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2002

8 1/4 x 10 1/2 in.
295 pp., 137 color photos, 1 map, 11 b&w illus.

Out of print

 
 
 
     

Amazon Sweet Sea
Land, Life, and Water at the River's Mouth

By Nigel J. H. Smith

 

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Table of Contents

  • Preface
  • 1. Where Titans Meet
  • 2. Reinventing Pristine Nature
  • 3. Jungle Cowboys
  • 4. Pillars of Life
  • 5. A Banquet of Wild Fruits
  • 6. In the Shadow of the Forest
  • 7. Chainsaw Orgy
  • 8. Fishing and Plants in the River-Sea
  • 9. The Hunt between Land and Water
  • 10. Misty Dawn
  • Appendix 1. Common and Scientific Names of Plants
  • Appendix 2. Common and Scientific Names of Animals
  • Notes
  • Further Reading
  • Index

Preface

When the first Europeans sailed near the mouth of the Amazon, they marveled at the colossal size of the river that seemed to push back the salty waters of the Atlantic and at the rich store of natural resources waiting to be exploited. In 1499, still far out to sea off the mouth of the Amazon, a Spanish explorer had a crew member dip a bucket into the ocean and found the water drinkable. Vicente Yáñez Pinzón, awestruck at so much freshwater with land nowhere in sight, described those parts as a mar dulce (sweet sea). Another early explorer near the mouth of the Amazon, Pedro Álvars Cabral—the "discoverer" of Brazil—also did not tarry long but remarked that the forests in the estuary were so thick they could supply virtually unlimited timber to the navies of Iberia.

The image of the Amazon's mouth as a vast natural warehouse of biological treasures persists today. This book explores how the use of these natural resources has altered in the light of technological change, rapid urban growth, and accelerated market integration. Often such developments are identified as major threats to the environment, but in the case of the Amazon estuary they have diversified agriculture and helped to save floodplain forests from wanton destruction. People have transformed "natural" forests into cultural forests by rearranging the biological furniture. Over generations, locals have deflected the normal fallow cycle in slash-and-burn farming and created agroforests rich in economic species. By so doing, they have retained a biologically diverse landscape that benefits not only wildlife but also their own livelihoods.

In spite of the relatively good news with respect to human-induced landscape changes in the estuary—in stark contrast to many other parts of the Amazon basin—several trends recently have emerged that do not augur well for the resiliency of the land and its people. Historically, cattle production in the Amazon estuary has been confined to seasonally flooded savannas, especially on Marajó. But pockets of pasture have started to appear in areas hitherto dominated by forests. Should this trend accelerate, the productivity of fisheries could be threatened because many species of fish important in commerce and subsistence need floodplain forest to feed and breed. Forests also provide locals with important supplements to their subsistence and income, including game. Another trend that could undercut the productivity of extractive activities is the removal of mangroves in some areas to make way for urban development. Mangroves in the estuary are critical habitat for crabs, the basis of an important commercial activity.

These trends are analyzed from a historical and natural history perspective. One of the principal objectives of this book is to underscore the importance of the estuary's diverse habitats for local folk and, through trade, for urban dwellers as well. Yet many of the plant and animal resources tapped locally do not enter markets and are thus undervalued. Policy makers may thus be tempted to promote development schemes that do not take into account the value of biodiversity to locals. A major aim of this book is to highlight some of the little-known plants and animals that not only enrich the lives of people today but also could become the next generation's crop plants and livestock—if they survive.

Another theme threading through the chapters dealing with how people use and sometimes abuse the natural resources in the Amazon estuary is the changing perceptions of nature over time and what this means for how people relate to the environment. In spite of rampant globalization, many ideas about respect for wild plants and animals still surface in tales recounted by hunters and fishers. Often folk beliefs are dismissed as mere superstition, but they influence the way people hunt and fish and are a means of transmitting a conservation message to future generations.

Scientific names are relegated to appendixes to render the text more readable to nonspecialists. The scientific names provided in the appendixes are best bets only, because many groups of plants and animals in the Amazon are in need of taxonomic revision. Literature is not cited in the text so as to improve its flow; published material consulted for this project is listed under "Further Reading."

