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Amazon Expeditions: My Quest for the Ice-Age Equator
A gripping tale of exploration, the pursuit of ice-age records, scientific invention and controversy, and revelations about the great Amazon forest
In this vivid memoir of a life in science, ecologist Paul Colinvaux takes his readers from the Alaskan tundra to steamy Amazon jungles, from the Galapagos Islands (before tourists had arrived) to the high Andes and the Darien Gap in Panama. He recounts an adventurous tale of exploration in the days before GPS and satellite mapping, and a tale no less exhilarating of his battle to disprove a hypothesis endorsed by most of the scientific community. Colinvaux’s grand endeavor, begun in the 1960s, was to find fossil evidence of the ice-age climate and vegetation of the entire American equator, from Pacific to Atlantic. The accomplishment of the task by the author and his colleagues involved finding unknown ancient lakes, lugging drilling equipment through uncharted Amazon jungle, operating hand drills from rubber boats in water 40 meters deep, and inventing a pollen analysis for a land with 80,000 species of plants. Colinvaux’s years of arduous travel and research ultimately disproved a hotly defended hypothesis explaining bird distribution peculiarities in the Amazon forest. The story of how he arrived at a new understanding of the Amazon is at once an adventurous saga, an account of science as it is conducted in the field, and a cautionary tale about the temptation to treat a favored hypothesis with a reverence that subverts unbiased research.
In this vivid memoir of a life in science, ecologist Paul Colinvaux takes his readers from the Alaskan tundra to steamy Amazon jungles, from the Galapagos Islands (before tourists had arrived) to the high Andes and the Darien Gap in Panama. He recounts an adventurous tale of exploration in the days before GPS and satellite mapping, and a tale no less exhilarating of his battle to disprove a hypothesis endorsed by most of the scientific community. Colinvaux’s grand endeavor, begun in the 1960s, was to find fossil evidence of the ice-age climate and vegetation of the entire American equator, from Pacific to Atlantic. The accomplishment of the task by the author and his colleagues involved finding unknown ancient lakes, lugging drilling equipment through uncharted Amazon jungle, operating hand drills from rubber boats in water 40 meters deep, and inventing a pollen analysis for a land with 80,000 species of plants. Colinvaux’s years of arduous travel and research ultimately disproved a hotly defended hypothesis explaining bird distribution peculiarities in the Amazon forest. The story of how he arrived at a new understanding of the Amazon is at once an adventurous saga, an account of science as it is conducted in the field, and a cautionary tale about the temptation to treat a favored hypothesis with a reverence that subverts unbiased research.
- GenresScienceNonfictionBiology
385 pages, Hardcover
First published March 3, 2007
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Displaying 1 - 4 of 4 reviews
April 6, 2025
Colinvaux describes his lifetime of work on pollen analysis, and the insights into ice age climate that came from it. He spent four years doing analysis in Alaska (starting in 1960), showing that the ice age tundra was more extreme than anything on the coast today, the major plants being sedges and arctic birch. Subsequent work was in the tropics. The book is well written and engaging, providing a nice example of how science works as the author describes the successive findings and how they shaped the understanding of past Amazon climate.
In the Preface, the author describes the techniques of pollen analysis where corings of sediments laid down over long periods can be examined, with the pollen showing the types of plants that existed over time. Done it every 10 cms of a 10 m cliff in Swedish peat diggings, and you have an outline history of the migration that led to the modern forest. While the technique has been extended to lake sediments in the temperate zone, there are many challenges to using it in the tropics: a huge pollen vocabulary (80,000 species in the Amazon), wind pollination rare, and no peat bogs.
Colinvaux's work provided insights into the evolution of plants in the tropics. In the 1800's it was thought that the low diversity in the north was due to glacial extinction, but that lead to the converse question of why the tropics supported high diversity. Ernst Mayr had argued that speciation required the physical separation of populations. Jürgen Haffer developed the refuge hypothesis whereby drought in the Amazon left small patches of wet hillsides, while the rest of the amazon was savanna. These refuges would then allow the development of separate species.
