Lake Tahoe, an enormous expanse of azure water flanked by gentle meadows and dark green forests and rimmed by snow-capped granite peaks, is one of the world's great scenic and ecological wonders.

It is one of the largest mountain lakes in the world (miles long and 12 miles wide), and also one of the deepest (1,645 feet). It holds enough water (126 million acre feet) to cover the entire State of California more than a foot deep. It contains twice the amount of water held in all other lakes and reservoirs in California combined.

Tahoe's water is world famous for its startling clarity. Even today, one can see objects 70 feet below the surface, a clarity matched by few large alpine lakes anywhere in the world.

Created in distant millennia by geologic, glacial and volcanic forces, the Tahoe Basin had a slowly evolving and essentially balanced environment for thousands of years, with surrounding forests, meadows and marshlands helping to maintain the clarity and purity of the lake. There was also a balance between human uses and the natural environment, for the Washoe left relatively little mark.

Historically, Lake Tahoe retained its renowned clarity because of the scarcity of nitrogen and phosphorous compounds and other nutrients that support the algae that commonly cloud the waters of other lakes.

Lake Tahoe lacked these nutrients for several reasons. For one thing, most of the Lake Tahoe Basin is taken up by the lake itself, so most of the basin's rain and snow fell directly onto the lake. What fell on the land was absorbed by trees, plants and soil, or passed through a natural filtering system of riparian areas, marshes and meadows, which took almost all of the sediments and nutrients out of the runoff before they could reach the lake.

Another factor was that under natural conditions the granitic and volcanic soils of this mountain region, which contain relatively low levels of nutrients in any case, tended to erode slowly. Consequently, there was little flow of sediment or nutrients into the lake from this source until human activity upset the balance.

This pristine environment also provided habitat for a rich diversity of plants and wildlife. Tahoe's tree-covered slopes and wetlands, meadows and clear small streams provided a home for deer and bear, for native fishes from trout to red-sided minnows, for hawks and eagles, ducks and Canada geese. Hundreds of species of native plants thrived in forest, marsh, and meadow. The hardiest even braved the highest peaks.

But now, in scarcely a century, an equilibrium that endured for thousands of years is rapidly being lost, and resource values are steadily deteriorating because of human activities.

Early Changes

The first major change in the environment came with the logging of the 1860s, when much of the basin's forest was clear-cut to provide timber for the mines of the nearby Comstock Lode. The logging tapered off with the collapse of the mining boom, but not before most of the Tahoe's virgin forest was gone.

The fisheries fared no better. The once-abundant runs of cutthroat trout were netted and shipped off, first to feed the hungry miners of the Comstock Lode, later to supply San Francisco, Chicago and New York restaurants, which imported Tahoe area trout by the carload.

By the turn of the century, farms and sheep ranches, resorts such as Tahoe Tavern and Lucky Baldwin's Tallac House, and the great "rustic" estates of the Popes, Ehrmans and other wealthy San Franciscans, began to appear.

By the 1920s, the automobile and better roads made Tahoe accessible to the ordinary visitor, and landholdings began to be subdivided for summer homes, especially along the southern and western portions of the basin.

Urbanization Takes Hold

The urbanization of the Tahoe Basin remained a relatively slow process until the 1950s, when the winter opening of Highway 50 and the completion of the Interstate 80 freeway brought the San Francisco Bay area within a four-hour drive.

Year-round access to the lake encouraged expansion of gaming, as modest clubs designed for seasonal business were transformed into towering casinos packed with visitors throughout the year. The new access in winter also attracted thousands to the basin's ski slopes, and the 1960 Olympics in Squaw Valley spurred rapid expansion of the ski industry. Today, recreation has become the centerpiece of a one and a half billion dollar economy which employs more than 20,000 people.

Between 1960-1980, as the number of businesses and their visitors grew, the permanent population of the region increased five-fold. These permanent residents in turn have needed homes, stores and services. In the meantime, second-home development has boomed, as more and more people have found themselves with the desire and the means to enjoy the amenities of the Tahoe Basin. In this same period, the number of houses grew from 500 to 19,000. By 1970, more than 49,000 subdivided lots had been created and more than 600 miles of roads had been built to serve the new subdivisions.

The permanent population is now about 54,000, and as many as 200,000 people visit during the busiest summer weekends. Annual visitation is estimated at 23 million visitor days.

This tremendous growth in population and visitor use has had an adverse effect on the capacity of the basin's many small watersheds to maintain the clarity of the water they discharge into the lake.

For with urbanization has come subdivision and development, much of it in environmentally sensitive areas. This has placed a severe strain on the ability of the land and its vegetation to absorb a greatly increased load of silt-laden water and to filter out the undesirable nutrients and pollutants.