Unless otherwise stated, all photographs are my own. I have found that the camera serves as a medium for breaking the ice as I take pictures of people and ask about what they are doing. Far from being an intrusion in their lives, most rural people with whom I interact find my photographic interest in their livelihoods equally intriguing. On returning from the field and scrutinizing the slides, I am often delighted to find details about plants and animals, or the size and shape of objects manufactured from local plants, that I had missed in my notes. In my thirty years of fieldwork in the Amazon, I can remember only two or three instances when people did not want to be photographed, and of course I respected their wishes. On return visits, I always make a point of bringing families samples of my photographs, which usually generate a great deal of excitement and laughter, including remarks about how large so and so's nose appears and denials that they really look like that.

I have undertaken fieldwork in the Amazon estuary intermittently since 1970. In the dry season of 1970, I spent several days on Fazenda Livramento, Marajó Island, during a field excursion organized by Hilgard O'Reilly Sternberg, now professor emeritus, Department of Geography, University of California, Berkeley. I also visited Macapá and its vicinity while on this field trip. Between 1970 and 2001 I made numerous short trips to town and country in the Amazon estuary. Most of the observations for this book, however, were made during a more concentrated period of fieldwork between 1994 and 2001. Although all the visits were brief, lasting between a few days and three weeks, I experienced the Amazon estuary during all seasons and in years of exceptionally heavy rains (1999) as well as in years that were relatively dry (1997).

Chapter 1: Where Titans Meet

The Amazon delta, the world's largest, has inspired awe among visitors for centuries because of the huge volume of freshwater it pours into the sea and its vast expanses of swamp forests, floating meadows, and mudflats. Locals respect its treacherous currents and white-capped waves, but they have also learned to adjust to its daily and seasonal rhythms and to tap its rich banquet of natural resources. The mouth of the Amazon, gaping some two hundred fifty kilometers wide, embraces a mosaic of habitats that locals have long tapped for food and other goods and in many cases have transformed.

Born in the lofty, snow-clad Andes, the Amazon flows four thousand kilometers until it confronts the Atlantic at the equator. The Amazon is not only the world's longest river; it carries more water than any other river—more than ten times that of the Mississippi, for example. One-fifth of all the water flowing off the face of the earth passes through the Amazon's mouth. Such is the force of the Amazon as it clashes with the Atlantic that it pushes out a vast plume of freshwater for hundreds of kilometers into the sea. Five centuries ago a Spanish explorer traveling up the coast of Brazil noted that at a certain point the sea tasted fresh, even though his ship was out of sight of land. Pinzón dubbed that spot the sweet sea (mar dulce), which historians and geographers take to be the mouth of the river, named after women warriors in Greek mythology.

The battleground between the Amazon and the Atlantic never ceases to amaze travelers. While sailing up the Brazilian coast toward Belém in 1865, a zoological expedition from Harvard noted their approach to the Amazon estuary thus:

Early yesterday morning, a few yellowish patches staining the ocean here and there gave us our first glimpse of the water of the Amazons. Presently the patches became broad streaks, the fresh waters encroaching gradually upon the sea, until, at about ten o'clock, we fairly entered the mouth of the river, though, as the shores are some hundred and fifty miles apart, we might have believed ourselves on the broad ocean.

The Southern Equatorial Current pushes this turbid plume, which reaches some 400 kilometers long and between 100 and 200 kilometers wide, in a northwesterly direction up the coast of Amapá and the neighboring Guianas. Because it is lighter, the freshwater overrides the salty ocean and dilutes and muddies the surface for up to one million square miles. No wonder that Pinzón and his crew were amazed at being able to taste freshwater so far out at sea.

This plume of freshwater was a sure sign to European traders of the sixteenth and seventeenth centuries that they were on course to the Amazon. In 1604 Charles Leigh, an English captain on his way to the Amazon to trade for tobacco, remarked on the change in water color of the Atlantic still two days' sailing time from the mouth of the Amazon: "We passed over to the West Indies, and upon the tenth of May comming in change of water, which shewed thicke and white, by the next day we were in fresh water." William Davies, an English surgeon on Captain Robert Thornton's trip to the Amazon in 1608, noted as their vessel was heading south from the West Indies, "[A]nd you shall see the Sea change to a ruddie colour, the water shall grow fresh, by these signes you may run boldly your course."

