by Whit Gibbons

July 14, 2003

Have you ever seen a pink dolphin or a river five miles wide and a hundred feet deep? I have. I just returned from the Amazon, where such sights are to be expected.

Professional ecologists are often advised to experience "the tropics" in order to appreciate the diversity of life and the multitude and complexities of species interactions. My own experiences in tropical regions have confirmed for me that they do indeed offer intrigue and biological mystery for anyone who is fascinated by the natural world.

The Amazon is unsurpassed for magnitude in all tropical environment categories. It is the mightiest of all natural environmental areas remaining in the world. Consider the following facts. The country of Brazil is approximately the size of the continental United States, and the upper half encompasses the Amazon River, which we all are familiar with by name. The Amazon Basin, the watershed that collects the water that forms the Amazon River from numerous tributaries, extends into Peru, Colombia, and a few other South American countries. Try to visualize the extent of this watershed, which covers more land area than a rectangle from Oregon to Maine to Florida to southern California. Imagine a single river that collects all the rainfall each year that falls inside the rectangle. An Australian friend told me that the Amazon River transports more water on one rainy day in the wet season than all the rivers in Australia carry in a year. I believe him. The river is enormous.

Water is the essence of the Amazon, and the annual transitions from wet to dry seasons control the events in the lives of Amazonian plants and animals, including people. The river system has what is comparable to a single tide schedule each year. During the dry season, which is roughly from June to December, the water levels of the river may fall more than forty feet below the average high water level. Last week I saw river freighters afloat in a three-mile-wide section of river where they would be grounded on a beach with sunbathers in a few more weeks.

Scientists have made and will continue to make countless wildlife observations about the natural wonder known as the Amazon. One colleague returned from a five-day excursion into the jungles. He was intrigued by the Amazonian bird life and said the bird color patterns he saw were as if a three-year-old child had randomly picked the brightest colors from a box of crayons and colored the birds. I saw some of these birds, and the color spectrum is fully represented.

Other colleagues were amazed by a fish that had been discovered the previous week. I saw the animal in an aquarium, as it stood upright underwater with its mouth at the surface, breathing air. The creature looked like a brown drinking straw with a single fin that went the length of its body across its back and under its belly. The fish was of more than casual interest from a scientific perspective: the ichthyologists did not know what species, genus, or family this air-breathing fish belongs to, and apparently it did not belong to any yet described order of fishes. Such discoveries can happen in the Amazon when scientists are on the lookout.

I'm not sure what was most fascinating to me, but the pink river dolphins bring an awareness of the biological strength and power of this freshwater ecosystem. The fact that a river system can be so immense and long-lasting that typical sea creatures, including stingrays as well as dolphins, can evolve into freshwater forms is hard to comprehend. And, by the way, two species of freshwater dolphins inhabit the Amazon River. A small gray form lives in some of the same regions as the pink one. Entire oceans have been involved in the evolution of different species of dolphins, and the fact that two species have developed their own identity in a river bespeaks volumes about the size and nature of that river.

The Amazon is truly the big top of the world's environmental attractions, with thousands of spectacular sideshows to keep anyone entertained.

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