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Located in northwestern California and southwestern Oregon, complex terrain, geology, climate, and biogeographic history have created one of the Earths most extraordinary expressions of temperate biodiversity in the Klamath and Siskiyou Mountains. Although well-known among biologists, few North Americans realize the uniqueness and importance of the species and communities in this ecoregion. Indeed, logging, mining, road building, and grazing continue to be intensive and pervasive threats to this area. To date no strict protected areas have been established in this rich region.
The Klamath-Siskiyou ecoregion is considered a global center of biodiversity (Wallace 1982), an IUCN Area of Global Botanical Significance (1 of 7 in North America), and is proposed as a World Heritage Site and UNESCO Biosphere Reserve (Vance-Borland et al. 1995). The biodiversity of these rugged coastal mountains of northwestern California and southwestern Oregon has garnered this acclaim because the region harbors one of the four richest temperate coniferous forests in the world (along with the Southeastern Conifer forests of North America, forests of Sichuan, China, and the forests of the Primorye region of the Russian Far East), with complex biogeographic patterns, high endemism, and unusual community assemblages. A variety of factors contribute to the regions extraordinary living wealth. The region escaped extensive glaciation during recent ice ages, providing both a refuge for numerous taxa and long periods of relatively favorable conditions for species to adapt to specialized conditions. Shifts in climate over time have helped make this ecoregion a junction and transition zone for several major biotas, namely those of the Great Basin, the Oregon Coast Range, the Cascades Range, the Sierra Nevada, the California Central Valley, and Coastal Province of Northern California. Elements from all of these zones are currently present in the ecoregions communities. Temperate conifer tree species richness reaches a global maximum in the Klamath-Siskiyous with 30 species, including 7 endemics, and alpha diversity (single-site) measured at 17 species within a single square mile (2.59 km2) at one locality (Vance-Borland et al. 1995). Overall, around 3,500 plant species are known from the region, with many habitat specialists (including 90 serpentine specialists) and local endemics. The great heterogeneity of the regions biodiveristy is due to the areas rugged terrain, very complex geology and soils (giving the region the name "the Klamath Knot"), and strong gradients in moisture decreasing away from the coast (e.g., more than300 cm (120in)/annum to less than 50 cm (20 in)/annum). Habitats are varied and range from wet coastal temperate rainforests to moist inland forests dominated by Douglas fir (Pseudotsuga menziesii), Pinus ponderosa, and P. lambertiana mixed with a variety of other conifers and hardwoods (e.g., Chamaecyparis lawsoniana, Lithocarpus densiflora, Taxus brevifolia, and Quercus chrysolepis); drier oak forests and savannas with Quercus garryana and Q. kelloggii; serpentine formations with well-developed sclerophyllous shrubs; higher elevation forests with Douglas fir, Tsuga mertensiana, Abies concolor and A. magnifica; alpine grasslands on the higher peaks; and cranberry and pitcher plant bogs. Many species and communities have adapted to very narrow bands of environmental conditions or to very specific soils such as serpentine outcrops. Local endemism is quite pronounced with numerous species restricted to single mountains, watersheds, or even single habitat patches, tributary streambanks, or springs (e.g., herbaceous plants, salamanders, carabid beetles, land snails, see Olson 1991). Such fine-grained and complex distribution patterns means that any losses of native forests or habitats in this ecoregion can significantly contribute to species extinction. Several of the only known localities for endemic harvestman, spiders, land snails, and other invertebrates have been heavily altered or lost through logging within the last decade, and the current status of these species is unknown (Olson 1991). Unfortunately, many invertebrate species with distribution patterns and habitat preferences that make them prone to extinction, such as old growth specialist species, are rarely recognized or listed as federal endangered species. Indeed, 83 species of Pacific Northwest freshwater mussels and land snails with extensive documentation of their endangerement were denied federal listing by the U.S. Fish and Wildlife Service in 1994 (J. Belsky, pers. comm. 1994). Rivers and streams of the Klamath-Siskiyou region support a distinctive fish fauna, including nine species of native salmonids (salmon and trout), and several endemic or near-endemic species such as the tui chub (Gila bicolor), the Klamath small-scale sucker (Catostomus rimiculus), and the coastrange sculpin (Cottus aleuticus). Many unusual aquatic invertebrates are also occur in the region. Habitat Loss Only 25 percent of the ecoregion is considered to be relatively intact. Remaining Blocks of Intact Habitat Larger blocks of relatively intact habitat include the Trinity Alps (1,910 km2), Marble Mountain (769 km2), Whiskeytown-Shasta (657 km2), Kalmiopsis (649 km2), Eel River (586 km2), Siskiyou (569 km2), and Yolla Bolly-Middle Eel River Nationa Forest Wilderness areas (555 km2), and the Klamath Wild & Scenic River (669 km2). Most of these larger blocks encompass higher elevation habitats. Few large blocks of lower elevation undisturbed habitat remain. The Dillon Creek watershed represents one of the last remaining lowland forest blocks, but is still unprotected. Degree of Fragmentation The biological communities of this ecoregion are naturally heterogeneous, but logging has greatly increased fragementation. Species that are found only within narrow altitudinal belts are particularly sensitive to the isolation, fragmentation, and reduction of their habitat. Degree of Protection Higher elevation habitats are well represented within a system of protected areas (e.g., Wilderness Areas), but middle and lower elevation sites are poorly protected. The ecological integrity of habitats within Wild and Scenic River areas are often compromised by landuse in surrounding areas and linear habitat configurations that do not favor viable ecological and population dynamics. Types and Severity of Threats The Klamath-Siskiyous native communities have been heavily impacted by commercial logging, fire suppression, mineral extraction, road building, and grazing of sheep and cattle. Many of the larger rivers and tributaries have been severely degraded by dredging for gold, toxic runoff from mining operations, and sedimentation and associated changes from excessive and poorly managed logging. Introduced species, particularly in aquatic habitats, have altered many natural communities.
The Klamath-Siskiyou ecoregion corresponds to Omerniks Klamath Mountains ecoregion and roughly overlaps with Baileys Klamath Mountains and Southern Cascades sections (M261A, M261D). Prepared by: D. Olson, R. Noss, G. Orians, J. Stritholt, C. Williams, and J. Sawyer. This text was originally published in the book Terrestrial ecoregions of North America: a conservation assessment from Island Press. This assessment offers an in-depth analysis of the biodiversity and conservation status of North America's ecoregions. All text by World Wildlife Fund © 2001 For more general information on this ecoregion, go to the WildWorld version of this description.
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