The PreColumbian Amazon had a Population of at Least One Million

Parts of the Amazon previously thought to have been almost uninhabited were really home to thriving populations of up to a million people, new research shows.

Archaeologists have uncovered evidence that there were hundreds of villages in the rainforest away from major rivers, and they were home to different communities speaking varied languages who had an impact on the environment around them.

Huge parts of the Amazon are still unexplored by archaeologists, particularly areas away from major rivers. People had assumed ancient communities had preferred to live near these waterways, but the new evidence shows this was not the case.

The discovery fills a major gap in the history of the Amazon, and provides further evidence that the rainforest -- once thought to be untouched by human farming or occupation -- has in fact been heavily influenced by those who lived in it.

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Amazon Rain Forest NOT Pristine: Western Amazon has Over 450 Large Earthworks From 2,000 Years Ago

The Amazonian rainforest was transformed over two thousand years ago by ancient people who built hundreds of large, mysterious earthworks.

Findings by Brazilian and UK experts provide new evidence for how indigenous people lived in the Amazon before European people arrived in the region.

The ditched enclosures, in Acre state in the western Brazilian Amazon, were concealed for centuries by trees. Modern deforestation has allowed the discovery of more than 450 of these large geometrical geoglyphs.

The function of these mysterious sites is still little understood - they are unlikely to be villages, since archaeologists recover very few artefacts during excavation. The layout doesn't suggest they were built for defensive reasons. It is thought they were used only sporadically, perhaps as ritual gathering places.

The structures are ditched enclosures that occupy roughly 13,000 km2. Their discovery challenges assumptions that the rainforest ecosystem has been untouched by humans.

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Potential Impacts of Precolumbian Disruption of the Amazon Rain Forest

Ancient human disturbances may be skewing our understanding of Amazonian forests

Authors:

McMichael et al

Abstract:

Although the Amazon rainforest houses much of Earth’s biodiversity and plays a major role in the global carbon budget, estimates of tree biodiversity originate from fewer than 1,000 forest inventory plots, and estimates of carbon dynamics are derived from fewer than 200 recensus plots. It is well documented that the pre-European inhabitants of Amazonia actively transformed and modified the forest in many regions before their population collapse around 1491 AD; however, the impacts of these ancient disturbances remain entirely unaccounted for in the many highly influential studies using Amazonian forest plots. Here we examine whether Amazonian forest inventory plot locations are spatially biased toward areas with high probability of ancient human impacts. Our analyses reveal that forest inventory plots, and especially forest recensus plots, in all regions of Amazonia are located disproportionately near archaeological evidence and in areas likely to have ancient human impacts. Furthermore, regions of the Amazon that are relatively oversampled with inventory plots also contain the highest values of predicted ancient human impacts. Given the long lifespan of Amazonian trees, many forest inventory and recensus sites may still be recovering from past disturbances, potentially skewing our interpretations of forest dynamics and our understanding of how these forests are responding to global change. Empirical data on the human history of forest inventory sites are crucial for determining how past disturbances affect modern patterns of forest composition and carbon flux in Amazonian forests.

Were the Exposed Continental Shelves Important Refugia for the Neotropical Rainforests During the Last Ice Age?

Neotropical forest expansion during the last glacial period challenges refuge hypothesis

Authors:

Leite et al

Abstract:

The forest refuge hypothesis (FRH) has long been a paradigm for explaining the extreme biological diversity of tropical forests. According to this hypothesis, forest retraction and fragmentation during glacial periods would have promoted reproductive isolation and consequently speciation in forest patches (ecological refuges) surrounded by open habitats. The recent use of paleoclimatic models of species and habitat distributions revitalized the FRH, not by considering refuges as the main drivers of allopatric speciation, but instead by suggesting that high contemporary diversity is associated with historically stable forest areas. However, the role of the emerged continental shelf on the Atlantic Forest biodiversity hotspot of eastern South America during glacial periods has been ignored in the literature. Here, we combined results of species distribution models with coalescent simulations based on DNA sequences to explore the congruence between scenarios of forest dynamics through time and the genetic structure of mammal species cooccurring in the central region of the Atlantic Forest. Contrary to the FRH predictions, we found more fragmentation of suitable habitats during the last interglacial (LIG) and the present than in the last glacial maximum (LGM), probably due to topography. We also detected expansion of suitable climatic conditions onto the emerged continental shelf during the LGM, which would have allowed forests and forest-adapted species to expand. The interplay of sea level and land distribution must have been crucial in the biogeographic history of the Atlantic Forest, and forest refuges played only a minor role, if any, in this biodiversity hotspot during glacial periods.

