The Klamath-Siskiyou Region

Renowned Biodiverse Area of Southern Oregon & Northern California

Deep Lake, Marble Mountains Wilderness

Deep Lake in the Marble Mountains Wilderness Area

The Klamath-Siskiyou Mountains are a place of raw, rugged beauty, renowned biodiversity and dramatic contrast. Tucked into the remote borderlands of the southern Oregon and northern California, the region is wild and largely inaccessible. This tangled knot of rocky ridges and deep forested canyons is transitional in terms of climate and vegetation. It is here, in the Klamath-Siskiyou Mountains where the fog drenched redwoods and temperate rain forests of coastal Oregon and Northern California collide with the western most vestige of high desert vegetation, reaching into the region from the arid Great Basin to the east. It is also here, in the Klamath-Siskiyou that the forests of the Pacific Northwest marching down the Oregon Coast Range and the Cascade Crest, meet and mingle, with the dry mixed-conifer forests, oak woodlands, grasslands, and chaparral that characterize the Sierra Nevada Mountains, Southern Cascade Mountains and the Central Valley of California.

World Class Botanical Diversity

The region contains an incredible variety of plant species and habitat types, creating some of the most diverse and unique plant communities in North America and some of the most diverse conifer forests in the world. Although the Klamath-Siskiyou represents only 15 percent of California’s landmass, the range contains 65% of the states native plant species. Known for its unusual conifer diversity, the Klamath-Siskiyou contains 35 species of conifers, many surviving in niches at the edge of their prevailing range, others are found no where else on the face of the earth. This rich conifer diversity is matched by an incredible variety of plant communities, including many range extensions and endemic species found only in Klamath-Siskiyou Mountains.

The evolution of the Klamath-Siskiyou flora is the product of hundreds of millions of years of evolutionary process, along with drastic climatic swings that triggered the expansion and recession of innumerable plant species. Notably, the Klamath-Siskiyou Mountains were largely ice free during the last ice age, allowing plant species to continue evolving and find refuge, when much of the continent was covered in glaciers and ice sheets.

As climatic patterns came and went, leading to successive waves of plant migration; species were isolated in unique microclimates that allowed them to persist, even as their larger, more contiguous populations receded. Due to this pattern, an astonishing array of plant species meet their geographic limits in these mountains. The southern most stands of Engelman spruce, Pacific silver Fir, subalpine fir and Alaska yellow cedar are found in cool, moist locations similar to those found in the High Cascades of Oregon. The northern most stands of foxtail pine grow in the interior Klamath-Siskiyou Mountains in locations much like the Sierra Nevada Mountains. In the lower country, gray pine, numerous chaparral species and California Buckeye also reach their northern limit on hot, dry exposures.

This pattern is also responsible for the numerous paleo-endemics that originally colonized the Klamath-Siskiyou Mountains during the Little Ice Age and became stranded as relicts of a widespread flora that existed roughly 65 million years ago. Portions of this ancient flora exist today only in the Klamath-Siskiyou Mountains. The region’s paleo-endemic species include Baker’s cypress, Brewer’s spruce, Port Orford cedar, Sadler’s oak, Kalmiopsis plant, Shasta snow wreath and Marshall’s current.

Despite the ancient evolutionary history in the Klamath-Siskiyou Mountains, the region  has not just provided habitat niches for ancient ice age relicts, the region is also actively evolving new species known as neo-endemics. These species are often found in very small geographic areas and have speciated in response to unique soil conditions or genetic isolation. Many of these species are currently evolving on the “serpentine” or ultra-mafic soils of the region.

The stark serpentine landscape of barren rock, twisted brush, nutrient starved pine trees, darlingtonia fens and colorful rock gardens is emblematic of the Klamath-Siskiyou Mountains and is a stronghold for biodiversity, including both ancient paleo-endemics and neo-endemics. Serpentine adapted neo-endemics include Siskiyou willow herb, numerous species of rock cress, fawn lily, wild buckwheat and many others.

Spectacular Geologic Diversity

Ultra-mafic outcrops on the Siskiyou Crest

Ultra-mafic outcrops on the Siskiyou Crest in the Red Buttes Wilderness

The geologic complexity of the region heavily influences the region’s plant diversity and the seemingly haphazard patchwork of ancient rock is equally impressive and unique.

