GALLERY FORESTS are commonly defined as any forest along a river or stream, especially in a grassland. Since geographers frequently cite Brazil as the best example of this phenomenon, we often use the Portuguese word galeria to identify it. Gallery forests are also found in places other than Brazil. For example, an article in the journal Landscape Ecology, discussing gallery forest expansion in Kansas, quotes the Spanish explorer Francisco Coronado as saying in 1541, “There is not any kind of wood in all these plains, away from the gullies and rivers, which are very few.” Gallery forests are common in tropical Africa, too. Brazil’s Amazon basin is covered mostly by tropical RAINFOREST. To the south, many tributaries of the Amazon River flow northward through tropical savanna grasslands. Detailed vegetation maps of Brazil show fingerlike extensions of tropical rainforest protruding from the Amazon along the banks of these tributary rivers. These protrusions are called gallery forests. On smaller streams, the crowns of gallery forest trees interlock above the stream. If you were to float down such a stream, you would travel through a long green tunnel or gallery of vegetation. Tropical rainforests typically exhibit tremendous biological diversity. A small patch may contain many species of trees. These trees are tall and form a leafy canopy 100 foot (30 meter) or more above the ground. This canopy prevents much sunlight from reaching the forest floor, which generally has limited amounts of undergrowth. Wherever sunlight does reach the forest floor, however, a profusion of bushy plants known as jungle vegetation is the result. One place where this occurs is along the banks of large rivers. Tropical gallery forests, therefore, contain plenty of jungle vegetation. Many of the animals that make the gallery forest their home live in the canopy. Arboreal animals are well adapted to life in the trees. South American monkeys, for example, have prehensile tails to help them grasp tree limbs. Birds seek foods such as the seeds in fruits or tree-dwelling insects. Most trees in Brazil’s gallery forests share some common traits. They are mostly hygrophytic (waterloving), well suited to an environment that undergoes prolonged flooding each year. Most are dense hardwoods such as mahogany and teak, prized by lumber merchants for such uses as flooring, cabinetmaking, boatbuilding and interior trim. Exploiting this resource is a challenge, however. First, the trees do not occur in pure stands. Second, once found and cut down, they are difficult to transport to the sawmill. Because the wood is so dense, the logs will not float. Despite these difficulties, loggers feel that the effort is worthwhile, since a single tree may fetch several thousand dollars. Loggers are taking even the less desirable trees, converting the wood into charcoal for use in 1 of Brazil’s iron smelters. Gold mining and other mining activities complicate the picture. Not only do mines scar the surface of the Earth, the mercury that the miners use to process the gold pollutes the rivers. Fish take up the poisonous mercury, making them unfit for human consumption.