Major Features of the Delta

The main channel of the Amazon flows into the northern part of the estuary, hugging Amapá's southern coast. The river is so broad along the northern channel that the horizon seems to melt with the sky. The sheer volume of freshwater flowing through the northern channel prevents much salt water from penetrating upstream, so mangroves are rare. Only when the Amazon heads north as it mixes with the Atlantic do red mangroves, with their distinctive stilt roots, become common. Washed by fresh sediment from the Amazon, waters in the northern estuary are especially muddy and bathe the richest farmland on floodplains.

A small arm of the Amazon branches south and hooks around southern Marajó. This sideshow is barely distinguishable on a remote sensing overview of the estuary but is the main route for river traffic between Belém, Macapá, and cities upstream, such as Manaus. Boat traffic between Macapá and Belém takes the longer, inland route via western Marajó because the waters off eastern Marajó are too risky. Only fishing boats venture off the seaward coast of Marajó. The southern estuary is less rich in sediments than the northern channel because clear and black water rivers dilute the muddy Amazon. The first river to mix with the southern arm of the Amazon, the Anapú, flows into the southwestern estuary. In the rainy season the Anapú is almost black as rainwater picks up tannins from leaves and other organic debris in floodplain forest. In the dry season the river runs almost clear. The next major river that merges with the southern arm of the Amazon is the clear water Tocantins in the southeast corner of the estuary. Less freshwater flushes through the southern estuary, so these waters are more brackish, especially during the dry season.

The contact zone between fresh- and salt water varies according to location within the estuary, the tide, and the season. The constantly changing interplay between the realm of fresh and salt waters has much to do with the availability of certain fish and other aquatic resources, the rhythm of economic activities, and the distribution of vegetation, especially mangroves. The shifting contours of fresh and salt waters allows some marine species to temporarily penetrate the estuary, such as certain jacks. During the low water season, therefore, a dozen or so catfish species are typically on display in local markets, ranging from those confined to freshwater, such as silvery dourada, to those adapted to saline conditions, such as olive gurijuba and steel gray bandeirado.

Geologic History of the River Mouth

To appreciate the diversity of environments in the Amazon estuary, the geologic footsteps that have led to the present landscape need to be traced. For most of South America's history, the Amazon has flowed west to the Pacific. The headwaters of the Amazon used to be in the east, probably in the vicinity of Óbidos, where rivers gnawed into broad granitic uplands, part of the original Gondwanaland before South America split off from Africa. As the South American plate began grinding over the Pacific plate some ninety million years ago, however, the Andes Mountains began to form. About thirty million years ago, the crumpling of the western edge of the South American plate combined with increased volcanic activity accelerated the formation of the Andes, eventually cutting off the Amazon's exit to the sea.

The history of the Amazon becomes a bit murky at this point, but it seems that the Amazon was dammed, at least for a while, forming a series of vast lakes and swamps. A number of marine ingressions also occurred as the Andes were forming, leading to brackish swamps and mangroves in what is now well-drained tropical rainforest.

In the meantime, however, the Amazon did not become a stagnant reservoir waiting to cut an exit to the Atlantic. It seems that the river turned north and flowed into the proto-Caribbean through what is now the Magdalena valley in Colombia. At present the Magdalena is completely cut off from the Amazon drainage, yet it shares many fish species, suggesting that they were once one and the same. As the South American plate continued to collide with the Pacific plate, various cordilleras formed offshoots to the backbone Andes in present-day Colombia and Venezuela, similar to ripples in a blanket as one pushes it across a bed. The Amazon was once again forced to find another exit, this time via the present-day Orinoco.

About eight million years ago, the Amazon broke through the granitic shield to the Atlantic. The itinerant Amazon forged its current route to the sea because of continental-scale forces at work. The massive granitic basement complex in northeastern South America had begun to split in half as far back as the Jurassic, forming the Guianan shield to the north and the Brazilian shield to the south. This split accelerated as the South American plate began to push against a spur of basaltic rocks that had solidified from magma spewed onto the surface along the eastern Andes in present-day Bolivia. As the two shields continued to separate, a deep trough formed along fault lines, leading to a down-dropped valley. The resulting gap made it easier for the headwaters of the Amazon to erode through the last impediment to the Atlantic.