Construction of roads, parking lots and buildings in inappropriate areas disturbs the soil and increases erosion and runoff. The impervious surfaces of buildings, paved roads, and parking lots cover the moisture-absorbing soil and its plant life. They increase runoff from unvegetated areas to the point that it erodes ditches and overloaded stream channels and pours nutrient-rich sediment directly into the lake.

Even air pollution -- carried in from outside the basin, or generated by the basin's own increased population and vehicular traffic -- affects Tahoe's clarity. For a great deal of these air-borne contaminants fall into the lake or are washed off into lake-bound ditches and streams.

The gradual degradation of the lake went largely unrecognized for some years, as the damage occurred little-by-little with each additional lot that was built on, each new road that went in.

There was one cumulative indicator, however -- the decline in the celebrated clarity of the lake.

Just since 1968, Tahoe's waters have lost more than 40 feet of their transparency. And the loss continues, at the alarming rate of a foot to a foot and a half every year. The algae growth rate, meanwhile, has doubled. In a few swift decades, Lake Tahoe's crystalline waters could become as clouded as the waters of any ordinary lake.

Urbanization has had other impacts on the basin as well. The beauty of Lake Tahoe attracts millions of visitors each year. However, public access is limited due to the lack of access points, or of adequate facilities at existing sites. As a result, the available beaches and other recreation facilities are often tremendously overcrowded. Traffic congestion is ever-worsening. This situation not only lessens the quality of the recreational experience, it also contributes to the degradation of the lake's water quality, because of erosion from unpaved but heavily-used overflow parking areas and increased air pollution from stalled traffic.

Many existing trails are not linked because key portions of public right-of-way cannot be obtained, making it difficult for people to get from one area to another by bicycle or by walking. Instead, many visitors today find themselves trapped in their cars, unable to catch more than a glimpse of the lake and its meadows and marshes through the wall of buildings and closed-off property that screens so much of the lake from view.

Wildlife has also suffered from urbanization. The basin provides habitat for more than 290 species of birds, animals, and fish, plus more than a thousand species of plants. Their preservation has been increasingly difficult as development and other human activities degrades or destroys more and more of their habitat.

The basin's original marshlands have been reduced by 75%, its meadows by 50% and its riparian areas by 35%. As a result of the loss of habitat, the huge flocks of migratory geese and other waterfowl that once visited every year no longer use the basin as a resting place. Ducks and geese have trouble finding nesting areas free from human disturbance. Bald eagles and ospreys lack undisturbed perching and nesting sites. Fish find it difficult to migrate up streams to spawn.

The forests that many wildlife species and Lake Tahoe's clarity depend upon have suffered from a number of problems since most of the original mixed forest of pines and firs was logged off for the Comstock mines.

The existing stands are overstocked and lack species and age diversity due to the lack of management and fire suppression. The problems have now become acute, however, as much of the basin's forest is dead or dying as a result of a seven-year drought and accompanying insect invasion. With tree mortality varying between 25% and 40%, there are serious concerns about the possibility of wildfires and other threats to public safety.

On the positive side, as the Conservancy and other land-managing agencies put extra effort into fire hazard control, they also have an opportunity to improve long-term forest health through measures ranging from revegetation of disturbed soils to the thinning of dense small trees.

The challenge before us is to accommodate our human activities to the natural system that has maintained the Tahoe Basin for thousands of years. Only then can we enjoy the lake without destroying the very qualities that make it so uniquely valuable.

To meet this challenge, a comprehensive basinwide effort is being undertaken by a wide range of federal, state, regional and local agencies and private organizations.

Two primary resource management strategies are being employed. One is an extensive regulatory and planning system administered by various agencies such as the bi-state Tahoe Regional Planning Agency (TRPA), the State Water Resources Control Board and the Lahontan Regional Water Quality Control Board, the California State Lands Commission, the U.S. Environmental Protection Agency, the U.S. Army Corps of Engineers, El Dorado and Placer counties, and the City of South Lake Tahoe.

The second strategy is a massive public acquisition and site improvement effort involving the Conservancy, the U.S. Forest Service, the U.S. Natural Resources Conservation Service, the California Conservation Corps, the California Departments of Parks and Recreation, Forestry and Fire Protection and Fish and Game; El Dorado and Placer Counties; the City of South Lake Tahoe; the North Tahoe, Tahoe City and South Lake Tahoe Public Utility Districts; the Tahoe Resources Conservation District; and the Tahoe-Tallac Association, the Tahoe Rim Trail Fund, and numerous other organizations.

Both resource management strategies involve information generated by research and monitoring activities conducted by TRPA, the Lahontan Regional Water Quality Control Board, the U.S. Forest Service, the University of California at Davis through its Tahoe Research Group, the U.S. Geological Survey, the Interagency Monitoring Program, and a number of other cooperating organizations.

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