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A Natural History

by Alice Outwater

212 pages, paperback, Basic Books, 1997

Praise for Water

"What a fresh and vital book this is, one that will change the terms of many debates. Bring back the beaver, bring back the prairie dog, and with them will come the water 'clear as dew' that once distinguished this continent.'--Bill McKibben

"This book is a real eye-opener--and also a real pleasure to read. That's a rare combination."--Noel Perrin

Quotes from Water

"Beavers do more to shape their landscape than any other mammal except for human beings, and their ancestors were building dams ten million years ago. These Miocene beavers were 7 feet long, felling trees ages before the mammoths roamed. Their underground spiral burrows can be found from western Europe to central Asia and North America; . . . Legends of these prehistoric giants were once widespread. The Indians of Nova Scotia claimed to know of an ancient beaver dam so vast that it flooded the Annapolis Valley; farther west, tales circulated of tribal ancestors using immense beaver teeth to hollow out their canoes.

" In tribes across North America, legend had it that the beaver helped the Great Spirit build the land, make the seas, and fill both well with animals and people: Long, long ago when the Great Waters surged in a blind and shoreless world, the gigantic beaver swam and dove and spoke with the Great Spirit. The two of them brought up all the mud they could carry, digging out the caves and canyons and shaping the mud into hills and dales, making mountains where cataracts plunged and sang. Some tribes believed that thunder was caused by the great beaver slapping his tail."

"It is estimated that as many as two hundred million beavers once lived in the continental United States, their dams making meadows out of forests, their wetlands slowly capturing silt. The result of the beaver's engineering was a remarkably uniform buildup of organic material in the valleys, a checkerboard of meadows through the woodlands, and a great deal of edge, that fruitful zone where natural communities meet. Beavers are a keystone species, for where beavers build dams, the wetlands spread out behind them, providing home and food for dozens of species, from migrating ducks to moose, from fish to frogs to great blue herons."

"The beaver is a clever engineer, but its brain is embarrassingly small . . . Beaver's don't have much gray matter, and they don't see well. Nevertheless, there is abundant evidence . . . that much of their building technique appears to be learned through their long childhood. Oddly, although the European beaver, Castor fiber, is nearly identical in appearance to the American beaver, it has no interest in dam construction; in most regions, European beavers confine their efforts to digging burrows in the stream bank. It seems likely that the fine points of dam construction were lost to Castor fiber during the centuries when only a few survived in parks."

. . .

"When the Hoover Dam went up, fish that had evolved to survive in the widely fluctuating and muddy flows of the Colorado lost their competitive advantage. The muscled humps of the humpback and bonytail chubs, designed to allow these fish to hold position or make progress against currents that swept most fish away, were suddenly superfluous. Eight dams on the lower Colorado and an aggressive dredging program to redirect the riverbed have contributed to the extinction or threatened status of eight species of fish native to the Colorado. As a kind of compensation, channel catfish and rainbow trout were introduced, and have prospered.

"Water takes much longer to move through a dammed river system, and nearly all the sediment and organic matter carried along by the water is permanently stored in the reservoirs. There is less organic matter in the water to fuel the aquatic ecosystem; worse, since natural river channels are maintained by a dynamic equilibrium of sediment deposition and erosion, water without sediment can trigger major riverbed erosion. When dams retain silt, erosion is accelerated for dozens of miles downstream. Below the Hoover Dam on the lower Colorado, for example, millions of cubic yards of sediment were scouted from the channel for 100 miles, and the channel slope was noticeably reduced. It took about twenty years after construction for the channel bed to be fully armored and stabilized--that is, transformed into a boilerplate of bedrock and boulders.

"The water that flows in a stream is well mixed and well oxygenated. When water rests in a reservoir, it starts to stratify. Since cold water sinks and warm water rises, reservoirs generally stratify all summer long. Phytoplankton proliferate near the surface of the reservoir, releasing oxygen and keeping the water saturated with it. Little mixing occurs, and the sunlight does not penetrate below the top few yards."

"When a watershed is dammed and lakes and reservoir-fed rivers replace the swift, turbulent, highly oxygenated water of a free river, the riverine species will begin to fade away. In time, the entire aquatic community of a dammed river will begin to resemble that of a lake ecosystem. Moreover, when rivers are dammed, the fish that mature in the ocean and swim inland to spawn in the rivers begin to disappear."

"In the 1930s, Canadian fisheries biologists showed that substantial releases of hatchery sockeye increased neither the commercial catch nor the number of fish spawning in the wild. Canada closed all of its Pacific salmon hatcheries, and a number of American hatcheries on the West Coast were closed. But the Washington Department of Fisheries expanded its network. In 1958, the first of twenty-five Washington fish farms was built. By 1966, the program, which used natural lakes to raise large numbers of confined fish, was abandoned, because almost no farm fish were coming back to spawn. But to prepare the selected areas for the farmed salmon, all the native fish had been poisoned, so the failed fish farms, in a addition to costing millions of dollars, removed dozens of wild salmon runs.

"Hatcheries continue to release many millions of salmon every year, and the salmon returns have continued to decline. In 1992, a study conducted by Terry DiVietti, a Central Washington University psychology professor, provided an explanation. When fish are raised in a hatchery, they learn far less than the tiny fingerlings that grow up in the riverbed. Hatchery fish in concrete tanks have no threats in their life; they flock to the surface for food, and swim in packs the rest of the time. By contrast, fish that grow up in a stream learn to survive dozens of predators, and will hide, dart out, and zip back under cover to eat. They swim alone. They know how to use rocks and logs to conserve energy, having honed their swimming technique in the variable complex flows of a stream. Hatchery fish learn none of these lessons in their tank. Releasing hatchery fish to the wild may be the piscine equivalent of sending a well-fed adolescent who has watched a lot of television into the woods to survive on his wits.

"The other problem with hatchery fish is genetic. In the last few decades, it has been found that stream fish are much more genetically dynamic than anyone had ever imagined. There once were roughly 1,000 breeding stocks of salmon, of which 106 are now extinct and 314 are threatened or endangered. A human being offers up a few genetic carriers to the world; a salmon offers up thousands of genetically unique offspring, and the few that make it through to adulthood are likely among the best of the lot. Therefore, salmon species adapt relatively quickly to local conditions. Genetically speaking, each stretch of river is home to its own strain, and every adult that returns is the pick of a very large litter. Hatcheries provide the protection that salmon are designed to do without, so hatchery-raised fish are genetically unculled. Releasing millions of hatchery fish plays havoc with the wild salmon, for both compete for the same food sources. Hatchery fish are much less likely than wild salmon to survive to adulthood, but they do apply pressure on the surviving wild stocks."

Table of Contents of Water

  1. The Fur Trade
  2. Nature's Hydrologists
  3. The Woods
  4. The Voyage of Rainfall
  5. A Sea of Grass
  6. Plowing the Plains
  7. The Water Over the Dam
  8. Mussels, Gators, and the Corps
  9. Aqueducts and Toilet Bowls
  10. Down the Drain, Up the Stack
  11. What Sludge Tells You

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