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The extensive Iquitos Várzea ecoregion includes the low, seasonally flooded river basins of the uppermost Amazon River in western Brazil, Peru, and, to a lesser degree, Bolivia. Várzea means "flooded forests," an appropriate name for this ecoregion. Here, the whitewaters of the Amazon and other rivers flood the land with a milky, cloudy current that churns with sediment carried from the slopes of the Andes. At the town of Iquitos, the Amazon River floods twice a year, covering the surrounding forest in 20 to 23 feet (6-7 m) of water for an expanse of up to 12 miles (19 km). These floods can cover the land for as much as ten months of the year! As the floodwater recedes, it deposits nutrient-rich sediments, creating incredibly fertile soil. Between 90 and 120 inches (2,286-3,048 mm) of rain falls each year.
The várzea landscape constantly changes as the rivers and floodwaters shift their sediment loads, moving sediment and depositing it in other places to create oxbow lakes, levees, point bars, and islands. Layers of evergreen tropical rainforest grow in the soil deposits in a succession of young to old. As waters recede, new growth quickly fills in the exposed areas. Grasses move into newly exposed habitats first, followed by woody shrubs, then early pioneer trees such as Annona, and, lastly, late-succession trees such as Chorisia. The várzea forest cycles nutrients, stabilizes flooded soils, and hosts a diversity of freshwater fish, terrestrial species, and even some aquatic mammals.
As the rains begin, the water rises and the forest begins its seasonal flood period. While some species begin migrating into the flooding forest to feast for the season, others are forced to seek higher ground in the surrounding hills. Immense fish called pacu swim in, lured by fruits that fall into the water from trees such as the yellow mombin and jauari palm. Unknowingly, these fish help the trees by spreading their seeds up and down the flooded forest. Manatees soon begin grazing on grasses submerged by the floods. Caimans move in to wait for an unsuspecting baby peccary to approach the water’s edge for a drink or for an opossum to fall from a low branch on its journey across a stream. The entrance of a jaguar upsets a group of red howler monkeys. The monkeys then alert the surrounding forest with their noisy howls. Lucky for them, the jaguar has different prey in mind: a turtle. The turtle makes an easier meal anyway, once the big cat cracks the shell with its powerful jaws. Meanwhile, arboreal spiny rats scamper through the canopy above, distracted by the abundance of fresh fruits. As night falls, they will become a tasty snack for a small cat called a margay. Spider monkeys, excited and energized from the fruits and insects they are eating, streak through the trees like circus acrobats.
Human activities pose the main threats to this ecoregion, particularly through habitat destruction and water contamination. Selective harvesting has eliminated some species from the area, including mahogany trees, tapirs, and several types of primates. For more information on this ecoregion, go to the World Wildlife Fund Scientific Report. All text by World Wildlife Fund © 2001
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