The region began as a volcanic island arc, which was “accreted” or fused onto the continent roughly 300 million years ago. As tectonic plates shifted, the great coastal and continental plates collided, over and over again, creating massive amounts of friction, pressure, folding and uplift. Ancient ocean sediments, portions of the granitic continental plate and pieces of earth’s mantle were scrapped and folded into a series of extremely diverse, arch shaped deposits of bedrock. Each successive arch-shaped deposit was welded to the body of the continent and pushed inland over millions of years.

Marble outcrops on the Siskiyou Crest near Swan Mountain
Marble outcrops on the Siskiyou Crest near Swan Mountain

The mantle rocks were pushed up from the depths of the ocean floor, to create the ultra-mafic, “serpentine,” or “red rock” soils the region is so well-known for. Ocean sediments were also scrapped onto the face of the continent and have been heated, folded and metamorphosed into layered outcrops of schist, mudstone and greenstones. Ancient coral reefs have also been pushed inland and uplifted into the towering summits of limestone in the Marble Mountains Wilderness and near the Oregon Caves National Monument.

The friction and pressure building beneath the continent as the massive tectonic plates collided, also created vast reservoirs of super heated granitic rock, known as plutons. Roughly 150 million years ago, these plutons began cooling beneath the surface of the earth. As the super heated granite began cooling it triggered a period of mountain rising and uplift. This uplift in turn triggered significant erosion, exposing the now solidified granitic mass in islands scattered across the landscape. River canyons were carved during this period and sediments from the eroding mountains filled valley’s such as the Applegate Valley with the erosion from uplifting mountains. Today plutons can be found as large granitic outcrops on the Salmon River, near Mt. Ashland and Grayback Mountain on the Siskiyou Crest and in the Trinity Alps Wilderness.

The region’s ancient, jumbled geologic history dramatically influences the region’s biodiversity. Each soil type sustains a distinct plant community and heavily influences both the structure and composition of plant communities throughout the Klamath-Siskiyou Mountains.

Wildlands and Wild Rivers

Canyon Creek Lakes in the Trinity Alps Wilderness

Canyon Creek Lakes in the Trinity Alps Wilderness

Fortunately, the Klamath-Siskiyou region is not just beautiful and diverse, it is also wild and largely undeveloped. In fact, the Klamath-Siskiyou contains the largest concentration of intact watersheds, and wildland habitats remaining on the West Coast. The region contains a vast, relatively well connected series of remote, lonely wilderness areas and roadless areas. Unlike many regions, the network of wildlands in the Klamath-Siskiyou contains an incredibly diverse array of habitats at both high and low elevations. These wildlands contain beautiful old growth forests, lush mountain meadows, craggy mountain peaks, dramatic cirque lakes, clear blue rivers, sunlit oak woodlands, dense chaparral, dry grasslands, vibrant rock gardens, and mixed hardwood forests.

The region contains numerous world class wilderness areas and hundreds of thousands of acres of unprotected roadless areas. These wildlands are the ecological foundation of the local conservation network and maintain much of the region’s biodiversity.

The Wild & Scenic Chetco River

The Wild and Scenic Chetco River

The Klamath-Siskiyou Mountain’s are defined by the beautiful rivers that drain their rugged slopes. The river’s of the Klamath-Siskiyou have carved deep, rocky canyons through jumbled mountains and deep forest, as they flow west into the Pacific Ocean. The region is home to the largest concentration of wild and scenic rivers in the lower 48 and the largest undammed river system in California. Many of the rivers contain strong native fisheries and some of the highest water quality in the world.  Rivers like the Rogue, the Chetco, the Salmon, the Trinity, the Illinois, the Smith, the Elk, the Mad, the Applegate and the Klamath are national treasures that should be protected, restored and cherished.

Diverse Ancient Forests

Dutch Creek Old Growth
Ancient fir forest on Dutch Creek in the Condrey Mountain Roadless Area.
The forests of the Klamath-Siskiyou are deep, diverse and mysterious. With their 35 conifer species, they are among the most diverse temperate forest habitats on the face of the earth. The region supports an amazing array of forest habitats from lush old growth forests of fir and coastal forests of redwood, Port Orford cedar, hemlock and western red cedar to interior habitats supporting subalpine forests, arid ponderosa pine stands, dry Douglas fir forest and Jeffery pine savannah. Perhaps most notable are the diverse, mixed conifer forests with their abundant hardwoods and towering conifer species.

