing this bio-char into soil could also more than offset the
carbon emitted not only during the burning process but also when the
energy is used.
"You wouldn't just be carbon neutral, you would be carbon negative,
drawing CO2 out of the atmosphere, producing energy, and actually
improving the climate in the process," Lehmann saysCK. Through
workshops with other scientists, he, like Neves, is trying to spread
the word about terra preta worldwide, carrying on where Peterson
left off.
****
On August 13, 2006, on the anniversary of his death, Neves and the
archeologists at Central Amazon Project held a daylong commemoration
traveling from site to site in a large caravan, describing each
excavation, and explaining how Petersen had contributed. Although he
helped revise the chronology of Northeast Native American and
Caribbean Pre-Columbian archeology, Peterson will perhaps be
remembered best for his work in the Amazon. He was not the first to
become enthralled with the puzzle of Amazonian prehistory, but he was
among the most passionate and effective in spreading his enthusiasm.
He never wanted to be the "one," Heckenberger recalls, instead
preferring to give credit to the "many." "He was a mentor to a lot
of people, but he never thought of it that way. He wasn't teaching.
He was sharing his experience. It wasn't a lecture, it was a
dialogue. Jim was simply the best archeologist and the most infectious
teacher I ever met."
At the end of the day, the extended group gathers on the sandy beach
at Autuba. Before us lies the breathtaking expanse of the Rio Negro.
Autuba-the first and most extensive site excavated in the Central
Amazon Project-is where this revolution in thinking about the Amazon
began. Covering up to 30 hectares (75 ACRES CK)or more, it had a
central plaza-like area surrounded by several mounds, established
agricultural fields within a circumscribed radius, defensive
earthworks and palisades near the river.
From the beach you can look out at the broad Rio Negro and imagine
what it must have been like for Spanish conquistadors exploring
the river. Were these the spectacular settlements that Orellana
described?
"I think the best homage we can pay to Jim is to continue the work,"
Neves says, "to keep asking questions and to keep looking for answers."
--End--
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