Sierra Nevada Forests

Category: Forest Biomes.

Geographic Location: North America.

Summary: The biologically diverse Sierra Nevada forests have been altered by intensive management practices that diminish forest health and resilience to wildfires.

The Sierra Nevada mountain range in the American West is renowned for forests with incredible biodiversity and spectacular scenery. Encompassed by peaks up to 14,000 feet (4,267 meters), river valleys, steep canyons, lakes, meadows, and rock outcroppings, the forests support remarkable plant and animal variety, and provide valuable natural resources and recreational opportunities for the region.

Logging, intensive forestry, wildfires, and urbanization threaten the Sierra Nevada forests, however, and also affect surrounding human communities. Though sizable forest segments are managed and protected by federal agencies, additional policy and community initiatives seek to improve forest health and maintain ecosystem services.

Vegetation

The Sierra Nevada forests are comprised of various forest types influenced by elevation, climate, and precipitation. Running northwest to southwest approximately 400 miles (644 kilometers) long by 50 miles (81 kilometers) wide, the eastern slope of the mountain range is much steeper and drier than the west. The towns and agricultural regions in the California Central Valley lead upwards into the chaparral and foothill woodlands on the west slope, followed at higher elevations by a mixed conifer forest dominated by ponderosa pine, sugar pine, Douglas fir, and white fir. Comprised of 27 species of conifers, the Sierra Nevada forest is considered one of the most diverse temperate coniferous forests in the world.

Above the mixed conifer forest, white fir, red fir, and lodgepole pine species are prevalent. Just below the timber line, high-elevation pine species may be densely or sparsely present, including mountain hemlock, whitebark, foxtail, and limber pine. On the eastern slope, high-elevation areas of tundra and bare rock extend down to forests composed of lodgepole pine, red fir, and Jeffery pine. Below 6,000 feet (1,829 meters) on the eastern face, the open woodland of pinyon pine and western juniper descends into the desert scrub species of the Great Basin.

Biodiversity

These biologically diverse forests contain robust plant and animal assemblages, and perform vital ecological functions. Half of California’s vascular plant species occur here, including 200 rare species and 400 that are endemic to the Sierra Nevada, that is, not found elsewhere. The forests support a host of fauna as well, with 60 percent of California’s vertebrate species found here, in addition to a diverse invertebrate population including many endemics and species with local distributions.

Among the animals found in this vast area, depending on elevation and climate, are black bear, mountain lion, mule and whitetail deer, gray fox, jackrabbit, California mouse, striped skunk, chickaree and chipmunk, and various varieties of squirrel.

Among the bird population are Bullock’s oriole, screech owl, California and mountain quail, red-breasted sapsucker, wild turkey, turkey vulture, Audubon and Nashville warbler, white-headed woodpecker, and the rock and winter wren.

Amphibians and reptiles abound, including bullfrogs, California newt, Pacific treefrog, red-eared turtle, Gilbert’s skink, and a range of snakes including coral-bellied ringneck, gopher, racer, sharp-tailed, Calley garter, and western rattlesnake.

The Sierra Nevada forests are known for trout, including brown or German brown trout; golden trout, which is California’s state fish; rainbow trout; and brook trout, which is often found in high-elevation alpine lakes and brooks.

Yosemite National Park is home to many creatures; wildlife biologists who monitor the park’s fauna have identified threatened species as a way to ensure their long-term survival. Among those listed as under federal and/or state protection are: Sierra Nevada bighorn sheep, California wolverine, Pacific fisher, and Sierra Nevada red fox.

Environmental Threats

Research in the Sierra Nevada region reveals declining and at-risk plant and animal populations in these significant forest habitats, as well as scores of newly described plant species. The World Wildlife Fund has given this temperate coniferous forest a critical/endangered conservation status; the Sierra Nevada was included in the top 10 ecosystems needing protection from climate change in a 2010 report by the Endangered Species Coalition. Species such as several frog populations have been proposed and added to lists of endangered species needing protection. For example, the foothill yellow-legged frog had disappeared from more than half of its California range by 2021 because of dams and water diversions, flooding, logging, mining, urban development, and other threats to its habitat.

