scientists and resource managers. They sample, test, measure, evaluate, and restore
the landscape and biodiversity.
The Lake Tahoe basin, one of the world's most spectacularly beautiful regions, is still troubled by environmental harms of the last century that scientists, governmental and community leaders seek to overcome in their struggle to preserve and restore its unique biological diversity.
When the Comstock mining boom felled vast forests of old-growth pine, it impaired the health and stability of this magnificent ecosystem.
Subsequent growth and development threatened the clarity of Lake Tahoe, known for its sapphire blue waters as the "jewel of the Sierra."
Lake Tahoe, which straddles the California-Nevada border high in the Sierra
Nevada, is the centerpiece of an ecosystem that is continually being examined by
scientists and resource managers. They sample, test, measure, evaluate, and restore
the landscape and biodiversity.
The Tahoe basin covers 200,000 acres, three-fourths of which have ecologically sensitive meadows, marshes and slopes. Its watershed is home to 260 wildlife and 1,000 plant species, including 16 that are threatened or endangered.
Economic growth and development have brought prosperity to the basin, but also adversely affected the soil and air. Overall, its biodiversity has declined, but development now is innovatively regulated to protect its natural riches, and public landowners are creatively reclaiming some troubled areas.
Approximately 85 percent of the land belongs to the U. S. Forest Service, Neva da Division of State Parks, the California Department of Parks and Recreation, and California Tahoe Conservancy. The remainder of the land is privately owned.
The challenges to biodiversity conservation at Lake Tahoe are many and inter related. Dr. Charles Goldman, an expert on Lake Tahoe for three decades, says en vironmental protection measures over the past 20 years have slowed the rate of deg radation caused by development, but "it takes a long time to heal," and use of the basin is heavy.
Lake Tahoe Faces Its Challenges
The major environmental problems confronting the lake basin are erosion, al gal
growth, and dead and dying trees.
Erosion from soil disturbance in the basin causes lasting detrimental effects on the lake's renown clarity. Sediment loaded with algae-feeding nutrients washes into the crystal water at the rate of 30,000 to 60,000 tons a year. But erosion can be stemmed in different ways, depending on soil conditions. Many projects have been successfully completed, and more are underway. Revegetation works well in richer soil and flat areas, while steep or rocky terrain may require physical bracing in screen fashion. Roadside erosion can be fixed with curbs, gutters and culverts.
Water, and the nutrients it contains, lingers for centuries in Lake Tahoe, taking 700 years to exchange its volume, and slowing the lake's natural ability to cleanse itself. This enables scientists to study long-term effects of watershed dis turbance by taking core samples from the lake bottom to compare conditions at dif ferent time periods. But it also helps to foster algal growth to such an extent that the lake's remarkable transparency is decreasing by 18 inches a year.
Lake Tahoe's average depth is 1,000 feet, dropping to 1,654 feet at the deepest point. In the years that Goldman has been studying the lake, its clarity has dimin ished at least 30 feet. Nevertheless, it is possible to see to a depth of 80 feet.
"It is still one of the clearest, cleanest lakes in the world," Goldman said.
A more visible environmental predicament is the proliferation of dead and dy ing trees in the national forest surrounding the lake that have fallen prey to se vere drought and a relentless bark beetle infestation. Other unhealthy forest condi tions are the result of activities that occurred more than a century ago, during the colorful Comstock era.
The Lake Tahoe basin was virtually wilderness until the Comstock silver and gold mining boom in Nevada attracted hordes of miners to the region from 1860-1880. The virgin forest that encir cled the lake was largely clear-cut to provide wood to shore up the mines and make railroad ties. The result was highly detrimental to the region's biologi cal diversity.
"They took the pine and left the fir. The seed source for pine was hauled away by the boxcar load," said John Swanson, who heads the fire and timber management program at Lake Tahoe for the Forest Service. Although three national forests ring the lakeTahoe, Eldorado and Toiyabethe portions within the Lake Tahoe basin are managed as one unit.
Clear-cut Reduced Biodiversity
After the clear-cut, a forest of mixed conifers, whose biological diversity had fur nished health and stability, became nearly a monoculture of fir.
A cycle of unusually wet weather and nearly a half-century of fire suppression resulted in a forest thick with fir and fuel.
"We have dramatically reduced the vegetative diversity in the Tahoe basin over the last 150 years," Swanson said.
Around the turn of the century, Lake Tahoe began to attract summer visitors. It grew more popular after World War II, when travel increased and word spread about the cool mountain climes, clear blue waters, and breathtaking vistas.
In the 1950s, the completion of Interstate 80 and winter maintenance of High way 50 into the basin put Lake Tahoe within four hours of San Francisco by car. The 1960 Olympic Games at Squaw Valley spurred expansion of the ski industry. High-rise hotel-casinos sprang up on the north and south shores on the Nevada side, and homebuilding and commercial development intensified. The permanent resident population swelled, and by the 1980s had quadrupled to about 60,000, becoming 200,000 on busy summer weekends.
Over the past 25 years, more than 29,000 acres have been developed. There are 49,000 subdivided lots, and more than 25,000 homes, 14,000 apartments, and 11,000 motel and hotel rooms. The economy supports 20,000 jobs and a $1 billion annual economy.
TRPA Promotes Biodiversity
Responding to the growing threat of pollution during the 1960s, the governors and state legislatures of California and Nevada approved a bi-state compact to oversee and regulate development at and near Lake Tahoe. Congress ratified the compact in 1969 and created the Tahoe Regional Planning Agency (TRPA), which became the nation's first bi-state regional environmental planning organi zation.