Was Amazonia Really Tamed by PreColumbian Natives?

Comment on Clement et al. 2015 ‘The domestication of Amazonia before European conquest’

Authors:

McMichael et al

Extract:

Clement et al. [1] paint a picture of cultural landscapes blanketing Amazonia prior to European arrival to the Americas in their recent publication entitled ‘The domestication of Amazonia before European conquest’. A colourful narrative indeed, but here we would like to comment on their misinterpretation of previously published literature, use of data that may not be associated with pre-Columbian activities, and the extrapolative nature of their review both in time and across space.

A 60 Million Year Record of the Amazon Basin's Ecosystems

A 60-million-year Cenozoic history of western Amazonian ecosystems in Contamana, eastern Peru

Authors:

Antoine et al

Abstract:

We provide a synopsis of ~ 60 million years of life history in Neotropical lowlands, based on a comprehensive survey of the Cenozoic deposits along the Quebrada Cachiyacu near Contamana in Peruvian Amazonia. The 34 fossil-bearing localities identified have yielded a diversity of fossil remains, including vertebrates, mollusks, arthropods, plant fossils, and microorganisms, ranging from the early Paleocene up to the late Miocene-?Pliocene (greater than 20 successive levels). This Cenozoic series includes the base of the Huchpayacu Formation (Fm.; early Paleocene; lacustrine/fluvial environments; charophyte-dominated assemblage), the Pozo Fm. (middle + ?late Eocene; marine then freshwater environments; most diversified biomes), and complete sections for the Chambira Fm. (late Oligocene–late early Miocene; freshwater environments; vertebrate-dominated faunas), the Pebas Fm. (late early to early late Miocene; freshwater environments with an increasing marine influence; excellent fossil record), and Ipururo Fm. (late Miocene–?Pliocene; fully fluvial environments; virtually no fossils preserved). At least 485 fossil species are recognized in the Contamana area (~ 250 ‘plants’, ~ 212 animals, and 23 foraminifera). Based on taxonomic lists from each stratigraphic interval, high-level taxonomic diversity remained fairly constant throughout the middle Eocene-Miocene interval (8-12 classes), ordinal diversity fluctuated to a greater degree, and family/species diversity generally declined, with a drastic drop in the early Miocene. The Paleocene–?Pliocene fossil assemblages from Contamana attest at least to four biogeographic histories inherited from (i) Mesozoic Gondwanan times, (ii) the Panamerican realm prior to (iii) the time of South America’s Cenozoic “splendid isolation”, and (iv) Neotropical ecosystems in the Americas. No direct evidence of any North American terrestrial immigrant has yet been recognized in the Miocene record at Contamana.

Contrary Report: PreColumbian Populations Only Impacted Amazon Rain Forest Within a Day's Walk of the Rivers

New research led by Florida Institute of Technology shows that the impacts of indigenous people prior to European contact impacted riverside forests, but that such impacts were largely limited to an area within a day's walk from a river.

The findings by the international team of archaeobotanists, paleoecologists and ecologists will be published online in the paper "Anthropogenic influence on Amazonian forests in prehistory: An ecological perspective" on Oct. 28 in the Journal of Biogeography.

The new research, conducted using plant fossils, estimates of mammal density, remote sensing and human population modeling, reinforces that Amazonian forests may be very vulnerable to disturbance by logging , mining and other large enterprises. The study refutes an emerging theory from some archaeologists and anthropologists that Amazonian rain forests are the result of ancient managed landscapes - a notion that undermines the ecological view of these forests as fragile ecosystems.

"Nobody doubts the importance of human actions along the major waterways," said Mark Bush, professor of biological sciences at the Florida Institute of Technology and the lead author of the paper. "But whether humans had a greater impact on the ecosystem than any other large mammal has yet to be established in much of western Amazonia."

Dolores Piperno, curator of archaeobotany and South American archaeology at the American Museum of Natural History and co-author of the study, said the recent emphasis on Amazonia as a manufactured and domesticated landscape overstates the facts.

"At nearly the size of the continental United States, Amazonia is a vast landscape with considerable biotic and abiotic heterogeneity. Extrapolations being made from relatively few archaeological sites mainly located along water courses as to the overall effect of prehistoric human occupation must be tempered in the face of available and yet-to-be-accumulated empirical data."