Numerous islands dot the Amazon estuary, especially along the northern channel where most of the sediment-rich Amazon flows to the sea. Most of them are alluvial in origin, resulting from the Amazon dropping some of its silt load, especially at high tide when the current slows. The Amazon discharges close to a billion tons of sediment into the sea every year, and a vast underwater sediment cone has formed off the continental shelf that stretches ten degrees north of the equator. Not all the sediment is dumped on that underwater mountain; significant quantities of silt from the Amazon are also carried north as far as the Orinoco delta. Most of the Amazon's suspended sediment, at least 80 percent, comes ultimately from erosion in the Andes. With so much sediment to work with, it is little wonder that the river has sculpted numerous islands at its mouth. Only the Ganges and the Yellow River rival the Amazon with respect to the amount of suspended sediment, in part because their watersheds have witnessed massive deforestation, much of it on steep slopes. The yellow-brown tidal creeks in northern Marajó are so laden with silt that they stir complaints at bath time. The mother of a cowboy family living in the headwaters of the Cajueiro River remarked to me that her kids emerge dirtier than ever after plunging into the tidal creek in front of their home.

But not all islands owe their existence to alluvium dropped by the Amazon. As recognized by the French geographer Élisée Reclus a century ago, some are outliers of uplands that have been separated from the mainland and are now increasing in area with accretion of sediments along their shores. These upland islands—Marajó, Caviana, and Mexiana—were cut off from the mainland by tectonic movements and alternating sea levels during the Pleistocene ice ages.

Sea level dropped several times during the ice ages, falling by as much as one hundred meters off the coast of Brazil. While large amounts of freshwater were locked up in ice sheets in polar and temperate regions, the Amazon and its tributaries excavated their channels. Rivers also scoured deeper in their headwaters, and some of them eventually joined in their upper courses. As the ice sheets melted and sea levels rose, patches of upland then became isolated, forming islands.

Such is the case of Colares Island near Vigia in the southern estuary. During the last Ice Age, hunters and gatherers probably waded across a narrow stream to hunt, fish, and collect wild fruits on Colares. Now one can only reach the potato-shaped island by boat. Upland islands in the estuary can easily be distinguished from those formed by pure alluvium because they have patches of terra firma (terra firme in Brazil) forest with different plant species than are found on floodplains. Also, upland islands often contain seasonally flooded savannas and in some cases nonflooded scrub savanna.

Marajó, another island anchored to terra firma, was cut off from the mainland much earlier than Colares. The Tocantins River separated Marajó from the mainland long before the Amazon breached the granitic basement and began flowing into the Atlantic. The Tocantins is one of several sizable rivers that drain the Brazilian shield; it has always flowed north, and in its final stretch it turns north-northeast into the Atlantic. The Tocantins now enters Marajó Bay (Baia de Marajó), a challenging expanse of water where ceaseless trade winds during the summer months whip up foaming waves. Immediately to the north of Marajó are Mexiana and Caviana Islands, both continental outliers now largely ringed by alluvium from the muddy Amazon.

Unlike Colares, though, the Amazon has added substantially to Marajó because it brushes against the northern and western perimeter of the island. Much of western Marajó is built up alluvium quickly colonized by floodplain forests. Seasonally wet savannas, upland forest, riparian forests, and tracts of scrubby, nonflooded savanna characterize the eastern half of the island. Southern and eastern Marajó is nevertheless fringed with floodplain forests and mangroves. Micro-relief features, combined with a highly dynamic geologic history, have created a mosaic of habitats for plants and animals, and people, both local and urban based, extract resources from all of them.

Another distinguishing feature of the Amazon estuary is the presence of a couple of tributary rivers with unusually broad mouths. The Tocantins is the most impressive; it is so broad that standing on one shore, one can hardly discern the other side. During the ice ages, torrents dug the lower Tocantins, creating a riverbed deeper than could be formed under present conditions. Starting ten thousand years ago, waters backed up as the sea level rose, thereby forming a generous mouth that was once a flourishing fishery until overfishing and dam building undercut this important resource. Geomorphologists refer to such mouths as rias; they share features with the fjords of Norway, which were ground by glaciers rather than water. Another impressive ria mouth is found in the lower Anapú. The Anapú is a modest-sized river, which also drains the Brazilian shield and has a mouth disproportionate to the volume of water it carries. At one time the Anapú likely flowed north into the Amazon; now it has been captured by the seaward flow of the southern estuary.

The Seasonal Pulse of Floodwaters

During the low water season, from June through November, underwater saltwater lenses can penetrate far into the southern estuary, thereby changing the mix of species available for local fishers. At Vigia, for example, several marine fish species come closer to shore and can be caught on day fishing trips. And siri crabs, which are locally appreciated and also are sold in markets, appear at this time from deeper waters and can be caught along shores.

