The Liquid Forest


July 31, 2012


Few riverine (bank) plant species will be found in the forest. These tend to resemble gap-colonizers and edge species that grow well in the strong sunlight of open areas. There is not a great diversity of riverside plant species, and rivers are often bordered by walls of vines which cover trees because of the access to bright tropical sunlight. The presence of this thick vegetation is largely why early explorers in the Amazon referred to the rainforest as an "impenetrable jungle."

Periodically inundated floodplain forests are quite different from terra firme forests found on well-drained soils. Since floodplain forests have high turnover rates, they are characterized by lower tree diversity and a less-developed canopy. Island forests typically consist of this type of forest. In the Amazon, floodplain forests have high densities of fruiting trees which attract large numbers of mammals.

Caiman. Photo by Rhett A. Butler


Many terrestrial animals depend on rainforest waters for survival, and some are found almost exclusively along rivers and lakes.

Reptiles are abundant along rainforest waterways. Lizards, including water dragons (Australia), monitors (Africa, Asia, Australia), iguanas (New World), and other species are especially common. One of the most interesting is the basilisk lizard of the New World. This lizard, popularly known as the Jesus Christ lizard, has the ability to run across water for considerable distances by using its long toes and tail. Any visitor to the rainforest can get countless hours of enjoyment by chasing these lizards off beaches and watching them use their quick stepping to support their weight as they escape across the water.

The giant snakes of the world, pythons of the Old World and boas and the Anaconda of the New, are found along waterways where they feed on large prey that comes down to drink at the river. Crocodiles, in various forms, are found worldwide, but perhaps the most impressive is the saltwater crocodile of Australia and New Guinea, which is famous for occasional attacks on humans. These giant crocodiles, which are found in marine, brackish, and freshwater habitats, may exceed 20 feet in length.

Adult wattled jacana. Photo by Rhett A. Butler

Bird life along rivers is prolific because of the availability of foods in the form of fish, insects, and fruits produced by riverside vine species. One interesting phenomenon is the gathering of macaws along the clay river banks of the upper Amazon where they lick the mineral-rich clay that binds to and detoxifies the harsh chemical content of the fruits they consume. River areas are among the best places for rainforest bird watchers, because they are open and bird life is abundant.

Mammals also are found along rivers. Jaguars are most often seen around rivers where they hunt and fish. Another predator found along rivers is the giant river otter of South America. This otter, which has no natural predators and is an efficient hunter, has been rendered rare by over-hunting, and can only found in scattered areas today where human presence is limited.

Hoatzin in Peru. Photo by Rhett A. Butler

Review questions:

  • How are floodplain forests different from upland forests?

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Continued / Next: Importance of Rainforest Rivers to People