Other explanations had been current, most notably G. Evelyn Hutchinson's 1961 "Paradox of the Plankton", wherein he observed that large numbers of species of plankton live together without ruinous competition leading to extinction. His explanation invoked vertical gradients of light or turbulence, symbiosis or commensalism, differential predation, and constantly changing environmental conditions.
When the author started his work, the support for refuge theory was increasing although no one had shown direct evidence of a dry Amazon during the ice age. The objective of his research was to core lakes in the new world tropics in order to examine the pollen record and determine what the vegetation cover was like at the time of the last ice age.
Many chapters of the book describe the difficulties in this work, a major problem being that most lakes do not provide cores going that far back in time. Initially, he was able to core two lakes in the Galapagos. Over the years he was able to find suitable lakes in the east Amazon, notably on the inselberg Hill of Six Lakes.
While grass genera cannot be separated by pollen, grasses secrete casts of the cell’s interior, called phytoliths, which can be used to determine the genus.
Colinvaux's conclusion was that a form of lowland rain forest had persisted in the western Amazon basin throughout the ice age, with subtly changing species composition as the northern glaciers came and went. While the temperature had dropped about six degrees during the ice age, the forests had persisted, with no sign of savanna. Increased presence of oak and other highland species was found during the ice age. As these trees prefer colder climate, this finding concurred with cooler temperatures at the time. The pollen evidence thus joins the geological and soils evidence in declaring that the Amazon basin has never been arid throughout at least the 170,000 years of the last two glacial cycles.
"But the bigger reward for us ecologists was its illustration of how even tropical forests meet climate change, they do not dissolve nor fragment, neither are they replaced by different vegetation, as both the ecology of the 1930's and the refuge paradigm still holds. Rather they slowly shuffle their populations and diversity, obeying the relative competitive advantage of individual species. Species suffer population fates, good or bad, but the forest lives on."
In the Preface, the author describes the techniques of pollen analysis where corings of sediments laid down over long periods can be examined, with the pollen showing the types of plants that existed over time. Done it every 10 cms of a 10 m cliff in Swedish peat diggings, and you have an outline history of the migration that led to the modern forest. While the technique has been extended to lake sediments in the temperate zone, there are many challenges to using it in the tropics: a huge pollen vocabulary (80,000 species in the Amazon), wind pollination rare, and no peat bogs.
Colinvaux's work provided insights into the evolution of plants in the tropics. In the 1800's it was thought that the low diversity in the north was due to glacial extinction, but that lead to the converse question of why the tropics supported high diversity. Ernst Mayr had argued that speciation required the physical separation of populations. Jürgen Haffer developed the refuge hypothesis whereby drought in the Amazon left small patches of wet hillsides, while the rest of the amazon was savanna. These refuges would then allow the development of separate species.
Other explanations had been current, most notably G. Evelyn Hutchinson's 1961 "Paradox of the Plankton", wherein he observed that large numbers of species of plankton live together without ruinous competition leading to extinction. His explanation invoked vertical gradients of light or turbulence, symbiosis or commensalism, differential predation, and constantly changing environmental conditions.
When the author started his work, the support for refuge theory was increasing although no one had shown direct evidence of a dry Amazon during the ice age. The objective of his research was to core lakes in the new world tropics in order to examine the pollen record and determine what the vegetation cover was like at the time of the last ice age.
Many chapters of the book describe the difficulties in this work, a major problem being that most lakes do not provide cores going that far back in time. Initially, he was able to core two lakes in the Galapagos. Over the years he was able to find suitable lakes in the east Amazon, notably on the inselberg Hill of Six Lakes.
While grass genera cannot be separated by pollen, grasses secrete casts of the cell’s interior, called phytoliths, which can be used to determine the genus.
Colinvaux's conclusion was that a form of lowland rain forest had persisted in the western Amazon basin throughout the ice age, with subtly changing species composition as the northern glaciers came and went. While the temperature had dropped about six degrees during the ice age, the forests had persisted, with no sign of savanna. Increased presence of oak and other highland species was found during the ice age. As these trees prefer colder climate, this finding concurred with cooler temperatures at the time. The pollen evidence thus joins the geological and soils evidence in declaring that the Amazon basin has never been arid throughout at least the 170,000 years of the last two glacial cycles.
