Lake Tahoe

Category: Freshwater Lake Biomes.

Geographic Location: North America.

Summary: Strikingly beautiful and a moist habitat oasis amid the high and dry peaks of the Sierra Nevada Mountains, Lake Tahoe must contend with overdevelopment by humans and an altered forestscape.

The Lake Tahoe basin, encompassing over 500 square miles (804 square kilometers) astride the California-Nevada border high in the Sierra Nevada Mountains, fills a geological trough, or graben, created by faults from ancient tectonic movements, later reshaped by glaciation. Perched at an altitude over 6,000 feet (1,828 meters), this freshwater lake is the 11th deepest on Earth, reaching a depth of 1,645 feet (501 meters). The 192-square-mile (309-square-kilometer) lake occupies montane and sub-alpine zones, and stretches in a rough oval 12 miles wide (19 kilometers) wide and 22 miles (35 kilometers) long.

Winter storms feeding the lake’s copious water supply also limit the growing season to less than 120 days, depending on the alternating El Nino-La Nina cycles that bring moisture off the Pacific Ocean mainly in the form of snowfall. Annual precipitation averages range from 30 inches (78 centimeters) falling as snow on the dry eastern slopes to over 70 inches (178 centimeters) on the western slopes.

In the midst of a desert, the lake’s water is a reliable reservoir, and its encircling forests an inland refuge of biological diversity. The mountain range’s extent and elevation create a rain shadow effect, giving rise to distinctly different vegetation communities along lines of longitude as well as changes in altitude.

Biodiversity

Sugar pine, once abundant throughout the basin, was extensively logged in the nineteenth century. The granite-derived, well-drained soils today support Ponderosa pine, lodge pole pine, and incense cedar; while Jeffery pine and piñon pine, and fire-dependent broadleaf-sclerophyll forests, or chaparral, is widely found in the rain shadow along the more arid east shore and south-facing slopes. Great Basin shrub species are also found in the drier terrains below the snowline.

Once-extensive wetlands, especially along the south shore and adjacent to some bays, still provide favorable conditions for sedges, cattails, and wildflowers that filter the runoff and nourish whitefish, trout, and birds, in addition to willows and black cottonwood trees. Thick stands of pine trees lined the lake shores in the 1850s, prior to being clear-cut.

Because of human-monitored fire suppression, forests in the Lake Tahoe biome commonly contain abundant stands of mountain hemlock, Sierra juniper, quaking aspen and big-leaf maple. At higher altitudes, the red fir and white fir forests dominate below the treeline, above which alpine wildflowers and lichens predominate in the often frigid reaches of passes and old glacial tarns.

Grizzly bears, wolverines, and peregrine falcons, once residents of the region, are extirpated, but the Forest Service has listed several other species common to the basin. Important to this assemblage of wildlife and fisheries was the role of beavers—before the fur trade—in sequestering water in ponds. Beaver dams had the effect of regularizing stream flow from snowmelt through the dry season; and as a keystone species, the beavers maintained ponds, attracting many other plants and animals dependent on the higher water levels.

In areas where seasonal fires rejuvenated fire-dependent species, the black-backed woodpecker, indicative of post-burn timbered lands, thrived in greater numbers than today. As land-use practices shifted due to a striking rise in human population, wildlife retreated. Introduced species have reduced the numbers and range of natives. For example, the Sierra Nevada yellow-legged frog is being restored to lakes in the Desolation Wilderness by removing introduced brook trout and rainbow trout from those stocked waters. The Desolation Wilderness is among the oldest reserved lands, since 1899 extending protection to 63,960 acres (25,883 hectares) of sub-alpine and alpine forest that grew since the initial logging after the California Gold Rush of 1849.

Human Impact

Railroad building and the discovery of silver in the Comstock lode of 1859 led to the loss of virtually all forested landscape on the Nevada, or eastern, side of the lake—and provoked the California Assembly to pass legislation in 1883 to appoint a forestry commission and sparked a movement for the protection of ample water to promote and sustain agricultural land uses in the foothills and valleys of the lower slopes.

A 1976 study of the land-use cover of different types within the basin distinguished five vegetation associations that were discernibly reduced after 1900. Findings revealed that three-quarters of the marshes, half of the mountain meadows, over one-third of the streamside-riparian zones, 15 percent of forests, and 5 percent of shrub lands here had been replaced by suburban expansion.

