The River of Doubt (21 page)

W
HEN
R
OOSEVELT EMERGED FROM
his thin balloon-silk tent on the morning of February 28, 1914, he stepped into the narrow clearing that his men had carved between water and forest. Before him rushed the River of Doubt, dark, swollen, and littered with debris from fallen trees. Having overflowed its banks, it coursed through the forest on either side in wayward streams and rivulets, picking up clots of leaves and displaced birds’ nests, and filling the jungle with a glasslike floor of water that mirrored the canopy above. The expedition’s dugouts rocked uneasily at their moorings, looking as unreliable at dawn as they had the afternoon before.

Although Roosevelt had hunted and camped in forests throughout the United States, marveling at California’s enormous redwoods, he had never seen anything like the prodigy of nature that surrounded him now. The massive trees rose so high that their crowns disappeared in the tangle of branches and flicker of sunlight above his head. Branches of neighboring trees wound around one another like interlaced fingers, and heavy epiphytes unfurled from the treetops like a ship’s rigging.

In the early-morning light, the scene that Roosevelt beheld was a breathtaking tableau of timeless nature—tranquil and apparently unchanging. That impression, however, could hardly have been more dangerous or deceiving. For, even as the men of the expedition gazed in awe at the natural beauty surrounding them, the creatures of the rain forest were watching back, identifying them as intruders, assaying their potential value, surveying their weaknesses, and preparing to take whatever they might have to give.

Far from its outward appearance, the rain forest was not a garden of easy abundance, but precisely the opposite. Its quiet, shaded halls of leafy opulence were not a sanctuary but, rather, the greatest natural battlefield anywhere on the planet, hosting an unremitting and remorseless fight for survival that occupied every single one of its inhabitants, every minute of every day. Though frequently impossible for a casual observer to discern, every inch of space was alive—from the black, teeming soil under Roosevelt’s boots to the top of the canopy far above his head—and everything was connected. A long, linked mat of fungi under the soil consumed the dead and fed the living, completing an ever-changing cycle of remarkable life and commonplace death which had throbbed without pause for millions of years—and of which Roosevelt and his men, knowingly or not, had now become a part.

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U
NLIKE THE
woods of New England, where Roosevelt had spent years exploring and learning about nature, the rain forest floor was not covered with thick leaf litter or plant life, but appeared largely empty, characterized only by a shallow layer of soil shot through with thin white threadlike fibers. Just as unusual, each tree in the Amazon rain forest appeared to be nearly unique. Many trees had commonly shaped leaves, but stands or groupings of a single tree species were very rare, and after identifying one tree the men could search for hours before finding another of the same kind. The trees themselves
were often strange and complex, characterized by huge buttresses, flowering trunks, or apparent branches that plunged back into the earth or were wrapped in enormous looped or curled vines. Most important, other than insects, which teemed everywhere, the forest seemed virtually empty, with little or no sign or sound of any inhabitants.

These odd characteristics were not mere natural curiosities or local quirks, but direct reflections of the deadly, exquisitely efficient competition for survival that was taking place all around Roosevelt and his men. They also reflected the profound impact of that evolutionary competition on all forms of life in the Amazon, where it has produced some of the most phenomenally diverse and specialized plants and creatures anywhere on earth.

While the process of evolution has continuously altered and selected the features of life everywhere on the planet, in few places have its workings been as conspicuous or its results as refined as in the Amazon. The extraordinary range of forms that characterizes the Amazon rain forest has been attributed to many causes, all of which are likely to have played some role in creating the immense cornucopia of living things that surrounded the expedition.