"But the bigger reward for us ecologists was its illustration of how even tropical forests meet climate change, they do not dissolve nor fragment, neither are they replaced by different vegetation, as both the ecology of the 1930's and the refuge paradigm still holds. Rather they slowly shuffle their populations and diversity, obeying the relative competitive advantage of individual species. Species suffer population fates, good or bad, but the forest lives on."
February 25, 2017
An interesting giving a picture of how the author`s research on climate in South America during the last Ice age
November 16, 2021
Colinvaux delivers an inspiring book on his life's mission to describe conditions in tropical America during the last ice age. The tale involves overcoming three huge hurdles - finding lakes in Amazonia and trecking to them through uncut forest, identifying thousands of species solely by their pollen, and persuading the scientific community that his observations disprove a fondly held delusion. The last is probably the biggest hurdle of all and the author is ostracized by many Amazonian researchers for his heretical views. To his credit Colinvaux treats his detractors without bitterness.
This is easily the best account I have ever read of a life in science - the difficulties and false paths, the search for evidence, and the way in which knowledge moves forward are all brought to life with Colinvaux's vigorous prose. But most of all it is a human story, of trials in the field, arguments at the conference, boredom in the customs shed, friendship and help from people who call the forest their home, and the thrill of finding the evidence you needed to support your theory.
This is easily the best account I have ever read of a life in science - the difficulties and false paths, the search for evidence, and the way in which knowledge moves forward are all brought to life with Colinvaux's vigorous prose. But most of all it is a human story, of trials in the field, arguments at the conference, boredom in the customs shed, friendship and help from people who call the forest their home, and the thrill of finding the evidence you needed to support your theory.
latin-america
September 30, 2017 This book was cited in 1491 to illustrate how populous the New World was before European-introduced diseases decimated the natives. Sure enough, at the end of the account we discover that Panama´s Darien Gap, viewed as an eco-tourist haven, was, through a pollen count, determined to have been an area which reverted to rainforest in the last 400 years following millenia of agricultural use.
Colinvaux´s overall purpose in the 6 expeditions he mounted along the equator in South America during his career was to find evidence for changing climate during ice ages to help support or refute the ¨refuge hypothesis¨ that sought to explain faunal and floral diversity in the Amazon basin. In the end, his evidence refuted the thesis.
\ The book is remarkable for its description of the political and logistical side of earth science. The very real problems of bringing equipment to remote areas; regulatory barriers, personal conflicts, and the degree to which reputation and authority can hinder a clear view of all the evidence.
He is wonderful at describing how his evidence (pollen counts from cores taken from the bottoms of freshwater lakes) is obtained, evaluated, and fits into the larger picture.
He is less engaging as a travel narrator, though he does have moments. Here are the ¨white sands:¨
¨Further upstream the banks tended to resolve into rolling mounds of glistening white, hurtful to eyes attuned to blck wter, dark forest, and gray skies. We stopped at one mighty mound the size of a soccer pitch, a smooth parabola of sand, the individual grains bleached whiter than the shirt in an advertisement for detergent. I ran along it like a child at the seaside, impossible not to.¨ (p. 215)
Colinvaux´s overall purpose in the 6 expeditions he mounted along the equator in South America during his career was to find evidence for changing climate during ice ages to help support or refute the ¨refuge hypothesis¨ that sought to explain faunal and floral diversity in the Amazon basin. In the end, his evidence refuted the thesis.
\ The book is remarkable for its description of the political and logistical side of earth science. The very real problems of bringing equipment to remote areas; regulatory barriers, personal conflicts, and the degree to which reputation and authority can hinder a clear view of all the evidence.
He is wonderful at describing how his evidence (pollen counts from cores taken from the bottoms of freshwater lakes) is obtained, evaluated, and fits into the larger picture.
He is less engaging as a travel narrator, though he does have moments. Here are the ¨white sands:¨
¨Further upstream the banks tended to resolve into rolling mounds of glistening white, hurtful to eyes attuned to blck wter, dark forest, and gray skies. We stopped at one mighty mound the size of a soccer pitch, a smooth parabola of sand, the individual grains bleached whiter than the shirt in an advertisement for detergent. I ran along it like a child at the seaside, impossible not to.¨ (p. 215)
Displaying 1 - 4 of 4 reviews