The low water season coincides with the drier months, known locally as verão. In the interior of Marajó, lakes shrink dramatically, making it easier to catch fish. Seasonally wet savannas dry out, providing extensive grazing land for cattle and water buffalo. And at low water, farmers can take advantage of nutrient-rich alluvium to plant short cycle crops, such as rice, watermelons, and squash. The brisk Southeast Trades blow during the dry season, thereby helping to propel numerous sail-powered boats and canoes. During the colonial period, annual trading and supervisory missions up the Amazon were attempted only during the dry season to take advantage of the favorable winds. The trades blow so strongly during this season that homes on the open plains moan, fanning stories about haunted houses.

Soon after the rains begin in earnest in about December, the water level starts to rise. The difference between high and low water levels in the estuary is not nearly as dramatic as along the middle and upper stretches of the Amazon, where the seasonal amplitude in water level can exceed ten meters. At the mouth of the Amazon, the difference between high and low water seasons is about three to four meters but is sufficient to dramatically alter the landscape. Once dry grasslands become marshes and rivers and creeks back up, canoes can enter floodplain forest and cross over into adjacent river systems.

The rising waters trigger a shift in economic gears. The pace of timber extraction in floodplains quickens at this time because it is easier to float out logs. Although production of açaí palm fruits declines, the tempo of heart-of-palm extraction quickens. Crop farming all but ceases, except on the highest portion of the floodplain and on patches of upland within the delta. Ranchers generally sell off parts of their herds to compensate for the reduced grazing area. Fishing returns in floodplain lakes decline as the fish disperse into floodplain forest and into seasonally flooded savannas.

Tides and the Tempo of Life

Superimposed on the annual variation in water level is the waxing and waning of the tides. This other leitmotiv determines the daily rhythm of activities for those eking out a living in the estuary. Whether it be fishing boats biding their time in midchannel for the incoming tide (afundiado) or passenger and cargo boats waiting for a favorable tide to shorten travel time, many economic activities are undertaken in synch with the daily flux of the water level. In the case of boats traveling from Afuá north to Macapá, for example, trips are usually planned for high tide, whereas river traffic moving upstream or downstream will often wait for an incoming or outgoing tide. High tide is the time to set up removable fences to cut off the retreat of fish that have entered creeks. At low tide fish are trapped behind the fence and can be easily drugged with piscicides and taken home for lunch or dinner.

Fish corrals are checked at low tide, and shipworm collectors have access to fallen red mangroves where the worms live. Crab hunters are also about at low tide, and people check gill nets that have been strung in aroid jungles growing on mudflats when the water is out. On the incoming tide, shrimpers deploy beach seines along the muddy shores of the Amazon and tidal creeks.

The difference between high and low tide varies according to location, season, and phase of the moon but usually ranges from one to three meters. At the spring and autumn equinoxes, exceptionally high tides can occur, sometimes associated with a dangerous tidal bore. Known locally as pororoca, tidal bores occur along certain rivers in both the northern and southern parts of the estuary. A loud roar announces the approach of a tidal bore, which has a wave up to four meters high. Pororoca races upstream for several kilometers, flinging any canoes still in the water onto banks and into trees.

Surfers from Rio de Janeiro travel to the Amazon estuary to catch pororoca in March and April. São Domingo do Capim in the southern part of the estuary hosts an annual surfing competition sponsored by Bad Boy, a manufacturer of surfing apparel. As would be expected in Brazil, the event includes a competition for Miss Surfing Pororoca. Pororoca has also captured the imagination of some songwriters and musicians. It is the title of a carimbó song, a popular music tradition that arose along the brackish coast of Pará. Pororoca is included in the repertoire of a group called Raizes da Terra (Roots of the Earth), which hails from Marapanim:

The sea is very treacherous, it's full of pororoca
Crazy waves are passing by, terns are flying past

***

Come here to see the terns land
After the pororoca of the sea have passed.

Plant Communities

The varied soils and relief of the estuary foster a mosaic of plant communities, all of which provide fruits as well as medicines, construction materials, and other useful products. Typically, conservation in the Amazon focuses on forests, but other types of vegetation, such as mangroves and grasslands, contain significant biodiversity and are important sources of income and subsistence. Many of the products obtained from the plant communities in the Amazon estuary never enter markets and therefore are not considered valuable by policy makers. They are nevertheless important because locals would have to substitute manufactured items—if available—or do without. Many of the plants have special cultural or spiritual significance, especially those used in healing, and therefore are priceless.