Perhaps the most frequently cited factor in the species richness of the Amazon is the region’s latitude, which has for millions of years produced generally stable temperatures and moist environmental conditions that have favored the uninterrupted development of the jungle and its inhabitants. Another prominent explanation is the repeated isolation and reconnection of the jungle to other continents and habitats over the broad sweep of time. Whereas some regions, such as Africa, have undergone fewer changes, and reflect a comparatively lower number of unique plant and animal species, the South American continent has at different points been cut off from, or rejoined to, other landmasses. The separation of South America from the rest of Gondwanaland, for example, created opportunities for the development of new indigenous species. That isolation was then interrupted
by the rise of the Panamanian Land Bridge, which permitted the arrival of new species from North America, and started new rounds of selection.

Within the Amazon itself, some scientists believe, localized changes of climate created shifting patterns of so-called refugia, or rain forest pockets, whose isolation offered unusual opportunities for the emergence of specialized plants, birds, insects, and other animals. New variants of life, particularly fish life, were also fostered by the long presence of an inland sea at the heart of the continent. Distinct new species are also thought to have emerged within enclaves set off by natural boundaries such as mountains and, of course, the channels and tributaries of the giant Amazon river system itself.

As in the development of a modern economy, with its ever-increasing specialization of labor and markets, each increase in competition among the inhabitants of the rain forest has itself been a powerful source of further speciation, rewarding entrepreneurial variations of life that can exploit skills and opportunities that previously went unrecognized or did not exist.

In the presence of such highly refined evolutionary pressures, every natural advantage and source of potential sustenance becomes an object of competition and is consequently used to its fullest. Despite the lush green vistas and overgrown shores that the expedition could see from the river, for example, the soil of many lowland rain forests is not rich or fecund but, rather, has adapted to recycle nutrients with extraordinary speed. The same abundant precipitation and steady temperatures that support life also leach minerals from the soil, and intense tree-and-plant growth exploits every available nutrient, leaving the floor of many tropical jungles, including the Amazon, permanently hovering at the margin of exhaustion.

For plants and trees, competition for available soil nutrients is paired with competition for sunlight, which is essential for the photosynthesis that green plants use to create carbohydrates from carbon dioxide and water. Every kind of plant or tree therefore represents a
unique trade-off between the quest for water and soil nutrients on one hand, and the quest for sunlight on the other.

Soaring more than 150 feet above Roosevelt’s head and out of sight in the green canopy were giant emergent tree species that had secured their survival by putting all their resources into the effort to outrace their competitors to the sunshine. For fast-growing trees, the trade-off for speed is inadequate defenses against insects and vulnerability to storms that cannot reach the lower, more sheltered layers of the forest. Unable to sink deep roots in the thin forest floor, canopy trees are also generally obliged to develop elaborate support systems at their base, either with giant triangular buttresses that surround the bole, or tree-trunk, or so-called flying buttresses that look like inverted branches.

On the forest floor, where the sky is all but obscured by such tall canopy trees, smaller plants or trees with limited resources must develop increasingly refined strategies to find a place in the sun. The most obvious of these strategies is to avoid the cost of building a structure capable of reaching the canopy by simply climbing a tree that has already done so. This opportunistic strategy, adopted by vines and lianas, can permit a newcomer to remain anchored in the forest floor while growing rapidly to the canopy. But since even vine construction requires substantial resources, it entails complex choices about which tree to climb—a requirement that has produced astonishingly sophisticated traits. Some Amazonian plants, for example, can shift as necessary between treelike form, when they receive sunlight, and a climbing vine, when they find themselves in shade. Others can transform themselves into trees once they reach the canopy, abandoning their host and winding their viny stems together into a trunk. While most plants naturally seek the sun, other Amazonian vines have adapted to seek out the dark bases of large canopy trees that might offer reliable support, and only then to turn upward toward the light.