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Amazon Region Expected to Have More Frequent, Extreme Droughts and Extreme Rains

A new paper co-authored by WHRC scientists Philip Duffy and Paulo Brando evaluates the accuracy of current climate models and uses them to project future drought and wet periods in the Amazon. They conclude that the whole of the Amazon will confront more hydrological extremes, and that most of the region will experience much more frequent and extensive drought. These changes would have profound implications for forest structure, composition, biomass, and carbon emissions.

According to Dr. Duffy, "Historically, the main source of CO2 emissions from Amazon forests has been direct human action, especially deforestation. However, in the future, climate change may cause large emissions that result from changes in the large-scale environment rather than from direct human action, and hence are much more difficult to control. This study, based on 35 climate models, suggests that future climate change will increase the frequency and geographic extent of meteorological drought in most of Amazon. This may contribute to forest degradation and increased emissions of CO2 to the atmosphere, amplifying global warming."

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Determining the Lifestyles of PreColumbian Amazonian Tribes Through Linguistics

In my class on October 5, 2015, we talked about how ancestral languages can be reconstructed on the basis of their present-day descendants and how such linguistic reconstructions (particularly reconstructions of the vocabulary) can be used to reimagine the lives of the speakers of such ancestral languages. While most of our examples in class dealt with Indo-European languages (with a brief foray into the Polynesian world), here I would like to present another example where the same sort of socio-cultural reconstruction can be done on the basis of unwritten languages who offer us a rare glimpse into the lives of the their speakers’ linguistic ancestors. This example concerns three indigenous South American language families: Arawakan, Tukanoan, and Nadahup. These languages are spoken in the Upper Rio Negro region, on the border of Columbia and Brazil (see the map on the left adapted from muturzikin.com). The present-day Arawak languages are shown in pale-green, Tukanoan languages are shown in yellow, and Nadahup languages in brown. (The best-known language in the Nadahup family—at least in linguistic circles—is Nadëb, which exhibits the rarest Object-Subject-Verb order, found only in a handful of languages around the world, 4 in the WALS sample.) Of the three families, only the Nadahup is limited to this region, while Tukanoan languages are also spoken elsewhere through South America and Arawakan languages are found from Brazil to the Caribbean.

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hat tip Randy.

Amazon Rainforest NOT Pristine, BUT Heavily Cultivated & Populated in PreColumbian Times

The domestication of Amazonia before European conquest

Authors:

Clement et al

Abstract:

During the twentieth century, Amazonia was widely regarded as relatively pristine nature, little impacted by human history. This view remains popular despite mounting evidence of substantial human influence over millennial scales across the region. Here, we review the evidence of an anthropogenic Amazonia in response to claims of sparse populations across broad portions of the region. Amazonia was a major centre of crop domestication, with at least 83 native species containing populations domesticated to some degree. Plant domestication occurs in domesticated landscapes, including highly modified Amazonian dark earths (ADEs) associated with large settled populations and that may cover greater than 0.1% of the region. Populations and food production expanded rapidly within land management systems in the mid-Holocene, and complex societies expanded in resource-rich areas creating domesticated landscapes with profound impacts on local and regional ecology. ADE food production projections support estimates of at least eight million people in 1492. By this time, highly diverse regional systems had developed across Amazonia where subsistence resources were created with plant and landscape domestication, including earthworks. This review argues that the Amazonian anthrome was no less socio-culturally diverse or populous than other tropical forested areas of the world prior to European conquest.

The Horror! The Horror! Larval Cthulhu Found in Peruvian Amazon

Deep in the Peruvian Amazon, an odd-looking caterpillar is doing its best to look like just another rain forest twig. But its four long tentacles are coiled, ready to respond to the first sign of danger.

