Published online by Cambridge University Press: 24 August 2009
The genus Sequoia has existed since Mesozoic times, and early Tertiary Redwoods occurred practically throughout the northern hemisphere. Today, the Coast Redwood (Sequoia sempervirens) is the only living species of the genus, and it is restricted to the coastal environments of California and the southern extremity of Oregon. Climatic factors determine the outer limits of Redwood distribution, while edaphic, biotic, and hydrologic, variables influence the occurrence of Redwood within the climatic range.
Human use of Redwood forests has altered the environmental conditions under which the Sequoia now grows. Logging has exposed the forest floor to increased light and higher temperatures, while in some places it has exposed the soil to accelerated erosion. Recent floods in the major watersheds of north-western California have been particularly disastrous in undercutting large trees along the river banks. Increased degradation rates on upper slopes have resulted in delivery of coarse sediments to floodplains, with possibly deleterious effects on living old-growth Redwoods.