An amendment in 1980 empowered the TRPA to adopt and enforce environmen tal quality standards, and a long-range regional plan took effect in 1987. The TRPA has extensive regulatory powers, and operates with participation of both lo cal and state governments.
"Lake Tahoe is a fabulous national resource in a very sensitive setting," said David Ziegler, TRPA executive director. "The main thing we've been able to do is hold the line on environmental quality and prevent the kind of degradation other ar eas have experienced."
In its planning, the TRPA has adopted regional goals to expand and promote bio logical diversity of plant communities, wildlife and fish habitat, restore unique ecosystems such as wetlands, and conserve sensitive plant species.
Ziegler says the health of the forest is of major concern, but the remedies also are troublesome.
"Everyone agrees we have a problem, and everyone is trying very hard," he said.
In recent years, a fierce bark beetle infestation, combined with six years of drought, and the forest's dense, unnatural vegetative monoculture, has weakened and killed at least 25 percent of the trees - up to 80 percent in places. One variety, the Jeffrey pine bark beetle, can be suppressed by removing larvae-infested trees before they have died.
Other threats are dealt with by regulations. A TRPA ordinance restricts grading between October and May to limit soil disturbance, reduce the potential for ero sion, and help protect water quality.
The Forest Service must survey proposed logging sites to locate and mitigate potential impacts on other resources, such as wildlife habitat, stream zones, and historical interests a costly and time-consuming, but necessary, procedure to safeguard them.
"We need to be patient, go through the procedures cor rectly, and look to the future," Swanson said.
Dead and dying trees create a more varied wildlife habitat and increase biodiversity, but also pose a fire hazard.
"In this century, the forest has been overprotected to the point that it's unhealthy. Like storing food in a jar too long, it's gotten to the rotten stage and needs to be thinned out," said Swanson.
The worst of the bark beetles is the fir engraver, so named for a pattern it leaves on the trees it destroys. There is no acceptable way to suppress it.
"It will run its natural course. We will see trees turn brown, then gray, then fall to the forest floor. Eventually, we won't see as many trees dying. A fire will come through, and then it will look very different barren and black," Swanson said.
To reduce fire hazard and restore vegetative and habitat diversity, the Forest Service is removing dead and dying trees, thinning areas of unnaturally dense forest stands, and implementing careful prescribed burns. Its proposed forest manage ment projects would promote biodiversity by providing for a healthy forest that could support a broader and more natural diversity of wildlife habitat.
But the Forest Service can only make a dent in the beetle problem. It sold 15 mil lion board feet of timber last year nearly four times as much as the forest man agement plan called for but visually it made little difference. Only 25 percent of the forest can be logged because of steep terrain, wilderness, or uneconomical con ditions, leaving 75 percent of the treesdead and alivewith no prospect of a chainsaw.
Dead fir loses its value as lumber in less than a year, and is no good for fire wood after a year and a half, Swanson said. Besides, he noted, most people cutting firewood won't venture more than 50 feet from the road, and there are few roads in the Lake Tahoe Basin Management Unit.
But progress is being made. Numerous federal, state and local agencies, fire districts, environmental and private groups, and individuals are working together to preserve and reclaim the natural environment, and to improve biological diversity, forest health, and air and water quality.
The Tahoe Conservancy an entity under the state Resources Agency has provided $26.8 million in grants for 65 locally sponsored erosion control projects.
The grants will enable local governments to revegetate more than 100 acres of land, construct 58 miles of roadside drainage facilities, and restore 30 acres of wetlands.
"We're learning about what is necessary to meet the multiple demands of the basin," said Dennis Machida, executive director of the Conservancy.
The state Department of Parks and Recreation, in cooperation with the Conservancy and the Forest Service, proposes to restore in 1995 the natural flow of a stream that was dammed and diverted, causing the drying and loss of valued wildlife habitat in an 80-acre meadow behind a golf course along Highway 50 at Meyers. The dam will be removed and the creek bed raised to allow the stream to flow into its original channel. The goal is to restore and enhance biodiversity by improving fish habitat, and allowing water to soak into the dried meadow, nourish plants, and invite the reappearance of birds and insects.
"When it's finished, we will have returned the stream to its natural water course and increased the diversity of the habitat so many more species of animals can use it," said Catherine MacDonald, a restoration hydrologist for the parks department.The Conservancy has authorized $3.3 million for 22 wildlife projects, including restoration of 180 acres of critical habitat in the Cold Creek, Washoe Meadows, and Meeks Creek areas of El Dorado County, and in the Upper Ward Creek, Blackwood Creek and Carnelian Canyon areas of Placer County.
The projects, which also involve the Forest Service and Department of Parks and Recreation, will restore 11.6 miles of stream in Cold, Taylor, Ward, Angora, General and Blackwood creeks, and in the Upper Truckee River.
The peregrine falcon is being reintroduced, and osprey nesting platforms have been built on tree tops near Baldwin and Kiva beaches.
The Conservancy's acquisition has preserved more than 100 acres of forest habitat, including several key parcels needed for travel corridors.
Restoration and protection programs will continue, so that the inevitable growth and economic development will not diminish Lake Tahoe's health and beauty.
"Tahoe is unique. We must balance the economic, recreational and environmental values," said Machida. "We can't go back to the way Tahoe was in the past, but we can stabilize the situation and prevent or mitigate new impacts."