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Hints of Human Presence in the Late Holocene in the Amazon From Charcoal in Lake Deposits

Palaeofires in Amazon: Interplay between land use change and palaeoclimatic events

Authors:

Campello Cordeiro et al

Abstract:

Interpreting the geological record of Amazon biomass combustion requires comparing charcoal accumulation rates in various biomes at different time scales. Charcoal accumulation rates, a proxy for palaeofire records, were obtained in sediment cores from Amazon lakes surrounded by several vegetation types and from a reservoirs in an intense land use change region. The records presented in this study were obtained in the following areas i) a reservoirs in Alta Floresta region (northern Mato Grosso State); ii) Lago do Saci (southern Pará State), a lake close to Alta Floresta and located at the southern border of Pará State; iii) a bog in an ecotone area in the Humaitá region (southern Amazonas State); iv) lakes in lateritic iron crust of the Carajás Hills (southeastern Pará State); v) Lago Comprido, a floodplain lake close to the Amazon River and surrounded by tropical rain forest (Monte Alegre, Pará State; vi) Lagoa da Pata in the Morro dos Seis Lagos alkaline complex (São Gabriel da Cachoeira, Amazonas State) and vii) Lago Caracaranã, a secluded lake in the northern Amazon cerrado (Roraima State). The highest charcoal accumulation rates were observed for modern records related to an intense change in land use at Alta Floresta, which had no precedent during the Holocene history of the Amazon. High charcoal accumulation rates that were observed in the Carajás region during low lake level phases in the Amazon in the mid-Holocene were comparable to those at the onset of the human settlement in Alta Floresta region. An increase in charcoal accumulation rate was observed in the late Holocene when the lake level was high, suggesting an interaction between climates and human presence. Low charcoal accumulation rates are typical of modern high rainfall environments, as observed in Lagoa da Pata where the environment is not susceptible to occurrences of wildfires even during relatively drier climatic phases. Low charcoal accumulation rates also exist in the relatively dry cerrado (savanna type) biome even during relatively dry phases in the Caracaranã region where the savanna-type vegetation biomass is lower and thus generates less charcoal particles than forest ecosystems.

Evidence of an Amazon Megaflood in ~ 700 BC?

A 2700 cal yr BP extreme flood event revealed by sediment accumulation in Amazon floodplains

Authors:

Moreira-Turcq et al

Abstract:

Climatic conditions are one of the most important factors affecting hydrological processes in fluvial systems. Higher discharges are responsible for higher erosion, greater transport, and also higher deposition. Consequently, sediment accumulation in Amazonia floodplain river-connected lakes can be directly related to hydrological patterns of the Amazon River mainstream. In this context, we analyzed five sediment cores taken in two floodplain systems situated in the lower Amazon River, to investigate sediment accumulation patterns during the Holocene. Our records show abrupt fluctuations in sedimentation rates in lakes that can reach more than 2 cm/yr during some periods. We find that in all cores, sediment stratigraphy is characterized by packages of sediments of uniform age, which are typically 10–80 cm thick and present a variegated color. The 14C age of the upper package is about 2700 cal yr BP. During this abrupt event, sediment accumulation rates in floodplain lakes can be at least 200 times higher than those of “normal” periods. This sedimentation event is interpreted as being the consequence of one or several successive extreme floods. The 2700 cal yr BP event has been also observed in other sites in South America and other regions in the world, although different impacts can be observed in each system. This event probably corresponds to a conjunction of favorable conditions for extreme Amazon discharge associated with the Middle to Late Holocene increase of austral summer insolation and shifts of the Intertropical Convergence Zone (ITCZ) from northern to southern positions. In this context, a marked negative peak in solar irradiance at 2700 cal yrs BP seems to have provoked cooling on the continents and a southward shift of the ITCZ associated with a probable reduction in the Atlantic Meridian Overturning Circulation.

The Civilizations of PreColumbian Amazonia Reconsidered

Integrated palaeoecology and archaeology – a powerful approach for understanding pre-Columbian Amazonia

Authors:

Mayle et al

Abstract:

The old paradigm that Amazonia's tropical ecosystems prevented cultural development beyond small-scale shifting agricultural economies, that had little environmental impact, no longer holds true for much of Amazonia. A diversity of archaeological evidence, including terra preta soils, raised fields, causeways, large habitation mounds, geometric earthworks, and megalithic monuments, all point to considerable cultural complexity and environmental impacts. However, uncertainty remains over the chronology of these cultures, their diet and economy, and the scale of environmental impact and land use associated with them. Here, we argue that a cross-disciplinary approach, closely coupling palaeoecology and archaeology, can potentially resolve these uncertainties. We show how, with careful site selection (pairing small and large lakes, close proximity to archaeological sites, transects of soil pits) and choice of techniques (e.g., pollen, phytoliths, starch grains, charcoal, stable isotopes), these two disciplines can be successfully integrated to provide a powerful tool for investigating the relationship between pre-Columbian cultures and their environment.