Studies reveal that since World War II, growth had incorporated a 2,000 percent increase in developed land in the southern lake basin. This region had been the more extensive and geographically diverse lakeshore landscape.

Although human influence on the landscape ecology, air quality, and water resources of the Lake Tahoe biome date to the silver mining rush of 1859, the dominant and persistent role of human-induced changes in the watershed changed markedly after 1945. These impacts peaked in the 1940–87 period, in terms of the most extensively affected terrains; this was due to an abrupt rise in the amount of impervious paved surface areas that accompanied residential, commercial, and municipal building.

The Tahoe Prosperity Center reported that in 2020, about 56,935 residents lived in the lake region; they largely account for the degradation of the area’s waters, forests, wetlands, fisheries and wildlife. The fragmentation of biological communities associated with landscape development has disproportionately affected keystone species, and thus diminished the biological diversity of the entire basin. That is because some identifiably important vegetation associations, such as meadows and wetlands, sustain a greater variety and density of wildlife when intact.

Before 1900, a more diverse array of fire-tolerant forests and dependent meadows sustained cattle and sheep here, but shepherding successively destroyed native grass cover and by 1899 there was extensive deterioration of pasturelands. With the failure of an effort to protect the lake as a National Park, in 1917 the State of California banned further fishing in Tahoe, so depleted were the native and introduced stocks from fish hatcheries.

After the construction of the transcontinental railroad over the Sierra summit to Nevada in 1869, tourism began to become a viable industry in addition to timber, mining, and fisheries.

The regeneration of the basin’s forests was shaped through management, and much of the policy after 1940 centered on strategies aimed at reducing perceived threats from the natural fire cycle. Fire suppression had the ironic counter-influence of both a loss in tree diversity and increased densities—so that when periodic drought cycles transpired, the loss of timber could be severe, as happened in the late 1980s and 1990s. Like so many drastically altered landscapes and water bodies, these extant natural features comprising the Tahoe region are actually artifacts of social desires and economic choices made long ago, but whose consequences currently linger; the past is persisting and ever intruding into all effective means and each collaborative step to restore the lake water’s clarity, scenic beauty, and allure of the mountain air.

In addition to locally and regionally generated direct and indirect pollution effects, climate change impacts have been noted in Lake Tahoe, specifically a noticeable long-term warming trend. Having coped with extractive industries, population growth, unhealthy levels of pollution, and about three million tourists annually (according to the US Environmental Protection Agency), and accommodating suburban sprawl beside an enigmatic wilderness, the regional planning safeguards created collaboratively by interests in this lake ecosystem’s development now contend with an appreciably murkier and warmer lake. According to the Tahoe Environmental Research Center, the lake's clarity had decreased to its lowest point at 59.7 feet in 2017 and the lake had reached its warmest average surface temperature on record to that point in July of that year at just over 68 degrees Fahrenheit. Heavy drought, which had also caused concerns about dry soil in the region's forests, followed by especially high amounts of precipitation were cited as causes of the severe reduction in clarity. Sustainability efforts are ongoing and increasingly collaborative to help reduce any further effects of climate change.

The terrain now harbors a measurably hotter climate with which its native and introduced species will have to cope. A cradle of biotic health and beauty amidst the granite monotony of a water-scarce Sierra Nevada Mountain Range, Lake Tahoe remains an alpine recreational magnet in an inevitably warming, forested watershed.

Bibliography

"About Lake Tahoe." US Environmental Protection Agency, 9 Mar. 2018, www.epa.gov/lake-tahoe/about-lake-tahoe. Accessed 27 July 2018.

Community Report for the Tahoe Region, March 2022, tahoeprosperity.org/wp-content/uploads/Tahoe-Community-Report‗March-2022‗Final.pdf. Accessed 31 Aug. 2022.

Goin, Peter. Stopping Time: A Rephotographic Survey of Lake Tahoe. U of New Mexico P, 1992.

Raumann, C.G., and M.E. Cablk. “Change in the Forested and Developed Landscape of the Lake Tahoe Basin, California and Nevada, USA, 1940–2007.” Forest Ecology and Management, vol. 255, 2008.

Strong, Douglas H. Tahoe: From Timber Barons to Ecologists. U of Nebraska P, 1999.

Tahoe: State of the Lake Report; 2018. UC Davis Tahoe Environmental Research Center, 2018, terc.ucdavis.edu/stateofthelake/sotl-reports/2018/SOTL‗complete.pdf. Accessed 27 2018.