These incredible forests follow both elevation gradients and climatic gradients. The forests closest to the coast receive up to 125″ of rain annually and support dense forests, including some of the worlds largest coastal redwoods. Roughly forty miles to the east, in a pronounced “rain-shadow,” portions of the Applegate Valley, Scott Valley and Shasta Valley receive less than 20″ of annual precipitation and support a unique mixture of grassland, oak woodland, chaparral, groves of western juniper and dry mixed conifer forests of pine and fir.

At higher elevations the forests of the Klamath-Siskiyou support diversified forests with Ice Age relicts, subalpine species and temperate forest species mixed together in a complex, jumbled mosaic. In one location, near Little Duck Lake in the Russian Wilderness Area, researchers have discovered the “miracle mile,” where 18 conifer species can be found growing in one square mile!

Beautiful High Country

East Boulder Lakes, Trinity Alps

East Boulder Lakes in the Trinity Alps Wilderness.

The Klamath-Siskiyou Mountains contain a rich variety of high mountain environments including mountain lakes, high elevation forests, wet meadows, rugged cirque walls, craggy summits and spectacular vistas. The region is a maze of ridges and peaks, sprawling across the large, sparsely populated region. The highest peak in the Klamath-Siskiyou Mountains is the broad, red hump known as Mt. Eddy (9,026′) on the divide between the Trinity River and the headwaters of Sacramento River. Although impressive, Mt. Eddy is dwarfed by snow capped Mt. Shasta (14,180′), a massive, singular volcanic summit in the nearby Cascade Mountains and rising from the arid Shasta Valley.

To the west, the Klamath-Siskiyou Mountains contain numerous distinct sub-ranges each with their own unique high mountain habitats. The most extensive high country is located in the massive 525,627 acre Trinity Alps Wilderness, where sharp granitic peaks rise to over 9,000′. The nearby Russian Wilderness and Marble Mountains Wilderness, along with the Scott Mountains, the Castle Crags, the Eddy Range, the Yolla Bolly Mountains and the Siskiyou Crest all contain beautiful high mountain scenery.

The high mountains of the Klamath-Siskiyou, with their dramatic lakes and lush meadows feed the mighty rivers of the region with cold mountain water. This cold mountain water sustains runs of salmon and steelhead in the Sacramento, Ell, Trinity, Scott, Klamath, Applegate, Rogue, Illinois and Smith River watersheds.

The high country of the Klamath-Siskiyou is also an important climate refuge, supporting incredible levels of biodiversity and vast unaltered habitats. The high country of the Klamath-Siskiyou provides important habitat connectivity including, the Siskiyou Crest, on the Oregon/California border. This unique mountain chain is the only high elevation connectivity corridor connecting the cool, temperate forests of the Coast Range to the snow forests of the Cascade Mountains.

The sacred high country of the Klamath-Siskiyou has also long provided inspiration, solitude and a sense of wonder to nearby human communities. The indigenous people of the region have long revered the high country for its sacred prayer seats and to learn personal lessons of respect, humility and connection to place. Many of the native tribes still utilize the high country for ceremonial purposes and other local residents and visitors to the region are also inspired by its beauty, complexity and mystery.


The Klamath-Siskiyou Mountains contain many unique and interesting sub-ranges in a tangled knot of rocky ridges and deep canyon. The region sprawls across northwestern California and southwestern Oregon. Numerous sub-ranges make up the Klamath-Siskiyou Mountains, these include the Yolla Bolly Mountains, Trinity Mountains, Trinity Alps, Salmon Mountains, Russian Mountains, Marble Mountains, Scott Mountains, Scott Bar Mountains, Siskiyou Mountains, the Eddy Range, and many others. KFA works to protect and maintain connectivity between the sub-ranges of the Klamath-Siskiyou Mountains.
Castle Crags

Castle Crags at the headwaters of the Sacramento River and the eastern margin of the Klamath-Siskiyou Mountains

Since 1989, KFA has advocated for the Klamath-Siskiyou Mountain Region through ongoing programs and environmental activism. Please consider supporting our work today.

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