Is the Amazon Rain Forest Only 2,000 Years Old?

Swathes of the Amazon may have been grassland until a natural shift to a wetter climate about 2,000 years ago let the rainforests form, according to a study that challenges common belief that the world’s biggest tropical forest is far older.

The arrival of European diseases after Columbus crossed the Atlantic in 1492 may also have hastened the growth of forests by killing indigenous people farming the region, the scientists wrote in the U.S. journal Proceedings of the National Academy of Sciences (PNAS).

"The dominant ecosystem was more like a savannah than the rainforest we see today," John Carson, lead author at the University of Reading in England, said of the findings about the southern Amazon.

The scientists said that a shift toward wetter conditions, perhaps caused by natural shifts in the Earth’s orbit around the sun, led to growth of more trees starting about 2,000 years ago.

The scientists studied man-made earthworks, uncovered by recent logging in Bolivia, that included ditches up to about a kilometer (1,100 yards) long and up to 3 meters deep and 4 meters wide.

They found large amounts of grass pollen in ancient sediments of nearby lakes, suggesting the region had been covered by savannah. They also found evidence of plantings of maize, pointing to farming.

link.

paper link.

Cutting the Amazon Causes Knock-on Effects Not Unlike El Nino

In research meant to highlight how the destruction of the Amazon rainforest could affect climate elsewhere, Princeton University-led researchers report that the total deforestation of the Amazon may significantly reduce rain and snowfall in the western United States, resulting in water and food shortages, and a greater risk of forest fires.

The researchers report in the Journal of Climate that an Amazon stripped bare could mean 20 percent less rain for the coastal Northwest and a 50 percent reduction in the Sierra Nevada snowpack, a crucial source of water for cities and farms in California. Previous research has shown that deforestation will likely produce dry air over the Amazon. Using high-resolution climate simulations, the researchers are the first to find that the atmosphere's normal weather-moving mechanics would create a ripple effect that would move that dry air directly over the western United States from December to February.

Specifically, a denuded Amazon would develop a weather cycle consisting of abnormally dry air in the sun-scorched northern Amazon around the equator weighted by wetter air in the cooler south. Research has speculated that this pattern would be similar to the warm-water climate pattern El Niño, which during the winter months brings heavy precipitation to southern California and the Sierra Nevada region while drying out the Pacific Northwest.

The Princeton-led researchers found that the Amazon pattern would be subject to the same meandering high-altitude winds known as Rossby waves that distribute the El Niño system worldwide from its source over the Pacific Ocean. Rossby waves are instrumental forces in Earth's weather that move east or west across the planet, often capturing the weather of one region — such as chill Arctic air — and transporting it to another. Because the Amazon pattern forms several thousand miles to the southeast from El Niño, the researchers report, the Rossby waves that put the rainy side of El Niño over southern California would instead subject that region to the dry end of the Amazon pattern. The pattern's rainy portion would be over the Pacific Ocean south of Mexico.

[...]

"The big point is that Amazon deforestation will not only affect the Amazon — it will not be contained. It will hit the atmosphere and the atmosphere will carry those responses," Medvigy said.

"It just so happens that one of the locations feeling that response will be one we care about most agriculturally," he said. "If you change the snowpack in the Sierra Nevada, where most of the irrigation for California's Central Valley comes from, then by this study deforestation of the Amazon could have serious consequences for the food supply of the United States."

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So what does an El Nino event look like under this climate regime?

Paleovegation and Paleoenvironmental Change From the Neogene to the Quaternary in the East Central Amazon

Neogene–Quaternary sedimentary and paleovegetation history of the eastern Solimões Basin, central Amazon region

Authors:

1. Afonso César Rodrigues Nogueira (a)
2. Rosemery Silveira (b)
3. José Tasso Felix Guimarães (c)

Affiliations:

a. Programa de Pós-Graduação em Geologia e Geoquímica, Universidade Federal do Pará, Rua Augusto Corrêa 1, Guamá, 66075-110 Belém, PA, Brazil

b. Departamento de Geociências, Universidade Federal do Amazonas, Av. General Rodrigo O. J. Ramos, 3000, Coroado, 69077-000 Manaus, AM, Brazil

c. Instituto Tecnológico Vale – ITV, Rua Boa Ventura da Silva, n° 955, 3° andar, Umarizal, 66055-090 Belém, PA, Brazil

Abstract:

Palynological and stratigraphical analyses were carried out on the outcrops of the Solimões River to present new information about freshwater paleoenvironments of a fluvial–deltaic and meandering river system, evaluate the vegetation changes in the upper Solimões and Içá Formations in the eastern Solimões Basin, and the role of the Purus Arc in the evolution of central Amazon during the upper Neogene. The upper Miocene to Pliocene Solimões Formation is related to a fluvial–deltaic system, with fine-grained sediments of the prodelta–lacustrine environment supplied by meandering distributaries and delta front environment. The lake and distributaries were surrounded by extensive deltaic and floodplains colonized by lowland freshwater forests under wet climate conditions, persisting until the Pliocene. The Içá Formation started to deposit unconformably on the Solimões Formation during the Pleistocene, following the development of extensive meandering channels surrounded by floodplains of an essentially fluvial system linked to development of the present eastward direction of the Amazon River until the Atlantic coast. These floodplains were colonized by few palm species and pteridophytes of lowland freshwater forests during the Pleistocene. Additionally, no algae and fungi were observed, which may be related to drier climate conditions and/or different morphological conditions than the upper Solimões Formation.

A Carbon Cycle Twist: Amazon River Exhales Almost All Carbon Absorbed by Rain Forest

The Amazon rain forest, popularly known as the lungs of the planet, inhales carbon dioxide as it exudes oxygen. Plants use carbon dioxide from the air to grow parts that eventually fall to the ground to decompose or get washed away by the region's plentiful rainfall.

Until recently people believed much of the rain forest's carbon floated down the Amazon River and ended up deep in the ocean. University of Washington research showed a decade ago that rivers exhale huge amounts of carbon dioxide – though left open the question of how that was possible, since bark and stems were thought to be too tough for river bacteria to digest.

A study published this week in Nature Geoscience resolves the conundrum, proving that woody plant matter is almost completely digested by bacteria living in the Amazon River, and that this tough stuff plays a major part in fueling the river's breath.

The finding has implications for global carbon models, and for the ecology of the Amazon and the world's other rivers.

"People thought this was one of the components that just got dumped into the ocean," said first author Nick Ward, a UW doctoral student in oceanography. "We've found that terrestrial carbon is respired and basically turned into carbon dioxide as it travels down the river."

Tough lignin, which helps form the main part of woody tissue, is the second most common component of terrestrial plants. Scientists believed that much of it got buried on the seafloor to stay there for centuries or millennia. The new paper shows river bacteria break it down within two weeks, and that just 5 percent of the Amazon rainforest's carbon ever reaches the ocean.

"Rivers were once thought of as passive pipes," said co-author Jeffrey Richey, a UW professor of oceanography. "This shows they're more like metabolic hotspots."

When previous research showed how much carbon dioxide was outgassing from rivers, scientists knew it didn't add up. They speculated there might be some unknown, short-lived carbon source that freshwater bacteria could turn into carbon dioxide.

"The fact that lignin is proving to be this metabolically active is a big surprise," Richey said. "It's a mechanism for the rivers' role in the global carbon cycle – it's the food for the river breath."

The Amazon alone discharges about one-fifth of the world's freshwater and plays a large role in global processes, but it also serves as a test bed for natural river ecosystems.

Richey and his collaborators have studied the Amazon River for more than three decades. Earlier research took place more than 500 miles upstream. This time the U.S. and Brazilian team sought to understand the connection between the river and ocean, which meant working at the mouth of the world's largest river – a treacherous study site.

"There's a reason that no one's really studied in this area," Ward said. "Pulling it off has been quite a challenge. It's a humongous, sloppy piece of water."

The team used flat-bottomed boats to traverse the three river mouths, each so wide that you cannot see land, in water so rich with sediment that it looks like chocolate milk. Tides raise the ocean by 30 feet, reversing the flow of freshwater at the river mouth, and winds blow at up to 35 mph.

Under these conditions, Ward collected river water samples in all four seasons. He compared the original samples with ones left to sit for up to a week at river temperatures. Back at the UW, he used newly developed techniques to scan the samples for some 100 compounds, covering 95 percent of all plant-based lignin. Previous techniques could identify only 1 percent of the plant-based carbon in the water.

Based on the results, the authors estimate that about 45 percent of the Amazon's lignin breaks down in soils, 55 percent breaks down in the river system, and 5 percent reaches the ocean, where it may break down or sink to the ocean floor.