With an alacrity that can seem almost human, rain forest vines send out tendrils that reach out delicately to encounter a potential host, then
curl to grasp it once it is found. A principal risk of the vine strategy is the danger that the host tree will sway and break the vine, so many vine species have adapted by developing slack in the form of elaborate loops, curls, and coils, lending the rain forest the distinctive draping character that Roosevelt could so easily see and admire. Another adaptation to this and other dangers is for the vine simply to abandon its connection to the ground and to derive its water and nutrients entirely in the canopy, becoming an air plant or epiphyte, a category of plant that has generated literally thousands of species, including bromeliads and orchids. After establishing themselves in the canopy, some epiphytes, in their turn, then reverse the entire process, sending aerial roots downward to establish a connection to the forest floor.

In reaction to the attempts of freeloading vines and epiphytes to benefit from their hard-won position in the canopy—and to protect themselves from being shaded over by such parasites—trees have developed many protection methods of their own. Some have developed smooth bark that keeps tendrils from attaching, and still others have adapted to slough off bark, leaves, or indeed entire branches to send epiphytes and vines crashing to the forest floor. Throughout the jungle, moreover, trees have adapted to prevent multiple deaths from tree falls or blights by separating themselves at regular distances from trees of the same species.

From his vantage point on the shaded forest floor, Roosevelt stood far below much of this unceasing evolutionary combat. Crowded with broad-leaved trees, crowning vines, and epiphytes, as well as the hundreds of insect and animal species that rely upon them, the upper canopy is difficult to see from the ground, except in the rooflike function that its name implies. By shading everything below it, the canopy helps to obscure much of the activity that takes place in the under-story, or middle level of the rain forest. Its shading action also contributes importantly to the relative absence of undergrowth on the forest floor, where the men of the expedition found that they could move about with surprising ease. While sunlight from the open river made the shoreline an almost impassable wall of trees, vines, and
dense underbrush, once that barrier was breached the dark interior of the jungle, broken only by occasional gaps in the canopy and a scattered, speckled light, revealed a labyrinth of tree trunks and vines, but little else.

As the men of the expedition arose and started their morning routine, Roosevelt was able to admire the complexity of the jungle before him, but could only guess at the mysteries that it held beyond his view. So complex and interdependent was the ecosystem he and his men had entered that the jungle itself could appear to take on the attributes of a living being. If Roosevelt had been able to see the rain forest from a distance, he could have watched it breathe. As the trees transpire, or, in a sense, sweat, they pump water into the atmosphere from their leaves. In the warm air, the water quickly evaporates and is recycled as rain. As the ex-president stood at the river’s edge, surveying the jungle he hoped to master and explore, the forest surrounding him met the dawn by exhaling thin white clouds of condensing moisture that rose over the canopy above him like the breath of a wolf on a winter morning.

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A
S HE
had during his telegraph line expeditions, Rondon approached the camp routine on the River of Doubt with military formality. To the task he brought not only strict discipline but even pomp and ceremony. Every morning, the men would gather in front of their Brazilian commander, who was dressed in his army khakis, to hear his Orders of the Day, laid out as formally as if he were addressing a regiment at war. Then, after a search through the surrounding forest for a piece of hardwood that would make a suitable marker, they would smooth one side of the wood with an adze, paint the camp number and the date on it, and drive it into the forest floor. They knew that rain, sun, and insects would likely destroy the markers long before they would be discovered by anyone who could read them, but they felt compelled nonetheless to leave behind a historical record of their journey.

This routine, which they planned to carry out every morning until they reached the mouth of the River of Doubt, was more than an empty ritual. It was a tangible connection to civilization and a constant reminder of who they were and why they were there. Rondon had learned through excruciating hardship how important routine, discipline, and military ritual were in maintaining morale during an expedition into the Amazon. Even on his 1909 journey, when he and all of his men nearly starved to death, Rondon had never deviated from his routine. “The ragged bugler had his bugle,” Roosevelt wrote, recording the last, traumatic days of the expedition as Rondon described them to him. “Lieutenant Pyrineus had lost every part of his clothing except a hat and a pair of drawers. The half-naked lieutenant drew up his eleven fever patients in line; the bugle sounded; every one came to attention; and the haggard colonel read out the orders of the day.”