Many of the fish caught for subsistence and commerce depend directly or indirectly on the survival of aquatic plant communities, from floodplain forest to floating meadows and mangroves. Pressures are mounting on these estuarine environments, which if left unchecked could undercut food resources not only for local people but also for consumers hundreds or even thousands of kilometers away. Nurseries for some migratory fish are found in the estuary, so landscape changes at the mouth of the Amazon could affect catches upstream. Dourada catfish, for example, spend the first few years of their lives in the Amazon estuary, where they depend on floodplain forest and other habitats for their nurture before migrating several thousand kilometers upstream to breed. And some of the fish caught in the estuary are salted and sun-dried for distribution by trade channels far inland.

Floodplain Forest

Most of the forests of the Amazon estuary are flooded, either daily by the tide or seasonally when rains swell the Amazon and its tributaries. Species composition varies markedly according to whether the waters are brackish at certain times of the year, how long the area is flooded, and whether the water is silt-laden, clear, or stained dark brown by tannins. Floodplain forests on alluvial islands in the estuary are washed with the creamed-coffee waters of the sediment-rich Amazon. Headwater rivers and streams on larger islands, such as Marajó, are often clear or black water, and their floodplain forests contain a different mix of species than those under the influence of the muddy Amazon. The same applies to affluents of the Amazon, such as the Maracá River in Amapá, where tributary black water streams form extensive swamp forests during the rainy season, especially at high tide.

Although species diversity of floodplain forests is lower than at upland sites, they nevertheless contain a wealth of useful plants. In the northwestern part of Marajó Island, for example, extensive stands of buriti palm, used for fruit and fiber, occur in what are locally called mondongo swamps along the sinuous border between savanna and forest. Arumã is a particularly useful plant in the understory of floodplain forests, for its leaf stems are split to make baskets for carrying farm produce and forest fruits, to sieve manioc dough and açaí palm juice, and to make fish and shrimp traps. Floodplain forests dominate western Marajó and many of the islands in both the northern and southern parts of the estuary. Strips of forest finger their way across the savannas of Marajó, and these gallery forests bordering streams provide fruits, building materials, and medicines to locals. Islands of forest, or ilhas, also characterize the open grasslands of Marajó, particularly in the transition zone to dense forest.

Fleshy plants in the aroid family often form dense stands along the fringes of floodplain forests. Aroids are best known to North Americans and Europeans as indoor ornamental plants with broad, showy leaves, such as dieffenbachia. In the Amazon several species of this pantropical family are aquatic, including aninga (known as arum in English), which has large elephant ear-like leaves growing from the top of a stem that can attain three meters. Stands range in width from a few meters to dozens of meters and may extend along riverbanks for several kilometers. In some areas locals have cut narrow corridors through these aroid jungles to extend gill nets. Fish become entangled in the nets at high tide when they swim into the aroid jungles to feed.

Upland Forest

Although not extensive, patches of upland forest are found on higher parts of Marajó, especially in the southeast. Because of their proximity to Belém, terra firma forests in the Amazon estuary have been essentially stripped of their valuable hardwoods. Nevertheless, locals still obtain wood from such forest patches to make fence posts and build their houses. Small patches of upland forest also provide a number of locally consumed fruits.

Open Savannas

Expansive savannas (campo), stretching for dozens of kilometers without a single tree, characterize large portions of eastern Marajó. Savannas also cover much of Mexiana Island off Marajó's north coast as well as the interior of some other islands, such as Colares in the southern estuary. On Marajó alone campos cover some twenty thousand square kilometers. Because they are so flat and low-lying, savannas are mostly underwater during the rainy season. They are flooded by rivers and streams backed up by the Amazon as well as by the torrential rains that unleash nearly three meters of water during the first few months of the year. At high water many roads and trails across the savannas are underwater, so travelers and cargo switch to boats.