The ecosystem services of the Sierra Nevada forests are critical to the well-being of California residents. More than half of the water, timber, and energy from hydropower used in the state originates from this region, while its trees—particularly the old-growth forest stands—are able to capture and store carbon dioxide better than many other terrestrial ecosystem processes.

Logging, forestry practices, fire suppression, and urbanization are some of the ongoing threats to the biome. More than 60 percent of these mixed conifer forests have been altered. The move toward tree plantations and intensive forestry practices has simplified forest structure and composition, causing reduced genetic variability, impaired function, and diminished resilience to disturbance. The lack of genetic diversity from monoculture replanting after timber harvesting has made forests more susceptible to pests and disease such as bark beetles and fungal pathogens.

Fire suppression was implemented as human populations increased in the mountains and foothills, although fire was historically part of the natural cycle in the Sierra Nevada forests. Forest simplification and fire suppression together contribute to the greatly increased number and severity of catastrophic wildfires in the area. The decline in natural firebreaks such as old-growth patches or moist riparian areas, combined with increased fuels from the understory, lowers resilience to forest fire, and affects the health of forests and residents alike. Additionally, ozone and other chemicals from air pollution in coastal and valley cities have damaged many tree species and hinder their beneficial carbon sequestering function.

Conservation Efforts

An early advocate for Sierra Nevada preservation, environmentalist John Muir was instrumental in creating the celebrated Yosemite National Park in 1890, as well as the prominent conservation organization Sierra Club. Since then, the federal government has established nine national forests, four national parks, two national monuments, and 26 national wilderness areas that cover more than 15 million acres (6 million hectares), and provides varying degrees of protection for the Sierra’s vast natural resources.

National forests account for the majority of the area, and the U.S. Forest Service administers multiple-use management of public lands that allows logging and grazing. The national parks share a high degree of protection for mid-elevation forests, and harbor the largest remaining blocks of relatively intact mixed conifer forests.

Sierra Nevada forest managers have faced the challenge of balancing multiple environmental perspectives and economic interests while addressing public safety. As a result, myriad partnerships concerning forest management and conservation have emerged. The Sierra Nevada Ecosystem Project, requested by Congress in 1992, was tasked with compiling an accurate, multidimensional ecosystem assessment to enable sustainable forest management and identify economic, ecological, and social linkages to inform future policy decisions. Following that initiative, the Sierra Nevada Forest Plan was created in 2001 and amended in 2004 and 2010, after significant public input, to improve protection of old forests, wildlife habitats, watersheds, and communities in the Sierra Nevada region.

In 2004, the U.S. Forest Service began the Forests with a Future campaign, aimed at protecting Sierra Nevada old-growth forests, wildlife, and communities from catastrophic wildfires by building public understanding and teaching tools to reduce wildfire damage. Numerous conservation coalitions also are actively engaged in contributing to forest management policies to ensure that biodiversity and ecosystem functions are preserved, especially as climate change affects forest and water resources, and vulnerable plants and animal populations. These collaborations and policy initiatives seek to maintain the comprehensive benefits derived from the Sierra Nevada forests now and in the future.

Bibliography

Murphy, Dennis D., Erica Fleishman, and Peter A. Stine. “Biodiversity in the Sierra Nevada.” In Proceedings of the Sierra Nevada Science Symposium, edited by D. Murphy and P. Stine. Albany, CA: Pacific Southwest Research Station, Forest Service, U. S. Department of Agriculture, 2004.

Storer, Tracy I., Robert L. Usinger, and David Lukas. Sierra Nevada Natural History. Berkeley: University of California Press, 2004.

Tucker, Jody. "Sierra Nevada Carnivore Monitoring Program." US Forest Service, 2021, www.fs.usda.gov/detail/r5/plants-animals/wildlife/?cid=FSEPRD590791. Accessed 1 Sept. 2022.

United States Forest Service. Sierra Nevada Forest Plan Monitoring Accomplishment Report for 2011. Washington, DC: Forest Service, 2012.