Dolores Piperno says native people have always played an important
role in sustainability
The Algodón River
flows through a forest of the Amazon Basin in the remote northeastern
corner of Peru. Scientists collected and analyzed a series
of 10 roughly three-foot-long soil cores from three sites,
each located at least a half-mile away from river courses
and floodplains. (Álvaro del Campo)
The Amazon, the world's largest and most biodiverse tropical forest,
spanning nine countries and more than 2.3 million square miles,
was once thought by scholars to hold untamed, unaltered, pristine
However, the Amazon rainforest has long been home to many indigenous
societies. In recent decades, researchers have found evidence of
the many ways since prehistoric times that Indigenous peoples have
shaped forest composition and its diversity, and domesticated native
The human footprint in a number of regions is undeniable. Agriculture,
fish weirs, roads, changes in soil composition and huge geometric
earthworks called geoglyphs are evidence of the many ways Indigenous
groups have had a significant impact.
Nevertheless, it is also becoming increasingly apparent that in
some regions for thousands of years and into the present, the rainforest's
native inhabitants have used forests in ways that didnt much
change them, leaving vast tracts of land little alteredno
forest clearing and no agriculture with plants such as maize, squash,
and maniocindicating that in an anthropogenic age, humans
have had little impact on these remote regions for as many as 5,000
The researchers also
conducted surveys of the modern forests and found a dizzying
diversity in the region; their inventory yielded 550 tree
species and 1,300 other species of plants. (Corine Vriesendorp)
A new study, published in the journal Proceeding
of the National Academy of Science and led by a Smithsonian
researcher, proves that over millennia, a region of rainforest in
the western Amazon shows no evidence of significant modification
by Indigenous societies.
The study uses phytoliths, the microscopic silica bodies left behind
by Neotropical plants after they decay, to determine what types
of plants were growing at various periods, along with charcoal for
the detection of the use of fire. Researchers working in the remote
Putumayo region in northeastern Peru, collected soil core samples
from three research campsites in the interfluvial areas, the forests
located far from rivers and major tributaries, known as tierra
There have been a number of studies done by ourselves and
others in the past decade or so, indicating little human modification
of these interfluvial forests in western and central Amazonia during
prehistory, explains archaeobotanist Dolores
Piperno, of the National
Museum of Natural History in Washington D.C. and the Smithsonian
Tropical Research Institute in Panama, who led the investigation.
So, this evidence is building, she says.
Most of the significant human habitation and modification documented
so far has been found around rivers and their tributaries, where
the soils for plant cultivation and agriculture are more fertile
and it's easier to find and catch game. The Indigenous communities
that live along these riverbanks today practice subsistence agriculture
in chacraspatches of land designated for growing foodand
house gardens, they fish and hunt animals like peccaries and paca,
and collect uncultivated products from the surrounding forests for
food, medicine and other uses.
Indigenous populations today and likely in the past were
living in and exploiting the riverine forests just a few kilometers
away from where we did our work, says Piperno. But the nearby
forests that are located further inland appeared to have been
much less impacted.
The unexplored forest
located between the banks of the Putumayo and the Algodón
rivers (above: Putumayo River is highlighted in pink) is characterized
by gentle rolling terrain, tierra firme forests, peatlands
and palm swamps. (Wikimedia Commons)
Piperno says this study offers key insight into how to better protect
these ecosystems. The 2019 wildfires, which devastated almost 3,500
square miles of rainforest, and which were exacerbated by the effects
of climate change, only emphasized the fragility of the Amazonian
ecosystems and reinforced the urgency for more effective action
to preserve them.
Indigenous people have always played a very important role
in the sustainable use of the forest and the conservation of biodiversity,
and they should continue to be central to it, especially because
of their deep knowledge of the forest and its relevance in their
daily lives, Piperno says.
This study began five years ago, when Pipernos co-authors,
Nigel C. A. Pitman, Juan Ernesto Guevara Andino, Marcos Ríos
Paredes, and Luis A. Torres-Montenegro, visited the unexplored area
located between the banks of the Putumayo and the Algodón
rivers, a forest characterized by gentle rolling terrain, tierra
firme forests, peatlands and palm swamps. The researchers conducted
an intensive core sampling of an area at the three research campsites,
Quebrada Bufeo, Medio Algodón and Bajo Algodón, using
an auger that drills out a column of soil about two to three feet
long. They also conducted a botanical inventory, analyzing 1,300
species of plants and 550 species of trees.