The landscape changes dramatically during the dry season. Days pass without a drop of rain. Much of the forage is parched, and cattle and water buffalo become thin. Cattle fare better at the beginning and end of the rainy season. Fires often rage across the savannas, resulting in large, black smudges as seen from the air. Lightning-set fires have swept across the savannas of eastern Marajó and some other islands for millions of years, but when people arrived tens of thousands of years ago, fires undoubtedly became more common. Indigenous folk deliberately burned the savannas to facilitate hunting, and Portuguese landowners and Catholic missions also set fires to improve forage for cattle. In the mid-nineteenth century, the great English naturalist Alfred Russel Wallace reported that ranchers on Mexiana Island set fire to the savannas in the dry season to promote fresh growth. Frequent fires set by people over millennia have helped to prevent the encroachment of trees on the savanna and have doubtless expanded the area occupied by treeless or "clean" plains (campo limpo).

Scrub Savannas

Some of the higher savannas are covered with scrub woodland, or cerrado. Patches of cerrado are found just inland from a belt of forest along the coast of southeastern Marajó; the landscape of gnarled trees interspersed with grasses gradually changes to open, seasonally flooded grassland as one travels to the interior of the island. Confined to uplands, cerrado grows on acidic and highly leached soils. Because of their low productivity, patches of scrub savanna are used mostly for extensive grazing of livestock. Cerrado is a good indicator of well-drained land now isolated from the mainland.

Floating Meadows

Floating meadows proliferate during the rainy season and are particularly well developed in the inland lakes of Marajó, especially Lake Arari. Floating meadows can form virtually impenetrable mats covering a square kilometer or more. Fishers and boat crews hack paths through them and often have to repeat the chore as the vegetation grows back so quickly. Winds can drive clumps of floating grasses, water hyacinth, and water lettuce across the entrances to channels, so regular waterways require constant maintenance. At ground level floating meadows are like a maze, but locals know which gaps lead to dead ends and which ones remain open to the other side.

Composed of several species of grass, rushes, and other aquatic plants, floating meadows are important habitat for many species of fish, especially in their juvenile stages, as well as numerous birds and mammals. Floating meadows are productive hunting grounds at high water because they provide food for large flocks of ducks and herons, as well as capybara, the world's largest rodent. Water buffalo munch through floating meadows, immersing themselves in the floating islands all day.

Mangrove

Mangrove, known in the Brazilian Amazon as manguezal, is confined to tropical and subtropical waters and provides important habitat for coastal fisheries. Although widely distributed, mangroves are nearly everywhere threatened by a variety of forces, ranging from cutting down the trees to obtain the bark for the tanning industry to clearing for shrimp culture, agriculture, and urban growth. In the Amazon locals have selectively cut mangroves for generations to provide building material and limited supplies of fuelwood, but only recently have mangroves begun to suffer wholesale destruction for industrial needs. Along the coast of Pará from São Caetano de Odivelas to Bragança, for example, the Brazilian botanist Samuel Almeida reports increased pressure on red and black mangroves to supply fuel for brick factories and bakeries. On a floodplain island near Abaeté, the owner of a small sawmill reported to me that he occasionally processes red mangrove to provide rafters for local markets.

At Terra Amarela along Rio Tauá-Pará near Vigia, I saw a charcoal-making kiln with stacks of red mangrove. As urban areas continue to grow, mangroves could come under increasing pressure from the charcoal trade geared to households in the poorer sections of towns and cities. In the Amazon charcoal is still used by many households to cook their daily meals rather than for the occasional barbecue, as in North America.

Mangroves are found throughout the estuary, though the density and species composition vary according to the degree of salinity. Mangroves are often intermixed with species typical of freshwater floodplains, such as açaí palm, stilt-rooted mututí, gnarled aturiá, and ananí, the latter a valuable timber species. Red mangrove, known locally as mangue, occurs sporadically inland as far as the Furo de Breves and Afuá, but in the southern estuary it frequently lines islands and sloughs, with black mangrove (ciriúba) found immediately behind.

Mangroves are concentrated in the southern part of the estuary because less freshwater flushes around southern Marajó and along the Atlantic coast of Amapá, which is washed by the equatorial current blended with freshwater from the Amazon. Estimates on the area of mangroves in Pará range widely, from 900 to 2,900 square kilometers, so it is hard to determine the area of mangroves at the mouth of the Amazon. It is probably safe to assume that several hundred square kilometers of mangroves, mostly mixed with some freshwater floodplain species, are found in the estuary. Although they account for a relatively small area, mangroves are nevertheless critical habitat for the several species of shrimp and crab and a regional delicacy, shipworm.

 

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