The soil cores were sent back to the United States and Amsterdam
to Piperno and ecologists Crystal McMichael and Britte Heijink,
two other co-authors of the paper. Piperno performed the phytolith
analysis, while McMichael and Heijink did the charcoal analysis,
in their respective labs.
By documenting the vegetation and fire history, the researchers
could better understand the level of human impact on the forest
over the past 5,000 years. Phytolith and charcoal analyses were
carried out on the ten soil cores collected. Phytoliths are used
to identify different types of tropical vegetation, and charcoal
fragments are evidence of fire.
have always played a very important role in the sustainable
use of the forest and the conservation of biodiversity, and
they should continue to be central to it," says Piperno.
(Sean Mattson, STRI)
Phytoliths document well many important tropical flora, from
weeds and other plants associated with human presences and disturbance
to various kinds of forested vegetation, says Piperno, who
pioneered the development of the procedures for archaeological and
vegetational history studies of phytoliths. Throughout her career,
she has worked extensively analyzing these plant microfossils in
archaeological sites in places like the Amazon and Central America
tropics, highlighting their importance as tools to better understand
the history of crop domestication and early agriculture.
[Phytoliths] are very durable, and can be found where other
plant remains are absent or poorly preserved, says Daniel
Sandweiss, a geoarchaeologist of the department of anthropology
and the Climate Change Institute of the University of Maine, who
was not involved in the study.
[They] alone or with other plant remains, such as pollen
and starch grains, have been used in a wide variety of studies,
often to understand better what species people used in the past,
he adds, noting that Piperno is the world's leading expert on phytoliths
The phytoliths analysis indicated there was no detectable human
influence on the diversity of species of plants and trees in these
zones. That means there were no telltale signs of crops being grown,
unlike the current areas of human settlements along the nearby rivers,
where a number of plants, like maize, squash, manioc and various
fruit trees are cultivated. Two kinds of palms that are important
food sources and have been domesticated as a source of food in Amazonia
were shown to not have increased over time, indicating that Indigenous
peoples had not planted them or caused them to grow in any larger
abundance in the tierra firme region.
Natural fires are rare in this region due to frequent precipitation;
fires would have most likely been started by humans in order to
clear areas for agriculture or for encampments or villages. Charcoal
quantities in the same soil cores revealed that fires seldom occurred
and were intermittent between the three campsites, indicating that
over hundreds of years human-caused fires had not had any impact
on the regions vegetation.
Seen under a microscope,
these long-lasting microfossil particles of dead plants called
phytoliths are smaller than the width of a human hair. (Dolores
Other indicators of human settlements were not found, such as ceramics,
stone tools and terra preta or terra mulata (dark or brown
earth)distinctive Amazonian dark soils made by human activities,
which often contain remains of artifacts, charcoal and other elements.
Piperno says that the study highlights the importance of integrated
paleoecological, archaeological, anthropological, ecological and
botanical research, to best understand the prehistoric legacies
of Amazonia societies. She points out that the researchers intend
to do more work in these remote tierra firme regions, which
alone comprises more than 90 percent of the land area of the Amazon
rainforest. It's a lot of territory yet to be explored in such depth,
but essential to determining the overall reach of human impact on
In addition to giving us a deeper understanding of how Amazon societies
have coexisted with the rainforest, the study has further significance.
Put simply, Indigenous peoples play a key role in protecting these
ecosystems. In the paper, the authors mention the collaborative
relationship they established with some of the Indigenous communities
in the region for conservation efforts, and highlight the importance
of further studies of this kind and the inclusion of present Indigenous
societies in the development of strong environmental policies.
It is important to include modern indigenous peoples in conservation
and sustainability efforts, says Piperno.
This study shows that Indigenous agricultural practices sustainably
managed the forest's natural biodiversity for millennia, says
Sandweiss, a scholar of the effects of climate change on cultural
development. It draws renewed attention to Indigenous practice
and urges planners to incorporate them to protect the Amazonian
rainforest's natural biodiversity.
Vanessa Crooks is a bilingual freelance journalist and writer located
in Panama City, Panama, working to bring science to all audiences.
She is also an illustrator, graphic designer and animator.